RESOURCE RECOVERY & REUSE SERIES 23 ISSN 2478-0529 Sewage Sludge: A Review of Business Models for 23 Resource Recovery and Reuse Avinandan Taron, Shirish Singh, Pay Drechsel, Chaya Ravishankar and Andreas Ulrich Resource Recovery & Reuse Series The Resource Recovery and Reuse (RRR) Series originated in 2014 under the CGIAR Research Program on Water, Land and Ecosystems (WLE), and continues since 2021 under the CGIAR Initiatives on Resilient Cities and Nature-Positive Solutions. The aim of the RRR series is to present applied research on the safe recovery of water, nutrients and energy from domestic and agro-industrial waste streams. IWMI’s research on RRR aims to create impact through different lines of action research, including (i) developing and testing scalable RRR business models, (ii) assessing and mitigating risks from RRR for public health and the environment, (iii) supporting public and private entities with innovative approaches for the safe reuse of wastewater and organic waste, and (iv) improving rural- urban linkages and resource allocations while minimizing the negative urban footprint on the peri-urban environment. IWMI works closely with the World Health Organization (WHO), Food and Agriculture Organization of the United Nations (FAO), United Nations Environment Programme (UNEP), United Nations University (UNU), and many national and international partners across the globe. The RRR series of documents present summaries and reviews of the research and resulting application guidelines, targeting development experts and others in the research for development continuum. RESOURCE RECOVERY & REUSE SERIES 23 Sewage Sludge: A Review of Business Models for Resource Recovery and Reuse Avinandan Taron, Shirish Singh, Pay Drechsel, Chaya Ravishankar and Andreas Ulrich The authors Taron, A.; Singh, S.; Drechsel, P.; Ravishankar, C.; Ulrich, A. 2023. Sewage sludge: a review of business Avinandan Taron is a researcher at the International Water models for resource recovery and reuse. Colombo, Management Institute (IWMI), Colombo, Sri Lanka. He has Sri Lanka: International Water Management Institute an academic background in environmental and resource (IWMI). 98p. (Resource Recovery and Reuse Series 23). economics. His work involves the analysis of institutions and doi: https://doi.org/10.5337/2023.211 investments towards a circular bio-economy focused on agriculture and rural–urban linkages. / resource recovery / resource management / reuse / sewage sludge / business models / circular economy / nutrients / Shirish Singh, PhD, is Senior Lecturer and Researcher at energy recovery / organic fertilizers / biosolids / phosphorus / IHE Delft Institute for Water Education, Delft, Netherlands. wastewater treatment plants / waste management / landfills He has more than 25 years of experience in overall program, / sewage treatment / technology / sludge dewatering / project, and technical management, advisory, research and anaerobic digestion / incineration / gasification / pyrolysis / strategic support with a focus on water, wastewater, sludge biochar / solid wastes / sludge disposal / composting / pellets (wastewater and fecal) and water drainage, including social, / biogas / electricity generation / public-private partnerships economic and financial analysis. / municipal authorities / policies / regulations / frameworks / market demand / costs / profitability / value chains / public Pay Drechsel, PhD, is a Senior Fellow and Research health / environmental health / soil composition / case Quality Advisor at IWMI. With over 30 years of professional studies / Europe / USA / UK / Italy / Netherlands / Germany / experience in developing countries, he coordinates multi- Belgium / Switzerland / Spain / Denmark / Australia / Japan disciplinary projects and programs on the safe recovery of / China / India / Sri Lanka / Tunisia / Oman / Chile / water, nutrients, and organic matter from domestic waste streams with a special interest in safe wastewater irrigation ISSN 2478-0510 (Print) and urban and peri-urban agriculture. ISSN 2478-0529 (Online) ISBN 978-92-9090-951-4 Chaya Ravishankar, PhD, is an environmental engineer with a PhD in social acceptance of reclaimed water use. Copyright © 2023, International Water Management Institute Chaya has 12 plus years of experience in water and (IWMI). wastewater treatment systems design, implementation, and related policy research, currently integrating it with larger Fair use: Unless otherwise noted, you are free to copy, sustainability strategy for industries. duplicate or reproduce and distribute, display, or transmit any part of this paper or portions thereof without permission Andreas Ulrich (1959–2020) worked as an integrated expert and to make translations, adaptations or other derivative at IWMI, Colombo, Sri Lanka, supported by the German works under the following conditions: Centre for International Migration and Development. With a background in agricultural sciences, water and sanitation, ATTRIBUTION. The work must be referenced according and experience as Executive Director of the Bremen to international citation standards, while attribution Overseas Development Association, Germany, Andreas was should in no way suggest endorsement by IWMI or the an expert in decentralized wastewater treatment systems. author(s). NONCOMMERCIAL. This work may not be used for commercial purposes. SHARE ALIKE. If this work is altered, transformed or Acknowledgments built upon, the resulting work must be distributed only The authors would like to thank Piumi Madhuwanthi, IWMI under the same or similar license to this one. intern, for helping with the editorial work. Front cover photograph: Treated wastewater in clarifier before its final discharge into the Litani River, Ablah, Syria Donors (credit: Jano Hatem). This work started under the CGIAR Research Program on Water, Land and Ecosystems (WLE) and was finalized under Editor: Pay Drechsel, International Water Management the CGIAR Initiative on Resilient Cities. The authors are Institute grateful for the support of CGIAR Trust Fund contributors Copyeditor: Terry Erle Clayton (www.cgiar.org/funders). Designer: ASM Graphics ii CONTENTS List of Figures .......................................................................................................................................................iv List of Business Model Canvasses ......................................................................................................................iv List of Tables .........................................................................................................................................................iv List of Boxes ......................................................................................................................................................... v Acronyms and Abbreviations ..............................................................................................................................vi SUMMARY ...........................................................................................................................................................vii 1. INTRODUCTION ............................................................................................................................................... 1 1.1 Sewage sludge related regulations, treatment, and disposal options .................................................... 2 1.2 Market potential for management and reuse of municipal sewage sludge .......................................... 10 1.3 The business model approach ................................................................................................................ 14 2. RECOVERING BIOSOLIDS ............................................................................................................................ 15 Business model 1: Formal sludge collection and treatment for use ........................................................... 17 Business model 2. Informal sludge collection and treatment for use ......................................................... 22 Business model 3: Producing co-compost................................................................................................... 26 Business model 4: Producing sludge pellets ................................................................................................ 30 3. RECOVERING PHOSPHORUS ...................................................................................................................... 33 Business model 5: Recovery of phosphorus from incinerated sludge ash ................................................. 35 Business model 6: Recovery of phosphorus from anaerobic sludge digestate ......................................... 39 4. RECOVERING ENERGY ................................................................................................................................. 43 Business model 7: Energy recovery from anaerobic digestion ................................................................... 44 Business model 8: Energy recovery from incineration ................................................................................. 49 Model A: Mono-incineration of sewage sludge ..................................................................................... 49 Model B: Co-incineration of sewage sludge .......................................................................................... 54 Business model 9: Energy recovery from gasification and pyrolysis .......................................................... 60 5. HYBRID MODELS .......................................................................................................................................... 65 Business model 10: Recovery of biosolids, biomethane and electricity from sludge digestion ................ 65 Business model 11: Recovery of energy/electricity from sludge incineration and phosphorus from the ash ............................................................................................................................................. 69 Business model 12: Recovery of phosphorus and energy from sewage sludge ........................................ 73 Model A: Recovery of phosphorus and energy from anaerobic digestion ........................................... 73 Model B: Recovery of phosphorus, biochar and energy through pyrolysis ......................................... 77 6. OVERVIEW OF BUSINESS MODEL ATTRIBUTES ......................................................................................... 81 6.1 Drivers for sewage sludge recovery and reuse pathways in Europe and USA ..................................... 81 6.2 Requirements for adaptation to and in the Global South ...................................................................... 84 REFERENCES ..................................................................................................................................................... 86 ANNEX 1. BUSINESS MODEL CANVAS (GUIDANCE) ...................................................................................... 88 ANNEX 2. BUSINESS PERFORMANCE POTENTIAL (KEY TO SCORES) ........................................................ 89 iii LIST OF FIGURES FIGURE 1. Resource recovery options for sewage sludge. 1 FIGURE 2. Distribution of biosolid use and disposal in the USA 2021 6 FIGURE 3. Regional analysis of sewage sludge markets and value share of reuse options. 12 FIGURE 4. Pathways for nutrient and energy recovery from sewage sludge. 15 FIGURE 5. Business model for use of chemically stabilized sludge. 19 FIGURE 6. Business model for recovery of dewatered and dried biosolids. 19 FIGURE 7. Informal business model for the recovery of dewatered and dried biosolids. 24 FIGURE 8. Business model for production of co-compost. 28 FIGURE 9. Business model for pellet production. 32 FIGURE 10. Phosphorus recovery at different stages of sewage sludge treatment. 34 FIGURE 11. Business model for recovery of phosphorus from sludge ash. 37 FIGURE 12. Business model for phosphorus recovery from sludge digestate. 41 FIGURE 13. Business model for recovering energy through anaerobic digestion. 46 FIGURE 14. Business model for recovering energy from mono-incineration. 51 FIGURE 15. Business model for co-incineration. 56 FIGURE 16. Business model for energy recovery through pyrolysis and gasification. 62 FIGURE 17. Business model for recovery of biosolids and energy (biomethane and electricity). 67 FIGURE 18. Business model for recovering energy and phosphorus. 71 FIGURE 19. Business model for energy and phosphorus recovery through anaerobic digestion. 75 FIGURE 20. Business model for recovering energy and phosphorus (and other nutrients via biochar). 78 FIGURE 21. German sewage sludge treatment targets for 2032 depending on phosphorus content. 83 LIST OF BUSINESS MODEL CANVASES Canvas 1. Formal collection and use of biosolids 19 Canvas 2. Informal collection and use of biosolids 24 Canvas 3. Co-composting 28 Canvas 4. Pellet production 32 Canvas 5. Recovering phosphorus from sludge ash 37 Canvas 6. Recovery of phosphorus from anaerobic sludge digestate 41 Canvas 7. Energy recovery from anaerobic digestion 46 Canvas 8. Energy recovery from incineration 51 Canvas 9. Energy recovery from co-incineration of sewage sludge 57 Canvas 10. Energy recovery from gasification and pyrolysis 63 Canvas 11. Recovery of biosolids and energy 67 Canvas 12. Recovery of energy and phosphorus by incineration 71 Canvas 13. Recovery of energy and phosphorus from sewage sludge 75 Canvas 14. Recovery of phosphorus, biochar and energy through pyrolysis 79 LIST OF TABLES TABLE 1. Sewage sludge disposal pathways in Europe. 4 TABLE 2. Minimum duration between application of Class B biosolids and harvest, grazing and access. 5 TABLE 3. Sewage sludge related regulations in selected countries (status 2021). 7 TABLE 4. Disposal and reuse costs in Europe. 9 iv TABLE 5. Sewage sludge disposal costs in Germany and Italy. 9 TABLE 6. Comparative cost (USD) of sewage sludge disposal options (per wet ton). 10 TABLE 7. Sludge management options, benefits, and costs in Vermont. 11 TABLE 8. Sewage Sludge disposal pathways in European countries. 13 TABLE 9. Details of Alan SRL recovery plants. 20 TABLE 10. Operational plants of CNP cycles GmbH. 42 TABLE 11. RWE Power Ag and EnBW use of sewage sludge. 59 TABLE 12. Estimates of plant capacity. 62 TABLE 13. SÜLZLE KOPF SynGas plants. 64 TABLE 14. Operation plants of Eliquo and PYREG in Germany 80 TABLE 15. Requirements and attributes for successfully implementing business models. 82 TABLE 16. Heat map of transferability of the business models to the Global South. 85 LIST OF BOXES Box 1. Precautions with land application and mandatory regulatory compliance. 16 Box 2. Adaptations of the Business Model 56 Box 3. Sewage sludge application on soils according to the German Sewage Sludge Ordinance 83 v ACRONYMS AND ABBREVIATIONS AbfKlärV Klärschlammverordnung (German Sewage Sludge Ordinance) CAGR Compound annual growth rate CFR Code for Federal Regulations CNG Compressed natural gas DBO Design, build, operate DBOO Design, build, own, operate EEA European Environment Agency GGE Gasoline gallon equivalent GmbH Company with limited liability (German abbreviation) GWI Global Water Intelligence GWRC Global Water Research Coalition ISO International Organization for Standardization MGD Million gallons per day MLD Million liters per day MPN Most probable number MSW Municipal Solid Waste NET Negative emission technology NuReSys Nutrients Recovery Systems PE Population equivalent PPP Public-private Partnership RRR Resource Recovery and Reuse SPV Special Project Vehicle Srl Società a Responsabilità Limitata (limited liability company) SSD Sewage Sludge Directive SWOT Strengths, Weaknesses, Opportunities, and Threats TS Total solids (dry matter) UBA Umweltbundesamt (German Environment Agency) ULB Urban local body USEPA United States Environmental Protection Agency UWWTD Urban Wastewater Treatment Directive WWTP Wastewater Treatment Plant vi SUMMARY Sewage sludge generated from wastewater treatment The extraction of organic fertilizers through dewatering, systems carries a stigma as an environmental hazard, thickening, stabilization or long-term storage drives the first set especially where it is inefficiently and unsustainably of models followed by technological advances in phosphorus managed as in many low- and middle- income countries. recovery. The business models on energy similarly start from Alternative options are needed given the increasing conventional energy recovery processes (anaerobic digestion) concerns and policies restricting sewage sludge and move toward incineration. The discussion covers recent dumping in landfills and elsewhere, and a growing advances in gasification and pyrolysis. Transforming sewage awareness about the resource value of sludge within a sludge into biochar, for example, can support soil fertility circular economy. and carbon sequestration. The final set covers integrative approaches supporting soil fertility and energy needs. Modern resource recovery technologies allow for the capture of biosolids, nutrients or energy from sewage sludge and the While technologies and business models generally have a reduction of the amount to be disposed of. Water utilities, favorable policy environment, the regulatory framework may municipalities and private entities are increasingly engaging restrict the use of recovered (waste-derived) resources for in these opportunities.1 certain applications, for example, in agriculture. Emerging economies, such as China and India, with high population This study reviews existing approaches and business growth and sludge generation are under pressure to models for resource recovery and moves the discussion formulate progressive regulations and policies for safe beyond technical feasibility. Case studies were analyzed in resource recovery while investing heavily in wastewater support of four main sets of business models depending treatment. A similar push is needed to increase industry on the targeted resource: (i) organic fertilizers, (ii) crop acceptance of recovered products like phosphorus to nutrients, (iii) energy, and (iv) organic fertilizers and nutrients penetrate agricultural markets despite the currently still along with energy. cheaper phosphate rock, which is a finite resource. 1 Biosolids are the organic materials resulting from the treatment of domestic sewage in a wastewater treatment facility (i.e., treated sewage sludge). Biosolids can be a beneficial source of essential plant nutrients and organic matter for crop production or landscaping depending on the presence of contaminants. vii SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE 1. INTRODUCTION This study reviews existing sewage sludge reuse efforts with entering the system (Spinosa 2011). With population a focus on related business models. The review extracts growth, progressive expansion of wastewater networks and describes models based on a comparative analysis of and industrial development, the quantity of sewage sludge similar cases for a particular resource recovery option based generated in municipal wastewater treatment plants on an understanding of the drivers, relevance, concepts, (WWTPs) is increasing. Sludge produced by WWTPs value chain and products, risks and benefits, and financial amounts to a small percentage by volume of processed parameters. Thus, instead of building theoretical business wastewater, but its handling can account for 40–60% of total models, each model is based on existing cases. As these operating costs, which calls for volume and cost-reducing models depend on technical options and the regulatory strategies, ideally combined with cost recovery (Foladori et environment, this report will provide insights to guide the al. 2010; Spinosa 2011). The situation is alarming in large selection of business models. and densely populated cities with limited land for treatment and regulatory pressure to end sludge disposal on over- Sewage sludge is a by-product of wastewater treatment full landfills. Fortunately, sewage sludge is increasingly plants connected to a sewer system.2 Where sewage recognized as a resource for energy recovery and soil sludge management is unsustainable, it can result in a amelioration (ADB 2012; GWI 2023a). Figure 1 shows the potential threat to human and environmental health because variety of resource recovery options, from those still under of a wide variety of domestic and industrial contaminants development to mainstreamed technologies. FIGURE 1. RESOURCE RECOVERY OPTIONS FOR SEWAGE SLUDGE (SOURCE: GWI 2023a). 2 Sewage sludge generated in wastewater treatment plants should be differentiated from fecal sludge accumulating in on-site sanitation systems like septic tanks (septage) or pit latrines. Business models and technological options for fecal sludge are presented in Issues 2, 3, 6 and 18 of the Resource Recovery and Reuse report series. 1 RESOURCE RECOVERY & REUSE SERIES 23 To incentivize resource recovery and reuse (RRR) a regulatory for the reduction of these hazards in the form of heavy metals, framework is needed with clear sets of end-of-waste criteria pathogens, organic compounds and disease vectors. and related standards which define when waste resources become a legal secondary raw material and can be traded Global guidance is available from the International and used. Organization for Standardization (ISO) which has two standards on sludge recovery, recycling, treatment, and In contrast to fecal sludge captured in household septic disposal: ISO 19698:2020 on the beneficial use of biosolids- tanks not connected to a public sewage system, the land applications, and ISO/TR 20736:2021 as guidance on chemical contamination of sewage sludge can be much the thermal treatment of sludge. ISO is developing more higher as it may be derived from residential and industrial standards such as ISO/NP TR 22707 as guidance on the suburbs and street runoff. Hence, quality control and regular processes and technologies for inorganics and nutrient chemical analysis for heavy metals and organic chemicals recovery.3 are important for sewage sludge recycling. This applies, in particular, to using sludge on land to improve soil fertility The European Union Regulatory Environment where depending on the soil type, it can reduce or even Operators of WWTPs within the European Union (EU) need offset the use of chemical fertilizers. Where the application of to comply with set directives. While earlier regulations related sludge on land is not possible or risky in view of contaminants, to waste materials such as sewage sludge had, as their its transformation into the relatively safer biochar or use main objective, the prevention of risks to the environment as energy after anaerobic digestion could be options. and human health, more recent revisions support waste Co-incineration of sewage sludge as a renewable fuel reuse and resource recovery as targeted in the European source can be applied in the power and cement industries, Union’s Circular Economy Action Plan (2020). especially for contaminated sewage sludge, whereas mono- incineration enables the recovery of phosphorus from ash. Urban Waste Water Treatment Directive 91/271/EEC, This is increasingly done in high-income countries. Carbon Amended 98/15/EC (UWWTD) sets regulatory practices footprint analysis is widely applied in developing sludge for the collection, treatment and discharge of urban and management strategies and selecting technical pathways industrial wastewater. Adopted in 1991, the UWWTD for sludge treatment and disposal. contains limited provisions on wastewater and sludge reuse and recovery of valuable components. On July 13, 2018, 1.1 Sewage sludge related regulations, the European Commission published the Consultation on treatment, and disposal options the Evaluation of the Urban Wastewater Treatment Directive Business models related to waste management and ahead of a potential revision. Since its adoption, new resource recovery, and in particular those related to a technical advances in treatment techniques for waste and potential hazard like sewage sludge, depend on what local, emerging pollutants have been developed to foster energy national or regional regulatory frameworks allow and the efficiency and recovery. available technical options. Although many countries do not have explicit regulations on sewage sludge, they may refer to Waste Framework Directive 2008/98/EC. This directive existing guidelines as a reference for developing them. This is the main driving force behind current waste management section briefly describes some often-referenced sewage practices. It sets out several principles and methods that sludge regulations and treatment and disposal options and member states must implement. The most important their costs. principles affecting sludge management practices are: 1.1.1. Regulatory Frameworks • Application of a waste management hierarchy: This Common disposal and reuse regulations for sewage sludge hierarchy gives priority to waste prevention and cover agricultural and non-agricultural land application encourages reuse and recovery techniques. The use, incineration, landfilling, energy recovery (heat and final disposal of waste is only a last resort after all electricity), use in construction, and open environment other options have been considered. disposal. From a regulatory perspective, the main challenge • Introduction of ‘the end-of-waste criteria’ concept: is land application as this can imply direct contact with farm This Directive explains when waste can be workers and indirectly with consumers through groundwater recategorized as secondary raw material. or the food chain. This implies a need for stricter health and environmental standards for reuse than for landfilling or Sewage Sludge Directive 86/278/EEC (SSD). This incineration. Typically, regulations for the reuse of sludge for directive was adopted to encourage the correct use of agricultural or non-agricultural purposes include thresholds sewage sludge in agriculture and regulate its use to prevent for a range of contaminants and management requirements harmful effects on soil, vegetation, animals and humans. 3 Standards by ISO/TC 275. https://www.iso.org/committee/4493530/x/catalogue/p/1/u/1/w/0/d/0 2 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE The principal benefit of the SSD is its role in the protection Member State cannot be exported or will require a new of human health and the environment against the harmful registration dossier for sale in another Member State except effects of contaminated sludge in agriculture. It prohibits where they have been mutually recognized by the authorities the use of untreated sludge on agricultural land unless it of the importing Member State.4 is injected or incorporated into the soil. The directive does not prescribe specific treatment technologies, which gives Landfill Directive 1999/31/EC. This directive provides countries some flexibility in what they choose to adopt. The measures, procedures and guidance to prevent or reduce directive requires a regular examination of sludge quality negative impacts on the environment, particularly the and soils at an interval of at least 12 months to check for pollution of surface water, groundwater, soil and air and environmental hazards. The SSD also requires that sludge the global environment, including greenhouse gas effects, be used in a way that accounts for the nutrient requirements as well as any other risk to human health that might result of plants and that the quality of the soil and surface and from landfilling with sewage waste. However, the directive groundwater is not impaired. The SSD emphasizes also supports resource recovery and reuse. According safeguarding the environment and human health more than to the Directive, the amount of biodegradable municipal reuse opportunities. waste had to be reduced to 50% in 2009 and 35% in 2016 compared to a 1995 baseline. By 2035, the amount of all The SSD does not address contaminants of emerging municipal waste in landfills should be reduced to 10% or concern (e.g., organic chemicals such as pharmaceuticals, less of the total amount of municipal waste generated (by micro-plastics or cosmetics containing polycyclic aromatic weight). hydrocarbons or per- and polyfluoroalkyl substances), and thus has recently been under review for revision. Over the This directive has led countries to seek alternative methods years, several European Union Member States have either such as land application of sludge, incineration and biogas set stricter requirements than those imposed by the directive production. Many EU countries have prohibited the disposal or have simply banned sludge use in agriculture on public of sludge in landfills. These countries include Austria, health grounds. Belgium, Denmark, Finland, Luxembourg, the Netherlands, Germany, Sweden and Estonia. The remaining EU countries Fertilizer Regulation (EC) No. 2003/2003. The conditions are decreasing the amount of sludge sent to landfills to meet for making fertilizers available within internal markets have the new directive targets. Although the directive mentions been partially harmonized through Regulation (EC) No. pre-treatment and quality monitoring, it does not set limits 2003/2003 of the European Parliament and the Council, on the amount of waste to be disposed of. These are usually which almost exclusively covers fertilizers from mined or set by national and regional regulations or individual landfill chemically produced, inorganic materials. However, nearly site operators. half the fertilizers on the EU market with organic components are not covered by No. 2003/2003. A new EU Circular Directive 2000/76/EC on the incineration of waste. This Economy Fertilizing Products Regulation (EU) 2019/1009 directive provides air pollution limits for sulfur and nitrogen was consequently approved by the European Parliament oxides, hydrochloride, particulates and heavy metals and and the Council of the European Union in 2019, repealing dioxins. The level of sludge pre-treatment required is not No. 2003/2003. defined in the regulation for either mono-incineration or co- incineration (coal-fired thermal plants or cement industries). The new version widens the scope of the regulation to include inorganic, organo-mineral and organic fertilizers, Directive (EU) 2018/2001 on the promotion of energy organic soil improvers, liming products, growing media, plant from renewable sources. This directive mainly sets a target bio-stimulants and agronomic fertilizer additives, including for renewable energy, biogas and syngas obtained from secondary raw materials such as those recovered and bio- wind, solar or organic waste, including sludge generated based fertilizing products. This will considerably facilitate through sewage treatment. market availability of both organic products containing recycled nutrients (e.g., processed biosolids, digestates, Circular Economy Action Plan (2020). Under section composts, biochars) and inorganic recovered phosphate 3.7 on Food, Water and Nutrients, the action plan says, products (e.g., struvite, phosphates recovered from sewage “The Commission will develop an Integrated Nutrient sludge, incineration ash). Fertilizing materials certified to Management Plan to ensure more sustainable application of comply with the new essential requirements outlined in the nutrients and stimulate the markets for recovered nutrients.” EU Fertilizer Regulation (minimum nutrient content, quality The Commission will also consider reviewing directives on and safety criteria) will be authorized for the EU internal wastewater treatment and sewage sludge and will assess market, whereas products registered as fertilizers in one natural means of nutrient removal such as algae. 4 Nutriman Newsletter. The new fertilizer regulation – consequences for farmers. https://nutriman.net/news/new-fertiliser-regulation- consequences-farmers 3 RESOURCE RECOVERY & REUSE SERIES 23 Presently, the sewage sludge produced in the European Union (8.7%) and other destinations for the remaining amount has four main destinations: agriculture (49.2%), incineration (4.9%) see Campo et al. (2021). The dominant sewage sludge (24.9%), cultivation and land reclamation (12.4%), landfill disposal methods by EU country are listed in Table 1. TABLE 1. SEWAGE SLUDGE DISPOSAL PATHWAYS IN EUROPE. Disposal method Countries Agriculture Bulgaria, Croatia, Czechia, Denmark, Ireland, Lithuania, Spain and Sweden, Italya Compost and other applications Cyprus, Estonia, France, Hungary, Luxembourg, Slovakia, Landfills Malta, Romania Incineration Austria, Belgium, Germany, Greece, Netherlands, Switzerland, Turkey Otherb Latvia, Poland, Portugal, Slovenia Source: EEA (2021). a Both compost and agricultural use. The data about waste management for 2019 reveals that in Italy, 56% of sewage sludge was disposed of (of which 13.2% was in landfills and 7.7% by incineration and 57% was biologically treated for agricultural use) and 41% was recovered, of which 67.9% was by activities of recovery/reuse of organic substances (ISPRA 2021). b Includes temporary storage at wastewater treatment plants and landfills, reuse at plant sites and in forestry and reclamation of land including agricultural land (Poland and Romania), export to other countries (e.g., in Slovenia, sludge is exported to Hungary), landscaping and landfill coverage (e.g., Sweden). The United States (US) Regulatory Environment dry weight) or Salmonella (< 3 MPN/4 g of total solids dry The U.S. has strict regulations for sludge disposal. The weight) and can be freely purchased in shops and applied Federal Municipal Sludge Regulations 40 Code for Federal virtually without regulation to agricultural lands.5 Regulations (CFR) Part 503 are more detailed than those in the EU Sewage Sludge Disposal regulation. Pollutant limits Class B biosolids have a higher level of pathogens (monthly and management practices for all three types of sludge geometric mean of fecal coliforms < 2,000,000 MPN) disposal (land application, incineration, and landfill disposal) or colony-forming units per gram of dry weight and can are covered in one document. The regulation was issued in be used for land reclamation and farming with certain 1993 and is part of the Clean Water Act. restrictions. These concern the minimum duration between the application of biosolids and harvesting of certain crops, Land application of municipal sludge – Part 503, animal grazing or public exposure and access. These subparts B and D. Subpart B specifies the pollutant limits minimum durations significantly reduce health hazards to for a range of heavy metals under ceiling concentrations, levels equivalent to those achievable with the unregulated cumulative pollutant loading rates, monthly average application of Class A biosolids (Table 2). concentrations and annual pollutant loading rates. Subpart D places restrictions on the pathogens and vector attraction For agricultural use, 40 CFR Part 503.14 requires that reduction in sludge by prescribing treatment steps to be biosolids must be applied to land at the appropriate performed. The subpart distinguishes Class A and Class agronomic rate, which is the sludge application rate B sludge based on the number of pathogen indicators designed to provide the nitrogen needed by a crop or present in the sludge after treatment. Class A biosolids vegetation grown on the land. The agronomic rate depends contain minimal fecal coliforms (< 1,000 MPN/g total solids on crop type, geographic location and soil characteristics. 5 The ‘most probable number’ (MPN) is a statistical method used to estimate the viable number of bacteria in a sample. 4 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE TABLE 2. MINIMUM DURATION BETWEEN APPLICATION OF CLASS B BIOSOLIDS AND HARVEST, GRAZING AND ACCESS. Class B biosolids Period between land application and harvest, animal grazing and public access Criteria Surface application Incorporation Injection Food crops in which the harvested 14 months 14 months 14 months parts may touch the soil or biosolid mixture (beans, melons, squash, etc.) Food crops in which the harvested 20–38 monthsa 20–38 months 20–38 months parts grow in the soil (potatoes, carrots, etc.) Food, feed and fiber crops (field maize, 30 days 30 days 30 days hay, sweet corn, etc.) Grazing animals 30 days 30 days 30 days Public access restrictions High potential for public exposureb 1 year 1 year 1 year Low potential for public exposure 30 days 30 days 30 days Source: USEPA (1993a, 1993b, 1995); Jayathilake et al. 2019. a The 20-month duration between application and harvesting applies when surface applied biosolids stay on the surface for four months or longer before incorporation into the soil. The 38-month duration is in effect when the biosolids remain on the surface for less than four months before incorporation. b This includes application to turf forms, which place turf on land with a high potential for public exposure. Stockpiling Class B biosolids on an open field should be avoided and, if practiced, runoff to surface water or any adjacent land where community members may be exposed must be avoided. According to Subpart D, one of the following recommended are currently no federal targets or national incentives in methods should be used to treat sewage sludge before place to reduce the amount of biodegradable waste going agricultural land application (also see USEPA 1993a, 1993b, to landfills. 1995).6 The lack of such directives in the US is reflected in the • Aerobic digestion for 40 days at 20° C or 60 days landfill statistics. In 2021, about 43% of the sewage sludge at 15° C. produced in the US was dumped in landfills (Figure 2), a • Anaerobic digestion for 15 days at 35 to 55° C or share that was only 22% in 2019. Land applications in 2021 60 days at 20° C. absorbed 42%; 10% less than in 2019. The incinerated • Air drying for at least three months. Two of the share remained similar (14–16%). In the European Union, months must have average daily temperatures agriculture and land reclamation absorbs about 61%, above freezing. incineration 25%, and landfills receive only 9% (Campo et • Composting or co-composting at temperatures al. 2021). greater than 40° C for five days. The temperature of all the material being composted must be greater Landfill disposal methods are primarily regulated through than 55–65° C for at least four hours during the Landfilling Regulation 1993 US Code Chapter 40 Part 258 five days. and the supporting legislation on Toxicity Characteristic • Lime stabilization to bring the pH higher than 12 for Leaching Procedure defined in 40 CFR 261.24. These 30 minutes or bring the pH higher than 9 for more legislations establish minimum criteria for all municipal than six months if the temperature is above 35° C solid waste landfills that are used to dispose of sewage or moisture is below 25%. sludge to ensure the protection of human health and the environment. They also define when a solid waste exhibits Land filling of municipal sludge Part 503, Subpart C. toxicity. A common disposal method is spreading sludge on The US regulations are less restrictive than in the EU, where the surface of a land area at regular intervals where it is left reduction targets are set for sludge going to landfills. There to dry. The sludge is then plowed into the ground. Sludge 6 Part 503 considers domestic septage as sewage sludge. 5 RESOURCE RECOVERY & REUSE SERIES 23 disposed of in this way must meet the defined thresholds Regulations in Other Countries: A Brief Description (e.g., for heavy metal concentrations). Alternatives to landfilling are considered in some countries for their benefits, while in other countries public health and Incineration of sludge. The two main pieces of environmental concerns make land application an exception legislation that regulate the operation of incinerators are (Table 3). In Brazil, for example, where land application for 40 CFR Part 503 Subpart E of the Clean Water Act and agriculture is allowed, it is difficult to comply with guidelines 40 CFR Part 129 of the Clean Air Act. These regulations that define about 60 chemical and microbiological indicators set standards for air pollutants from the combustion which are in part more stringent than elsewhere and do not process and restrictions on site-specific concentrations consider local and regional specifics and capacities, making for arsenic, cadmium, chromium, lead and nickel in it unfeasible to adopt a circular alternative to landfilling. The sewage sludge being fed to an incinerator. The exact limitations are different in Oman, where the national legislation values are based on site-specific variables such as supports composting and reuse of sludge in agriculture but incinerator type, dispersion factor, control efficiency, still lacks legislation for other options such as converting it to feed rate, and stack height. a fuel or using it for manufacturing bricks (Jaffar et al. 2017). # FIGURE 2. DISTRIBUTION OF BIOSOLID USE AND DISPOSAL IN THE USA 2021. # A monofill is a landfill that has been designed to handle only one material. Source: United States Environmental Protection Agency. https://www.epa.gov/biosolids/basic-information-about-biosolids. 6 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE 7 TABLE 3. SEWAGE SLUDGE RELATED REGULATIONS IN SELECTED COUNTRIES (STATUS 2021). Japan Australia New Zealand China UAE Oman Brazil Legislation • New Sewage Law • Federal Clean • New Zealand • Pollution and control Laws are different • MD 145/93 dated • Agricultural guiding sewage (1970s) Water Act (1970s) Guidelines for of treatment and for different June 13, 1993, application of sludge • Fertilizer Law (1950) • State Fertilizers Biosolids disposal of municipal Emirates, e.g. Regulations for sludge Resolution management • Waste Management Act and application on sludge (2009) • Abu Dhabi Wastewater CONAMA No. and Public Cleaning Waste Act land (2003) • Land improvement Recycled Water Reuse and 375/2006 Law (1970) • National Water (GB/T 24600–2009) and Biosolids Discharge by the • Landfilling Law No. • Soil Contamination quality • Gardening (GB/T Regulation Ministry of 12.305/2010 Countermeasures management 23486–2009) RWB) 2010; Regional National Policy on Law (2001) strategy • Agriculture • Dubai Water Municipalities, Solid Waste • Guidelines for (CJ/T30-009) Environment Environment and Sewerage • Forest application Regulations Water Resources Systems Biosolid (CJ/T 362- 2011) (EN 5.0) Management • Landfilling regulation (2004) (GB/T23485-2009) • State-specific • Incineration regulation guidelines GB/T24602-2009; and more Landfilling Allowed only for Abandoned in most Major disposal Allowed for municipal Allowed Was a major disposal Major disposal incinerating ash states except method and industrial sludge method but most method; historical (being discouraged) Virginia and as a cover for landfills WWTPs now follow records of discarding USEPA regulations for sludge into open producing sludge environments for composting and land applications Agricultural use Not widely used Major use (heavy Promoted but still Major use (heavy metals, Promoted with Promoted with Promoted but rarely (basic inspected (carbonized, dried metals, organic scarce use (heavy Organic Compounds, restrictions only on restrictions only on used (different parameters) and composted compounds, metals, organic pathogens, disease heavy metals heavy metals pathogenic sewage sludge or pathogens, disease compounds, vector reduction) and organic indicators (coliforms, sewage sludge vector reduction) pathogens, disease compounds Salmonella, ashes used) vector reduction) helminths, viruses), different nutrients, 11 heavy metals and 34 organic substances) (Continued) RESOURCE RECOVERY & REUSE SERIES 23 8 TABLE 3. SEWAGE SLUDGE RELATED REGULATIONS IN SELECTED COUNTRIES (STATUS 2021). (CONTINUED) Japan Australia New Zealand China UAE Oman Brazil Other None Forestry, land Forestry, land Forestry, land Land reclamation Land reclamation None application uses reclamation, mine reclamation, mine reclamation, mine sites sites, landfills, of e.g. mine sites, and agriculture building materials production Thermal Major use (highly Not preferred, Not applied Incineration, thermal Not applied Not applied Not applied treatment promoted (>70%) limited hydrolysis and application anaerobic digestion common Phosphorus Highly promoted, Viewed as a need Not yet Viewed as a need Not yet Not yet Not yet recovery from commercial sewage sludge applications Source: Adapted from Christodoulou and Stamatelatou (2016) for Japan Australia and New Zealand; GWI (2012) and Wei et al. (2020) for China, UAE, Oman and Brazil. SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE 1.1.2. The legislation, technology and disposal government policies alter, disposal costs are also likely to costs nexus change (GWI 2012). The operational costs of sludge treatment and disposal are, Common sludge management systems include sludge in general, a function of the technology used, the reuse target screening, thickening, dewatering, and drying for further (energy, compost, etc.) and transport distance (Foladori et processing or disposal. At each step in the process, WWTP al. 2010). However, local, national, or regional regulations managers can select from several technical options. The can use fees to steer or restrict certain disposal options and solution selected for each treatment step must balance pathways and demand sludge quality standards. This will efficiency, performance and reliability alongside cost, determine the technological preference, disposal and reuse capacities required for operation and other technical options and treatment costs. The Chinese government, considerations aside from the disposal or resource recovery for example, introduced regulations that prevent landfills target. Table 4 shows the cost range of different strategies from accepting sludge with a solid content below 40%. As for management of sewage sludge in Europe. TABLE 4. DISPOSAL AND REUSE COSTS IN EUROPE. Methods of sludge use Minimum (USD /ton) Maximum (USD /ton) Land application 28 235 Landfilling 140 285 Composting 168 347 Thermal drying 90 235 Incineration 90 490 Source: Capodaglio and Olsson (2020) Specific costs of sewage sludge disposal in Germany and Italy are shown in Table 5. TABLE 5. SEWAGE SLUDGE DISPOSAL COSTS IN GERMANY AND ITALY. Country Reuse and disposal Cost of sewage sludge Remarks management range (EUR/ton of dry residue) Germanya Agricultural 160 – 320 Pre-treatment: Costs for drying sludge application sewage sludge are between EUR 20–25/ton of dry solids. Cost variations reflect different Mono-incineration 280 – 480 amounts and transport costs. Italyb Agriculture 129 In Italy, the management of sludge (loading, transport, Incineration (cement factories) 120 (115) analysis and recovery or disposal), was estimated at Landfill 212 15–40% of the costs of a WWTPc Source: Author’s creation. a Roskosch and Heidecke 2018; bDomini et al. 2022; cATIA ISWA Italia 2019. 9 RESOURCE RECOVERY & REUSE SERIES 23 In the US, where cost data are reasonably well documented, air to facilitate drying, and an abundance of nearby land for disposal costs vary greatly between states. The distances application, have much lower land application costs (< 165 involved in hauling can be long and greater than the cost USD/ton of dry solids) (GWI 2012). An example of a simple of land application. In New York, for example, costs are cost comparison is shown in Table 6. A direct comparison relatively high (> USD 330/ton of dry solids) because material of disposal costs across states or countries suffers from is sometimes trucked to distant states. On the other hand, regional variations in tipping fees, variations in fuel costs and cities, such as Phoenix, Arizona, which have naturally hot dry hauling distances and state and local taxes. TABLE 6. COMPARATIVE COST (USD) OF SEWAGE SLUDGE DISPOSAL OPTIONS (PER WET TON). Management New Hampshire Pennsylvania CSWD (Vermont)a Landfill USD 75 USD 75 USD 94 Land application USD 40 USD 62 USD 130 (class A) USD 100 (class B) USD 90 (Grasslands) Incineration USD 71 USD 71 No data a Chittenden Solid Waste District, Vermont. Source: Kelly and Twohig 2018. The cost of various management options relative to monitoring, product quality assurance, transportation, each other can be more consistent. It appears from the etc.) rather than from tipping fees charged by end- example in Table 6 that land application can provide a cost management facilities (Kelly and Twohig 2018). An advantage over landfilling and incineration, similar to the attempt at comparison specific to the Chittenden County data in Table 4. The New Hampshire and Pennsylvania case in Vermont is shown in Table 7. studies show there is a distinct economy of scale with an increasing cost advantage over other disposal options 1.2 Market potential for management and with an increasing volume of biosolids being managed. reuse of municipal sewage sludge In Vermont, this cost differential is not expected to be as great as in other jurisdictions, primarily due to the costs The global biosolids market is estimated to be around USD added for monitoring that are not required in most other 1.7 billion in 2023, and is anticipated to grow at compound jurisdictions. These requirements, though not unique to annual growth rate (CAGR) of 4.5-4.7% up to 2.6-2.7 Vermont, include more frequent analyses of biosolids, billion at the end of 2033 (Fact.MR 2022; GWI 2023a). groundwater, soil, and plant tissue testing, a ban on field Figure 3 shows the breakdown for biosolids applications in storage of biosolids (meaning that a storage facility at a agriculture, non-agriculture and for energy recovery and the WWTP is necessary) and requirements to incorporate market shares by main regions. Other regions to observe biosolids into the soil following application. An additional are Latin America and South Asia and Oceania, and with the cost in Vermont comes from the imposition of the Franchise relatively smallest expected volume of 0.1 billion the Middle Tax on Waste Facilities. While landfilling and incineration East and Africa. are subject to tax, composting and land application are not (Kelly and Twohig 2018). Bloomberg (2021) summarized the key findings from the Fact.MR survey as follows: In general, it is difficult to compare costs between • The leading biosolids markets will remain North alternative options, predominantly regarding what America, Europe, and China. expenditures should be included in the calculation • With around 60% market share, the agricultural of a total cost. A comparison of the relative costs of segment will continue to dominate the biosolids switching from one management strategy to another market through 2031. can be similarly confounded. This is largely due to cost • Based on product type, class A and class A differentials derived from upfront processing charges (Exceptional Quality7) types are projected to related to preparing sludge for disposal (electricity, account for over half of overall biosolids sales auxiliary heating, dewatering, chemical addition, during the forecast period. 7 Class A (Exceptional Quality) sewage sludge meets the most stringent pollutant, pathogen, and vector attraction reduction requirements under US EPA’s regulations. https://www.epa.gov/sites/default/files/2020-11/documents/land-application-classa-memo-2020.pdf 10 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE TABLE 7. SLUDGE MANAGEMENT OPTIONS, BENEFITS, AND COSTS IN VERMONT. Management Option Benefit Cost per wet ton Liquid sludge → dewatering → landfill • none USD 91–95 Liquid sludge → dewatering → Casella • land applied as EQ USD84–89 Grasslands facility Liquid sludge → dewatering → thermal drying • land applied as EQ USD 200–285 Liquid sludge → dewatering → thermal drying • produces methane usable as fuel USD 300–350 → gasification Liquid sludge → dewatering → composting • land applied as EQ USD 110–175 Liquid sludge → dewatering → alkaline • land applied as EQ USD 100 stabilization Liquid sludge → mesophilic anaerobic • land applied as Class B digestion → dewatering • produces methane usable as fuel USD 130–150 Liquid sludge → thermophilic anaerobic • land applied as EQ digestion → dewatering • produces methane usable as fuel USD 140–160 Liquid sludge → mesophilic anaerobic • land applied as EQ digestion → thermophilic anaerobic • produces methane usable as fuel USD 110–130 digestion → dewatering Note: EQ: Exceptional Quality biosolids subjected to an advanced pathogen reduction treatment process Source: Kelly and Twohig 2018 Key drivers, according to Bloomberg’s summary are: and land reclamation (12%), landfill dumping (9%), • Increasing adoption of biosolids as an and other destinations (5%) (Campo et al. 2021). affordable alternative to chemical fertilizers However, countries like Germany, the Netherlands, within the agriculture sector will boost the and Switzerland are shifting from using sewage sludge market. for agriculture towards incineration (EEA, 2021). Table • Implementation of stringent norms and regulations 8 provides a description of disposal mechanisms in on the use of chemical fertilizers is positively selected countries. impacting the biosolids market. • Rise in the number of wastewater treatment In Asia, there is huge potential for resource recovery in India plants along with favorable governmental support and China. India is planning to expand its existing capacity will accelerate the biosolids demand during the for sewage treatment. Over 1,700 million liters per day (MLD) forecast period. treatment capacity is in the planning or construction stage.8 • Expanding scope of biosolids in non-agricultural It has been estimated that the sector has the potential to and heat generation applications is projected generate 15.3 × 105 and 8.6 × 105 MWh of energy annually to create lucrative opportunities for the market from incineration and anaerobic digestion, respectively players. (Singh et al. 2020). In China, 5,476 municipal WWTPs were operating, leading to an annual sludge productivity of 39 Key restraints are: million tons (8% water content). Overall, 29% of the sludge • High cost associated with sludge treatment plants in China was disposed of via land applications, followed is likely to limit the market growth in some regions. by incineration (27%) and sanitary landfills (20%) (Wei et al. • Availability of conflicting information 2020). Further regulations like direct reuse of treated water regarding biosolids on the public domain is to substitute groundwater and restrict wastewater discharge expected to create negative impact on the from industries is increasing importance on wastewater market demand. treatment and resulting sludge disposal or reuse (GWI 2023b). Further regulations like direct reuse of treated water to The situation in European countries mirrors this summary substitute groundwater and restrict wastewater discharge but also shows likely changes. The main destinations of from industries is increasing importance on wastewater sewage sludge in Europe are so far agriculture (49%), treatment and resulting sludge disposal or reuse (GWI incineration and energy production (25%), cultivation 2023b). 8 https://cpcb.nic.in/status-of-stps/ (accessed on November 5, 2022) 11 RESOURCE RECOVERY & REUSE SERIES 23 North America Europe East Asia Market Share 18% 30% 22% CAGR (2021-2031) Note: Pie chart indicates market share by region. Arrow indicates the rela�ve growth of the market in the region. SourScoe:u hrtctpes:: //Fwawcwt..wMhaRtech.com/og/markets-research/materials-chemicals/732574-biosolids-market-value-expected-to-reach-us-2-4-billion- by-2031 (accessed on May 5, 2023) Value Opportunity (2021 – 2031) Agricultural Non-agricultural Energy recovery & Produc�on Low High SourSceo: uhtrtpcse://:w Fwawc.fatc.MtmrR.com/report/biosolids-market (accessed on October 31, 2022) FIGURE 3. REGIONAL ANALYSIS OF SEWAGE SLUDGE MARKETS AND VALUE SHARE OF REUSE OPTIONS. 12 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE TABLE 8. SEWAGE SLUDGE DISPOSAL PATHWAYS IN EUROPEAN COUNTRIES. Country Disposal of sewage sludge Italy Organic matter recovered and reused following a biological treatment has grown at an average rate of 8% per year between 2009 and 2018, with the total volume increasing from 4.4 to 7.8 million tons. The total production is about 395,000 tons dry solids/yeara. Mininni et al. (2019) describe the use of sewage sludge as follows: • 9.9% is used in agriculture without further treatment • 26.4% and 5.6% is used in compost and soil conditioner production respectively • 5.9% is sent to incineration or co-incineration plants • 35% is sent to external sludge centers for further treatment (manly chemical and physical processes) before recovery/disposal • 17.2% is sent to landfills France Over 1 million tons of dry solids are produced from wastewater treatment plants.b Pradel (2019) describes the use of sewage sludge as follows: • 4% of the sludge produced is used for land applications (agriculture and urban landscaping) • 31% composting, • 22% incineration • 3% landfill • 1% in cement plants UK The financial value to UK agriculture of nutrients in biosolids is around USD 73 million per annum constituting mainly phosphate and nitrogen as well as sulfur, potash and magnesium. A strong demand from farmers (worth USD 400 per hectare) in nutrients drives the market: • Around 87% of all biosolids are applied to agricultural lands • 4% incinerated • 3% goes to industrial use (cement plants) • 6% for land reclamation or restoration Germany Roskosch and Heidecke (2018) indicate the following uses of sewage sludge: • Disposal via thermal treatment (70%) om coal-fired plants, cement works and co-incineration with municipal waste, maintaining a limit that sewage sludge should not exceed 20% • Sludge applications in agricultural (20%) • Landscaping (10%) Landfilling of sewage sludge is no longer permitted in Germany since 2005. Application of sewage sludge in organic farming, forests, gardens, grasslands, arable land and fruit and vegetable cultivation is also prohibited in Germany. Netherlands About 1.5 million tons of dewatered sewage sludge (2% dry matter) is produced per annum and used for:c • Mono-incineration (50%) • Drying and co-incineration in bio-energy plant/HVC, and in and cement plants) (25%) • Composting (biological drying) and co-incineration in power plants (19%) • Co-incineration along with municipal solid waste (6%) Notes; a https://smartwatermagazine.com/blogs/madhuri-patil/biological-wastewater-treatment-market-italy-driven-growth-pulp-paper-industry (accessed on November 5, 2022) b https://www.eureau.org/resources/publications/members-reports/5299-public-water-and-waste-water-services-in-france/file (accessed on November 5, 2022) c https://www.nweurope.eu/media/3386/1_p4y_environ2018_hvc-snb_ruijter.pdf (accessed on November 5, 2022) 13 RESOURCE RECOVERY & REUSE SERIES 23 The Middle East and North Africa is extending wastewater but the conscious creation of value with a market orientation, treatment systems and will need capacity to deal with aiming at maximizing waste reduction and resource and increased sludge volume. GWI (2012) estimated a CAGR cost recovery. of 8% (2011–2017) with a market size of USD 780 million in 2017. Sewage generation across the region is rising by Business models for managing sewage sludge and leading 25% every year.9 to resource recovery and reuse depend on several factors, such as: For example, Kuwait has six wastewater treatment plants with a combined capacity for treating 12,000 m³ of • Existing government priorities, regulatory municipal wastewater per day. This produces around 250 frameworks and financial instruments (taxes, fees). tons of sludge daily. Similarly, Tunisia has approximately • Management choices given assets and operations 125 wastewater treatment plants which generate around as it influences the characteristics of the generated one million tons of sewage sludge every year. In Jordan, sludge (e.g., decentralized treatment technology). over 105,000 tons of dried sewage sludge are produced in • The internal capacity or availability of a partner to 29 wastewater treatment plants annually, and the volume support product-specific distribution, sales, and is expected to increase to 139,000 tons by 2035. Most marketing activities of the recovered resource. sludge is stored on-site or transported to unsuitable landfills which negatively affects the quality of the surrounding water All business models are presented in a common template, sources and causes high greenhouse gas emissions. These starting with the Business Model Canvas (Osterwalder and practices waste both energy and material resources and Pigneur 2010) which describes the building blocks of the lead to high disposal costs.10 value proposition (see Annex 1). The business description, including the model relevance and strategies, is followed Most of the sewage in Middle East and North African by the risks and benefits and financial parameters. Five countries is sent to landfills. Sewage sludge generation indicators are used to determine each Business Performance is bound to increase at rapid rates due to the increase Potential: (i) profitability and cost recovery, (ii) social impact, in the number and size of urban habitats and growing (iii) environmental impact, (iv) scalability and replicability, and industrialization. Learning from European countries like (v) innovation. Each criterion was evaluated with a three- Germany and Switzerland, sewage disposal for reuse in the level scale, except the environmental criteria. The scoring of cement industry as an alternative fuel might be one way to parameters and the resulting rank of indicators was based tackle the growing volume of sewage sludge. on qualitative and quantitative data (see Otoo and Drechsel 2018, page 27-29, and Annex 2). 1.3 The business model approach The term ‘business model’ in our context follows the definition The suitability of the business model canvas for businesses by Magretta (2002) and Osterwalder and Pigneur (2010): in the domain of resource recovery and reuse was verified by Otoo and Drechsel (2018). The strength of the canvas A business model is defined by who your customers are, lies in its simplicity and ability to provide a holistic qualitative which markets you operate in, who your partners are, what overview of the essential components of the business costs you have, where your revenues come from, which model while falling short in providing quantitative data which activities you engage in, and how value is created and would depend largely on the scale of a particular case. The delivered to customers, within its enabling environment. canvas is best used for planning activities to map options for developing a business strategy. The approach helps to capture from a ‘business perspective’ what is needed to understand resource recovery and reuse The models presented here are based on empirical cases. (RRR) solutions for sewage sludge, such as their costs, The presentation of each model is followed by examples of the potential for revenue generation, required partnerships, such cases. The analysis of the business models was and engagement between diverse stakeholders. The term constrained by the limited availability of (e.g. financial) ‘business’ in this context should not imply ‘profit generation’ data provided by the studied cases. 9 https://www.ecomena.org/sewage-cement/ (accessed on November 5, 2022) 10 https://www.giz.de/en/worldwide/102143.html (accessed on November 5, 2022) 14 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE 1.3.1. Navigating this Report Figure 4 provides an overview of these options based The present report analyses business models derived on the to be recovered resource and technology from existing cases in several countries. The models are used. The fourth (vertical) resource recovery and categorized into those which are: reuse pathway in the figure for recovering nutrients (i) recovering biosolids (for soil amelioration) and energy is called a hybrid business model which (ii) recovering specific nutrients (phosphorus; carbon/ uses a combination of technologies. The strengths, biochar) weaknesses, opportunities, and threats (SWOT) are (iii) recovering energy (biogas, electricity) compared for each model in the text. (iv) recovering carbon, nutrients, and energy Sewage sludge Resources to be Biosolids Nutrients Energy Nutrients + Energy recovered Stabilization Anaerobic Digestion, Technologies (dewatering/drying), Mono Anaerobic Anaerobic Mono Co- Pyrolysis Incineration, composting, incineration Digestion Digestion incineration incineration or Pyrolysis, pelletization Gasification Gasification Biochar, Bio Sludge cake, liquid Phosphorus Sludge as Resources to be methane, rom sludge Struvite Energy Thermal alternative Energy recovered sludge, composts, f ash from biogas Energy Phosphorus, pellets fuel electricity, heat BM 10, BM11, Business models BM 1, BM 2, BM 5 BM 6 BM 7 BM 8A BM 8B BM 9 BM 12 A & B (BM) BM 3, BM4 FIGURE 4. PATHWAYS FOR NUTRIENT AND ENERGY RECOVERY FROM SEWAGE SLUDGE. Source: Author’s creation. 2. RECOVERING BIOSOLIDS Introduction non-renewable plant nutrient phosphorus (Cordell and The application of well-treated municipal sewage sludge White 2011). as biosolids in agriculture and landscaping is one option for safe sludge disposal as it provides an opportunity The commercial value of generated biosolids can be to support the circular economy across the sanitation increased depending on market demand by subjecting them and agricultural sectors while saving money on more to processes that enhance their safety, storability, and ease expensive disposal costs or fees. It allows to (i) recycle of application (e.g., through composting and pelletizing) or essential nutrients (N, P, secondary nutrients, and micro- boost their fertilizer value (e.g., through blending with other nutrients), and (ii) improve soil physical, chemical, and nutrient sources). Using sludge as an organic fertilizer could biological properties due to the high organic matter reduce dependence on conventional fertilizers, but as the (i.e., biosolids) content of the sludge. The support of the nutrient levels are much lower in organic than chemical circular economy is especially important in view of the fertilizers, biosolids help mostly to ameliorate soils low in 15 RESOURCE RECOVERY & REUSE SERIES 23 organic matter, than to replenish nutrient-poor soils like an Ministry of Agriculture banned the use of sludge for industrial fertilizer could do. farmland applications. Land-use options for sewage sludge is limited to soil enhancement for degraded Sludge use, in particular in agriculture, needs to follow soils, abandoned mining sites, forests and urban strict safety standards because of chemical pollutants and greening (Dong et al. 2018). pathogens, which many treatment systems cannot eliminate to a risk-free level. Its use should therefore be based on However, the enforcement of these regulations varies (post) treatment processes and best practices as defined in between countries, which can push more responsibility on regional, national, or local guidelines.11 product safety to the WWTP operator as the second model presented here will show. The most important consideration is that the biosolids should be pathogen free and maintain the standards This section will introduce four business models which we regarding chemical contaminants such as heavy observed. metals and pharmaceutical residues (Box 1). Although 1. A service provider formally contracted by land application is a convenient disposal pathway for wastewater treatment plants (WWTPs) to collect sludge, several countries have tried to restrict the and (further) treat the sludge for land application use of sewage sludge for and beyond agriculture. within a well-respected regulatory framework For example, many European countries have set 2. Farmers, farmer associations or an informal service even more stringent limits for heavy metals, synthetic provider relieving WWTPs of their (at least partially organic compounds, and microbial contamination treated) sludge within a suboptimal institutional and than the European Sewage Sludge Directive (SSD) regulatory environment. 86/278/CEE.12 In Germany, the use of sewage sludge 3. A service provider collecting organic waste from in organic farming, forests, gardens, grasslands, different sources including WWTPs to produce a arable land, and fruit and vegetable cultivation has quality co-compost for land application. been prohibited under Sewage Sludge Ordinance 4. A service provider collecting settled sludge from (1992, amended 2017). Similarly, Italy set its limit the WWTP to produce pellets from it which can values at the lower end of the ranges specified in be mixed with other soil ameliorants or fertilizer for the SSD for sewage sludge applied to soil.13 China’s land application. BOX 1. PRECAUTIONS WITH LAND APPLICATION AND MANDATORY REGULATORY COMPLIANCE. For any type of land application, the users are responsible for providing the following information to regulatory bodies: (i) Classification of the sludge and origin (ii) Chemical analysis of the sludge (iii) Information about sludge storage (iv) GPS information or cadastral information for fields where the sludge will be used (v) Soil composition (vi) Crops and plants to be treated if the sewage analysis and classification is found suitable for cultivation (vii) Proposed amount of application and frequency (viii) Details of the agreement between the farmer and sludge provider and the date of application Additional risk management measures should be taken to prevent the transmission of pollutants or pathogens through: • Prohibiting applications in environmentally sensitive areas • Prohibiting applications on steep slopes and areas where the water table is close to the soil surface • Limiting contact between biosolids and vectors such as mosquitos, flies and rodents • Requiring buffer distances around residential areas, wells, streams, rivers and sinkholes • Restricting crop harvesting and grazing for specified time intervals after biosolid application • Mandatory training of individuals responsible for land application programs Source: United States Environmental Protection Agency Part 503.3. Standards for the Use or Disposal of Sewage Sludge (1993) (modified). 11 See rgulations mentioned in the previous section. 12 Like Denmark, Estonia, France, Germany, Czech Republic, Sweden, Poland, Belgium, and The Netherlands while countries like Italy, Ireland, and Portugal have set their regulatory limits as per the lower limits of the SSD. https://www.slideshare.net/dakar2/sewage-sludge- management-legislation-in-italy-121782867?from_action=save (accessed on January 5, 2023) 13 In Italy, National Decree 75/2010 governs the use of fertilizers which are produced from sewage sludge and manure and are used in agriculture. The limits are set under National Decree 99/1992 as revised by Decree 130/2018. The regulation bans the application of sludge on flooded soils, land intended for pasture or animal feed five weeks before harvest, land intended for horticulture and fruit growing, or when cropping is in progress. 16 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE BUSINESS MODEL 1: FORMAL SLUDGE COLLECTION AND TREATMENT FOR USE Brief Businesses collecting and treating biosolids for land application (see Business model 2 for similar services by the informal sector) Location Peri-urban and rural areas Waste input type/stream Stabilized sewage sludge Value offer Biosolid collection, drying and/or stabilization and sanitization of biosolids, application on farms. Documentation of the process and report to regulators. Environmental risk Land application of biosolids should be undertaken with the utmost precautions mitigation following all regulatory compliances for pathogens and chemical pollutants, in particular if agricultural land is targeted for food production. Regulators need to be highly vigilant about the process of biosolid application. Organization type and Private entities operating with a profit motivation. profit objective Major stakeholders Municipalities and WWTP operators, private entity processing the biosolid and applying in farms, farmers and regulators. PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of recovering stabilized sludge. • The business model scores high on profitability and cost recovery, and social and environmental impacts. For farms, addition of soil enrichers (phosphorus, carbon and nitrogen) reduces the costs for chemical fertilizers. • This is an effective disposal mechanism with relatively low environmental and social impact, compared to disposal in landfills or incinerators. However, the most important requirement for the businesses is to monitor the quality of biosolids and the condition of the soil before application. • The land application should be restricted for specific crops or as specified under regulations. • The business is subject to any changes or additional restrictions by the regulatory framework on biosolid characteristics during the contract period. 17 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Simple and low-cost resource recovery • Dependent on rigid quality management technique based on simple sludge treatment of sewage sludge and acceptance of treated and management. sludge by contracted farms. • Adapted to extensive farming operations with maize and cereal cropping patterns as well as fodder or forests. Opportunities Threats • Adaptation of technology to low- and • Changing regulatory frameworks that minimize mid-income countries for low-risk sludge use of sewage sludge on land. from non-industrial sources and with • Persistent reluctance of consumers to buy food suitable agricultural, landscaping or produced with sludge-based fertilizers. forestry soil and land conditions. Business Model Description contracted farmers where sludge is applied by specially A business model involves the engagement of an entity designed vehicles during field preparation and early growth bridging the gap between municipalities and farmers through stages of fodder crops and maize. To prevent leaching the collection and application of stabilized municipal sludge or runoff, the practice is limited to appropriate soils and (biosolids) e.g., to farmlands. These businesses are mostly topographies. Quality control of sludge products is privately owned and can take several forms: provided by both the treatment plant and the SSM service provider. Field applications are documented according to • operate solely in the collection and transportation, regulatory requirements by agricultural and environmental treatment/storage, and land application of the departments. biosolids, and • part of a larger operation that includes other The model is based on the demand from small to medium services along with biosolids management; like WWTPs without sludge storage facilities that provide only construction, operation and maintenance of basic wastewater and sewage sludge treatment in regions wastewater treatment plants. where the application of stabilized sludge meets farmers’ demands for low-cost organic fertilizer (Canvas 1). The business process is driven by the payment of disposal fees by treatment plant operators to external sewage sludge Outsourcing SSM to the private sector is practiced mostly by management (SSM) service providers eligible for collection, small WWTPs in agricultural regions. Application of sludge treatment and disposal of sewage sludge according after chemical stabilization and pathogen inactivation falls to quality standards set out in environmental laws and into the low-cost category of SSM and is typically practiced regulatory frameworks. Typically, private service providers in non-elevated, scarcely populated agricultural regions in are contracted long term by WWTPs operators or operating the US wheat belt and the mid-west, where organic fertilizer agencies of WWTPs which lack space for sludge storage, is in high demand. disposal or use. Disposal fees for sludge are paid per cubic meter by the contracting WWTPs. Expansion of the SSM business within a region is determined by sludge transport costs and available agricultural land The SSM business transports stabilized sludge to its for reuse near storage and treatment facilities. According facilities where it is stored, homogenized in tanks and to business cases from the US, UK and Italy, successful treated e.g., with quicklime (Calcium oxide) to achieve businesses have set up additional storage and treatment an exothermic reaction to inactivate pathogens. Others facilities in neighboring districts and states. A schematic rely on sludge drying, e.g. via heat treatment. Stabilized representation of the technical options (drying, chemical sludge is then transported by truck, for example, to treatment) is provided in Figures 5 and 6. 18 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Lime & 96% Sulphuric Land banks Biologically acid registered stabilized sludge Storage of stabilized WWTPs Transport & storage of Chemical sludge Land $ stabilized sludge stabilization transport to farmers application Contractual agreements- Agronomic Regulatory fees/cubic advisory compliances meter External SSM business FIGURE 5. BUSINESS MODEL FOR USE OF CHEMICALLY STABILIZED SLUDGE. Source: Author’s creation. Operation & Maintenance External business $ Contractual agreements- Operation fees/cubic & meter Maintenance Land banks registered Storage of WWTPs Dewatering plant Land Liquid dewatered sludge application stabilized sludge Agronomic advisory Regulatory compliances FIGURE 6. BUSINESS MODEL FOR RECOVERY OF DEWATERED AND DRIED BIOSOLIDS. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Regulatory bodies • Collection and • Collection, • Direct with dedicated • Wastewater • Farmers transport of transportation, and vehicles for collection treatment plant • Urban local stabilized sludge treatment of of stabilized sludge operators and bodies • Storage of sludge sludge • Land application of urban local bodies and chemical • Nutrient recovery biosolids • Farmers stabilization • Process • Contracts with documentation sludge users which includes • Documentation sludge analysis, required for soil testing and regulators determining the application rate Resources for different crops Channels • Dedicated vehicles • Safe and • Long-term for collection and productive disposal contractual transport of sludge of sewage sludge agreements with • Available land customers and and contracts direct engagement with farmers with them • Long-term contracts with WWTPs or local authorities and farms Cost structure Revenue streams • Infrastructure for storage of processed liquid sludge • Main revenue from recycling and disposal fees • Salary and wages obtained from WWTP/municipality operators • Operation and maintenance of vehicles • Fuel costs and utility charges Environmental and social costs Environmental and social benefits • Occupational health risks might arise due to handling • Safe application of sludge i.e. recovering the nutrients of waste and reducing pollution • Job creation • Minimizes capital investments and operational costs for sludge disposal CANVAS 1: FORMAL COLLECTION AND USE OF BIOSOLIDS 19 RESOURCE RECOVERY & REUSE SERIES 23 Case Studies Among the services offered are transportation of treated sludge and further treatment to stabilize it with lime to meet Alan SRL, Italy the US Environmental Protection Agency (EPA) regulation 503 Alan SRL has two plants in northern Italy (Sommo and and working with farmers to develop a market for biosolids Bascapè)14 which receive biological sludge from urban for land application.17 The biosolids are transported to the WWTPs and industries. The sludge is treated with lime registered farm fields (permitted through EPA). The business followed by sulfuric acid to stabilize it and obtain biomass is specialized in different types of land application such as (i) that meets regulatory requirements (Table 9). This treatment surface application of liquid, (ii) sub-surface injection (liquid process allows for the recovery of organic substances sludge), (iii) surface application of dewatered material, and and nutrients, supporting a circular economy. These (iv) incorporation. It maintains and uses equipment suitable end products are transported to farms affiliated with the for land application of liquid materials. These units have business. Application of the end product (organic fertilizer) high-flotation tires to minimize ground compaction during is done with tractors and manure spreaders according to land application. Liquid sludge products are applied with regulatory restrictions. field applicator units designed to prohibit spills and provide even application during surface application. Biosolids in liquid Centro di Ricerche Ecologiche (CRE), Italy form are injected below the soil surface or incorporated at the Centro di Ricerche Ecologiche (Center for Ecological time of application. Biosolids, lime sludge and other products Research) (CRE) is a UNI EN ISO 9001 and 14001 certified managed by Burch Hydro which are in semi-solid form are business that produces certified fertilizers through biological applied using ‘side-slinger’ type manure spreaders. Biosolids treatment and recovered sludge in agriculture.15 The center in dry form are also incorporated if required following surface has two plants in Maccastorna and Meleti and recovers application to prevent issues with runoff and odor. 250,000 tons of biosolids every year through lime treatment. CRE collaborated with 250 farms where the certified organic Merrell Bros. Inc., USA sludge is applied. CRE is 75% of Gadfer, which looks after the Merrell Bros. works across several states in the USA with logistics of the sludge value chain. Through ownership of a offices in Texas, Indiana, Missouri and Florida.18 The company wide range of vehicles (tractors and trailers equipped with roll- manages biosolids for municipalities, industries and agricultural off bodies, trucks and work vehicles), Gadfer can cover all the operations. The company is specialized in transporting biosolids requirements in terms of capacity. Having suitable vehicles for (liquid and dewatered) from WWTPs to land application sites access to agricultural fields offers the possibility of carrying complying with all state and federal regulations. They maintain out transport related to the agronomic recovery of sludge. a fleet of vehicles (semi-tankers and trucks) and machines (terragators) capable of handling any amount of sludge for the Burch Hydro Inc, USA mechanical application of biosolids. Burch Hydro Inc. (presently a subsidiary of Synagro Technologies Inc. from January, 2023) is a biosolids Cleanaway Waste Management Ltd., Australia management company based in Ohio providing land Cleanaway provides waste management solutions and application of treated municipal sludge and lime sludge.16 services to several sectors and industries. One service TABLE 9. DETAILS OF ALAN SRL RECOVERY PLANTS. Plant Process description Volume of sludge handled Sommo Phase 1: use of lime to stabilize the sludge 48,500 tons annually Phase 2: pure lime and liquid CO2 is added to obtain calcium carbonateª Bascapè Phase 1: use of lime to stabilize the sludge 66,000 tons annually Phase 2: 96% sulfuric acid is added thus activating hydrolysis that generates calcium sulfateb a In compliance with the Decreto Legislativo 75/2010 on fertilizers and soil conditioners. b In compliance with the Decreto Legislativo 75/2010 2010 on fertilizers and soil conditioners. Source: https://alansrl.it/impianti/ 14 https://alansrl.it/impianti/ (accessed on September 10, 2022) 15 http://www.cresrl.net/ (accessed on September 10, 2022) 16 http://burchhydro.com/Services/Biosolids-Program-Management (accessed on September 12, 2022) 17 https://www3.epa.gov/npdes/pubs/owm0031.pdf (accessed on July 13, 2022) 18 https://merrellbros.com/ (accessed on September 12, 2022) 20 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE is land application of treated and stabilized sludge both company maintains stock for year-round delivery and in liquid and dewatered form across Australia.19 Liquid have specialized contractors for delivery and spreading biosolids are injected below the surface of the soil using of biosolids.20 specialized equipment. The liquid sludge is treated, monitored and applied in accordance with Australian Lystek International Inc, USA regulatory requirements. The company takes care of logistics Lystek International offers biosolids processing solutions management of organics transport to the site. Cleanaway for municipal wastewater treatment plants and organic carries out market surveys and biosolids research as well as waste materials from industrial, commercial and stakeholder engagement and community consultations on agricultural sectors.21 The company offers patented the application of biosolids. design and build services to implement thermal hydrolysis and associated systems. It also produces LysteGro, Severn Trent Plc. UK a pathogen-free, nutrient-rich fertilizer that meets the Severn Trent Plc. has been operating in the UK from 1974 standards of a USEPA Class A material. LysteGro is also with the establishment of Severn Trent Water Authority. registered with the Canadian Food Inspection Agency. The The Authority was established through the amalgamation company can be contracted to provide a comprehensive of the Severn River Authority, the Trent River Authority, biosolid management system which includes fertilizer and the sewage disposal responsibilities of the councils sales and marketing, regulatory engagement, and within its area. The business recycles annually about agronomic planning, and coordination of transportation 600,000 tons of biosolids on approximately 30,000 and field application. The core of the Lystek technology hectares of land. For this, the sludge is dewatered, in part is a process involving a combination of heat, alkali, and using thermal hydrolysis treatment, while lime additions high shear mixing to produce a high-solid, pathogen-free are only used occasionally. The methane produced is and nutrient-rich biofertilizer product. One advantage used to power the sites. Severn Trent has a team of farm of the Lystek process is that it produces a safe, stable, liaison officer trained in Fertilizer Advisers Certification low viscosity biofertilizer with a solid concentration in and Training Scheme. The farm liaison officers complete the range of 14–17%. The product can be transported a mapped field risk assessment, outlining health and and applied using conventional handling equipment. safety and environmental hazards. The actual cost The company claims its biofertilizer can also be used as savings for farmers compared with buying conventional raw material for commercial anaerobic digestion plants fertilizers has been estimated as over £200 per hectare as it enhances methane production and the subsequent on nitrogen, phosphate, potash and sulfur. The public profitability of biogas plants. 19 https://www.cleanaway.com.au/waste/biosolids-waste-management/ (accessed on September 12, 2022) 20 https://www.severntrent.com/sustainability-strategy/environment/bioresources/biosolids/ (accessed on April 24, 2023) 21 https://lystek.com/ (accessed on August 10, 2022) 21 RESOURCE RECOVERY & REUSE SERIES 23 BUSINESS MODEL 2. INFORMAL SLUDGE COLLECTION AND TREATMENT FOR USE Brief Businesses involved in recovering dewatered/dried biosolids (similar to Business model 1 but with informal sector partners) The model is not recommended but reality in many low-income countries. There are options to reduce its environmental risks. Location Peri-urban and rural areas Waste input type/stream At least partly stabilized sludge from a treatment plant Value offer Sludge (treatment and) use for resource recovery Environmental risk mitigation Where (there is a risk that) regulations and land monitoring are absent or not observed, it is imperative for the WWTP operator to accept responsibility and to offer only safely treated sewage sludge that complies with international standards for chemical and microbial contaminants. Organization type and profit Mostly informal or semi-informal agreements offering the WWTP a solution objective for its waste and farmers an organic fertilizer Major stakeholders Urban local bodies and WWTP operators, private entities, farmers, regulators if available. PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of recovering dewatered and dried biosolids. • This model is rated high on providing social and environmental benefits as it can effectively close the resource loop, IF safety regulations are followed. • The model reduces the burden of disposal costs for local bodies and hence lower bills for the authorities and citizens. • Disposal is only safe if formalized but can create environmental harm if reuse takes place informally without monitoring. • The model is a profitable proposition for a private entity and where there are informal agreements with farmers it provides a win-win solution with a reduction in transaction costs. • The model has potential for vertical scaling; however, horizontal scaling might face challenges due to ambiguity of product acceptance in a new market (e.g., among farmers for land application). 22 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Low capital expenditure and operating • The absence of a regulatory framework and expense requirements. weak legal status results in environmental risks • Low technological know-how required, and low credit worthiness of a business and hence semi-skilled workers can be hired. minimizes the potential for growth and • Adapted to an environment with missing sustainability. regulations or their enforcements. Opportunities Threats • Low expenditure is needed by utilities and • Contamination of sewage sludge will lead to a WWTPs to ensure sewage sludge disposal. contaminated fertilizer products if no quality • Quality control measures (composting, control is in place. quality analysis) by the WWTP or operator • New regulatory frameworks and quality can enhance safety, and increase demand standards for biosolid fertilizers may affect the for the product. sustainability of the model. Business Model Description treatment steps (for pathogens) are the septic tank and The model is common in countries where the informal (months-long) sun-exposure on farm in the dry season sector is involved in (or even leading) the collection of before the sludge is mixed with the soil. If this exposure dewatered and dried biosolids for land applications and is sufficiently long before cereals are grown, pathogenic regulatory bodies do not have the capacity to implement risks can be controlled (Keraita et al. 2014). However, in (monitor) safety standards. The model is from a technical contrast to septic sludge, sewage sludge has a much perspective largely similar to the previous one while higher probability of chemical contaminants, which calls for potentially missing environmental safety compliances regulations on disposal frequency and amounts, to avoid once the sludge is leaving the WWTP. In other cases, heavy metal accumulation in soils. The cases from Tunisia the end-users are directly served by the WWTP, which is are addressing this challenge pro-actively (see below). even more risky from an environmental and human health perspective. The model thus puts more responsibility on As the WWTPs consider the sludge as a costly waste, it is the WWTP operator to offer a well-treated and stabilized offered for free to informal handlers, allowing the WWTP to product for collection and reuse. If this is not the case, save on alternative disposal costs. The handler is charging sludge treatment has to continue off-site the WWTP farmers for the (ideally composted) sludge as organic including on the farm. This is also the case in the situation fertilizer (Canvas 2). From the handler’s (or service provider’s) described by Buijs et al. (2018) e.g., from Ghana and India point of view, the growth of the business depends highly where septic sludge (septage) is collected from household on sludge processing costs, sludge transport costs and on-site sanitation systems and deposed off on farms. sludge demand in operational proximity. Demand can be In these cases, the households pay the operators for high in areas with plantation crops but depends on farmers collecting the septage and the farmers pay (a token) for acceptance. A schematic representation of the business the delivery of the liquid fertilizer. Sludge storage between model for recovering dewatered and dried biosolids through collection and on-farm disposal is seldom, thus the only informal entities is provided in Figure 7. 23 External origin Internal origin RESOURCE RECOVERY & REUSE SERIES 23 Transported & stored by external Composting Free pick-up of business dewatered / $ dried sludge Price of compost Storage of Land WWTPs dewatered / dried sludge application Free pick-up of dried sludge and application by farmers No documentation for regulatory requirements FIGURE 7. INFORMAL BUSINESS MODEL FOR THE RECOVERY OF DEWATERED AND DRIED BIOSOLIDS. Source: Author’s creation. Case Studies Partners Activities Propositions Customer Customer relationships segments • Urban local bodies • Collection and • Collection of • Direct relationships • WWTP operator and /WWTP transport of dewatered and between businesses • Farmers or farmer operators dewatered and dried (ideally fully of farmers and representatives • Farmers or farmer dried sludge stabilized) sludge WWTP operators associations • Storage of sludge for land • Direct interactions • Regulatory bodies and (if possible) application. between the business (if available) composting • Recovery of organic entity and farmers/ • Contracting matter and nutrients plantations • Savings in alternative Resources disposal costs for Channels • Dedicated vehicles the WWTP operator • Long-term contractual for the collection agreements for sludge and transport of procurement sludge • Direct trading or • Land available for enrollment of farmers further sludge in farmers’ treatment associations Cost structure Revenue streams • Salary and wages • Sale of dried sludge, compost • Operation and maintenance of vehicles • Fuel costs and utility charges • Land rent if leased Environmental and social costs Environmental and social benefits • Health risk of laborers’ handling the dewatered/dried • Safe disposal of sludge if regulations are followed sludge during transportation or during composting • Recovery of organics for soils • Possible environmental risks if sludge treatment was • Creation of jobs insufficient CANVAS 2: INFORMAL COLLECTION AND USE OF BIOSOLIDS 24 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Colombo, Sri Lanka fertilizer producers, horticulturalists, and sugar cane farmers The Ratmalana Municipal Sewage Treatment Plant in the at irregular intervals. south of Colombo has a treatment capacity of 25,500 m3/ day. The Ja-Ela WWTP, north of Colombo, has a treatment El Kef and Jendouba, Tunisia capacity of 14,500 m3/day. It was foreseen that a sanitary These cases show positive examples where the WWTP landfill would be established to handle sludge from these is trying to offer well-treated sludge and link with a large plants, but this has not been implemented. Based on an number of farms to reduce the risk of contaminant informal arrangement, the dewatered sludge from the plants accumulation. Both treatment plants are located in the is - for the time being - collected by an organic fertilizer trader northern cereal belt of Tunisia. The WWTPs produce about who facilitates transport, storage, and drying of the biosolids 600 to 1,275 tons of sewage sludge annually. The plants at its premises in a rural area near Colombo. Compliance do not operate mechanical driers and rely on 14- 25 drying with environmental regulations is a potential bottleneck beds, respectively, for dewatering and drying sludge to a dry which is compounded by the dependance of the National matter content of 70% within 60-66 days. Drying beds are Water Supply and Drainage Board on this single entity for manually emptied by plant staff during the summer and the sludge disposal as there is no alternative. partially dried sludge is further decomposed in uncovered windrows which also serve as areas for sludge storage. Hyderabad, India In their respective districts, 419 and 876 ha of suitable Hyderabad’s sewage treatment plant is on the periphery of farmland are available for sludge application, over four times Amberpet City and has a treatment capacity of 339,000 m3/ the area officially required to minimize the accumulation of day. The main biological treatment stage of the large WWTP chemical contaminants. Dried sewage sludge is collected is based on anaerobic upflow and anaerobic sludge blanket informally by farmers or agricultural companies and applied technology followed by an aerobic lagoon as a polishing unit. during the first soil preparation on fields designated for Sludge is anaerobically stabilized within the UASB reactors cereal crops. Environmental monitoring ends however at with a retention time of 33 days before excess sludge is the WWTP22. The informal business model saves the plant removed and pumped to a belt-filter press for dewatering. operators between USD 30,000 and 45,000 in operational That process results in the production of approximately 165 costs per annum compared to disposal in controlled landfills cubic meters of stabilized and dewatered sludge per day. or co-incineration in cement plants. Dewatered sludge is further dried openly in windrows by the WWTP before it is removed (unregulated and for free) by Source: All cases through author’s field visits, 2015-2020 22 Status 2015. 25 RESOURCE RECOVERY & REUSE SERIES 23 BUSINESS MODEL 3: PRODUCING CO-COMPOST Brief Production of co-compost from sewage sludge and other organic waste Location Peri-urban and rural areas Waste input type/stream Dewatered sewage sludge, organic domestic waste, green waste (yard trimmings, wood waste, leaves), food waste Value offer Dewatered sludge used for co-compost which is otherwise disposed of in landfills, implies savings in disposal costs, resource recovery, and revenue from sales of co-compost. Environmental risk mitigation Chemical contaminants in the compost must be monitored. Organization type and profit Public or private, incl. not-for-profit. objective Major stakeholders Urban local body, public entity (WWTP operator), service provider for solid waste management. PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of producing co-compost. • The business model scores high on environmental and social impact since it links to and includes also other organic waste streams for volume and risks reduction and can offers many jobs. • The scalability of the business is a challenge since the availability and integration of waste streams can be constrained and requires appropriate institutional arrangements, especially when incorporating private businesses competing for the same (waste) feedstock. • Public businesses integrating waste streams for co-compost are mostly run to maximize social impacts rather than earn profits and hence private-public partnership models can be considered for long-term feasibility and scalability. 26 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Sale of quality controlled organic fertilizer to • Profitability depends on availability of poor commercial farms and government soils and crops that require heavy doses institutions for use in agriculture, horticulture, of quality compost. and gardening. • Requires a strong network of stakeholders • Strong social and environmental benefits. across supply and demand. Opportunities Threats • Further blending of compost with sawdust • Blending treated sludge with other compost etc. could be a substitute for peat where peat feedstock is banned by leading compost use is increasingly restricted. business networks such as the European • Transformation into biochar could further Compost Network. reduce the sludge volume but also nutrient • In many developing countries, there are no value. specific guidelines for compost quality, which • Carbon market may reduce acceptance among farmers or open informal reuse doors. Business Model and Description or forestry, or if of high quality to horticulturalists, farmers, The business model transforms sludge into a soil ameliorant. and gardeners in bulk or packets through retailers and The composting helps eliminating pathogens, but not wholesalers. chemical contaminants. The co-composting of sludge and another organic feedstock can improve the composting The model is based on demand from landscapers, conditions (carbon-nitrogen ratio) and final co-compost farmers and commercial gardeners for large quantities quality. It is a win-win for carbon rich feedstock (like market of sludge-based co-compost. A continuous income waste) and nitrogen-rich feedstock (likes sludge). Co- from disposal fees from treatment plants will allow composting is thus often a request to meet particular reuse entrepreneurs, such as fertilizer traders and blenders, to demands like of horticulture crops and particular soil types. make long-term investments in infrastructure, equipment, In the case of private composting providers, contractual and land (Canvas 3). A basic requirement for the business agreements with treatment plant operators stipulate after- is the availability of land for processing and storing large treatment sludge quality and collection fees based on quantities of co-compost without disturbing neighboring the sludge volume. Service providers need to consider residents. management and disposal of sludge-derived products according to the standards set by the relevant regulatory Expansion of a sewage sludge management business within bodies. Any additional treatment as specified in regulations a region is determined by transport costs and available implies the collection and transport of sludge from treatment agriculture land for reuse near storage and treatment plants to facilities where it can be further homogenized, facilities. According to business cases from the US and stabilized, dewatered, and stored before being mixed and Italy, successful businesses have set up additional storage composted with e.g. organic solid waste from neighboring and treatment facilities in neighboring districts and states. A areas. Various co-composting mixtures can be certified schematic representation of the business model producing according to national standards and sold for landscaping co-compost is shown in Figure 8. 27 External origin Internal origin RESOURCE RECOVERY & REUSE SERIES 23 External SSM business Storage, sales and marketing of Compost compost Dewatered sell sludge WWTPs Co-composting plant Farmers $ fees/cubic $ meter Co-composting with solid wastes bio-residues FIGURE 8. BUSINESS MODEL FOR PRODUCTION OF CO-COMPOST. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Sludge stabilization • Savings from a • Direct relationships • WWTP operators and public water utilities • Collection and reduction in between WWTP urban local bodies and private service transport of sludge disposal costs of operators and • Farmers providers (where for composting sewage sludge to business entities compost • Transport of landfills • Direct links with production is leased green waste for • Production of farmers for compost out), public and co-composting quality compost and fertilizer sales • private providers • Composting, (ISO standards) for solid waste packaging, • Use of other waste management marketing and streams for sales of quality resource recovery compost and reuse • Recovery of organic material and Resources nutrients for soils Channels Dedicated vehicles and crops, or Through bulk and for the collection landscaping wholesale outlets of and transport of either the private dried sludge; land service provider or for co-composting the public water utility Cost structure Revenue streams • Capital costs: mechanical equipment, vehicles, land • Revenues generated from disposal fees from for drying beds and composting WWTPs/municipalities. • Salary, wages, interest. • Revenue from sale of compost (organic fertilizers) • Operation and maintenance of WWTPs, composting to farmers. yards • Carbon market (maybe in association with other service • Fuel costs and utility charges. providers) Environmental and social costs Environmental and social benefits • Labor health risks might arise due to the handling of • Safe application of sludge recovering the nutrients and sewage sludge and other waste streams. reducing pollution. • Job creation. • Land requirement for landfills is reduced in the long term as there is less disposal to landfill sites. CANVAS 3. CO-COMPOSTING 28 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Case Studies Haya Water Utility established the Kala compost plant as part of its efforts to protect the environment and meet the Azienda Agri Allevi SRL, Italy regulatory requirements of restricted landfill disposal at the Allevi is a traditional agricultural company that began Al Amerat landfill site. Kala Compost is produced according experimenting with the use of non-hazardous waste as to the following steps: soil conditioners and then scaled up for third parties.23 The company operates mostly in Italy providing solutions • Dewatered sludge from Haya Water’s WWTPs is to municipalities. It reported a revenue of USD 7 million in transported by truck to the Kala Composting Plant. 2018 by producing, distributing and applying about 20,000 • The dewatered sludge is mixed with a bulking m3 of co-composted biosolids annually through contracted agent (green waste such as yard trimmings, wood farms (about 60 in number over an area of 6,000 hectares). waste, horse bedding, leaves, etc.). The company collects 200,000 tons of waste annually • The mixture of dewatered sludge and green waste which comprises: (i) waste from agriculture, aquaculture, is composted using an open agitated windrow silviculture, horticulture, hunting and fishing, food processing system. and preparation, (ii) wastes from wood processing and production of pulp paper and cardboard, (iii) wastes from Kala Compost is the first product in Oman produced using an processing leather and fur as well as the textile industry, (iv) open agitated windrow system on such a large scale. With wastes from organic chemical processes, and (v) sludge a capital expenditure of USD 6.25 million, the Kala plant has produced by wastewater treatment plants. The company an in-house laboratory for quality assurance. The equipment adds value by specifying the correct use of sludge, methods was imported from the US and Europe. The capacity of the of use, and period of application. This is especially important Kala plant is 40,000 tons of compost per year. Compost for soils poor in organic matter that have been subjected to is sold for USD 60–100/ton. The company has reported mineral fertilizers which have depleted the humus-rich soil increasing sales over the years (Oman Observer 2017). horizon. The company produces co-compost using different Kala Compost is a commercial product currently sold to mixtures of the above listed feedstocks. The sludge is pre- governmental bodies, farmers and landscaping companies. treated with lime followed by sulfuric acid to stabilize it and The Kala plant has been accredited by the United Nations to recovery both, the organic matter and nutrients contained Development Program Clean Development Mechanism in the sludge. (UNCDM). It is the first organic fertilizer plant in the Middle East to receive certification. Through the UNCDM program, Kala, Oman the Kala Composting Plant is aiming to achieve a total CO 2 In 2007, a decision was made to build a modern centralized emission reduction of 318,000 tons over 10 years. sludge treatment facility capable of treating the sludge produced by all WWTPs operating in Haya and making a Haya Water, in collaboration with Sultan Qaboos University, quality product that meets local regulations and US EPA conducted research from 2013 to 2015 to study the standards for Exceptional Quality by commissioning a effects of Kala Compost on crops. The results showed no compost plant at Al Multaqa in Amerat. In December 2010, accumulation above the normal levels for heavy metals or Haya Water, a public sector unit in charge of wastewater harmful pathogens in the soil or on the crops. The study services in the Governorate of Muscat in the Sultanate of indicated that compost derived from sewage sludge Oman, launched Kala Compost, a product produced at increases soil fertility and improves soil water retention the Kala plant. Kala Compost is produced from the 150 to retain. It also provides plants with a range of nutrients that 250 tons of wet municipal sludge generated each day by increase the quantity and quality of various crops (Jaffar et treatment plants under the management of Haya Water. al. 2017). 23 Azienda Agri Allevi SRL Home page. https://www.aziendaagricolaallevi.it (accessed on September 15, 2022). 29 RESOURCE RECOVERY & REUSE SERIES 23 BUSINESS MODEL 4: PRODUCING SLUDGE PELLETS Brief Production of pellets from sewage sludge Location Peri-urban or rural areas based on the location of the WWTPs Waste input type/stream Liquid or semi-liquid form of sludge Value offer Pelletized sludge for mixing with fertilizer or other soil conditioner Environmental risk mitigation Low risk through heat treatment, monitoring of heavy metals needed Organization type and profit Private, for profit objective Major stakeholders Municipalities, water utilities, fertilizer traders PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of pellet production • The business model scores high on innovation using advanced technology based on thermal treatment producing organic fertilizer pellets. • This technology reduces the sludge volume which would have otherwise ended up in landfills adding to disposal costs. • Scalability requires capital investment in the technology and integration of decentralized WWTPs for achieving economies of scale as the investment costs are high. 30 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Pelletizing improves sludge transport to • Energy-intensive process that involves high locations where sludge is being processed operational costs and high CO2 footprint to for energy or nutrient recovery. dry sludge. • The smaller the pellets the more options to mix them with other feedstock or later on other fertilizers. Opportunities Threats • The use of pelletized sludge for energy • The business model might not be sustainable recovery allows also the use of contaminated where agricultural demand for organic sludge not suitable for farming. fertilizers or refuse-derived fuels is low. • Carbon market for organic fertilzer sludge, • This would lead to a large accumulation of storage and disposal costs. treated. Business Model Description on market conditions and regulatory frameworks, non- This business model involves the production of Class contaminated sludge is processed to pellets and sold to A Exceptional Quality (a category of Class A biosolids), organic fertilizer traders who might further refine and blend that applies to pellet fertilizers made after thermal drying. the pellets with nutrient additives into organic fertilizers for Municipalities or public water utilities operating WWTPs special cultivation applications. Sludge pellets can also be contract private service providers to treat and manage used as dry fuel for combustion in waste-to-energy and sewage sludge. The private service provider operates a coal-fired power plants and the cement industry (Canvas 3). combined drying and pelletizing plant to process semi-liquid This business model is appropriate for small and medium sludge, usually on the plant premises. The contract might be WWTPs without sludge storage capacities that provide only for design, build, own and operate with full financing of the basic wastewater and sewage sludge treatment and where project or design, build and operate if sufficient public finances there is a demand for organic fertilizer. A private service are available. The contract is usually for more than 10 years provider can then operate through contractual agreements. and depends on the infrastructure depreciation period. Business expansion within a region is determined by sludge transport costs and available agriculture land for The process typically involves transferring dewatered or reuse near storage and treatment facilities. A schematic stabilized sludge to a drying installation combined with a representation of the business model producing pellets is pelletizing facility on-site at the treatment plant. Depending provided in Figure 9. 31 External origin Internal origin RESOURCE RECOVERY & REUSE SERIES 23 External SSM business Storage, sales and Soil marketing of pellets conditioner Dewatered sell sludge WWTPs Pelletizing facility Farmers $ fees/cubic $ meter FIGURE 9. BUSINESS MODEL FOR PELLET PRODUCTION. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Sludge • Savings from the • Direct interaction with • WWTP operators public water utilities stabilization reduction of sewage wastewater treatment and local urban and private service • Collection and sludge to landfills plant operators to bodies providers transportation of • Recovery of dry fuel receive sludge • Farmers • Regulators sludge for or organic fertilizers • Direct interaction with (environmental, pelletization for use as a soil the farmers agricultural) • Producing pellets conditioner with a slow release of Resources nutrients to the soil Channels • Dedicated vehicles • Option to have • Direct sourcing of for collection and product sales and sludge from WWTP transport of dried marketing teams • Direct sell sales of sludge handling land pellets to farmers • Appropriate application and the technology for required regulatory heat drying and arrangements pelletizing Cost structure Revenue streams • Capital costs: mechanical equipment, vehicles • Revenues generated from fees provided by • Salary, wages, rent, interest WWTPs/municipalities • Utility and fuel costs • Revenue generated from sale of pellets • Costs associated with marketing and selling fertilizers (organic fertilizers or dry fuel) Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Reduce pollution in waterbodies and natural habitats sludge. as sludge is safely disposed of. • Reduction of human exposure to untreated and partially treated sludge. • Reduces land requirements for landfills as treated sludge is not disposed of in landfills. • Job creation. CANVAS 4: PELLET PRODUCTION 32 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Case Studies Veolia, USA28 Veolia produces Nutri-Pel, a biosolids-based commercial Synagro, USA24 fertilizer using sludge from the Ashbridges Bay WWTP.29 Synagro was founded in 1986 to support biosolids Sludge from the plant is heated at a high temperature and management for municipalities with a wide array of services. turned into pellets rich in nutrients and organic matter. It is producing granulite fertilizer and renewable fuel pellets. The fertilizer is sold under the Canadian Fertilizers Act The fertilizer is produced through an advanced heat drying and Regulations. The product has been reviewed by the and pelletizing process in which municipal biosolids are Canadian Food Inspection Agency for safety, efficacy and heated and dehydrated to create fertilizer that meets the label requirements and has a guaranteed minimum nitrogen, U.S. Environmental Protection Agency’s (EPA) Exceptional phosphorus and potassium ratio (NPK) of 4.5–6–0. The Quality standards while reducing the sludge volume by 70% pellets also contain secondary macro-nutrients (calcium, and producing dried biosolids that can be used as (or mixed sulfur, magnesium) and micro-nutrients for plant growth. The with other) organic fertilizers and are safe for use even on company claims that approximately 60% of the nitrogen is vegetables.25 In addition, Granulite fertilizer can be used on released in the first year, 30–35% in the second year and flowers, lawns and turf (golf courses, playing fields and sod). the remaining 5–10% in the third year. All the phosphorus is available in the first year, as are all the other nutrients.30 In its Baltimore-Black River Pelletech Facility, Synagro’s design, However, these rates depend on soil temperature and build, own, and operate plant operator promised to process up moisture and can fluctuate somewhat. to 110 dry tons of biosolids per day (20,000 tons of biosolids annually)26 and management of all disposal operations, Today, Veolia produces and sells 25,000 metric tons of producing pellets that are clean, odorless, easy to handle Nutri-Pel annually, but in 2007, when the plant had just and store, and can be sold as a slow-release fertilizer or soil started, sales were low (5,000 tons per year). Farmers were conditioner. The advanced heat drying method for pelletizing reluctant to use the product and their cause of concern municipal biosolids that meet the US Environmental Protection was the presence of heavy metals. Tests were conducted Agency’s Exceptional Quality standards. Granulite has been for eleven metals and the results were used in discussions used successfully on crops such as citrus, corn, cotton, fruits, about the product. The city of Toronto renewed its contract rice, soybeans, vegetables and wheat. It can also be used on for pellet production for a decade based on the satisfactory flowers, lawns, golf courses, playing fields, and sod.27 results of these tests. 24 https://www.synagro.com/ (accessed on September 15, 2022) 25 https://www.synagro.com/wp-content/uploads/2020/03/Services-Heat-Drying-and-Pelletization-2018.pdf (accessed on September 15, 2022) 26 Synagro. https://www.synagro.com/locations/baltimore-back-river-pelletech-facility/ (accessed on September 15, 2022) 27 Synagro. https://www.synagro.com/granulite-fertilizer-pellets-2/ (accessed on September 15, 2022) 28 Veolia. https://www.planet.veolia.com/en/pellet-takes-nutrients-wwtp-field (accessed on September 15, 2022) 29 Veolia. https://www.veolia.ca/en/case-studies/pelletizer-facility-ashbridges-bay-wastewater-treatment-plant-toronto-ontario (accessed on September 15, 2022) 30 Veolia. https://nutri-pel.ca/wp-content/uploads/2020/04/Analysis_MV-pp-rev-2020.pdf (accessed on September 15,2022) 33 RESOURCE RECOVERY & REUSE SERIES 23 3. RECOVERING PHOSPHORUS Introduction 2. From sludge, (a) including the aqueous sludge Phosphorus, an essential element for all life including crops, phase before dewatering (5–20% of the initial is extracted from geological deposits of rock-phosphate. phosphorus load), and (b) from sludge liquor The countries with noteworthy phosphorus reserves are after dewatering (≤ 25% of the phosphorus load). only a few: Morocco, China, Egypt, Algeria and Syria. These With forced phosphorus dissolution, the maximal reserves face an irreversible depletion of their reserves recovery rate can reach 50%. (Shown as ‘2a’ and and till then the economic and energetic barriers to their ‘2b’ respectively) exploitation will increase, calling for investments to recover 3. From mono-incineration sludge ash. This has as much phosphorus as possible from current waste the highest phosphorus recovery potential of streams (Cordell and White 2011). over 80% of the pre-treatment phosphorus load. (Shown as ‘3’) Phosphorus is abundant in sewage sludge, however, the quantity recovered depends on its concentration. The Recovering phosphorus following the thermal treatment choice of technology for phosphorus recovery must be of sewage sludge is called downstream recovery. There based on technical and financial viability. Phosphorus can are different emerging technologies for phosphorus be recovered through mono-incinerated sewage sludge recovery.31 or standalone technologies customized for separating phosphorus from sludge. In this section we will present two models: one based on phosphorus recovery from incinerated sludge ash (model At municipal WWTPs, phosphorus can be extracted or 5), and one on the recovery of phosphorus from anaerobic recovered mainly from three sources (Figure 10): digestion (model 6). While model 5 has the advantage of recovering a significant share of phosphorus, model 6 1. Direct use of sewage sludge with 40–90% is first of all a cost-saving model as it helps to minimize phosphorus recovery potential compared to the unwanted (and maintenance cost intensive) struvite pre-treatment phosphorus load. (Shown as ‘1’) crystallization. FIGURE 10. PHOSPHORUS RECOVERY AT DIFFERENT STAGES OF SEWAGE SLUDGE TREATMENT. Source: Kabbe et al. 2015. 31 There is a regularly updated online catalogue - https://phosphorusplatform.eu/images/download/ESPP-NNP-DPP_nutrient-recovery_tech_ catalogue.pdf (last accessed on April 24, 2023) 34 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE BUSINESS MODEL 5: RECOVERY OF PHOSPHORUS FROM INCINERATED SLUDGE ASH Brief Recovering phosphorus from sewage sludge ash obtained from incineration Location Urban and peri-urban areas based on the proximity of incineration facilities Waste input type/stream Sewage sludge ash Value offer Recovery of phosphorus from ash, which is otherwise disposed of, leads to two value propositions: (i) phosphorus is a finite resource, recovery produces a close substitute for agricultural application, and (ii) reduces the cost of disposal for the WWTP operator. Environmental risk mitigation Processes needed to separate phosphorus from heavy metals. Organization type and profit Both public and private operators; the public operator might not operate objective with a profit motive whereas the private entity would seek profit. Major stakeholders WWTP operator, phosphorus recovery plant operator, fertilizer sellers (networks of wholesalers and retailers). PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of recovery of phosphorus from sludge ash. • The business model scores high on innovation and reduction in environmental impacts. • The business model includes advanced technology for maximizing phosphorus recovery and hence reduces the risk of environmental pollution. • The technology can be adapted for WWTPs with an option for incineration and can be scaled to meet demand. 35 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Modular units for treating sewage sludge • High investment costs for plant installation. ash and recovering significant shares of • When a phosphorus recovery plant is installed phosphorus make it easier to upgrade the far from a WWTP or incinerator, transportation WWTP. of ash leads to increased transportation costs. • Scaling up to meet future demand is easier • Obtaining licenses and permits can be a since the installation is modular. complex and expensive process. • Reduces the volume of sludge ash for disposal. Opportunities Threats • More research and development to improve • Reluctance among farmers and fertilizer the quality of recovered phosphorus. traders to accept fertilizer products derived • In some countries. phosphorus recovery is from sludge. being made mandatory and will require • The ash might be contaminated. WWTP operators to implement this business model. Business Model Description private entity engaged in phosphorus recovery then contacts Phosphorus recovery from mono-incinerated sludge ash is fertilizer traders for marketing. However, due to recent public usually much greater than that derived from raw sludge or discussions on phosphorus recovery, some incineration plant digestate. Phosphorus can be recovered from sewage sludge operators think that since sludge ash is an input, they should ash via one of two processes: (i) wet chemical treatment be paid by the phosphorus recovery unit and technology (acid or alkaline ash leaching), and (ii) a thermochemical providers could be looking at higher costs (GWI 2012). process. In both cases, a phosphorus recovery unit can be established within a WWTP as a modular plant or elsewhere. This business model is appropriate when a clustered However, the latter option would need to consider the cost approach is pursued and there is an economy of scale. of transporting the sludge ash to the recovery unit. Downstream options of phosphorus recovery tend to be costlier and have a longer return on investment (GWRC 2019) This business model can be initiated by a public or private entity and therefore it is important to consider the economics of based on regulations or the availability of appropriate technology. reaching an optimal scale. Another important consideration Publicly initiated phosphorus recovery units can be public-private is the price of the fertilizers derived from the ash and the partnership initiatives where regulations restrict proper disposal revenue stream it can provide for the business entity. A of sewage ash or the availability and willingness of private entities schematic representation of the business model producing as technology providers. A public operator (usually a wastewater pellets is provided in Figure 11. treatment plant operator) operating an incinerator needs to dispose of ash according to regulations and hence may seek Nättorp et al. (2017) reported on the cost of two technical help from government agencies. Government collaboration can processes: (i) leaching with sulfuric acid, solid-liquid lead to grants for installation. The government may also provide separation, pH increase and precipitation of calcium seed grants for research and development and establishing a monophosphide and calcium hydroxide; and (ii) leaching pilot project which can later be scaled up. ash with phosphoric acid, separation of phosphoric acid and metal ion fractions via staged ion exchange Private technology providers can be contracted by WWTP regenerated by hydrochloric acid and yield of concentrated or incinerator operators for the disposal of sewage sludge. phosphoric acid. Since sludge ash is considered waste, it is mostly disposed of in industrial landfills since it can be classified as hazardous Investment costs include material and energy, personnel, waste (GWI 2012). A treatment plant or incinerator operator and other costs which can be amortized over 10 years at pays the phosphorus recovery unit for ash disposal. A an interest rate of 3% to find the yearly cost (Canvas 5). 36 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Dewatered Fertilizer traders sludge and other networks Phosphorus extraction WWTPs Mono-incineratio Faramnedn Sludge L Phosphate rs ash application $ Operation Operation Phosphorus fertilizer Public entity Private entity Technology provider FIGURE 11. BUSINESS MODEL FOR RECOVERY OF PHOSPHORUS FROM SLUDGE ASH. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Technology • Sludge stabilization, • Recovering a • Direct contact with • WWTP operators and providers and drying, potentially high-value the WWTP operators incinerator operators • WWTP operators incineration fertilizer • Direct network with • Fertilizer traders and municipalities • Recovering and sale • Savings in disposal fertilizer traders • Fertilizer traders of phosphorus costs to landfills • Obtaining permits and certifications for fertilizer products Resources Channels • Technology for • Through bulk and phosphorus wholesale outlets of recovery private sector entities • Existing (sometimes with incineration private-public treatment systems partnerships) • Link with fertilizer • May be possible to traders and private engage the public entities to market sector in marketing fertilizer products and sales Cost structure Revenue streams • Capital costs: installation of modular phosphorus • Revenue generated from fees provided by WWTP and recovery systems, vehicles for sludge transport incinerator operators • Salary, rent, interest, insurance • Revenue generated from sales of high-value fertilizer • Transaction costs for penetrating fertilizer markets • Cost savings from lower pipe maintenance and disposal • Fuel costs and utility charges costs Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Safe sludge application, recovering nutrients and sludge and other waste streams. reducing pollution. • Job creation. CANVAS 5: RECOVERING PHOSPHORUS FROM SLUDGE ASH 37 RESOURCE RECOVERY & REUSE SERIES 23 Similarly, the processing costs include improved dewatering City used advertising campaigns, including free sample and reduced sludge volume to be disposed of, lower offers, a briefing session for farmers, advertisements demand for polymers in dewatering, and savings in energy in a local magazine, and leaflet distribution. Following consumption for return load treatment in mainstream WWTP this, the National Federation of Agricultural Cooperative since phosphorus and nitrogen content in the return load is Associations (JA) launched sales and marketing reduced due to struvite precipitation in the liquor. campaigns for Gifu-no-daichi®. Presently, the product is sold in 20 kg packets through JA branches and has In both these cases, it is assumed there is already mono- achieved recognition among farmers. Gifu City started incineration and no costs are incurred for the downstream selling in bulk in 2011 which has improved the cost installation except for the phosphorus recovery unit. recovery of operations. However, the cost recovered is The estimated cost was USD 5.25 per kilogram (kg) still lower than the operational cost of landfill disposal due and USD 0.75 per kg, respectively, for phosphorus to the high cost of chemicals. recovered. Assuming an amortization period of 15 years, the second process results in payback within 10 years METAWATER Co. implemented the same business and makes some profit due to sales of highly purified model in the city of Tottori at Akisato WWTP in 2013 and phosphoric acid. Similarly, the specific cost per unit recovers 150 tons of hydroxyapatite per annum from of sludge indicates a higher cost for the first technical about 500 tons of sewage sludge ash per annum. The process (USD 40.7 per ton of sludge compared to USD biggest barrier to scaling is the small size of incineration 7.9 per ton). plants which impedes economies of scale. Clustering and cooperation of various ash producers may help Case Studies lower the operational costs for ash treatment (GWRC 2019). Meta Water Company, Japan Gifu is a city in central Japan that operates four WWTPs ICL Amfert, Netherlands generating a total of 29,000 tons of dewatered sludge per In 2019, ICL Netherlands Amfert (Phosphate BU) initiated its annum (Nakagawa and Ohta 2019). Two WWTPs have a first phosphate recycling project unit aimed at using recycled mono-incinerator that is fed solely with dewatered sludge. phosphates from waste streams as a raw material.32 This The other plants transport their sludge by road to plants project was encouraged by a subsidy of USD 560,000 with incinerators. Initially, Gifu City government used the from the Dutch Province of Noord-Holland. Incinerated sludge for manufacturing construction bricks for surfacing sludge ash from WWTPs as well as meat and bone meal sidewalks and parks in the city. The demand for bricks ash are the main inputs. ICL Amfert is replacing about 10% gradually declined over the years because of spending of phosphate rock with secondary phosphates in fertilizer cuts for public works. This led to an interest in recovering products at the pilot recycling unit. phosphorus from sewage sludge ash. The goal is for ICL Amfert to substitute up to 100% of METAWATER Company was engaged in a collaborative phosphate rock with recycled sources, depending on project for developing the technology supported by the market demand and the availability of raw materials. Ministry of Land, Infrastructure, Transport and Tourism. After Recovered materials are mixed with phosphate rock or a project evaluation in 2006, Gifu City acquired a license phosphoric acid-based fertilizer, either during acid attack according to the Japan Sewerage Law in 2007 for the by- of the rock or later when the product still has some product. A full-scale plant was constructed in 2009 at a cost residual acidity. Any contaminants in the ash are diluted of approximately USD 9.75 million. The plant started operating in the final product. This is legal under EU regulations on in 2010 and presently generates 200–300 tons per annum the condition that the ash is not classified as hazardous. recovering 30–40% of the phosphorus present in the ash. The final product is covered by EU Fertilizing Products Regulation STRUBIAS annexes. ICL also has an operation When the plant started operating, there was no channel in Germany where ash is processed and has also tested for the distribution and sale of Gifu-no-daichi®. Gifu the use of ash in fertilizer production in Fertiberia Spain. 32 ICL 2021 Corporate Responsibility Report. https://icl-group-sustainability.com/reports/producing-fertilizers-with-recycled-phosphate/ (accessed on September 17, 2022) 38 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE BUSINESS MODEL 6: RECOVERY OF PHOSPHORUS FROM ANAEROBIC SLUDGE DIGESTATE Brief Recovering struvite from sludge digestate and dewatered sludge liquor Location Urban or peri-urban area based on the location of the WWTP Waste input type and stream Sludge digestate after anaerobic digestion and sludge after dewatering Value offer Recovery of phosphorus for use as a green fertilizer; savings in disposal costs; prevention of scaling in digesters and pipes which leads to savings on chemicals and digester maintenance Environmental risk mitigation Extracted struvite is without particular environmental risks Organization type and profit Private entities operating within the WWTP with a profit motive objective Major stakeholders WWTP operators, municipalities, fertilizer dealers and other networks of wholesalers and retailers PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of phosphorus recovery from digestate. • The business model scores high on innovation with the use of advanced technology. • The business is profitable with good prospects for cost recovery by the public partner and the possibility for revenue generation from the sale of fertilizer products and treatment fees. • High positive impacts on the environment due to the reduced risk of eutrophication in waterbodies. • The business model is scalable and can be adapted to many wastewater treatment processes. 39 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Helpful Harmful Strengths Weaknesses • Upgrading a WWTP is easier since the • High investment costs. phosphorus recovery unit is modular and can • Obtaining licenses and certifications for be scaled to meet demand. products can be a complex process and delay • The technology providers share the risk of the revenue flows from the sale of high-value revenue generation. fertilizer products. Opportunities Threats • More technology providers as more research • Acceptance among traders and farmers can be and development takes place. low as the product is relatively new and its dissolution different from other phosphorus sources. Business Model Description In the treatment fee model, the technology provider pays for installation and retains ownership, while Anaerobic digestion is one of the most common methods the municipality or treatment plant operator pays for used for treating sewage sludge. Using anaerobic operation and maintenance based on the agreed quality digestion, WWTPs can reduce the weight and volume of of effluent or performance of phosphate removal. In sewage sludge and recover energy from sludge biomass. both cases, the technology provider has an off-take After anaerobic digestion, the digestate undergoes solid- guarantee (for the recovered phosphorus) in the contract liquid separation and dewatering. The high-phosphate for several years, which reduces the burden of the liquor (filtrate or concentrate) from sludge dewatering is WWTP to engage in phosphorus handling, marketing or typically returned to the sewage treatment process. This disposal. The off-take guarantee from the technology unnecessarily increases the phosphorus load as well as provider reduces the involvement of the treatment plant ammonia, making nutrient removal more difficult. Targeted operator in marketing the product and they derive a phosphorus recovery as struvite before it crystallizes part of the revenue from sales. In the absence of any where it should not within the system, is an ideal way guarantee, the treatment plant operator must invest in to simultaneously reduce the internal phosphorus and marketing and create networks and channels for sales. ammonia maintenance burden and recover them as If this capacity is lacking, the operator will likely see a resources. Struvite can be recovered either from the liquor loss. A schematic representation of the business model (filtrate or concentrate) or directly from the digested sludge. for recovering phosphorus from sludge is provided in Figure 12. There are two financing models for large investments in struvite recovery: (i) the capital purchase business model, The business model is appropriate for WWTPs with and (ii) the treatment fee model (Drechsel et al. 2018). In the anaerobic digesters and where the operator is willing to capital purchase model, the WWTP owner (or the client) pays upgrade the phosphorus recovery process. There is also for installation and recovers the cost through savings derived a possibility to integrate two resource, reuse and recovery from lower operational and maintenance costs over three to pathways, i.e., energy and fertilizers. For 190 million liters seven years (maximum ten years). Net operational savings per day or 50 million gallons per day, a capital investment are accrued from reduced struvite deposition in the digester of around USD 2 to USD 5 million is required (Drechsel which then require less maintenance, improves dewaterability, et al. 2018). The operational and maintenance costs nitrogen removal, struvite biosolids avoidance, and reduces vary between USD 9 to USD 120 per kg of phosphorus chemical and polymer consumption (Canvas 6). recovered (Bashar et al. 2018). 40 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Fertilizer traders and other networks Phosphorus Dewatered ge Thermal hydrolysis stripping Land WWTPs slud & Struvite Farmers application $ Anaerobic digestion $ Contractual Phosphorus agreements - DBO contract or fertilizer fees/cubic service contract meter Special project vehicle (SPV) or Private entity DBO contract or service contract FIGURE 12. BUSINESS MODEL FOR PHOSPHORUS RECOVERY FROM SLUDGE DIGESTATE. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Technology • Capturing • Recovering a • Direct contact with • WWTP operators and provider phosphorus from potentially high-value municipalities and municipalities • WWTP operators the treatment fertilizer through a WWTP operators • Fertilizer markets and municipalities process modular • Direct network with (traders and networks) • Fertilizer traders • Marketing and phosphorus fertilizer traders, sales of recovered removal systems associations, struvite • Savings in operations wholesalers and • Obtaining permits and maintenance retailers and certifications costs for removing for fertilizer products unwanted struvite crystals. Resources Channels • Technology for • Direct technology phosphorus removal sales to the client • Existing WWTP with (municipalities, anaerobic digestion WWTP operators) • Enabling • Direct sales of environment for the phosphorus fertilizer sale of struvite (with to traders proper certification) Cost structure Revenue streams • Capital costs: modular phosphorus recovery unit • Sales of high-value fertilizer • Salary, rent, interest • Savings from lower operational and maintenance costs • Struvite collection, storage and marketing costs; (less struvite in pipes) transaction costs related to penetrating fertilizer value chains with small phosphorus volumes • Research and development, validation, licensing and certification Environmental and social costs Environmental and social benefits • Uncertain acceptance of the product by traders and • Environmental benefits from preventing eutrophication. farmers. • Supporting circular economy jobs and added-value by • Need to acquire new technology. phosphorous and nitrogen recovery. • Extended lifetime of a finite resource. • Potentially a cheaper phosphorus resource than rock phosphate. CANVAS 6: RECOVERY OF PHOSPHORUS FROM ANAEROBIC SLUDGE DIGESTATE 41 RESOURCE RECOVERY & REUSE SERIES 23 Case Studies Since treatment plant operators are often not familiar with fertilizer marketing and the related bureaucratic burdens, Higashinada WWTP, Japan this business model reduces their risk of recovering The Higashinada WWTP in Kobe City has a sewage the costs through the sale of the product. The off-take treatment capacity of 241,500 m3 per day. In 2012, guarantee provides an income for the WWTP operator Mitshubishi Shoji Corporation Agri-Service and Swing since long-term contracts ensure that the struvite produced Engineering Corporation (the Japanese technology provider onsite will be marketed by Ostara and this can pay back the of Rephosmaster®) initiated a two-year demonstration plant operators. Considering a WWTP handling 50 million project to test nutrient removal and resource recycling at gallons of wastewater per day, the estimated investment is the plant. In 2014, on completion of the pilot project, a full- about USD 5 million (standard installation of two Pearl®2K scale plant was ready for operation along with registration of systems), which would result in a net present value of the fertilizer. The plant is owned and operated by Kobe City approximately USD 15 million in 20 years with the total and has the capacity for treating 239 m3/day of digested capital investment recovered in five years.34 sludge. This is equivalent to a quarter of the digested sludge generated at the treatment plant and recovers 360 kg/ CNP Cycles GmbH, Germany day (150 tons/year) of struvite. On average, it can recover CNP Cycle GmbH supply process technologies and plants approximately 40% and 90% of total phosphorus and soluble for water and sludge treatment as well as recovery of carbon, phosphorus, respectively, from digested sludge. The struvite nitrogen and phosphorus. CNP developed AirPrex®, a process recovery reduces the volume of dewatered sludge by 3.3% that improves biological phosphate elimination. The digested on average and prevents struvite-scaling problems in the sludge is fed into the reactor where it is subjected to CO2 stripping sludge treatment process. The recovered struvite has been through aeration. This significantly increases the pH level of the registered as a chemical fertilizer approved by the Ministry sludge. At the same time, magnesium salts are added, which of Agriculture, Forestry and Fisheries of Japan in 2014 and leads to the precipitation of magnesium, ammonium, and distributed in the Kobe area through fertilizer companies. In phosphate in the form of struvite. The recovered nutrients can be 2019, Japan Agricultural Cooperatives Hyogo Rokko started used as a fertilizer. The patent for the AirPrex® technology was selling it under the brand name Kobe Harvest 10–6–6–2).33 held by Berliner Wasserbetriebe (BWB) and CNP-Technology Water and Biosolids GmbH in Hamburg, Germany obtained the OSTARA Nutrient Recovery Technologies Inc. license in 2013. Presently, eight full-scale plants are in operation. Ostara Nutrient Recovery Technologies Inc. started its In these plants, 80–90% of the phosphate is removed from the operation in 2005 with headquarters in Canada and has liquid phase of the digested sludge. Table 10 summarizes the 23 commercial installations across Canada, the USA and current operational plants. Europe. Ostara provides the technology and a fertilizer combined with a marketing strategy. The company has At the Amsterdam plant, EUR 3 million was invested using 14 recovery units globally which are using Pearl® and the AirPrex® system. It is estimated that this investment WASSTRIP® and recover struvite sold as a premium fertilizer produced benefits of EUR 500,000 (EUR 1.2 million as (tradename Crystal Green®). Their most important strategy total benefits while reducing EUR 700,000 from disposal is off-take guarantees which reduce the struvite related and operational costs) per year resulting in a return on maintenance risk for water service agencies and WWTPs. investments of six years (Veltman 2017). TABLE 10. OPERATIONAL PLANTS OF CNP CYCLES GMBH. COUNTRY LOCATION AND OPERATOR OPERATION PERSON CAPACITY OF DESIGN STRUVITE SINCE EQUIVALENT AIRPREX® PRODUCTION (M³/DAY) KG/DAY Germany MG-Neuwerk, Niersverbandª 2009 995,000 1,500 1,500 Germany Wassmannsdorf, Berliner Wasserbetriebeb 2011 1,000,000 2,400 3,000 Netherlands Echten, Drents Overijsselse Deltac 2013 190,000 400 500 Netherlands Amsterdam-West, Waternetd 2013 1,000,000 2,500 4,000–5,000 a CNP Cycles. https://cnp-cycles.de/en/installations/plants-built-airprexr-license-us/monchengladbach-neuwerk (accessed on September 17, 2022) b CNP Cycles. https://cnp-cycles.de/en/installations/airprexr-installations/berlin-wassmannsdorf (accessed on September 17, 2022) c CNP Cycles. https://cnp-cycles.de/en/installations/plants-built-airprexr-license-us/reest-wieden-nl (accessed on September 17, 2022) d CNP Cycles. https://cnp-cycles.de/en/installations/plants-built-airprexr-license-us/amsterdam-west-nl (accessed on September 17, 2022) Source: Author’s creation. 33 KOBE Harvest project. https://www.sec.swing-w.com/eng/products/f5e45g00000006pa.html (accessed on September 17, 2022) 34 Ostara. http://ostara.com/wp-content/uploads/2017/03/Ostara_NRS_BROCHURE_170328.pdf (accessed on September 17, 2022) 42 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Nutrients Recovery Systems (NuReSys), Belgium There are several other examples such as NuRESys is a Belgian company founded in 2011 and Phosphogreen® at the Marselisborg WWTP in supplies controlled struvite crystallization technology. The Denmark. This is the largest plant in Nordic Europe, flexibility of the NuReSys process allows it to be adapted with an operational capacity of 200 tons of struvite per in several combinations to resolve critical phosphate year.37 Similarly, Veolia (Struvia®) also offers compact issues. Since NuReSys technology can be applied to installations and has demonstrated struvite recovery in both digested sludge or post-dewatering, several case- the WWTP of Samoëns, France. The Struvia® solution specific approaches are possible, including combined is appropriate for WWTPs equipped with biological applications. Some combined applications have been dephosphorylation and plant operators who want to designed and are operational at municipal and industrial install sludge digestion and for plants equipped with scales.35 The price of the BioStru® is between EUR anaerobic digestion and plant operators who want to 80–120 per ton.36 install biological phosphorus treatment.38 4. RECOVERING ENERGY Introduction heating or for generating electricity via a steam turbine. The importance of energy recovery from waste streams is In pyrolysis, combustion occurs in an inert atmosphere evident from the fact that waste minimization and alternative to produce pyrolytic oil, biochar and non-condensable energy generation can improve resource optimization. The gases. Biochar, non-condensable gases, and bio-oil can advantages to municipalities and companies include energy be used as solid, gaseous and liquid fuel, respectively, cost savings, reduced environmental impact and compliance for electricity and heat generation via combustion. Bio- with stricter regulations. Recovering renewable energy also oil can also be reformed as a synthesis gas for energy reduces greenhouse gas emissions and offers the option recovery while biochar can be used as a soil conditioner. of earning renewable energy credits. Sludge streams have Lastly, gasification involves the conversion of organic high calorific values and are rich in energy sources that can compounds via partial oxidation at high temperatures be recovered. There are different pathways for generating for the production of synthesis gas which can be used energy from sewage sludge as briefly described below. for heat and electricity generation. • Co-incineration and co-processing: Sewage sludge • Anaerobic digestion: This is a biological conversion can be used in co-incineration and co-processing. Co- method widely used due to its low cost and ability to incineration involves burning municipal sludge in municipal use organic waste with high moisture content without solid waste incinerators. In co-processing, sewage sludge reducing the high calorific value of the gas produced (a serves as an alternative fuel in cement kilns and coal-fired combination of methane and carbon dioxide). power plants. This requires additional fuel with a calorific • Thermochemical conversion routes: This includes value higher than the sewage sludge. The process combustion or mono-incineration, pyrolysis and replaces 15–20% of conventional fossil fuels. gasification. These processes require lower moisture levels in the sludge because the energy efficiency of This section will present the following models: the process is reduced due to the energy consumed • Biomethane production from anaerobic digestion for drying the sludge.39 Incineration is one of the most (business model 7) prominent technologies although not originally meant • Energy recovery from mono- incineration of sewage for energy recovery but to reduce the volume of waste sludge (business model 8A) and destroy harmful contaminants. The process of • Energy recovery from co-incineration (or co-processing) of heat recovery converts the traditional incinerator into a sewage sludge (business model 8B) combustor where heat is harnessed from flue gas and • Energy recovery from gasification and pyrolysis of sewage is used as a heating fluid which can be used directly for sludge (business model 9) 35 NuReSys. http://www.nuresys.be/ (accessed on September 17, 2022) 36 NUTRIMAN Information Sheet. https://nutriman.net/sites/default/files/2019-12/INFO%20SHEET-PRODUCT-%20Struviet%20Nuresys.pdf (accessed on September 17, 2022) 37 Phosphogreen brochure. https://www.suez.com/-/media/suez-global/files/dk/brochures/brochure-phosphogreen-marselisborg-case-english. pdf?open=true#:~:text=Marselisborg%20Wastewater%20Treatment%20Plant%20uses,of%20maintaining%20the%20sewage%20works. (accessed on September 17, 2022) 38 Veolia. https://www.veoliawatertechnologies.com/sites/g/files/dvc2476/files/document/2019/02/3351%2C150354_Mkt_Mun_Brochure_ STRUVIA_EN_.pdf (accessed on September 17, 2022) 39 Solar drying is one of the way to circumvent the use of other forms of energy. 43 RESOURCE RECOVERY & REUSE SERIES 23 BUSINESS MODEL 7: ENERGY RECOVERY FROM ANAEROBIC DIGESTION Brief Biomethane production from anaerobic digestion Location Peri-urban areas Waste input type/stream Sewage sludge with possibilities to include other waste streams and organic waste from households, industry and agriculture Value offer Generation of thermal energy and electricity (energy self-sufficiency); savings on disposal costs due to reduction in sludge residue Environmental risk mitigation Chemical contaminants of digestates have to be monitored before disposal or reuse Organization type and profit Public or private based on the size of the operation objective Major stakeholders Municipalities, water utility service providers, energy and electricity transmission agencies, private entities working on landscaping and agricultural soil conditioning PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of energy recovery from anaerobic digestion. • The business is highly scalable in both developed countries and emerging economies and contributes positively toward environmental and social goals. • Anaerobic digestion is one of the most applied technologies and the application of thermal hydrolysis increases the efficiency of energy recovery. • The business allows for the integration of other organic waste streams and small and medium WWTPs can plan for a clustered approach to achieve economies of scale. • Possibility to recover biosolids (digestate) which adds to the revenue stream. 44 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Strengths, weaknesses, opportunities, and threats (SWOT) Helpful Harmful Strengths Weaknesses • Traditional technology with advancements in • Demand for considerable capital for research and development. investment. • Low operation and maintenance and high • Need for strong institutional arrangements. revenue. Opportunities Threats • Electricity demand is growing. • Preference toward upcoming research and • Integration of waste streams. development in advanced technologies for • Integrating thermal hydrolysis to increase energy recovery. energy recovery. • May need high investments to mitigate the • Option of using digestate as a fertilizer. risk of gas leaks. • Option of participating in carbon markets. • Lack of regional cooperation and support for undertakings and investments toward cluster approaches for small and medium WWTPs. Business Model Description generated through digestion can be cleaned and upgraded to biomethane as a substitute for natural gas or it can be The business model involves an operator recovering energy used in combined heat and power plants to produce heat from sewage sludge using anaerobic biodigesters. The and energy for boiler systems and dryers or to generate operator could be a public or private entity. The operator electricity for use at the plant site. The organic material not signs a long-term contract with a municipal or government degraded by the process (digestate) can be composted and water agency for a WWTP. The municipality or the public sold as organic fertilizer to nearby farmland (Canvas 7). water utility uses the collected sewage tariffs paid by water users (households and commercial hubs) for contracting The contract might be design, build, own and operate with such services and providing thickened sludge for stabilization full financing of the project, or design, build, and operate and energy recovery. if sufficient public finances are available. The contract is usually for at least 10–15 years and depends on the The input to the digester can be supplemented by including depreciation period for the infrastructure provided by private organic waste from industries and households as well as service providers. manure and organic waste from agriculture. The management process involves advanced anaerobic digestion followed by This business model is appropriate for small and medium traditional anaerobic digestion. Advanced anaerobic digestion WWTPs lacking sludge storage capacity that provides only generates a larger volume of biogas than traditional anaerobic basic wastewater and sewage sludge treatment and for digestion. During advanced anaerobic digestion, sludge regional hubs where more than one treatment plant can streams are pretreated to break down cells and organic be served. Sometimes, different waste streams can be matter in the sludge, making them more easily digestible. This combined through such regional hubs where organic wastes helps reduce the retention time in the digester and makes the from households, agriculture and industries can be co- biogas generation process more efficient. digested. The private service provider can operate through contractual agreements for using energy for the plant and Advanced anaerobic digestion pretreatments include: connecting to a grid for supplying excess heat or electricity. (i) thermal hydrolysis process, (ii) enzymic hydrolysis, (iii) Business expansion within a region is determined by the ozonation, and iv) ultrasonic sludge disintegration. possibility for economies of scale achieved by integrating treatment plants and transportation costs for the different An operator might set up an anaerobic digestion plant within waste streams. A schematic representation of the business a WWTP or construct and commission a regional plant for model recovering energy from sewage sludge is shown in energy recovery to benefit from economies of scale. Biogas Figure 13. 45 External origin Internal origin RESOURCE RECOVERY & REUSE SERIES 23 Capital investments for anaerobic digestion for harnessing at USD 4,124/kW (EUR 3,050/kW) (World Bank 2015). gas amounts to USD 365/m3 while recovering electricity The operating cost for extracting gas is USD 3.67/m3, requires combined heat and power technology in addition while the cost for electricity generation is USD 5.30/m3. to the digester and therefore requires more investment (e.g., The operation and maintenance of a combined heat and USD 525/m3) (Mohammed at al. 2017). The associated power system is reported to be short-term expenses of cost of combined heat and power technology is estimated USD 0.02/kWh (EUR.015/kWh) (World Bank 2015). Other wastestreams Bottling plant $ Combined Heat Electricity / Energy Stabilized Cleaning and Thermal Electricity / sludge Thermal hydrolysis biogas (CHP) WWTPs Biomethane Electricity / LEandergy & Energy atprapnlicsamtioisnsion $ Anaerobic digestion company Contractual $ agreements - Feed-in-tariff DBO / DBOO fees/cubic contract meter Energy utilization with plant Special project vehicle DBO / DBOO contract FIGURE 13. BUSINESS MODEL FOR RECOVERING ENERGY THROUGH ANAEROBIC DIGESTION. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Biological sludge • Energy recovered • Direct interaction with • Water utility services public water utilities stabilization through the recovery municipalities, WWTP or municipalities • Energy and electricity • Use of combined process operators and public • Electricity transmission heat and power • Digestate can be water utilities companies companies technology for used for non- • Direct interaction with • Private entities thermal energy agricultural purposes electricity engaged in using and electricity or can be upgraded transmission digestate for • Feeding electricity to fertilizers for companies landscaping, to grid agricultural uses agriculture and • Digestate for soil • Savings from costs upgrading to fertilizer conditioner or incurred for disposing • Private and public fertilizer of sludge cake waste collectors if the other waste Resources Channels streams are • Establishing and • Through the operation integrated commissioning of a digestion plant • Local contractors the plant • Heat and electricity for +-plant fed to grid construction if required Cost structure Revenue streams • Capital costs: mechanical equipment, digester and • Revenue from electricity sales combined heat and power technology • Revenue generated from fees provided by • Salary, rent, interest, insurance WWTP operator/waste management company • Operation and maintenance of WWTPs, composting yards • An added source of revenue can be the sale of • Fuel costs and utility charges the digestate as organic fertilizer Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Safe application of sludge, recovering nutrients and sludge and other waste streams. reducing pollution. • Job creation. • Low human exposure due to less disposal and contamination. CANVAS 7: ENERGY RECOVERY FROM ANAEROBIC DIGESTION 46 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Case Studies labor, electricity and chemical agents and are estimated to be USD 11 per ton. The main revenue channels include CNG Xiangyang City, China production (6,000 m3) and sales of digested sludge cake. In 2012, Xiangyang City in Hubei Province, China installed a thermal hydrolysis and anaerobic digestion plant in The CNG is sold at USD 0.74/m3 which generates USD response to the increasing volume of waste caused by 1.41 million annually, while the price of sludge cake with rapid urbanization. Anaerobic digestion is used to convert 60% moisture varies between USD 2.9–4.4 per ton and sludge waste into biogas and digested sludge for profit and dried sludge cake with 10% moisture at USD 20–22 per ton. for reducing greenhouse gas emissions. The facility used a Revenue from the sale of dried sludge cake is estimated build, operate, and own contracting arrangement between to be USD 0.12–0.13 million per year. The facility planned local government agencies (Xiangyang Urban Construction for a third source of revenue from the sale of tree saplings Committee and Xiangyang Urban Management Bureau) to grown with the help of dried sludge cake. Estimates showed treat sludge and the private sector (Toven Co. Ltd.). Two that using 60 tons of sludge cake each year, 216,000 trees agreements for sewage sludge and food waste were signed could be planted and sold for USD 29 per tree. This would between government agencies and the private entity with earn revenue of USD 6.3 million per year. The plant broke a concession period of 23 years, including a construction even thanks to subsidies of USD 37 per ton and since period of two years). The operator receives a subsidy from 2015 increased sales of dried sludge cake have made the the local government and revenues through the sale of operation profitable. compressed natural gas (CNG) to the municipal taxi fleet and the sale of biochar and saplings (Fu et al. 2017). Toyohashi City Japan Toyohashi City Biomass Utilization Center in Toyohashi City, The facility has a capacity of 300 tons/day (annual capacity of Aichi Prefecture was completed in 2017. The integrated 110,000 tons/day), which includes: (i) sludge (180–220 tons/ renewable energy facility for combined anaerobic digestion day), and (ii) kitchen waste (80–120 tons/day). Kitchen waste was planned for the treatment of sewage sludge, septic tank is crushed at restaurants and transported to the plant. The sludge, and food waste. The plant was commissioned by project operator is responsible for installing the kitchen waste Toyohashi City as a private-public partnership under a build, crusher and transporting the waste. The two main products transfer, and operate contract. The private entity raises funds derived from the plant are biogas and digested sludge. Half the for construction and on completion, ownership is transferred biogas produced is used for electricity generation used within to Toyohashi City and the private entity operates the plant. the plant, while the other half is purified, compressed, and used to replace 6,000 m3 or 1,668 gasoline gallon equivalent The project to build and operate the facilities comprises: (GGE) per day of gasoline to fuel 300 municipal taxis. The Xiangyang project also built a CNG fueling station with a • Selling electricity generated by the biogas power storage volume of 6,000 m3. The digested sludge is further plant dried to produce 55–60 tons of sludge cake (40% moisture • Selling fermented sludge to other companies as content) each day which serves as a soil amendment. carbonized fuel • A large-scale solar power plant using idle land as a The project made a total investment of USD 20.7 million subsidiary business comprised of USD 13.8 million for sludge treatment equipment and USD 6.9 million for pre-treatment equipment The operating body of Toyohashi City Biomass Utilization for kitchen waste, a CNG station and kitchen waste collection Center is Toyohashi Bio Will KK, a special purpose company trucks. The project used three sources for funding: (i) 30% financed by JFE Engineering Corp, Kajima Corp, Kajima corporate equity, (ii) 60% from low-interest loans provided by Environment Engineering Corp and Otec. Toyohashi Bio Will the Export-Import Bank of China and KfW Bankengruppe, KK was contracted to operate and maintain the center for and (iii) 10% provided in the form of subsidies from the local 20 years. Power generated by the facility will be sold using a government. feed-in tariff scheme.40 Fixed costs for sludge treatment were estimated at USD 16 Aguas Andinas, Chile per ton (80% moisture content). The operating costs are Aguas Andinas is Chile’s largest water utility company USD 16 per ton (80% moisture). The operation is comprised and manages water and sanitation for the Santiago of these components:(i) labor (27%), (ii) electricity (23%), (iii) Metropolitan Region. The business case of the La Farfuna chemical agents (23%), iv) equipment (9%), and v) other wastewater treatment plant and RRR pathway is based on costs (18%). Costs for the kitchen waste operation include a venture between Aguas Andinas and SUEZ for reclaiming 40 Bioenergy International. https://bioenergyinternational.com/japans-largest-integrated-food-wastewater-treatment-renewable-power-project- opened/ (accessed on September 21, 2022) 47 RESOURCE RECOVERY & REUSE SERIES 23 wastewater and Aguas Andinas and Metrogas for biogas Veolia, China, Germany and US generation. Among its offerings, Veolia has developed a process for transforming sewage sludge recovery solutions into In 2005, Aguas Audinas contracted SUEZ to construct a biogas. This complies with environmental regulations and wastewater treatment plant of 760 million liters per day.41 reduces residual sludge volumes and creates a revenue The main aim was to treat over 50% of the wastewater stream by using the energy on-site or by selling it to the generated by the city before discharging it into the local grid. Veolia offers several technical solutions to treat Mapocho River. The plant was implemented through a sewage sludge and recover energy, including Exelys™ build, operate, and transfer arrangement between Aguas and Bio Thelys™. By coupling thermal hydrolysis with Andinas and SUEZ. SUEZ was entirely responsible for anaerobic digestion, Bio Thelys™ and Exelys® offer the design, supply, engineering, construction, testing, enhanced performance over conventional digestion and and commissioning of the treatment plant. The plant is optimize sludge treatment by producing: (i) 25 to 35% still operated under renewable five-year operation and less dry solids, (ii) 30 to 50% more biogas, and (iii) a maintenance contracts. safe and high-quality digestate for land application. This has benefits for the treatment plant operators as The treatment plant was further modified for capturing there are additional income sources from energy and biogas for residential use. Aguas Andinas and Metrogas additional capabilities to process organic waste. Below signed a memorandum of understanding and Aguas are some examples where Veolia technologies have been Andinas will export the residual biogas generated at the implemented. treatment plant to the Metrogas town gas factory. The factory will use the biogas as feedstock to produce town The City of Urumqi in China decided to improve its gas and then distribute it to around 30,000 customers in wastewater treatment by modernizing its treatment the city of Santiago. This is an important aspect of the plant. Under the first private-public partnership signed business model since the production of upgraded biogas by the city, Veolia started operating six digesters is not considered part of the duties of Aguas Andinas under capable of processing more than 80,000 m3 of sludge the water regulations. and producing 930,000 m3 of biogas per month. This biogas is then used to heat the plant and re-injects La Farfana produces about 800 tons of sludge a day. 800,000 kWh of green electricity per month into the local After the dewatering and drying process, the plant yields electricity network.42 about 120 tons a day of dry biosolids. Aguas Andinas has explored alternative uses for its biosolids. About In Braunschweig, Germany, a wastewater treatment plant 40% of the biosolids are used in agriculture at no cost is now 100% self-sufficient due to the intervention of BSI to farmers. The total cost of the project was about USD Energy, a subsidiary of Veolia which operates the site. It has a 6 million. The capital investment was divided equally population equivalent capacity of 275,000 people. Biological between Grupo Agua Andinas and Metrogas. While wastewater treatment, thermophilic sludge digestion and Aguas Andinas contributed to expanding the biogas co-digestion with organic waste, cogeneration and recovery catchment and improving treatment, they later invested of biogas have resulted in the plant being energy self- in a 13.5-kilometer gas pipeline and the final treatment of sufficient.43 biogas. In 2017, Aguas Andinas earned a profit of USD 1 million with revenue from the sale of biogas of USD 3 million Veolia’s solutions have been applied in a wastewater and USD 2 million spent on operations and maintenance. treatment plant in Gresham, the fourth largest city in Metrogas spent USD 3 million to purchase biogas from the state of Oregon in the United States. The plant has Aguas Andinas but saved an estimated USD 1.6 million, undergone a profound transformation. Once the most which is the price it would have paid for imported biogas. energy-intensive plant in the city, it is now 94% self-sufficient The estimated amount of emission reductions claimed in due to the recovery of biogas from sewage sludge. The its first crediting period (2011–2018) was 138,516 tons plant’s electricity costs have dropped by an average of USD of CO 2 equivalent (19,788 tons a year), another source of 23,100 per month.44 potential extra revenue. 41 World Bank. https://documents1.worldbank.org/curated/en/284951573498126244/pdf/Wastewater-From-Waste-to-Resource-The-Case-of- Santiago-Chile.pdf (accessed on September 17, 2022) 42 Veolia. https://www.veolia.cn/en/urumqi-wastewater-treatment-project (accessed on September 15, 2022) 43 Veolia. https://www.veolia.com/en/solution/sewage-sludge-green-energy-biogas-wastewater (accessed on September 20, 2022) 44 Veolia. https://icma.org/sites/default/files/305996_Veolia%20North%20America%20-%20The%20City%20of%20Gresham%20Oregon.pdf (accessed on September 20, 2022) 48 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE BUSINESS MODEL 8: ENERGY RECOVERY FROM INCINERATION Under model 8 we distinguish between mono-incineration (Model A) and co-incineration (Model B). Model A: Mono-incineration of sewage sludge Brief Energy recovery from incineration of sewage sludge Location Urban and peri-urban areas Waste input type/stream Dewatered and dried sewage sludge Value offer Self-sufficiency in energy and the potential for phosphate recovery Environmental risk mitigation Pollutant control mechanisms are needed to limit air pollution Organization type and profit Private entities with a profit motive objective Major stakeholders Urban local bodies, public water utilities, energy and electricity transmission companies, private entities engaged in phosphate recovery, landfill operators for disposing of remaining sludge ash PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance for energy recovery from mono-incineration. • The business uses incineration, which is backed by regulations making the business model more scalable. • The business model is becoming increasingly relevant in European countries switching over to phosphorus recovery as per regulatory restrictions. • The incineration produces sludge ash reducing the volume of disposal which helps reduce transaction costs. • There are multiple sources of revenue that increase the financial feasibility of the business model. 49 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Traditional technology with know-how and • Demand for considerable capital for investment easy integration of pollutant capture • High operational costs. technologies. • Requirements for proper handling of sewage • Energy sufficiency of the operation. sludge ash and flue gas. • Multiple revenue streams. Opportunities Threats • Option of recovering and using phosphate • Lack of support for undertakings and from sludge ash. investments. • Opportunities for using sludge ash in cement • Environmental laws for the disposal of sludge plants. ash and public acceptability challenges, • Favorable legislation for the incineration of especially near residential areas. sewage sludge in developed countries. 50 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Energy utilization within plant for dewatering Stabilized sludge WWTPs Electricity / ElectricityL a/nd Mono-incineration Energy Energaypplication transmission company $ Contractual agreements DBO / DBOO contract Special project vehicle (SPV) or $ Private entity Feed-in-tariff FIGURE 14. BUSINESS MODEL FOR RECOVERING ENERGY FROM MONO-INCINERATION. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Transportation of • Energy is recovered • Direct relations • Water utility services public water utilities dewatered sludge making the between sludge or the municipalities • Energy and • Recovery of operation producers and • Farmers (potential) electricity energy efficient • Savings from incinerator operators transmission thermal energy disposal costs companies and electricity • Potential for • Private entities from incineration phosphate recovery engaged in • Use of electricity from sludge ash phosphate within the plant recovery (potential) for drying sludge • Landfill operators or feeding to the for disposal of grid remaining sludge • Sludge ash for ash phosphate recovery (potential) Resources Channels • Establishment and • Contractual commission of the agreements for the plant operation of • Phosphate recovery incineration plants mechanism (if phosphate is recovered) Cost structure Revenue streams • Capital costs: mechanical equipment • Revenue from electricity sales • Salary, rent, interest • Recovery of phosphate is a potential source of revenue • Operation and maintenance of incineration plants, phosphate recovery technology (if commissioned) • Fuel costs and utility charges Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling of • Reduction of sludge volume for disposal which is odorless sewage sludge and other waste streams. and pathogen free. • Flue gas containing furans, dioxins, and heavy metals. • Job creation. • Potential for phosphate recovery reducing dependence on natural phosphate. CANVAS 8: ENERGY RECOVERY FROM INCINERATION 51 RESOURCE RECOVERY & REUSE SERIES 23 Business Model Description Case Studies The energy generated by incinerating sewage sludge Outotec, Switzerland is used within the plant for dewatering sewage sludge, Outotec sewage sludge incineration plant designs are making this model appropriate for energy efficiency and based on fluidized bed technology which meet air emissions cost savings in terms of energy recovered and reused. requirements as defined in plant operating permits.45 The Incineration is an expensive treatment for sludge streams facilities where Outotec had been the service provider were due to high energy requirements. Using incineration as turnkey projects where Outotec was responsible for the a sludge management process mostly applies to large design, manufacture, and supply of all equipment, installation cities with treatment plants that generate a large volume and commissioning activities, including all construction of sludge. The business is initiated by a private operator work, start-up support, and operator training assistance. contracted by municipal water utility services to reduce The Canton of Zurich, which is the most populous and the volume of sludge for disposal. There are possibilities economically prosperous Canton in Switzerland, has 69 for joint ventures with private entities for setting up and public sewage treatment facilities treating 230 million m3 commissioning the plant as the investment costs are high. of wastewater annually and producing 100,000 tons of dewatered sludge (30% dry solids). Until 2005, agricultural A regional incineration facility is also an option for smaller applications of dewatered sludge was a possibility, after and mid-sized plants. These plants share the cost of which there was a national ban on using dewatered sewage incineration and transport their sludge streams to a central sludge directly in agriculture. This led to the formulation site for combined processing. In the case of large WWTPs, of a disposal plan comprised of 65% to waste-to-energy municipalities or a water utility service provides a long-term plants, around 9% dried in cement works, around 25% contract for the private entity to construct and commission in two smaller mono-incineration plants with no separate an incineration plant using the sewage sludge and pays deposition of ash containing phosphorus, and around 1% private companies through user fees collected from sludge management in plants outside the Canton. In 2006, household and commercial establishments. The private some recognized that the existing disposal concept would entity can also use a public-private partnership model to lead to bottlenecks in capacity starting in 2015. It also set up and operate an incineration plant. In such cases, the became increasingly apparent that phosphorus is a limited public authority provides land for the incineration plant and resource and the supply of low-pollutant mineral fertilizers helps with sludge ash disposal contracts with local landfill is no longer adequately secured. The Canton of Zurich operators. The municipality or water utility service usually formulated the following clear limiting conditions in 2007 opts for a design, build, own and operate contract with the in its decision regarding the Implementation of a Sewage private entity. Sludge Disposal Plan (RRB 572/2007). The impetus of the plan was phosphorus recovery and energy use (Morf et al. This business model is appropriate for cities with land 2019). constraints and large sludge volume generation. Despite the high costs associated with sludge incineration, this High transport and logistics costs for sludge containing approach is expected to grow in the coming years due to more than 70% water and strict emission restrictions from stricter regulations affecting landfilling and land application incineration facilities are common challenges faced by of sludge. Generally, mono-incineration plants have higher WWTP operators. The technology provided by Outotec is investment costs (between USD 250 and USD 450 per ton built onsite, is environmentally friendly and is an economically of dry matter). The operation and maintenance costs for viable solution for treating municipal and industrial sludge an incineration plant with energy recovery are around USD without additional fuel consumption. The technology is 200 per ton of dry matter per annum. The model can be beneficial in providing self-sustaining thermal energy with boosted in terms of cost savings and opening a revenue minimal emissions and an opportunity of using the residue source by recovering phosphorus from sludge ash making ash for phosphorus recovery. it available for agriculture as a fertilizer substitute (Canvas 8). Currently, sewage sludge is disposed of in a landfill or Transformation Park, Hong Kong used in the production of construction materials and mine Transformation Park in Hong Kong is the region’s first filling. All these disposal routes are a cost to the incineration sludge treatment facility and operates the world’s largest plant as they need to pay for disposal. Figure 14 provides incinerator.46 The facility is designed for incinerating 2,000 a schematic representation of the business model for tons of sewage sludge per day. It collects sludge from all recovering energy from incineration of sewage sludge. 11 wastewater treatment works in Hong Kong, 70% via 45 Outotec. https://www.energy-xprt.com/downloads/outotec-waste-to-energy-plants-brochure-1004000 (accessed on September 17, 2022) Presently Metso Outotec. https://www.mogroup.com/corporate/media/news/2012/11/outotec-to-build-the-largest-and-most-advanced- sewage-sludge-thermal-treatment-plant-in-switzerland/ (accessed on September 17, 2022) 46 T. Park. https://www.tpark.hk/en/ (accessed on September 20, 2022) 52 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE vessel and 30% via truck. Phase 1 (1,600 tons/day) has pollutants and heavy metals are neutralized or captured. The been in operation since April 2015 and Phase 2 (400 tons/ cleaned flue gas is constantly monitored by a continuous day) started in April 2016. The current management and emission monitoring system to ensure full compliance with operation of the facility is contracted to VW-VES(HK) Ltd., stringent international emission standards. a wholly-owned subsidiary of Veolia. The facility is a joint venture between the Environment Protection Department of The facility is self-sufficient in terms of the thermal energy the Hong Kong Government (Special Administrative Region) produced and generates a surplus of 2 MW of electricity in 2010. A long-term contract for design and build and 15 when operating at full capacity. This meets the electricity years of operation was offered to Veolia. Presently, the facility demand of 4,000 households. Incineration also results in handles 1,200 tons of sewage sludge which is estimated a reduction of 90% of the original sludge volume to be to increase to 2,000 tons by 2030.47 The incinerator uses disposed of in the landfill. Therefore, it not only reduces fluidized bed incineration technology coupled with a series disposal costs but also reduces the emission of greenhouse of treatments for flue gas. These treatments are comprised gases by up to 237,000 tons a year. The treatment facility is of multi-cyclones, dry reactors and bag filters where large unique in design and generates revenue from recreational and fine particles are removed and acidic gases, organic and educational complexes in the park.48 47 T. Park. https://www.tpark.hk/en/story/ (accessed on September 20, 2022) 48 T. Park. https://www.tpark.hk/en/process/ (accessed on September 20, 2022) 53 RESOURCE RECOVERY & REUSE SERIES 23 Model B: Co-incineration of sewage sludge Brief Energy recovery from co-incineration or co-processing of sewage sludge Location Peri-urban areas based on the location of waste-to-energy plants, thermal plants and cement kilns Waste input type/stream Dewatered and dried sewage sludge Value offer Energy recovered from co-incineration, reduction in disposal costs Environmental risk mitigation Pollutant control mechanisms needed to limit air pollution Organization type and profit Public water utilities wanting to dispose of sludge objective Major stakeholders WWTP operators, partnerships with waste-to-energy plants, thermal powerplants and cement kilns PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of co-incineration of sewage sludge. • The business model supports disposal of sewage sludge generated at WWTPs through the co-incineration of dried sludge in waste-to-energy plants, thermal power plants and cement kilns. • The business is scalable since cement plants are willing to accept dried sludge as an alternative fuel source and disposal fees are usually lower than landfill fees. 54 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Strengths, weaknesses, opportunities, and threats (SWOT) Helpful Harmful Strengths Weaknesses • Elimination of potential environmental • No recovery of phosphate possible risks through burning sludge at • Additional investments for modifying temperatures up to 1,450° C incinerators to accept different fuel sources • Reduction in the volume of sludge disposed • Fuel cost reduction and additional income through tipping fees for the cement industry and thermal power plants • Support sewage waste management if co-incinerated with municipal solid waste • Energy sufficiency Opportunities Threats • Option of using sludge ash in manufacturing • Restrictive regulations based on mandatory Portland cement or brick production. phosphorus recovery through mono- incineration can be a limitation. • Co-feedstock might contain additional pollutants. Business Model Description conventional fuels are expensive. The sludge is used as a fuel source in cement kilns along with fossil fuels, which The co-incineration process involves incinerating dried have a higher caloric value. Sludge can substitute for sludge with other waste and fuel sources and can be in one 15–20% of the conventional fossil fuels used in cement of the following forms to derive energy from the process. kilns (Box 2). Co-incineration with municipal solid waste. This involves The sludge is typically dried and made into pellets, which the combustion of dried sludge with municipal sludge in makes it easier to use as fuel. The drying process is municipal solid waste incinerators. The process provides necessary to ensure that the cement kilns reach the required more potential for energy recovery than mono-incineration. temperatures of up to 1,450° C. The high temperatures However, the ash produced is not suitable for phosphate destroy any organic pollutants in the sludge. The cost for a recovery as in mono-incineration. In some cases, where multi-fuel kiln with a capacity of 5,000 tons of clinker a day sludge drying facilities are not available within the WWTP, amounts to USD 250,000 to USD 300,000. The cost for waste-to-energy plants can provide energy for drying. corresponding drying equipment that uses process heat to dry sewage sludge ranges from 25% to 90% and is USD 10 Co-incineration in coal-fired thermal power plant. to USD 15 million.49 Coal-fired thermal power plants in developed countries are interested in reducing their fossil fuel footprints by mixing This business model is driven by: (i) regulations that dried sludge thereby reducing costs to sustain operations. prohibit or limit the disposal of sewage sludge in landfills and agriculture and mandates resource recovery and Co-incineration in cement plant. Common where reuse through alternative fuels, and (ii) the presence of regulations restrict the use of sewage sludge in agriculture waste-to-energy plants using municipal solid waste for or disposal in landfills or where disposal fees are high. Co- incineration, coal-fired power plants or cement kilns in incineration in the cement industry is a possibility when nearby areas, (iii) the availability of combustion 49 Information provided by Mr. Werner of Schwenk Cement industries (telephonic interview) 55 External origin Internal origin RESOURCE RECOVERY & REUSE SERIES 23 BOX 2. ADAPTATIONS OF THE BUSINESS MODEL Two beneficial uses of cement kiln sludge ash are directed toward material recovery and can create a new value chain. These options for material recovery include using sludge ash for Portland cement and brick production. Cement kiln sludge ash generated through co-incineration in the cement plant can be integrated into clinker production. The clinker is cooled, mixed and ground with gypsum for the production of Portland cement. Adding sludge ash saves the cost of conventional raw materials used for cement production. The heavy metal pollutants in sludge ash are stabilized in the clinker and there are no further sludge residues or hazardous materials left over. Similarly, sludge ash has the potential to replace clay in brick production. However, the quality of the bricks produced depends on two factors: (i) 20–40% by weight of sludge ash should be added to the clay, and (ii) the firing temperature for baking the bricks should be 1,000 °C. Source: GWI 2012. technologies that allow for incineration of waste-derived and co-incineration as an alternative fuel in the cement alternative fuel sources with various dry matter, and iv) a industry provides a tested and sustainable solution at scale. suitable tariff structure of tipping and disposal fees paid by Scaling up the business requires co-incineration plants to the WWTPs to coal- and waste-to-energy power plants. have storage and drying capacities for sewage sludge to In the last case, the WWTP and the waste-to-energy plant increase the calorific value. As a source of alternative fuel, might be operated by the same private entity contracted the sludge should not exceed 20% in a fuel mixture.50 A through the municipality, which leads to easier disposal schematic representation of the business model recovering and use of sewage sludge for co-incineration. Most energy through co-incineration is shown in Figure 15. waste-to-energy, coal-fired thermal power and cement plants in high- and mid-income countries have adjusted For co-incineration in a waste-to-energy or coal-fired thermal combustion equipment according to the regulations, power plant, the investment costs for smaller plants (40,000 especially those related to emissions. tons/annum) amounts to about USD 41 million and USD 1,026 per ton respectively. The investment costs for larger Typically, WWTPs deliver dewatered or dried sludge to the plants (250,000 tons/annum) amount to USD 169 million waste-to-energy or coal-fired thermal power plants where and USD 680 per ton. For co-incineration in cement plants, it is stored and further dried and processed so its physical investment in equipment for storage, drying, processing, properties match the requirements of the burners and delivery and feeding sludge into multi-fuel kilns for medium- combustion equipment. The treatment plant operator needs sized factories with production capacities of 5,000 tons of to pay for disposal and tipping. This payment is necessary clinker/day can be up to USD 10 million. However, solar to justify the capital and operating costs in modifying drying sewage sludge will significantly reduce the investment incinerators to be acceptable for co-incineration. needed for drying equipment at WTTPs or cement industries. The annual operational costs for co-incineration in waste-to- This business model is appropriate for large WWTPs energy or coal-fired thermal power plants are estimated at disposing of sewage sludge in a manner that enhances a 5–7% of the investment cost, i.e. USD 2.05 to 2.87 million circular economy and reduces disposal costs (Canvas 9). for 40,000 tons/annum plant and USD 8.45 to USD 12 This applies where RRR in agriculture is not a feasible option million for the larger plant respectively. Energy utilization within plant for dewatering $ savings Electricity / Dewater energy sludge Land WWTPs Co-incineration Electricity / $ Electricity / Energy Energaypplication Disposal fees transmission /cubic meters $ company Feed-in-tariff FIGURE 15. BUSINESS MODEL FOR CO-INCINERATION. Source: Author’s creation. 50 Personal communication with manager of waste-to-energy plants in Bremen. 56 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Transportation of • Energy is recovered • Direct relations • Waste-to-energy public water utilities dewatered and through the process between the WWTP plants • Energy recovery dried sludge making it energy operators and energy • Thermal power plants plants, waste-to- • Recovery of thermal efficient and a cost- recovery units (i.e. using coal energy plants, energy and effective alternative waste-to-energy, • Cement plants thermal/cement electricity from fuel for cement and plants and cement plants incineration thermal power plants plants) • Power transmission • Use of electricity • Savings from lower companies in the within the plant for disposal costs case of waste-to- drying sludge or energy and thermal feeding to the grid plants as cost recovery Resources Channels • Establishing and • Contractual commissioning agreements for use incinerators that of sewage sludge at accept multiple incineration plants fuel types Cost structure Revenue streams • Capital costs: mechanical equipment, incinerator and • Cost savings from using alternative low-cost fuel combined heat and power • Revenue generated from feed-in-tariff • Salary, rent, interest • Disposal fees paid by WWTP operators • Operation and Maintenance of incineration plants, mechanized equipment • Fuel costs and utility charges Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Reduction of the sludge volume for disposal which is sludge and other waste streams. odorless and pathogen free. • Flue gas containing furans, dioxins and heavy metals. • Creation of jobs. • Potential of phosphate recovery reducing the dependence on natural phosphate. CANVAS 9: ENERGY RECOVERY FROM CO-INCINERATION OF SEWAGE SLUDGE Case Studies: Co-incineration in Cement supply all the alternative fuel needed by a cement plant, Plants homogeneous feed is an important consideration. Every supplier or treatment plant is producing alternative fuel with Cementos Molins Group, Spain sometimes slightly, sometimes markedly different material Cement manufacturers worldwide strive to increase properties, Cement industries are interested in uniformly alternative fuel use such as sewage sludge. The activity drying sewage sludge to achieve a homogenous final of Cementos Molins (2020) focuses on manufacturing, product. Cementos Molins is dealing with different batches distributing and selling cement, concrete, mortar, aggregate of granulated dry sludge humidity ranging from 10–15%. and concrete prefabricates, and running activities and production. Molins operates plants in Spain, Argentina, Schwenk, Germany Uruguay, Mexico, Bolivia, Columbia, Bangladesh, India Schwenk has long-term contracts with several WWTPs for and Tunisia. As dried sewage sludge is an ideal fuel for the the co-incineration of 30 tons of dewatered sewage sludge main burner in cement kilns, Cementos Molins is using this per day in its cement kilns. Costs for technical upgrading of fuel plus biomass.51, 52 Since one supplier usually cannot the cement plant amounted to USD 10 million, 90% of which 51 The renewable fuels used were agricultural waste, biomass, wood and sawdust, sewage sludge, and paper and cardboard. Cementos 52 Molins, Annual Sustainability Report. 2020. Cementos Molins https://sostenibilidad.cemolins.es/en/pilares/economia-circular/ (accessed on September 22, 2022) 57 RESOURCE RECOVERY & REUSE SERIES 23 was used for the installation of drying equipment that uses the waste). This is used as a filling and sealing material in thermal energy of process heat, and 10% for installing a multi- mining or for road and landfill construction. The major fuel kiln.53 Dried sewage sludge is regarded as a CO2 neutral savings come from less use of fuel (250 liters of heating fuel. As the cement industry generally has difficulty cooling its oil or 250 cubic meters of natural gas per ton of residual kilns and clinker products, they welcome the use of excess waste. heat for drying dewatered sewage sludge with special heat exchange technologies. If dried sewage sludge is used, the Case Studies: Co-incineration in Coal- recommended dry sludge is > 90% to allow for pneumatic Fired Thermal Power Plant feeding of dried sewage sludge particles into the kilns. The plant is a leader in using secondary fuel in Germany.54 Frechen, Hürth-Knapsack, Heilbronn, and Lippendorf Germany In Germany, cement production facilities are designed to Schmitz (2009) in Wiechmann et al. (2013) indicates the receive only dewatered sludge as this is most profitable for authorized volume of sewage sludge used in different the industry due to the high disposal fees paid by WWTPs thermal power plants adds up to 716,000 tons, only 500,000 and utilities. On the other hand, this payment covers the tons can be used from a technical standpoint. Roskosch capital and operating costs of modifying incinerators at and Heidecke (2018) report that in 2016, the amount of cement plants to use alternative fuel and high investments in sludge used by the plant was 401,000 tons considering co- drying equipment to reduce the sludge water content before incineration in both lignite and hard coal-fired power plants. it can be fed into the kilns. Typically, the lower the disposal The report mentions that in most coal-fired thermal power fees paid by the sludge producers, the higher the dry matter plants, the sewage sludge used is up to 5% of the fuel mass content demanded by the cement plants. and the current use rate of the approved co-incineration capacity is just under 50%. As reported by Schmitz (2009), Case Studies: Co-incineration with MSW RWE Power Ag has the largest authorized capacity of 213,700 tons of sewage sludge. Weber et al. (2020) report Bamberg, Germany that eight coal-fired power plants are authorized to co- The Bamberg waste-to-energy plant has been operating incinerate sewage. RWE Power Ag and EnBW use sewage for more than 30 years and serves the district of Bamberg, sludge in different power plants along with lignite and hard Forchheim, Erlangen and Erlangen- Höchstadt. The coal (Table 11). plant treats 144,000 tons of household, commercial, and bulk waste as well as dewatered sewage sludge Although using sewage sludge in coal-fired thermal per year.55 The sewage sludge is mixed with other waste power plants is one mechanism for disposal for the and subjected to thermal treatment. The plant treats WWTP operator, using sewage sludge is becoming more approximately 126,000 m3/year with 3% dry residue difficult due to the increasing cost of complying with content (about 30% dry residue after dewatering).56 The regulations and meeting standards. The heavy metal plant owner, the Association of Waste-to-Energy Plants load entailed by sewage sludge use is significant when in the city and district of Bamberg invested EUR 50 million it comes to emission values. Therefore, using larger in 2007–2009 to upgrade the plant, which now produces amounts of sewage sludge requires the installation of 11.3 MW of electricity and 51 MW of heating output. waste gas scrubbing equipment and hence additional This is mainly used for district heating and electricity for investment and operational costs. Additionally, fly ash the Bamberg public utility. The electricity generated is generated after co-incineration is recycled for use in approximately 80,000 MWh per year with 75,000 MWh construction materials and needs to comply with the used for district heating.57 The plant produces 35,000 applicable construction materials standards, which tons of bottom ash per annum (250 kg from one ton of further limits its use. 53 Information provided by Mr. Werner of Schwenk Cement industries (telephonic interview). 54 Schwenk. https://www.schwenk.de/en/company/sustainability/ (accessed on September 22, 2022) 55 Bamberg. https://www.hz-inova.com/files/2014/11/hzi_ref_bamberg_en.pdf (accessed on September 22, 2022) 56 The feedstock used in the plant comprises of 133,000 tons of waste along with 12,000 tons of sewage sludge per year. 57 MHKW Bamberg. https://www.mhkw-ba.de/index.php/nachhaltigkeit-umwelt.html. (accessed on September 22, 2022) 58 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE TABLE 11. RWE POWER AG AND ENBW USE OF SEWAGE SLUDGE. Businesses Installations Description RWE Power Ag Frechen, North Rhine-Westphaliaa Founded in 1902, the plant co-fires sewage sludge and lignite to generate electricity. Hürth-Knapsack, North Founded in 1992, this plant uses lignite-fired power with process Rhine-Westphaliab steam extraction. The plant co-incinerates sewage sludge and generates 40 MW for district heat. EnBW Heilbronn thermal power plant With an electrical output of 1,000 MW and an extractable thermal output of 320 MW, this t is one of EnBW’s largest coal-fired power plants. Lippendorf power plantc The plant started operation in 1999 and EnBW, along with Vattenfall. Europe Generation Ag, operates the plant producing 1840 MW. Sewage sludge has been co-incinerated in Lippendorf since 2004. ª RWE. https://www.rwe.com/en/our-portfolio/our-sites/frechen-factory b RWE. https://www.rwe.com/en/our-portfolio/our-sites/knapsacker-huegel-power-plant/ c ENBW. https://www.enbw.com/company/the-group/energy-production/fossil-fuel/locations.html Source: Author’s creation. 59 RESOURCE RECOVERY & REUSE SERIES 23 BUSINESS MODEL 9: ENERGY RECOVERY FROM GASIFICATION AND PYROLYSIS Brief Energy recovery from gasification and pyrolysis of sewage sludge Location Peri-urban areas. The plant can be located at the WWTP Waste input type/stream Sewage sludge and other biomass as feedstock Value offer Energy recovery and reduced disposal costs Environmental risk mitigation Lower emissions than incineration but requires monitoring, especially for chemical contaminants in residue, although the risk is lower for biochar than sludge Organization type and profit Private operations with a profit motive, private-public partnerships objective between WWTP and technology providers Major stakeholders Municipalities, water utility services, private companies and technology providers PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of energy recovery from gasification and pyrolysis. • The business model scores evenly across the parameters used to determine performance primarily because of innovative technology and scalability. • The technology developed can be used in a modular form, customized for a large operation or in a decentralized manner and thus helpful for small -and medium-sized WWTP. • The operations are energy self-sufficient and save both energy and disposal costs. 60 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Higher efficiency of energy recovery. • Sludge dewatering and drying are needed. • Reduced emissions and ability to handle • Complex technology and hence few most inorganic compounds in sludge. commercial applications. • Production of biochar. • Extensive gas cleaning is needed for syngas • Reduced disposal costs. applications. • High investment and operation costs, economies of scale and automation favor large-scale operations. Opportunities Threats • Niche market and energy self-sufficiency in • Legislation favoring the recovery of soil WWTPs. nutrients might lead to a shift toward • Potential for co-feeding with other types of other processes. biomass. • Markets for bio-oil, and biochar is not well- • Development of by-products (bio-oil and developed. The market needs development biochar) for promoting circularity. for the promotion of pyrolysis. Business Model Description facilities represent the largest energy consumers in the public sector and energy-self-sufficient treatment plants This business model is appropriate for a private entity are the key to cutting costs. Gasification and pyrolysis for contracted by a WWTP operator who wants to manage energy recovery are still in the nascent stage of application sludge volume and reduce disposal costs. Wastewater and are mainly found in developed countries. Gasification: A process that converts sludge into fuel gas which is called synthesis gas or syngas for short. Syngas fuel can be used on-site to generate electricity for plant use or can be used in applications such as thermal drying systems. Syngas can be converted to liquid fuel for offsite applications and use in the chemical industry. Ash is a by-product of the gasification process. The ash can be sent for disposal at landfill sites, or it can be sent for resource recovery. Pyrolysis: A thermal process that decomposes sludge by heating it (usually above 500-600ºC) in the absence of oxygen. The process converts sludge into a high-carbon solid called biochar. Other products of the pyrolysis of biomass are a mixture of syngas and bio-oil. The process can be tailored to produce different ratios of biochar to bio-oil. While biochar is pathogen- free, it can still contain heavy metals, but largely immobilized. Both processes begin with thickening and dewatering the plant while ownership remains with the public utility service. sludge which is then dried up to 90% dry solids content. Figure 16 illustrates the business model for recovering These are necessary steps to improve energy efficiency. energy from sludge through gasification or pyrolysis. The installation and operation of the plant can be of two types: (i) a private entity installs the plant as a turnkey Gasification project financed by a WWTP operator, and (ii) a public- The capital investment, including the dryer, varies between private partnership between a treatment plant operator and EUR 6 to EUR 12 million (USD 7 to USD 14 million) for a technology provider. In the first case, the treatment plant handling 4,000 to 6,000 tons per annum. The operating operator might obtain financing from donors or through their expenses are USD 350,000 to USD 830,000 per annum own public finance mechanisms and contract a technology which provides a return of 15–25% per annum. The payback provider to commission the plant. In the second case, period is four to seven years. The costs for gasifying sewage long-term contracts are prepared between public utilities sludge significantly exceed the costs of incineration and and technology providers for a design, build, and operate pyrolysis due to both the high cost of equipment and the system. The private entity designs, builds, and operates the complexity of maintaining the gasification process. 61 External origin Internal origin RESOURCE RECOVERY & REUSE SERIES 23 Pyrolysis already operational are reaping the benefits of reduced Mills (2015) indicates the capital expenditure for a thermal disposal costs and new revenue streams. The Loganholme hydrolysis plant with a dryer and a pyrolysis plant of 100 example from Australia (see below) shows how spending tons/day is USD 76 million. Adding a thermal hydrolysis AU$1.8 million annually on bio-solid hauling contractors plant and dryer increases the efficiency of electricity can be turned around into returns of almost AU$1 million generation. per year through reduced disposal costs and revenue from carbon credits (GWI 2023a). The same author calculates operational and maintenance costs as USD 2.15 million per ton per annum. The Due to the high carbon content of biochar and its ability operating and maintenance costs also include disposal to sequester carbon, it can also create revenue from the costs. Considering electricity generated and tipping fees voluntary carbon market. IPCC (2018) highlighted biochar as the revenue sources (USD 3.8 million per ton of sludge as a central carbon dioxide removal technology (negative per annum), the study projects a net present value of USD emission technology, NET) and estimates by the European 48 million and an internal rate of return of 18.6% with a Biochar Industry Consortium suggest that approximately payback of 5.2 years. 300-500 kg of CO 2 could be permanently stored per ton of dried sewage sludge. This is a stark contrast to Table 12 provides a detailed estimate of a plant capacity of the incineration of sewage sludge which releases CO2 2.1 tons/hour operational for 8,000 hours per annum. The into the atmosphere. Compared to other carbon sinks, study highlights that revenue from the sales of the biochar biochar is an extremely cost-effective option and creates and tipping fee for the sewage sludge are important a viable business model (GWI 2023a). Although biochar revenue sources for the financial sustainability of the can contain heavy metals, the potential risk of biochar model (Canvas 10). on soil and groundwater contamination is lower than for sewage sludge as some are volatilized (Hg, Cd) and the Most plants creating sewage sludge biochar are in the bio-availability of others is reduced (Lu et al. 2016; Zangh United States or Australia, with a few in Europe. Those et al. 2021). TABLE 12. ESTIMATES OF PLANT CAPACITY. Equipment Section Purchase costs (USD)a Belt dryer 486,943 Char storage 220,706 Pyrolysis gas burner 376,590 Rotary kiln burner 1,157,550 Scrubber 116,527 Direct capital costsb 4,784,540 Indirect capital costsc 2,700,950 Working capital 524,756 Total capital expenditures 10,332,472 Annual total operating costs 1,018,644 a 1 CDN = 0.7717 USD in 2018. b Includes installation, piping, instrumentation and control, electrical installation, building and services, land and site development, utilities and service facilities. c Includes engineering and supervision during construction, construction expenses, contractor’s fees and contingencies. Source: Barry 2018. Electricity / Dewater energy sludge WWTPs Pyrolysis / Land Electricity / Energy Electricity / Gasification Enaeprpglicyation $ Disposal fees transmission /cubic meter $ company Feed-in-tariff FIGURE 16. BUSINESS MODEL FOR ENERGY RECOVERY THROUGH PYROLYSIS AND GASIFICATION. Source: Author’s creation. 62 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Dewatering and • Energy is recovered • Direct • Water utility services public water utilities drying sludge through the process and municipalities • Energy and • Transportation of making it energy electricity dried sludge in case efficient transmission of regional plants • Savings from companies • Recovery of disposal costs • Local contractors thermal energy • Potential for using and electricity other by-products • Use of electricity in case of pyrolysis within the plant for drying sludge or feeding to the grid Resources Channels • Establishing and • Contractual commissioning the agreements for plant establishing and • Dewatered and operating the plant dried sludge Cost structure Revenue streams • Capital costs: mechanical equipment, combined heat • Revenue from selling electricity and power technology, thermo hydrolysis and pyrolysis • Tipping fees and drying units, gasification and pyrolysis units • An added source of revenue can be the recovery of • Salary, rent, and interest bio-oil and biochar in the case of pyrolysis • Operation and maintenance of all units • Carbon credits • Fuel costs, chemical costs and utility charges • Savings on disposal costs Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Near or close to zero disposal required sludge and other waste streams • Job creation • Fewer health issues CANVAS 10: ENERGY RECOVERY FROM GASIFICATION AND PYROLYSIS Case Studies: Gasification Kiyose Water Reclamation Center, Japan The Bureau of Sewage (Tokyo), Tokyo Metropolitan Sewerage SÜLZLE KOPF SynGas, Germany Service Corporation and METAWATER Co. conducted a SÜLZLE KOPF SynGas offers comprehensive and innovative demonstration test in the Tobu Sludge Plant and established solutions for decentralized sewage sludge use with energy a wastewater sludge gasification process. The plant has recovery. On-site energy recovery and use not only use a been in operation since 2010 as a public-private venture CO2-neutral energy source, but also significantly reduce where the 20-year design build and operate contract covers pollutant emissions from sewage sludge disposal. SÜLZLE design, construction and operation and maintenance of the KOPF designs and implements these solutions based on a system as a single entity. The plant produces 150 kW of patented method that constitutes an economical and proven electric power which accounts for approximately 30% of the alternative to the standard processes.58 The company has entire power consumed in the sewage sludge gasification commissioned three plants in Germany in Balingen, Koblenz process. The gasification process also provides heat for and Mannhein. The details of the three plants are shown in sludge drying.59 Table 13. Loganholme Wastewater Treatment Plant, Australia The examples above of small WWTPs that are not financially Sludge gasification is an emerging technology and there are viable, can implement such technologies with high efficiency examples where local authorities are taking the initiative and in energy recovery. Due to reduced energy costs, the implementing this business model. The Loganholme WWTP payback period for installing such plants are relatively short. in Australia is upgrading its treatment plant and investing 58 Koph Syngas. https://kopf-syngas.de/en/start-2/ (accessed on September 23, 2022) 59 Kiyose Bureau of Sewerage. https://www.gesui.metro.tokyo.lg.jp/english/news/r_and_r08/index.html (accessed on September 23, 2022) 63 RESOURCE RECOVERY & REUSE SERIES 23 USD 17.28 million to commission a gasification plant to in sludge weight from 17,000 tons of wet sludge (20–22% dry generate renewable energy and sustainably produce biochar matter) to 4,000 tons per annum with a residual moisture of for agricultural purposes. The Loganholme plant services approximately 10%. However, the weight reduction was not 300,000 people in the Logan region, producing 34,000 tons satisfactory as the sludge pellets formed after drying needed of biosolids per annum (an average of 90 tons a day).60 This to be transported to the Po River valley about 300 km away. requires a 300 kilometer trip to Darling Downs agricultural Following this, EISENMANN proposed thermal treatment of area where it is used as soil improver costing USD 1.8 million the sludge using the Pyrobuster® process. The Pyrobuster® (30% of the WWTP operating costs).61 Biosolids treatment plant was installed for the incineration of dried sludge pellets and disposal costs are increasing due to rising electricity (calorific value of 12,000 kJ/kg) operating at a capacity of 550 prices, an increasing population, and the likely tightening kg/hour for 7,500 operating hours a year. The heat recovered of regulations associated with carbon footprint reduction from thermal treatment was used to heat the thermal oil which and managing persistent organic pollutants in soils. The in turn heats the sewage sludge dryer. This process saves 70% gasification plant would reduce the volume of biosolids by of the energy required for drying and produces less carbon 90% and produce a safe, environmentally friendly biochar. dioxide. The accumulated ash can be disposed of in landfills The plant would be energy neutral and reduce carbon taken by a recycling company and further processed for reuse. dioxide output by 4,800 tons per year. It is estimated that accounting for all these changes would save operating Case 2. Biomass-fueled power plant combined with costs of USD 0.38 million. The project is a private-public sewage sludge 64 partnership between the City of Logan Water and Sewage KSV GmbH, at Dinkelsbühl, a special-purpose sewage sludge and Downer Group, with a USD 6.2 million grant from the company, was formed under the management of the public utility Australian Renewable Energy Agency awarded to Logan Stadtwerke Crailsheim GmbH. Stadtwerke Crailsheim GmbH City Council. The initiative is estimated to save ratepayers serves 27 municipalities and approximately 200,000 inhabitants. around USD 20 million in operating costs over the next 20 This special-purpose sewage sludge company disposes of years.62 regional sewage sludge along with biomass using the Pyrobuster® process. The plant receives about 18,000–22,000 tons of Case Studies: Pyrolysis mechanically dewatered sewage sludge annually. The sludge contains approximately 25% dry matter which is transformed into Eisenmann, Germany a granulate with a dry matter content of about 88% before it is Case 1. Thermal sewage sludge treatment in the pyrolyzed. The energy required for drying is generated from the Central Puster Valley 63 pyrolysis process which is capable of producing up to 72 million In 1998, ARA Tobl GmbH (presently ARA Pustertal AG) kilowatt hours (kWh) per annum. The plant is energy self-sufficient procured a sludge drying plant. Drying achieved a reduction and the remaining ash is used for further processing. TABLE 13. SÜLZLE KOPF SYNGAS PLANTS. Item Balingena Koblenzb Mannheinc Year established 2001 upgraded in 2011 2017 2010–2011 Operating capacity 2,000 tons/annum (dry 4,000 tons/annum (80–85% 5,000 tons/annum sludge 75–85%) dry sludge) (dry sludge 80%) Power generation 215 kW 425 kW 530 kW Heat generation 265 kW 535 kW 665 kW a Koph Syngas. https://kopf-syngas.de/en/syngas-sewage-plant-in-balingen/ (accessed on September 23, 2022) b Koph Syngas. https://kopf-syngas.de/en/syngas-sewage-plant-in-koblenz/ (accessed on September 23, 2022) c Koph Syngas. https://kopf-syngas.de/en/syngas-sewage-plant-in-mannheim/ (accessed on September 23, 2022) Source: Authors’ creation. 60 Australian Renewable Energy Agency. https://arena.gov.au/news/wastewater-treatment-plant-to-use-gasification-for-waste-disposal/ (accessed on September 23, 2022) 61 Australian Renewable Energy Agency. https://arena.gov.au/projects/logan-city-biosolids-gasification-project/ (accessed on September 23, 2022) 62 Downer Group. https://www.downergroup.com/downer-commences-100-million-upgrade-of-logan (accessed on September 23, 2022) 63 Eisenmann. https://cdn2.hubspot.net/hub/133998/file-1576391265-pdf/PDF/Pyrobustor_en.pdf (accessed on September 23, 2022) 64 Op.cit. 64 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE 5. HYBRID MODELS Introduction • Recovery of energy/electricity from sludge incineration This section describes business models where more than and phosphorus from the ash (model 11) one resource recovery pathway is included. It includes • Recovery of phosphorus and energy from anaerobic the following models: digestion (model 12A) • Recovery of biosolids, biomethane and electricity • Recovery of phosphorus, biochar and energy through from sludge digestion (model 10) pyrolysis (model 12B) BUSINESS MODEL 10: RECOVERY OF BIOSOLIDS, BIOMETHANE AND ELECTRICITY FROM SLUDGE DIGESTION Brief Recovering biosolids from digestate and biogas from anaerobic sludge digestion Location Urban and peri-urban areas Waste input type/stream Sewage sludge and other waste such as farm and food waste, agricultural and industrial waste can be integrated Value offer Recovered energy makes the plant self-sufficient and provides a revenue source; digestate is a Class A quality biosolid and can be used as organic fertilizer for land application; reduction in disposal costs; upgrading existing treatment systems to make the profitable Environmental risk mitigation Heavy metal concentrations in the digestate require monitoring Organization type and profit Public-private partnerships with a profit motive objective Major stakeholders Sludge producers, water boards, utility service agencies, private technology providers, construction companies, electricity transmission companies and other line ministries (e.g., agriculture and forestry) PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of recovery of biosolids and energy. • The business model uses traditional technology for harnessing energy and organic soil ameliorants thereby reducing dependence on fossil fuels. • The model scores high on environmental and social measures. • In recent installations, technological improvements such as thermal hydrolysis show that system efficiency can beincreased and scaled to achieve economies of scale. • Centralized systems with integrated waste management systems, including sludge from wastewater, food waste and agro-waste or clustered treatment for small and medium WWTPs in a district can enhance profitability. 65 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Known technology used and hence operation • Requirement for regional collaborations or and maintenance is easier. strong institutional partnerships for scaling up • Using thermal hydrolysis adds to the and achieving economies of scale. efficiency of the digester process. Opportunities Threats • Potential for co-feeding with food waste and • Quality of waste from other waste streams. a agro-waste. • Legislation favoring incineration and recovery • Possibilities for job creation across sectors in of soil nutrients may lead to a shift. case of integrated waste streams. • Clustered approach for small to medium wastewater treatment plants can lead to economies of scale. Business Model Description In a clustered regional operation, the digester and the electricity recovery plant can initially be in one of the This business model is suitable for regional sludge centers treatment plants and other plants can join in the recovery that connect multiple WWTPs, usually 3–4 with a capacity process. Wastewater treatment plants usually provide ranging from 100,000–500,000 m3/day, and run by private thickened sludge for advanced anaerobic digestion or public entities contracted by a municipality or water utility. followed by thermal hydrolysis. This model requires The digestion process is enhanced by integrating thermal economies of scale to be financially sustainable and hence hydrolysis. The business model can be implemented through setting up regional collaborations among treatment plants a private-public partnership model where the private entity is an important step. The sludge-to-energy process is can design, build, own and operate the digester plant along estimated to cost USD 52 million considering a 100 tons with energy recovery. The dewatered digestate could be dry solid/day plant (Rus et al. 2017).65 This includes pre- marketed as a Class A biosolid as it is pathogen free and treatment and thickening, thermal hydrolysis, combined can be used on agricultural or non-agricultural land (Canvas heat and power technology and electrical installations. 11). Apart from feeding electricity to the grid, another aspect The net present value after 20 years is approximately of the business could be the production of upgraded biogas USD 31 million with an internal rate of return of 13.6% for household and commercial establishments. The service and a payback of approximately seven years.66 Figure provider operating the digester plant can contract another 17 provides a schematic representation of the business provider for distribution to households. model. 65 Considering GBP 1 = USD 1.289 with inflationary factor of 1.21. The dollar had an average inflation rate of 3.86% per year between 2017 and the present, producing a cumulative price increase of 20.83%. 66 Similar conversion as above. 66 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Energy utilization within plant for dewatering $ Other wastestreams Savings Conbined Heat Cleaning and Thermal Electricity / Energy biogas (CHP) Electricity / Energy Biomethane Electricity / transmission company Energy Thermal hydrolysis WWTPs & $ $ Anaerobic digestion Feed-in-tariff Contractual Organic Digestate fertilizer DBO / DBOO agreements - Farmers contract fees/cubic $ meter Energy utilization within plant Special project vechicle (SPV) FIGURE 17. BUSINESS MODEL FOR RECOVERY OF BIOSOLIDS AND ENERGY (BIOMETHANE AND ELECTRICITY). Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Pre-treatment and • Energy is recovered • Direct relationship • Sludge producers, public water utilities thickening of sludge making the operation with the municipality/ water utility services • Biogas, energy at WWTP more energy efficient WWTP operator and municipalities and electricity • Transportation of • Savings from disposal • Energy, electricity transmission sludge from other costs incurred from transmission companies WWTPs in case of lower sludge volume companies • Local contractors regional plants • Potential of using the • Farmers • Regulating bodies • Recovery of biogas biosolids from for energy and digesters as an electricity agricultural soil • Use of electricity conditioner or within the plant for upgrade it as a dewatering and fertilizer for drying sludge or subsequent use feeding it to the grid Resources Channels • Establishing and • Contractual commissioning the agreements for plant establishing and • Pre-treatment and operating plants thickening sludge • Connection to • Use of thermal energy grids hydrolysis Cost structure Revenue streams • Capital costs: mechanical equipment, combined heat • Revenue from electricity, energy (heat) and biogas sales and power technology, thermo hydrolysis and pyrolysis • Tipping fees and drying units, biogas scrubbers • Cost savings from disposal fees • Salary, rent, and interest, insurance • Sale of biosolids and organic fertilizers • Operation and maintenance of thermo hydrolysis, pyrolysis and digester units • Fuel costs, chemical costs and utility charges Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Near or close to zero disposal required. sludge and other wastes. • Job creation of jobs across sectors. • Fewer health issues from reduced sludge to waterbodies and groundwater. CANVAS 11: RECOVERY OF BIOSOLIDS AND ENERGY 67 RESOURCE RECOVERY & REUSE SERIES 23 Case Studies soil conditioner on forestry land in the surrounding areas of Beijing. Based on this application, advanced anaerobic Gaoantun Sludge Treatment Centre, Beijing, China digestion using thermal hydrolysis pre-treatment has gained Gaoantun Sludge Treatment Center Is the largest in China strong interest both in academic institutes and in several and treats sewage sludge from four WWTPs, Gaoantun industrial suppliers within China. We therefore expect to see (200,000 m³/d), Qinghe II (500,000 m³/d), Jiuxianqiao a considerable increase in the use of advanced digestion (200,000 m³/d), and Beixiaohe (100,000 m³/d).67 This of sludge and food waste in China in the next five to ten amounts to the daily treatment of 4.5 million population years.70 equivalent with a capacity to treat 146,000 tons of sewage sludge dry matter per year. In 2014, Beijing Drainage Group Billund Biorefinery, Denmark decided to upgrade and expand existing treatment plants Billund Biorefinery combines new technologies to process as water reclamation plants and recover resources from raw materials comprised of wastewater, organic household sludge.68 This entailed treatment using anaerobic digestion waste and organic waste from agriculture and industries. and thermal hydrolysis to enhance digestion efficacy The outputs are purified water, energy (in the form of heat and convert the organic matter to recovery biogas and and electricity) and organic fertilizer for agricultural use. The biosolids to meet Class A quality standards. A private-public project was initiated in 2015 and started operation in 2017 partnership model was initiated between Beijing Drainage as a public-private partnership between the Danish Utility Group and CambiTM to implement the project with a long- company Billund Vand A/S and Krüger A/S, a Veolia Water term design, build, and operate contract. Technologies subsidiary with a payback of only nine years.71 The sludge treatment line was equipped with pre-treatment The plant size of 70,000 population equivalent is a fine (thickening and centrifuge dewatering), sludge silos, the example of how urban waste streams can be turned into Cambi thermal hydrolysis pre-treatment process which profitable resources with environmental and health benefits. operates at 39° C, anaerobic digesters, a chamber filter The total budget for upgrading the project was EUR 9 million press for final dewatering and a filtrate treatment system with a grant of EUR 2 million from the Danish Eco-innovation before it is sent back to the head-works of the wastewater Program and the Vandsektorens Teknologiudviklingsfond.72 treatment plant nearby. The total digester capacity of the Upgrading the existing treatment system resulted in: plant amounts to 88,000 m³ per day. • An increase in energy production by more than 160% After installation of CambiTM thermo hydrolysis and pyrolysis from approximately 8.5 million kWh to about 22 million units in 2017, biogas production reached 350 m³ per ton of kWh per year. The energy is used within the plant and dry matter. The final sewage sludge cake after dewatering the rest is converted to electricity and sold to the grid. has a dry matter content of 40% and is a Class A biosolid • Expenses for sludge treatment were reduced by 30–40%. (pathogen and odor free.)69 The sludge cake is transported • Plant capacity to receive approximately 40,000 tons of offsite by the treatment plant operator and is used as a waste from the food industry. 67 Cambi. https://www.cambi.com/resources/references/asia/china/beijing-gaoantun/#:~:text=Gaoantun%20Sludge%20 Center&text=Gaoantun%20 treats%20400%20tDS%20of,put%20into%20operation%20in%202017 (accessed on September 25, 2022) 68 Aquaenviro. https://www.aquaenviro.co.uk/proceedings/advanced-digestion-of-sludge-enhances-shift-of-biosolids-management-strategy-in- beijing/liao-et-al_-advanced-digestion-enhances-shift-of-biosolids-management-in-beijing/ (accessed on September 25, 2022) 69 Aquaenviro. https://www.aquaenviro.co.uk/proceedings/advanced-digestion-of-sludge-enhances-shift-of-biosolids-management-strategy-in- beijing/liao-et-al_-advanced-digestion-enhances-shift-of-biosolids-management-in-beijing/ (accessed on September 25, 2022) 70 Aquaenviro. https://www.aquaenviro.co.uk/proceedings/advanced-digestion-of-sludge-enhances-shift-of-biosolids-management-strategy-in- beijing/liao-et-al_-advanced-digestion-enhances-shift-of-biosolids-management-in-beijing/ (accessed on September 25, 2022) 71 Billund Biorefinery. https://www.billundbiorefinery.com/ (accessed on September 25, 2022) 72 Veolia. https://www.veoliawatertechnologies.com/sites/g/files/dvc2476/files/document/2019/06/170324_VWT_NA_WAVE_Sludge_web%20 %281%29.pdf (accessed on September 25, 2022) 68 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE BUSINESS MODEL 11: RECOVERY OF ENERGY/ELECTRICITY FROM SLUDGE INCINERATION AND PHOSPHORUS FROM THE ASH Brief Recovering electricity through sludge incineration and phosphorus from sewage sludge ash Location Peri-urban areas close to WWTPs where incinerators and phosphorus recovery can be integrated Waste input type/stream Dewatered and dried sewage sludge Value offer Recovering phosphorus which can be used as a green fertilizer; electricity generation contributes to plant energy self-sufficiency; savings in disposal costs Environmental risk mitigation Processes are needed to separate phosphorus from heavy metals; pollution control mechanisms are needed to limit air pollution Organization type and profit Public utility services operating for social motives; possibility of private entities objective as technology providers and marketing fertilizers Major stakeholders WWTP operators, incinerator operators, phosphorus recovery unit operators, fertilizer marketing agencies PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of phosphate and energy recovery. • The business model scores high on innovation by using advanced technology. The proportion of phosphorus recovery from sewage sludge ash is substantial which makes the operation of more energy self-sufficient. • Potential for cost recovery and positive environmental impacts with reduced disposal in landfills. 69 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Modular units are more easily installed and • Horizontal and vertical links among and scaled. between partners across the value chain are • Cost recovery through different revenue required, which implies agreements and streams. strong institutional management. Opportunities Threats • More technology providers as more research • Public perception risks and strong competition and from development is undertaken. phosphate fertilizers. • Favorable regulations for using sludge ash • Lacking regulations to promote recovered for phosphorus recovery. phosphorus fertilizer products. Business Model Description Wet chemical approaches (Leachphos®, TetraPhos®, EasyMiningTM) leach phosphate from the ash through acidic This business model extends the mono-incineration process dissolution. The wet process retains impurities of iron and through which energy is recovered. The incineration of aluminum and hence sometimes the thermochemical municipal sewage sludge concentrates nutrients in sludge process is preferred. The thermo-chemical process allows for ash, which contains high concentrations of phosphorus. the removal of heavy metals and increases the bioavailability Ash generated from mono-incineration is more suitable of the phosphate. However, in the wet chemical process, for phosphorus recovery than ash generated from co- there is a possibility to recover concentrated phosphoric incineration. Sludge ash is typically sent to a landfill due to acid which adds to the revenue stream. the presence of heavy metals, which make it unsuitable for agriculture. Recovering phosphorus from sludge ash provides This model is appropriate for WWTPs where regulations opportunities for the beneficial use of sludge streams. have restricted treated sewage sludge disposal in landfills or incineration facilities and municipalities are willing to upgrade This model is therefore driven by a desire to reduce their systems to reduce the disposal of ash in landfills. Figure disposal fees for incinerated ash. Mandatory regulations 18 provides a schematic illustration of the business model to recycle and reuse phosphorus are another prominent for recovering energy and phosphorus from sewage sludge. driver. Typically, private operators are contracted by WWTP Scaling up a project requires partnerships among WWTP operators to construct and operate incinerators. Phosphorus operators, municipalities, technology providers, and private recovery is a separate business provided by companies with agencies with experience in agronomic advisory services phosphorus recovery technologies (Canvas 12). and fertilizer marketing as well as local contractors and suppliers. Investment costs are high and to benefit from There are two technology streams to recover phosphate economies of scale, cooperation between municipalities for from incinerated ash, wet chemical and thermo chemical. sludge treatment is a necessity. 70 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Fertilizer traders and other networks Phosphorus Sludge extraction Phosphate Farmers ash $ Dewatered sludge Phosphorus WWTPs Mono-incineration fertilizer Private Technolgy entity provider Operaion Operaion Public entry Electricity / Electricity / $ Energy Energy transmission Energy Utilization within plant for Feed-in-tariff company dewatering FIGURE 18. BUSINESS MODEL FOR RECOVERING ENERGY AND PHOSPHORUS. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Pre-treatment and • Energy is recovered • Direct contact with • Water utility services, public water utilities thickening sludge through the process municipalities, public municipalities • Incinerator plant at WWTP making it energy utility companies, / • Energy, electricity operators • Transportation of efficient (especially WWTP operators transmission • Energy and sludge from other for sludge drying) • Direct networking with companies electricity WWTPs in case • Phosphorus recovery the fertilizer trading • Fertilizer traders transmission of regional plants for making high-value companies (networks and companies • Drying sludge fertilizer products • Direct links with associations) • Local contractors • Incineration of • Savings from energy distribution • Regulating bodies sludge disposal costs companies • Companies • Phosphorus dealing with recovery fertilizers sales Resources Channels • Technology for • Contractual incineration and agreements phosphorus establishing and recovery operating plants • Permits and licenses • Connection to • Capacity for energy grids the sale of phosphorus- Cost structure Revenue streams • Capital costs including phosphorus recovery units • Revenue from electricity and energy sales • Salary, rent, interest • Sale of green fertilizer • Operational costs including phosphorus recovery units • Tipping fees • Transaction costs to penetrate fertilizer value chains with small phosphorus volumes • Research and development, validation, licensing and certification Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Near or close to zero disposal required. sludge and other waste streams. • Energy recovery. • Uncertain acceptance of phosphorus fertilizer recovered. • Fewer health issues from reduced exposure of sludge to waterbodies and groundwater. CANVAS 12: RECOVERY OF ENERGY AND PHOSPHORUS BY INCINERATION 71 RESOURCE RECOVERY & REUSE SERIES 23 Case Studies for agriculture.74 To ensure regulatory compliance, thermal treatment and phosphorus recovery were initiated by ZWK. ZVK – Zweckverband Klärwerk Steinhäule, Germany ZWK is a corporation under public law and a special purpose This sewage sludge is dewatered enough to be thermally association for sewage treatment in Steinhäule. The recycled in a fluidized bed furnace and achieves dry solid association comprises 31 cities, municipalities, municipal content of 25–30%. The flue gas is cooled in a heat recovery companies and special purpose associations with a primary boiler and the steam created in the process is used to aim to recycle sewage sludge in Steinhäule.73 The Steinhäule generate electricity via steam turbines. The plant generates wastewater treatment plant is designed to treat wastewater 6.1 million kWh/annum, which is fed to the grid and used in from 440,000 inhabitants in the region. The plant generates the plant for dewatering sludge. Thermal treatment destroys 1,000,000 m3 of sewage sludge annually with 10,000 contaminants in the sludge and about 99% of the phosphorus tons of dry matter. Another 10,000 tons of sewage sludge remains in the ash. Phosphorus recovery is estimated to be accumulates in the treatment plants of the other association 580 kilograms daily (about 650 tons per year). The phosphate members. The incineration plant was initiated following the ash is enriched with nutrients and other additives. Since 2014, updated Sewage Sludge Ordinance (AbfKlärV) and Fertilizer SePura GmbH markets the ash as a phosphate fertilizer for Ordinance (DüMV) in 2017. Until 2012, the plant was limited use in agriculture.75 The residues from the fabric filter are used to treating wastewater and using the biosolids produced as fill materials in mining operations. 73 Zweckverband Klärwerk Steinhäule. https://www.zvk-s.de/en/administrative-union-zvk/?lang=en (accessed on September 25, 2022) 74 Zweckverband Klärwerk Steinhäule. https://www.zvk-s.de/en/treatment-plant/sludge-treatment-and-recycling/?lang=en (accessed on September 25, 2022) 75 IWAM Interactive Water Management. http://www.iwama.eu/sites/iwama/files/12_recycling_sewage_sludge_ash_for_agricultural_application_ in_germany_plank.pdf (accessed on September 25, 2022) 72 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE BUSINESS MODEL 12: RECOVERY OF PHOSPHORUS AND ENERGY FROM SEWAGE SLUDGE Under model 12 we distinguish between the recovery of phosphorus and biomethane from anerobic digestion (Model A) and through pyrolysis (Model B). Model A: Recovery of phosphorus and energy from anaerobic digestion Brief Recovering energy and phosphorus from anaerobic digestion in large-scale WWTPs Location Peri-urban areas, usually through regional energy and nutrient plants Waste input type/stream Sewage sludge Value offer Energy recovery makes the plant self-sufficient and generates electricity generated households and commercial establishments Recovered phosphorus sold through commercial arrangements Cost savings from reduced maintenance Environmental risk mitigation Extracted struvite is without particular environmental risks Organization type and profit Public-private partnership seeking financial viability of operations objective Major stakeholders Water and wastewater utility services, private operators (designing and operating plant, technology providers, subcontractors, suppliers), electricity transmission companies, local companies selling fertilizers PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL 1.0 INNOVATION IMPACT 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of energy recovery (biomethane) and phosphorus. • The business model is suitable for most WWTP operators using anaerobic digestion, which is widely used. • The scalability of the business depends on the willingness of different WWTPs to cooperate for establishing a centralized regional facility. • The phosphorus recovery unit is modular and uses advanced technology. • Digester efficiency can be increased through advanced technologies such as thermal hydrolysis. • The business provides risk sharing for revenue generation and has a strong positive impact on the environment and society. 73 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Strengths Weaknesses • Known technology used to make operation • The business model needs to achieve and maintenance easier. economies of scale and is therefore suitable • Using thermal hydrolysis increases digester for large WWTPs and regional collaborations. efficiency. • Strong institutional links are required for efficient operation. Opportunities Threats • More technology providers as more research • Public perception risks and strong competition and from development is undertaken. phosphate fertilizers. • Favorable regulations for using sludge ash • Lacking regulations to promote recovered for phosphorus recovery. phosphorus fertilizer products. Business Model Description diagram of the business model for recovering biomethane and phosphorus from sewage sludge. These business models are mostly public-private partnerships between water utility services and technology This business model is suitable for WWTPs with treatment providers. Sometimes, the private entity is a partnership facilities serving 200,000–300,000 population equivalent between a technology provider and a design, build, and and willing to upgrade the plant for nutrient recovery and operate organization. The private-public partnership make it more energy efficient. Sometimes, regional hubs for contracts are mainly for design, build, and operate for 10 sludge management are effective ways for promoting such to 20 years. These business models are often initiated businesses. by stringent environmental regulatory frameworks that prohibit direct disposal and application of sewage sludge The acceptance within the fertilizer industry for blending in controlled landfills and agricultural use and mandates their phosphorus sources with struvite might still be low, resource recovery. These models are also possible where with reasons related to low quantities and limited solubility water utility agencies consider upgrading for energy than alternative phosphate sources (Drechsel et al. 2018). recovery and plan to reduce the cost of chemicals, labor and Moreover, in many countries legislation is lacking, unclear, maintenance from struvite deposition in pipes and digesters or prohibits the reuse of resources recovered from waste. through phosphorus removal and recovery with a potential reuse market. More progressive legislation is needed that allows penetrating conventional phosphorus markets by mandating a certain Electricity generated through anaerobic digestion is mix-ratio of recovered phosphorus. Additionally, certification improved through thermal hydrolysis, which can make the of plants recovering phosphorus through periodic monitoring plant operation energy self-sufficient and generates revenue should be made a necessary condition for reuse and hence by feeding additional electricity to the grid (Canvas 13). this might be one way of reducing barriers. The capital Phosphorus recovery offers another source of revenue for the expenditure of a phosphorus recovery plant (e.g., 50 tons/ water utility service. The long-term contract offers revenue day) is USD 7 million. The investment costs can be recouped sharing from fertilizer sales for the technology provider in five (3-10) years through savings from reduced cost of the who is also the off-taker. The water utility service agency unwanted crystallization of struvite in pipes, complemented need not participate in downstream product sales, which by additional revenues where the recovered phosphorus become the responsibility of the technology provider. The can be sold as fertilizer. associated marketing and off-take risks are transferred to the technology provider and therefore this business model offers The net present value of a 50-ton a day plant over 20 an opportunity for spreading risk and a more sustainable years is about USD 16 million, of which net savings on the operation. The payback period of these businesses varies operations provide about 80% of the net present value and between three to ten years. Figure 19 provides a schematic the remaining from fertilizer revenue. 74 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Fertilizer traders and other networks Phosphorus stripping Farmers Struvite Dewatered sludge Thermal hydrolysis WWTPs $ & Phosphorus Anaerobic digestion fertilizer $ Biomethane Cleaning Cobin DBO/DBOO Contractual ed Heat Electricity / Electricity / Energy agreements biogas and Thermal contract Energy (CHP) transmission company $ Feed-in-tariff $ Special project vehicle (SPV) Savings DBO/DBOO Energy utilization within plant contract for dewatering FIGURE 19: BUSINESS MODEL FOR ENERGY AND PHOSPHORUS RECOVERY THROUGH ANAEROBIC DIGESTION. Source: Author’s creation. Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Pre-treatment and • Energy is recovered • Direct relations • Water utility services public water utilities thickening sludge making the operation between sludge and the municipalities • Biogas, energy and at WWTP more energy efficient producers and • Energy and electricity electricity • Transportation of • Phosphorus technology providers transmission transmission sludge from other recovery companies companies WWTPs in case of • Savings from • Farmers • Local contractors regional plants disposal costs • Regulating bodies • Recovery of biogas incurred from lower for energy and sludge volume electricity • Potential to use • Use of electricity biosolids from within the plant for digesters as an drying sludge or agricultural soil feeding to the grid conditioner or upgrade it as a fertilizer Resources Channels • Establishing and • Contractual commissioning agreements for plants establishing and • Pre-treatment and operating plants thickening sludge • Connection to • Use of thermal energy grids hydrolysis Cost structure Revenue streams • Capital costs: mechanical equipment, combined heat • Revenue from electricity, energy (heat) and biogas sales and power technology, thermo hydrolysis and pyrolysis • Sale of fertilizers and drying units, biogas scrubbers • Tipping fees • Salary, rent, and interest • Savings from reduced pipe maintenance • Operation and maintenance of thermo hydrolysis and pyrolysis and digester units • Fuel costs, chemical costs and utility charges Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Near or close to zero disposal required sludge and other waste streams • Job creation • Reduction in health issues from reduced sludge to waterbodies and groundwater CANVAS 13: RECOVERY OF ENERGY AND PHOSPHORUS FROM SEWAGE SLUDGE 75 RESOURCE RECOVERY & REUSE SERIES 23 Case Studies to participate in the downstream product sales as all the associated marketing and off-take risks are transferred to Amersfoort, Netherlands the technology provider. The combined application of energy Amersfoort WWTP in the Netherlands is owned and operated and nutrient recovery with a guaranteed long-term off-take by the Dutch Water Board Vallei en Veluwe. In 2013, the agreement results in a payback period of just under seven board awarded a project to Eliquo Water and Energy (Eliquo years. Marketing the fertilizer is easier since this fertilizer Group) to upgrade the existing wastewater and sludge is European Certified in the same category as the highest processing facilities into a regional hub for recovering quality fertilizers and marketed exclusively by Ostara. energy and nutrients using innovative commercially tested technologies. The sludge produced from the treatment Chicago, USA of wastewater from communities in Amersfoort, Soest, The Chicago-Stickney WWTP is one of the largest wastewater Nijkerk and Woudenberg (315,000 population equivalent) is treatment plants in the world and is designed to treat up approximately 50,000 m3/day. All the sludge is digested at to 550,000 m³/day. The Metropolitan Water Reclamation the Amersfoort treatment plant. Digestion is enhanced with District of Greater Chicago (MWRDGC 2019) wanted a thermal pressure hydrolysis using LYSOTHERM® to increase closed-loop and cost-effective phosphorus management biogas yield and produce green electricity. The entire WWTP strategy to meet the challenge of more stringent regulatory and sludge facilities are energy self-sufficient. A surplus of limits for effluent discharge in addition to a wastewater approximately 2,000,000 kWh is supplied to the national system that was experiencing an unwanted accumulation of power grid and this is sufficient to provide 600 households minerals in struvite form. In 2013, MWRD selected Black & with green electricity annually.76 Veatch and Ostara Nutrient recovery technologies to design and build a nutrient recovery system at its Stickney Water Amersfoort WWTP uses a biological phosphorus removal Reclamation Plant in Cicero, Illinois.79 The objective was to process by Ostara, where phosphorus is retained in activated capture the phosphorus before it creates problems within sludge and recovered thereby producing a high-quality the pipe system which would be costly to address, while commercial fertilizer called Crystal Green®. Phosphorus helping to exceed the environmental regulation target of 1 is extracted from the activated sludge before anaerobic mg/liter total phosphorus in the treated effluent.80 digestion by applying a patented waste-activated sludge stripping process (WASSTRIP®). Phosphorus-rich filtrate The Ostara process for nutrient recovery is based on a from the WASSTRIP® is treated with the rejected water from closed-loop process whereby phosphorus and nitrogen the sludge dewatering in a Pearl® reactor, producing Crystal in wastewater are recovered to form a commercial Green® pellets. The pellets are dried, classified and bagged fertilizer marketed by Ostara. The Stickney treatment for transport. The reactor can produce two tons of Crystal plant has installed three Pearl® reactors with an installed Green® per day.77 The combination of the WASSTRIP® and production capacity of up to 9,000 tons of pelletized Pearl® processes reduces the amount of chemical sludge phosphate fertilizer per year (Ostara 2023). As the plant formed when phosphorus is removed from wastewater by operator, the district pays Ostara as it saves on every ton chemical dosing via conventional removal methods.78 It also of phosphorus removed by Ostara’s technology before it improves dewatering of digested sludge. The uncontrolled can damage the system. On the other hand, Ostara buys deposition of struvite is avoided, saving the water board back the recovered struvite produced by plants utilizing significant ongoing costs associated with the maintenance its technology (municipal plant operators are usually not in and replacement of pipes and other mechanical equipment. the fertilizer business), providing in this way a guaranteed revenue stream for the treatment plant. Depending Water board revenue is generated through a long-term on regulations for end-of-waste products and market agreement for the off-take of the fertilizer produced by acceptance Ostara can then earn revenue for every ton the technology provider. The water board does not have of fertilizer sold.81 76 Eliquo Technologies. https://www.eliquo-tech.com/en/references-details.html?articles=omzet-amersfoort-4983 (accessed on September 27, 2022) 77 Eliquo Technologies. https://www.eliquo-tech.com/en/references-details.html?articles=omzet-amersfoort-4983 (accessed on September 27, 2022) 78 Ostara. https://ostara.com/nutrient-recovery/nutrient-recovery-solutions/ (accessed on September 27, 2022) 79 Koch Lefler Britton. https://www.mi-wea.org/docs/Koch_Lefler_Britton-Phosphorus_Recovery.pdf (accessed on September 27, 2022) 80 Ostara. http://ostara.com/wp-content/uploads/2016/05/Ostara_MWRD_CaseStudy_web.pdf (accessed on September 17, 2022) 81 Ostara. http://ostara.com/wp-content/uploads/2017/03/Ostara_NRS_BROCHURE_170328.pdf (accessed on September 17, 2022) 76 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Model B: Recovery of phosphorus, biochar and energy through prolysis Brief Recovery of phosphorus, biochar, and energy from sewage sludge Location Peri-urban areas Waste input type/stream Sewage sludge; other organic wastes; pyrolysis can handle both digested and undigested sludge Value offer Energy sufficiency; reduction in disposal costs; biochar production as a soil conditioner Environmental risk mitigation Pyrolysis efficiently degrades organic toxins but enhances heavy metals in the biochar. However, these are largely immobilized resulting in a much lower risk than for sewage sludge Organization type and profit Mainly private entities and for-profits objective Major stakeholders Water utility services, municipalities and urban local bodies, regulatory organizations, especially those related to the use of biochar as a soil conditioner or fertilizer PROFITABILITY / COST RECOVERY 3.0 2.0 ENVIRONMENTAL IMPACT 1.0 INNOVATION 0.0 SOCIAL IMPACT SCALABILITY & REPLICABILITY Business performance of energy and phosphorus recovery or biochar though pyrolysis. • The business model scores high on innovation by using advanced technology to recover phosphorus. • Phosphorus recovery through pyrolysis can be adapted and integrated by WWTPs to upgrade their systems. • The business model provides opportunities for cost recovery and reduces the risk of the WWTP as there are off-take guarantees. • The business model provides positive environmental impacts and the use of the generated biochar has been approved for agriculture so far in three EU countries (Sweden, the Czech Republic, and Denmark) which is an important signal for other countries. 77 RESOURCE RECOVERY & REUSE SERIES 23 Strengths, weaknesses, opportunities, and threats (SWOT) Helpful Harmful Strengths Weaknesses • Upgrading a WWTP is easier since the units • High investment costs. are modular and can be scaled to meet licenses • Obtaining and permits can be difficult demand. and expensive which can delay revenue • Technology providers share the risk of revenue generation. Opportunities Threats • Little competition in niche markets. • Acceptance from traders and farmers is low as • Regulations by local governments in certain the product is relatively new. areas favor the marketing and use of biochar. Business Model Description and public subsidies that allow for financing additional investments for improved sewage sludge treatment and These business models are decentralized and blend two resource recovery. technologies for recovering energy and phosphate from sewage sludge. The technologies are often complimentary The pyrolysis process produces syngas, bio-oil and and technology providers usually form partnerships to biochar. This model is oriented toward making the business recover energy and soil nutrients. Although the technologies energy self-sufficient. The energy generated through are advanced, these businesses have completed pilot pyrolysis is used within the plant for dewatering sludge. stages in most cases and are running at full scale. However, Figure 20 shows a schematic diagram of the business the enterprises might be still small scale and decentralized, model dependent on pyrolysis for energy and biochar primarily because marketing biochar requires regulatory production. The plethora of end-uses for sewage sludge approval before being scaled up. biochar make it an exciting opportunity, especially with the bonus of carbon sequestration (Canvas 14). Nevertheless, WWTPs or water utility providers form joint ventures, supporting regulations are needed to fully exploit its value which might be private-public partnerships for design, and consolidate off-take markets. Until then biochar also build, and operate arrangements for 10 to 20 years. provides a desperately needed alternate avenue for a safe Sometimes these begin as pilot projects and gradually and compact bio-solid disposal (GWI 2023a). grow to full-scale operations complying with regulatory norms. The business model is driven by environmental These business models are suitable for WWTPs serving regulatory frameworks that prohibit direct disposal and 200,000 to 300,000 population equivalent or more with application of sewage sludge in controlled landfills and basic wastewater and sludge treatment facilities and without for agricultural use and mandate resource recovery. sludge storage capacities. These treatment plants incur Since these are emerging technologies, setting up and higher operating and maintenance costs for transportation commissioning a plant requires significant investment. and sludge disposal and sludge treatment and recovering WWTPs need to ensure there are adequate water tariffs fertilizers provides additional revenue. Energy use within plant for $ dewatering Savings Electricity / Dewatered Energy sludge Energy WWTPs $ Syngas transmission Disposal fees company per cubic meter Pyrolysis $ Feed-in-tariff Fertilizer traders Biochar Farmers $ FIGURE 20. BUSINESS MODEL FOR RECOVERING ENERGY AND PHOSPHORUS (AND OTHER NUTRIENTS VIA BIOCHAR). Source: Author’s creation. 78 External origin Internal origin SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE Partners Activities Value propositions Customer Customer relationships segments • Urban local bodies, • Pre-treatment and • Energy recovered • Direct contact with • Water utility services public water utilities, thickening sludge making plants more municipalities and and municipalities WWTP operators at WWTP energy efficient WWTP operator • Energy companies • Biogas and • Transportation of • Savings from • Direct networking • Fertilizer traders and electricity sludge from other disposal costs with fertilizer traders their networks of transmission WWTPs in case of • Recovering potentially wholesalers and companies regional plants high-value fertilizers retailers • Local contractors • Capturing and biochar • Regulating bodies phosphorus or • Cost recovery in • Fertilizer traders biochar terms of maintenance • Using electricity of the WWTP within the plant for drying sludge or feeding to the grid • Marketing and sales • Obtaining permits and certifications for fertilizer products Resources Channels • Establishing and • Contractual commissioning agreements plants for establishing and • Pre-treatment and operating plants thickening sludge • Connections to the • Use of thermal power grids hydrolysis Cost structure Revenue streams • Capital costs: modular phosphorus recovery units • Revenue from electricity, energy (heat), biogas and • Salary, rent, interest fertilizer sales • Struvite collection, storage and marketing costs • Tipping fees • Transaction costs related to penetrating fertilizer value • Cost savings from disposal fees chains with small phosphorus volumes • Carbon credits • Research and development, validation, licensing and certification Environmental and social costs Environmental and social benefits • Labor health risks might arise due to handling sewage • Near or close to zero sludge disposal required sludge and other waste streams • Fewer health issues from reduced sludge to • Uncertain acceptance of products by traders and waterbodies and groundwater farmers • Bioavailability of micro-nutrients for soil amendment using biochar CANVAS 14: RECOVERY OF PHOSPHORUS, BIOCHAR AND ENERGY THROUGH PYROLYSIS Case Studies technology for thermal energy (ELODRY®) while PYREG is the technology provider for recovering phosphorus Homburg and Linz, Germany via pyrolysis. Both have patented technologies that are The Eliquo Water Group and PYREG formed a complementary and support an autothermic process partnership for recovering energy and valuable fertilizer generating phosphorus of superior quality. A brief substrates (biochar) from sewage sludge in two WWTPs description of the two plants in operation is provided in in Homburg and Linz-Unkel. Eliquo provides the Table 14. 79 RESOURCE RECOVERY & REUSE SERIES 23 TABLE 14. OPERATION PLANTS OF ELIQUO AND PYREG IN GERMANY. Homburg wastewater treatment planta Linz-Unkel wastewater treatment plantb Client and EVS - Saarland Linz-Unkel Joint Waste Management design Waste Disposal Association Association capacity Capacity of 75,000 PE up to 60,000 m³/day of Capacity of 30,000 PE wastewater, creating around 1,400 t/a dry residue of MSS Contract EUR 1.5 million EUR 1.4 million value Project The PYREG® module reduces the volume of sewage PYREG® module used reduces the volume description sludge by 90% and converts it into a high-quality to around 40% of the original volume with fertilizer raw material with a high proportion simultaneous full conversion to a high-grade of plant-available phosphorus. fertilizer material. In this project, ELIQUO STULZ GmbH was the Same as with Homburg WWTP, Eliquo subcontractor to PYREG GmbH providing EloDry® STULZ GmbH has provided the EloDry® NT32 for low-temperature belt drying and was and operates the plant. responsible for implementing the treatment facility Process In general, thermal hydrolysis processes help to improve the anaerobic digestion of sewage sludge, flow which is required to sanitize the sludge, while increasing gas yield, reducing residual biosolids (and relate digestate management costs), and improving dewaterability. The high ammonium and phosphate release into the liquid phase (digestate) from anaerobic digestion can be valorized through pyrolysis resulting in (nutrient rich) biochar. The need for digestate valorization is important because the application potential of digested sewage sludge as such in agriculture is limited due to concern regarding the potential presence of organic contaminants, pathogens, microplastics, etc. which processes like (dry) pyrolysis or hydrothermal carbonization (wet pyrolysis) can eliminate at high temperatures. In the PYREG PX 750 process, for example, the sewage sludge is dried using an (energy self-sufficient) drying belt system which feeds the sludge into the PYREG reactor where it is carbonized within a few minutes at temperatures of 500°C to 700°C. Phosphorus recovery can reach over 90%. The generated biochar (phosphorus content of about 15%) can be monetized on carbon markets as a Negative Emissions Technology (NET).c ª Eliquo. https://www.eliquo-tech.com/en/references-details.html?articles=homburg (accessed on September 28, 2022 b Eliquo. https://www.eliquo-tech.com/en/references-details.html?articles=linz-unkel (accessed on September 28, 2022) c https://pyreg.com/ (accessed on June 6, 2023) Bioforcetech, California, USA necessary to reduce the moisture content and requires Based in California, Bioforcetech (BFT) partnered with 50% less energy than traditional processes. Heat from PYREG GmbH, Germany in 2016 to initiate a full-scale thermophilic bacteria cultivated within the biodryer installation to recover phosphorus and energy in a WWTP dries biosolids from 80% moisture content to 10–20% managed by Silicon Valley Clean Water).82, 83 In 2017, moisture content. The dried sludge complies with Class operations were initiated and in 2019 they received a US A biosolid standards. The second step is a phosphorus pyrolysis permit. series pyrolysis system that transforms biosolids and organic waste streams such as food waste and green The BFT system is comprised of a biodryer and a waste and converts them into biochar and renewable phosphorus series pyrolysis unit which can individually energy. The self-sustained and automated process handle both dry and wet material and produce biochar ensures a high-quality biochar output without the need from sewage sludge. The biodryer patented by BFT is for fossil fuels.84 82 Pyreg biochar (from sewage sludge) is registered as a fertilizer in Sweden (PYREGphos generated from Hammenhög wastewater treatment plant). Although sewage sludge biochar has received European Biochar Certification (EBC a voluntary standard), it is yet to be included in current EU Fertilizing Products Regulation STRUBIAS proposals. 83 Bioforcetech. https://www.bioforcetech.com/pyrolysis.html (accessed on September 28, 2022). 84 Bioforcetech. https://www.bioforcetech.com/biodryer.html (accessed on September 28, 2022) 80 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE 6. OVERVIEW OF BUSINESS MODEL ATTRIBUTES Table 14 shows the different requirements and attributes for and these countries are switching to alternatives or successfully implementing these business models. The table implementing innovative technologies. For example, indicates that investments and operating and maintenance mono-incineration, advanced digestion, co-incineration in costs required for nutrient and soil amendments recovery the cement industry and phosphorus recovery are among are low compared to energy recovery models. The the disposal routes local authorities are planning for or applicability of these models for emerging and developing have already implemented. countries depends on the country’s context (ADB 2012). Energy recovery models through sludge digestion and co- Local authorities in Germany are restricting the use of incineration are highly applicable. Land application is also sewage sludge in agriculture (Box 3) while supporting feasible using sludge digestate and composting. The ADB alternative sludge treatment through an increase in sludge study suggests that coal substitution, composting and storage facilities, improved dewatering, and scaling up gasification are feasible in China, provided the necessary anaerobic digestion and mono-incineration. The move from regulations and infrastructure are in place. Careful land application to incineration will entail a higher cost for consideration of these attributes is important when planning farmers to replace the sludge and the taxpayer (ca. Euro resource recovery and reuse pathways. Another key factor 7-8/household/year; see also Table 5) but not reduce the can be public perceptions. Despite numerous biochar emphasis on resource recovery. In contrary, the 2017 projects being operational globally, only a few use biosolids amendment of the Sewage Sludge Ordinance (AbfKlärV) as feedstock thus far – primarily due to regulatory barriers provides for the first-time comprehensive specifications and a negative public perception of the feedstock (GWI for phosphorus recovery from sewage sludge or sewage 2023a). sludge incineration ash, and set as target a phosphorus content reduction of at least 50 % (based on sewage sludge 6.1 Drivers for sewage sludge recovery and TS) or of at least 80 % from sewage sludge incineration ash reuse pathways in Europe and USA (Roskosch and Heidecke 2018). Figure 21 shows the 2032 phosphorus (P) recovery obligations and possible recovery While there are sludge management facilities in Europe, methods for wastewater treatment plants serving more the sector is still developing as numerous companies than 50,000 capita. According to this, sewage sludge must are developing improved solutions. Regulatory drivers, undergo phosphorus recovery if the phosphorus content in renewable energy incentives and government agendas the sewage sludge reaches or exceeds 2% of the total solids promoting improved technologies are supporting these matter (TS). Estimates show that, depending on regional innovations (GWI 2012). Landfill bans, restrictions on conditions, wastewater charges may increase through direct use and inappropriately treated sludge in agriculture mandatory phosphorus recovery by around Euro 3 to 11/ are landmark regulations forcing industries to look for person/year. Soil application will no longer be permitted for alternatives or face significant fees. Denmark, Germany, the plants of this size, but remain an option for smaller plants, Netherlands, the Scandinavian countries and Switzerland e.g., in more rural settings where co-incineration capacities have imposed restrictions on agricultural applications are lacking. 81 RESOURCE RECOVERY & REUSE SERIES 23 82 TABLE 15. REQUIREMENTS AND ATTRIBUTES FOR SUCCESSFULLY IMPLEMENTING BUSINESS MODELS. Source: Author’s creation SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE BOX 3: SEWAGE SLUDGE APPLICATION ON SOILS ACCORDING TO THE GERMAN SEWAGE SLUDGE ORDINANCE The amount of sewage sludge that may be used in Germany in agriculture for fertilization purposes is limited to prevent the transmission of pathogens (like salmonellae) and chemical contaminants. Thus, according to the 2017 amended Sewage Sludge Ordinance (AbfKlärV), sludge, sewage sludge mixtures or sewage sludge compost are only allowed to be applied on or introduced into soils if certain heavy metal and organic contaminants threshold values are not exceeded. According to the Sewage Sludge Ordinance, up to 5t of sewage sludge dry matter per hectare may be applied within three years, or 10t once. In principle, only sewage sludge originating from municipal wastewater treatment plants may be used, not industrial or smaller plants if the type of sludge differs. The application of sewage sludge is generally prohibited in organic farming, in forests, gardens, on grassland and arable land, in fruit and vegetable cultivation as well as in water conservation areas and nature reserves, but can be used e.g., for maize grown for biogas production. Rules and quantities can differ slightly depending on the frequency of application as well as for sewage sludge mixtures and sewage sludge composts. Source: http://www.bgbl.de/xaver/bgbl/start.xav?startbk=Bundesanzeiger_BGBl&jumpTo=bgbl117s3465.pdf In the North American sludge management market, the to open up. Although the EU’s Fertilizer Regulation main drivers are costs, regulations and public perceptions update (implemented in July 2022) excluded sewage associated with sludge management. The price of sludge sludge as an acceptable biochar feedstock, various EU disposal in landfills is high and therefore municipalities are member states such as the Czech Republic, Denmark looking for technologies that can reduce the volume of and Sweden have recently taken matters into their own sludge, increase biogas production and reuse energy for hands, each introducing regulation which allows sewage sludge drying. Regulations are continuously influencing sludge derived biochar to enter as fertilizer their markets treatment and disposal routes. For example, regulations (GWI 2023a). related to sludge incineration might have a marked effect on sludge movement. Similarly, 50% of the sludge reuse in Up until recently the drivers for phosphorus or ammonium the US is for land applications, which is possible due to both recovery have been maintenance costs, pollution control stringent regulations that local authorities monitor and public and regulatory compliance. The potential for contributing opinion on abiding by these regulations. to economics, greenhouse gas mitigation, carbon and nutrient neutrality are now additional incentives making Although there are many beneficial uses for biochar, ammonia recovery for reuse more economically attractive, for the European market the unfavorable regulatory especially as the current process of generating ammonia, landscape has historically been a significant constraint. the Haber-Bosch process, is wholly dependent on a Changes to the regulatory climate could help the market fossil fuel input (GWI 2023a). Sewage sludge from wastewater treatment < 2% P (> 50,000 PE) Thermal < 2% P < 2% P Ash disposal > 2% P treatment P-recovery from > 2% P Long-term ash process water landfilling sludge water sewage sludge > 2% P Thermal Sewage sludge > 2% P treatment > 2% P P-recovery from ash or ash recycling FIGURE 21: GERMAN SEWAGE SLUDGE TREATMENT TARGETS FOR 2032 DEPENDING ON PHOSPHORUS CONTENT Source: AbfKlärV (Roskosch and Heidecke 2018) 83 RESOURCE RECOVERY & REUSE SERIES 23 6.2 Requirements for adaptation to and in the based on which RRR operations can be Global South proposed. The cases analyzed in this study are from existing businesses • Define an institutional framework and operating in Europe and North America and some in management strategies by establishing the Global South. The main drivers in Europe and North organizations. Along with policies and regulations, America are regulatory frameworks, public opinion and suitable organizations to manage projects are of environmental risk awareness, technological innovations for utmost importance. For example, public sector cost reductions, and the need to increase the efficiency of agencies that took the lead in managing projects resource recovery. In the Global South, lower awareness include the Public Utilities Board (Singapore), about technological options and business models, and Mekorot Water Company (Israel), South Australian limited willingness to regulate the sector (positive and Water (Australia), eThekwini Water Services (South negative incentives) are often cited reasons for limited Africa), Water Development Department (Cyprus), progress and business development. City of Stockholm and Stockholm Vatten (Sweden), Orange County Water and Sanitation District Business models related to recovering soil nutrients and (California), and CONAGUA (Mexico). organic fertilizers require stringent regulations and positive public perceptions before there is wider acceptance • Mechanisms to enhance public perception. and use of recovered products for soil amendment. The Government agencies, NGOs and community- transferability of phosphorus recovery or thermal treatment based organizations have a major role to play in of sewage sludge for producing pellets requires access improving public perceptions of wastewater systems. to technology. Access to technology is a key requirement International experience shows that including once public awareness and basic infrastructure can be politicians and public figures, targeted interventions facilitated before it will be attractive to technology providers. through subsidies, mass media campaigns, and Emerging economies in the Global South have started positive messages from successful projects help win investing in wastewater management infrastructure for public confidence and ensure acceptance. treatment, for example, in China, India and Latin American countries. However, the basic infrastructure for wastewater Although countries in the Global South are working treatment is still lacking in big cities which is quite essential toward renewable energy, access to technology and for establishing businesses. capacity to manage it, can be a determining factor in business implementation. Similar to the situation with The critical step for emerging economies is to develop a nutrient recovery, infrastructure is a necessary condition wastewater management strategy and link it to a circular for upgrading wastewater treatment plants with the economy framework. Treatment of wastewater and reuse of necessary energy recovery technologies. For example, the reclaimed water, followed by sewage sludge treatment opening waste-to-energy plants would allow for co- and management, should be integrated into the strategy. To incineration, and regulations for the use of sewage sludge drive wastewater management, economies need to plan for in cement plants would allow for the transferability of the following: business models. • Supporting policies and regulations. Policies and We identified three important potential drivers/obstacles regulations are critical to positively (or via punitive fees) toward energy recovery and recovering soil amendments: incentivize alternative sludge management options and regulations, public awareness, and access to technology. favor establishing utilities for wastewater management These three are complemented by another three, namely with resource recovery and reuse pathways (as in existing infrastructure, skilled labor, and access to finance. Singapore and Mexico). In some countries, existing infrastructure and the availability of skilled labor can be a challenge, while for some emerging • Access to finance. Upfront investments economies, there is infrastructure and skilled labor which and professional operation and maintenance of bodes well for establishing new and upgrading existing treatment plants are the two main businesses. Since technology is a strong requirement, challenges of WWTPs. Municipalities and public countries need to regulate technology procurement with agencies should integrate a costrecovery framework long-term agreements. Long-term contracts would further into the implementation of their WWTPs. help governments and local authorities provide more infrastructure for scaling up a business. Table 15 shows a • Determine the scale of intervention. Plan for heat map of these six parameters applied to the discussed centralizedordecentralizedmscale of operations business models. 84 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE TABLE 16. HEAT MAP OF TRANSFERABILITY OF THE BUSINESS MODELS TO THE GLOBAL SOUTH. Hierarchy Business Model Business Model 1: Formal sludge collection and treatment for use Recovering Business Model 2: Informal sludge collection and biosolids from treatment for use sewage sludge Business Model 3: Producing co-compost Business Model 4: Producing sludge pellets B usiness Model 5: Recovery of phosphoru s from incinerated sludge ash Business Model 6: Recovery of phosphorus from anaerobic sludge digestate Business Model 7: Energy recovery from anaerobic digestion Recovering B usiness Model 8A: Mono-incineration of sewage sludge energy from sewage sludge Business Model 8B: Co-incineration of sewage sludge Business Model 9: Energy recovery from gasification and pyrolysis Business Model 10: Recovery of biosolids, biomethane and electricity from sludge digestion Business Model 11: Recovery of energy/electricity from Hybrid models s ludge incineration and phosphorus from the ash B usiness Model 12A: Recovery of phosph o rus and energy from anaerobic digestion Business Model 12B: Recovery of phosphorus, biochar a nd energy through pyrolysis Not decisive Somewhat High Very high 85 Regulations Existing Infrastructure Public Awareness Access to Technology Access to Finance Skilled Labor RESOURCE RECOVERY & REUSE SERIES 23 REFERENCES ADB (Asian Development Bank). 2012. Promoting beneficial sewage sludge utilization in the People’s Republic of China. Mandaluyong City, Philippines: ADB. ATIA ISWA Italia. 2019. Tavolo tecnico Fanghi di depurazione [Technical Group Sewage Sludge]. Available at https://atiaiswa.it/file/Tavolo-tecnico- fanghi-ATIA_ISWA_finale.pdf (accessed on April 4, 2022). Barry, D.J. 2018. Pyrolysis as an economical and ecological technological treatment option for solid anaerobic digestate and municipal sewage sludge. Master’s thesis. The University of Western Ontario, Canada. Electronic Thesis and Dissertation Repository. Available at https://ir.lib. uwo.ca/etd/5187 (accessed on April 2, 2021). Bashar, R.; Gungor, K.; Karthikeyan, K.G.; Barak, P. 2018. Cost effectiveness of phosphorus removal processes in municipal wastewater treatment. Chemosphere 197: 280–290. https://doi.org/10.1016/j.chemosphere.2017.12.169 Bloomberg. 2021. Biosolids Continue to Replace Chemical Fertilizer, Demand to Surpass USUSD 2.4 Billion by 2031. Available at https:// www.bloomberg.com/press-releases/2021-10-18/biosolids-continue-to-replace-chemical-fertilizer-demand-to-surpass-us-2-4-billion- by-2031 (accessed on December 11, 2022). Buijs, J.; Drechsel, P.; Otoo, M. 2018. Outsourcing fecal sludge treatment to the farm - Business Model 15. In Otoo, M.; Drechsel, P. (Eds.). Resource recovery from waste: business models for energy, nutrient and water reuse in low- and middle-income countries. Oxon, UK: Routledge - Earthscan. pp. 516-526. https://cgspace.cgiar.org/handle/10568/93291 Campo, G.; Cerutti, A.; Lastella, C.; Leo, A.; Panepinto, D.; Zanetti, M.; Ruffino, B. 2021. Production and destination of sewage sludge in the Piemonte Region (Italy): The results of a survey for a future sustainable management. International Journal of Environmental Research and Public Health 18(7): 3556. https://doi.org/10.3390/ijerph18073556 Capodaglio, A.G.; Olsson, G. 2020. Energy issues in sustainable urban wastewater management: Use, demand reduction and recovery in the urban water cycle. Sustainability 12(1): 266. https://doi.org/10.3390/su12010266 Cementos Molins. 2020. Annual Report. Available at https://sostenibilidad.cemolins.es/wp-content/uploads/2022/02/c-molins-sustainability-2020. pdf (accessed on September 22, 2022). Christodoulou, A.; Stamatelatou, K. 2016. Overview of legislation on sewage sludge management in developed countries worldwide. Water Science & Technology 73(3): 543–462. https://doi.org/10.2166/wst.2015.521 Cordell, D.; White, S. 2011. Peak Phosphorus: Clarifying the key issues of a vigorous debate about long-term phosphorus security. Sustainability 2011, 3, 2027-2049. https://doi.org/10.3390/su3102027 Domini, M.; Abba, A.; Bertanza, G. 2022. Analysis of the variation of costs for sewage sludge transport, recovery and disposal in Northern Italy: A recent survey (2015–2021). Water Science and Technology 85(4): 1167–1175. https://doi.org/10.2166/wst.2022.040 Dong, L.; Tang, J.; Yang, Z.; Turner, J.L.; Liu, C. 2018. Scaling sludge mountains: Breaking down barriers for Chinese cities to turn sludge waste into energy. Wilson Center, China Environment Forum. Available at https://globalmethane.org/documents/393289300-Scaling-Sludge- Mountains-Breaking-Down-Barriers-for-Chinese-Cities-to-Turn-Sludge-Waste-Into-Energy.pdf (accessed on October 8, 2022). Drechsel, P.; Danso, G.K.; Hanjra M.A. 2018. Phosphorus recovery from wastewater at scale. In: Resource recovery from waste: Business models for energy, nutrient and water reuse in low- and middle-income countries. Otoo, M.; Drechsel, P. (eds.) Oxon, UK: Routledge – Earthscan: 538–546. EEA (European Environment Agency). 2021. Sewage sludge and the circular economy. Available at https://forum.eionet.europa.eu/nrc-eionet- freshwater/library/urban-waste-water-treatment/sewage-sludge-and-circular-economy (accessed on August 12, 2022). Fact.MR 2022. Biosolids market growth outlook (2023-2033). https://www.factmr.com/report/biosolids-market (accessed May, 5, 2023) Foladori, P.; Andreottola, G.; and Ziglio, G. 2010. Sludge Reduction Technologies in Wastewater Treatment Plants. IWA Publishing, London. https://doi.org/10.2166/9781780401706 Fu, X.; Zhong, L.; Jagannathan, V.; Fang, W. 2017. Sludge to energy: An environment-energy economic assessment of methane capture from sludge in Xiangyang City, Hubei Province. Working Paper. Washington, DC: World Resources Institute. Available at https://www.wri.org/ research/sludge-energy-environment-energy-economic-assessment-methane-capture-sludge-xiangyang-city (accessed December 14, 2022). GWI (Global Water Intelligence). 2012. Sludge management. GWI. Oxford, United Kingdom: Media Analytics Ltd. GWI (Global Water Intelligence). 2023a. Sewage sludge biorefineries: a future for biosolids disposal. GWI Market Map (19 January 2023) Vol 24 (1): 37-42 GWI (Global Water Intelligence). 2023b. Desalination and Reuse. GWI Market Focus Deck (October 2023). Oxford, UK GWRC (Global Water Research Coalition). 2019. Global compendium on phosphorus recovery from sewage/sludge/ash. Global Water Research Coalition. Available at https://www.vesiyhdistys.fi/wp-content/uploads/2019/12/GWRCPhosphorusCompendiumFinalReport2019- March-20.pdf (accessed on November 19, 2020). IPCC 2018. Special report: Global Warming of 1.5 ºC. http://www.ipcc.ch/report/sr15/ Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA). 2021. Rapporto rifiuti speciali [Report on Special Waste]. Rapporti 344 - 2021, Roma. Available at https://www.isprambiente.gov.it/files2021/pubblicazioni/rapporti/rapportorifiutispeciali_ed-2021_n-344_ versioneintegrale.pdf (accessed on December 5, 2022). Jaffar, S.; Khaliq, A.; Ahmed, M.; Al-Wardy, M.; Al-Busaidi, A.; Choudri, B.S. 2017. Wastewater and sludge management and research in Oman: An overview. Journal of the Air & Waste Management Association 67(3): 267–278. https://doi.org/10.1080/10962247.2016.1243595 Jayathilake, N.; Drechsel, P.; Keraita, B.; Fernando, S.; Hanjra, M.A. 2019. Guidelines and regulations for fecal sludge management from on-site sanitation facilities. Colombo, Sri Lanka: International Water Management Institute (IWMI). CGIAR Research Program on Water, Land and Ecosystems (WLE). 57p. (Resource Recovery and Reuse Series 14). https://doi.org/10.5337/2019.211 Kabbe, C.; Kraus, F.; Nättorp, A. 2015. Sustainable sewage sludge management fostering phosphorus recovery and energy efficiency. Available at https://publications.kompetenz-wasser.de/pdf/Kabbe-2015-839.pdf (accessed on November 19, 2020). Kelly, E.; Twohig, E. 2018. Wastewater treatment sludge and septage management in Vermont. Vermont Department of Environmental Conservation Waste Management & Prevention Division Residual Waste & Emerging Contaminants Program. Available at https://dec.vermont.gov/sites/ 86 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE dec/files/wmp/residual/RMSWhitePaper20180507.pdf (accessed on January 12, 2022). Keraita, B.; Drechsel, P.; Klutse, A.; Cofie, O. 2014. Onfarm treatment options for wastewater, greywater and fecal sludge with special reference to West Africa. Colombo, Sri Lanka: International Water Management Institute (IWMI).32p. (Resource Recovery and Reuse Series 1). doi:10.5337/2014.203 Lu, T.; Yuan, H.; Wang, Y.; Huang, H.; Chen, Y. 2016. Characteristic of heavy metals in biochar derived from sewage sludge. Journal of Material Cycles and Waste Management 18: 725–733. https://doi.org/10.1007/s10163-015-0366-y Magretta, J. 2002. Why business models matter. Available at https://hbr.org/2002/05/why-business-models-matter (accessed on March 10, 2021). Mills, N. 2015. Unlocking the full energy potential of sewage sludge. PhD Thesis, Surrey University, United Kingdom. Available at https:// openresearch.surrey.ac.uk/esploro/outputs/doctoral/Unlocking-the-full-energy-potential-of-sewage-sludge/99515301502346 (accessed on April 2, 2021). Mininni, J.; Mauro, E.; Piccioli, B.; Colarullo, G.; Brandolini, P; Giacomelli, P. 2019. Production and characteristics of sewage sludge in Italy. Water Science and Technology 79(4): 619-626. doi:10.2166/wst.2019.064. Mohammed, M.; Rgyir, I.S.; Donkar, A.K.; Amoah, P.; Nyarko, S.; Boateng, K.K.; Ziwu, C. 2017. Feasibility study for biogas integration into waste treatment plants in Ghana. Egyptian Journal of Petroleum 26(3): 695–703. https://doi.org/10.1016/j.ejpe.2016.10.004 Morf, L.; Schlumberger, S.; Adam, F.; Díaz Nogueira, G. 2019. Urban Phosphorus Mining in the Canton of Zurich: Phosphoric Acid from Sewage Sludge Ash. In: Ohtake, H.; Tsuneda, S. (eds) Phosphorus Recovery and Recycling. Springer, Singapore. https://doi.org/10.1007/978- 981-10-8031-9_10 MWRDGC (Metropolitan Water Reclamation District of Greater Chicago). 2019. Factsheet: Stickney water reclamation plant. Available at https:// mwrd.org/sites/default/files/documents/Fact_Sheet_Stickney.pdf (accessed on March 30, 2022). Nakagawa, H.; Ohta, J. 2019. Phosphorus recovery from sewage sludge ash: A case study in Gifu, Japan. In: Ohtake, H.; Tsuneda, S. (eds.) Phosphorus recovery and recycling. Springer Nature Singapore. pp. 149–155. https://doi.org/10.1007/978-981-10-8031-9_9 Nättorp, A.; Remmen, K.; Remy, C. 2017. Cost assessment of different routes for phosphorus recovery from wastewater using data from pilot and production plants. Water, Science & Technology 76(2): 413–424. Oman Observer. 2017 Kala compost a hit with farmers. Available at https://www.omanobserver.om/article/66338/Local%20front/kala-compost- a-hit-with-farmers (accessed on September 15, 2022) Ostara. 2023. Case Study – Stickney Water Reclamation Plant. Available at https://www.ostara.com/case-study-stickney-water-reclamation- plant/ (accessed on November 7, 2023). Osterwalder, A.; Pigneur, Y. 2010. Business model generation: A handbook for visionaries, game changers, and challengers. Hoboken, NJ, USA: Wiley. Otoo, M.; Drechsel, P. (eds.) 2018. Resource recovery from waste: Business models for energy, nutrient and water reuse in low- and middle- income countries. Oxon, UK: Routledge - Earthscan. 816p. Pradel, M. 2019. Survey data of sewage sludge treatment and disposal routes originated from activated sludge water treatment in France. Data in Brief 26: 104541. https://doi.org/10.1016/j.dib.2019.104541 Roskosch, A.; Heidecke, P. 2018. Sewage sludge disposal in Federal Republic of Germany. German Environment Agency. Available at https:// www.umweltbundesamt.de/sites/default/files/medien/1410/publikationen/190116_uba_fb_klaerschlamm_engl_bf.pdf (accessed on April 21, 2023). Rus, E.; Mills, N.; Shana, A.; Perrault, A.; Fountain, P.; Thorpe, R.B.; Ouki, S.; Nilsen, P.J. 2017. The intermediate thermal hydrolysis process: Results from pilot testing and techno-economic assessment. Water Practice and Technology 12(2): 406–422. https:// doi:10.2166/wpt.2017.031 Schmitz, E. 2009. Perspektiven der Mitverbrennung von Klärschlämmen [Perspectives on co-incineration of sewage sludge]. 6. Klärschlammtage der DWA (The Network of experts for water, wastewater and waste); Fulda. Singh, V.; Phuleria, H.C.; Chandel, M.K. 2020. Estimation of energy recovery potential of sewage sludge in India: Waste to watt approach. Journal of Cleaner Production 276: 122538. https://doi.org/10.1016/j.jclepro.2020.122538 Spinosa, L. (ed.) 2011. Wastewater sludge: a global overview of the current status and future prospects. IWA Publishing Volume 10. https://doi. org/10.2166/9781780401195 USEPA (United States Environmental Protection Agency). 1993a. Part 503 - Standards for the use or disposal of sewage sludge. Available at https://www.ecfr.gov/cgi-bin/R?gp=2&SID=3ba5c96eb4bfc5bfdfa86764a30e9901&ty=HTML&h=L&n=pt40.30.503&r=PART (accessed on November 6, 2020). USEPA. 1993b. A guide to the federal EPA rule for land application of domestic septage to non-public contact sites. Available at . https://www. alabamapublichealth.gov/environmental/assets/septage_guide.pdf (accessed on January 10, 2023). USEPA. 1995. Process Design Manual: Land Application of Sewage Sludge and Domestic Septage. Available at https://www.epa.gov/sites/ default/files/2018-12/documents/process-design-manual-land-application.pdf (accessed on November 20, 2022). Veltman, A. 2017. Enhanced sewage sludge treatment with struvite recovery. Available at https://conferences.aquaenviro.co.uk/wp-content/ uploads/sites/7/2017/08/Alex-Veltman-Waternet.pdf (accessed on September 2, 2022). Weber, K.; Quicker, P.; Hanewinkel, J.; Flamme, S. 2020. Status of waste-to-energy in Germany, Part I – Waste treatment facilities. Waste Management & Research. 38(1_suppl), pp. 23–44. doi:10.1177/0734242X19894632 Wei, L.; Zhu, F.; Li, Q.; Xue, C.; Xia, X.; Yu, H.; Zhao, Q.; Jiang, J.; Bai, S. 2020. Development, current state and future trends of sludge management in China: Based on exploratory data and CO2-equivaient emissions analysis. Environment International 144: 106093. https:// doi.org/10.1016/j.envint.2020.106093 Wiechmann, B.; Dienmann, C.; Kabbe, C.; Brandt, S.; Vogel, I.; Roskosch, A. 2013. Sewage sludge management in Germany. Umweltbundesamt (German Environment Agency). Available at https://www.umweltbundesamt.de/sites/default/files/medien/378/publikationen/sewage_ sludge_management_in_germany.pdf (accessed on April 21, 2023). World Bank. 2015. Annexes: Wastewater to energy. A Technical Note for Utility Managers and Decision Makers on Urban Sanitation in East Asian Countries. Available at https://documents1.worldbank.org/curated/en/448741468187805293/pdf/ACS13221-v2-WP-P145830- PUBLIC-Box393171B.pdf (accessed on March 15, 2021). Zhang, Z.; Ju, R.; Zhou, H.; Chen, H. 2021. Migration characteristics of heavy metals during sludge pyrolysis. Waste Management 120: 25-32. https://doi.org/10.1016/j.wasman.2020.11.018 87 RESOURCE RECOVERY & REUSE SERIES 23 88 ANNEX 1. BUSINESS MODEL CANVAS (GUIDANCE) Partnerships Activities Value propositions Customer relationships Customer segments Who are the Which activities are required for What bundle of products and What type of relationships does For whom are we creating value? main partners? creating the value proposition? services are you offering to each each of our customer segments customer segment? expect to establish and maintain? Which goods and services are What resources are What are the channels required and customers looking for? derived from the how would partners develop customer What is the value added for How are they integrated with the partners? relationships? the customer? rest of our business model? Who are the most important customers? Which activities do Which activities would generate What are the problems solved the partners perform? revenue for the business? through the business? Which customer needs are Resources satisfied? Channels What resources are needed for creating What is unique about the product What are the channels we use to the value of the goods and services? or service compared to others in reach customer segments? the market? What are the resources needed for How are the channels integrated developing customer relationships and with customer routines? channels? What are the resources needed for revenue generation? Cost structure Revenue streams What are the most important costs in the business model? What are customers willing to pay? Which elements derive the costs? How much are the customers currently paying, how are they paying and for what? How much does each cost item contribute to the overall costs? How much does each revenue stream contribute to the overall revenue if there are different products and services? Social and environmental costs Social and environmental benefits What are the potential environmental risks of doing business? What are the potential benefits the business can bring to the environment and what health benefits for society? What are the potential risks to the health of workers and society? Can the business model improve health and reduce health hazards? Does it create new jobs? Source: Otoo and Drechsel 2018 SEWAGE SLUDGE: A REVIEW OF BUSINESS MODELS FOR RESOURCE RECOVERY AND REUSE ANNEX 2. BUSINESS PERFORMANCE POTENTIAL (KEY TO SCORES) INDICATOR GUIDING QUESTIONS PARAMETERS SCORE Profitability and What is the level of operational profit and cost Loss-making 1 cost recovery recovery achieved by the business model on an annual basis? Break-even 2 Profit 3 How many revenue streams does the business One strong revenue source 1 model depend on and how strong are these revenue line items? Two or more revenue sources 2 with one strong revenue line Two or more revenue sources 3 with two strong revenue lines How many of these factors represent a risk of More than 3 factors applicable 1 increased costs to the business model? Factors are: 1) high worker and managerial skill 2–3 factors applicable 2 requirements, 2) diverse customer base, 3) diverse products, 4) need for R&D and 5) self-distribution of product to end customer 0–1 factor applicable 3 Social impact How many jobs are created by the business Low 1 model compared to the range of all the business cases within the same section (energy or Medium 2 nutrients or water)? High 3 Number of people with increased positive health Low 1 impacts from the business model compared to the range of all the business cases within the Medium 2 same section (energy or nutrients or water). High 3 On how many of these factors does the business Meets 0–2 factors 1 model have an improved or increased positive impact? Factors are: 1) water security, 2) food security, 3) energy security, 4) improved living standards, 5) reduced government costs for Meets 2–4 factors 2 waste management services (sanitation), health services and 6) gender Meets more than four factors 3 Environmental What quantity of waste is being processed and Low 1 impact reused compared to the range of all the business cases within the same section (energy or Medium 2 nutrients or water)? High 3 On how many of these factors does the business Meets 0–1 factor 1 model have an improved or increased positive impact? Factors are 1) health of water bodies, Meets 2–3 factors 2 2) reduced greenhouse gas emissions, 3) soil fertility, 4) renewable sources of raw material and 5) reduced deforestation Meets more than 3 factors 3 89 RESOURCE RECOVERY & REUSE SERIES 23 INDICATOR GUIDING QUESTIONS PARAMETERS SCORE Scalability and How many of these factors limit the replication Meets more than four factors 1 replicability potential of the business model elsewhere? Factors are 1) new technology, 2) policies and regulations, Meets 3–4 factors 2 3) strong institutional capacity, 4) specific waste availability 5) market demand and 6) ambiguity of Meets 0–2 factors 3 product acceptance What is the ease of scaling the business model Low potential for vertical AND 1 vertically and horizontally? horizontal scaling High potential for either vertical 2 OR horizontal scaling High potential for vertical and 3 horizontal scaling How easy is it to finance the business model Investment is HIGH and financing 1 elsewhere? is UNIQUE Investment is HIGH and financing 2 is COMMON Investment is LOW and financing 2 is UNIQUE Investment is LOW and financing 3 is COMMON Innovation How innovative is the technology or process? Known technology or process 1 Relatively new to developing 2 countries (technology transfer) New to the world 3 How innovative are the partnership arrangements? No partnerships required 1 Partnerships within the same 2 sector Partnerships crosscutting 3 different sectors (PRIVATE- PUBLIC PARTNERSHIP, R&D, finance) How innovative is the product or value proposition? Standard product and value 1 proposition Relatively new product or value proposition 2 New to the world 3 Source: Otoo and Drechsel 2018 90 RESOURCE RECOVERY AND REUSE SERIES 23 Sewage sludge: A review of 22 Public-private partnerships for 21 Gender dimensions of solid and business models for resource the circular bio-economy in the liquid waste management for reuse recovery and reuse Global South: Lessons Learned in agriculture in Asia and Africa https://doi.org/10.5337/2023.211 https://doi.org/10.5337/2023.205 https://doi.org/10.5337/2021.223 20 Safe and sustainable business 19 Business models for urban food 18 (Special Issue) Business models for water reuse in aquaculture waste prevention, redistribution, models for fecal sludge in developing countries recovery and recycling management in India https://doi.org/10.5337/2021.212 https://doi.org/10.5337/2021.208 https://doi.org/10.5337/2020.209 Free access is provided to all reports in the Resource Recovery and Reuse series. Visit: http://www.iwmi.org/publications/resource-recovery-reuse/ Photo: Gabrielle Joly International Water Management Institute (IWMI) The International Water Management Institute (IWMI) is an international, research-for-development organization that works with governments, civil society and the private sector to solve water problems in developing countries and scale up solutions. Through partnership, IWMI combines research on the sustainable use of water and land resources, knowledge services and products with capacity strengthening, dialogue and policy analysis to support implementation of water management solutions for agriculture, ecosystems, climate change and inclusive economic growth. Headquartered in Colombo, Sri Lanka, IWMI is a CGIAR Research Center with offices in 15 countries and a global network of scientists operating in more than 55 countries. Resource Recovery & Reuse Series The Resource Recovery and Reuse (RRR) Series originated in 2014 under the CGIAR Research Program on Water, Land and Ecosystems (WLE), and continues since 2021 under the CGIAR Initiatives on Resilient Cities and Nature-Positive Solutions. The aim of the RRR series is to present applied research on the safe recovery of water, nutrients and energy from domestic and agro-industrial waste streams. IWMI’s research on RRR aims to create impact through different lines of action research, including (i) developing and testing scalable RRR business models, (ii) assessing and mitigating risks from RRR for public health and the environment, (iii) supporting public and private entities with innovative approaches for the safe reuse of wastewater and organic waste, and (iv) improving rural-urban linkages and resource allocations while minimizing the negative urban footprint on the peri-urban environment. IWMI works closely with the World Health Organization (WHO), Food and Agriculture Organization of the United Nations (FAO), United Nations Environment Programme (UNEP), United Nations University (UNU), and many national and international partners across the globe. The RRR series of documents present summaries and reviews of the research and resulting application guidelines, targeting development experts and others in the research for development continuum. International Water Management Institute (IWMI) Headquarters 127 Sunil Mawatha, Pelawatte, Battaramulla, Sri Lanka Mailing address: P. O. Box 2075, Colombo, Sri Lanka Tel: +94 11 2880000 Fax: +94 11 2786854 ISSN 2478-0510 (Print) Email: iwmi@cgiar.org ISSN 2478-0529 (Online) www.iwmi.org ISBN 978-92-9090-951-4 Photo: Gabrielle Joly