Anaerobic digestion of organic wastes in Kenya: Biomethane yields and circular bioeconomy opportunities

Mulat, D.G., Ngwa, M., Chernet, T.F. and Mwangi, S. 2025. Anaerobic digestion of organic wastes in Kenya: Biomethane yields and circular bioeconomy opportunities. Report. Nairobi, Kenya: ILRI.

Kenya generates significant volumes of organic waste from urban markets, households, livestock farms, and slaughterhouses, which pose serious environmental, health, and climate risks due to poor waste management. At the same time, these wastes represent untapped potential for clean energy production via anaerobic digestion. This study assessed the biomethane potential (BMP) of representative organic waste streams in Kenya to inform biogas investment and circular economy transitions.

Through laboratory-based BMP assays, organic waste samples from market, household and invasive plants in lake in Kisumu, Slaighterhouse in Isiolo, market in Embu, market and restaurant in Nakuru, cattle farm in Nairobi, including fruit, vegetable, fish, food, household, and market wastes, water hyacinth, cattle manure, and slaughterhouse wastes, were analyzed for methane yield and digestate quality. The results revealed methane production ranging from 230 to 441 mL/g volatile solids (VS), confirming the high biodegradability and energy potential of these feedstocks. A combination of market (fruit and vegetable) waste and fish waste produced the highest methane yields, while co-digestion of market or food waste with fish waste or manure increased biogas output by up to 33%.

Feedstock composition analyses showed significant variation in carbon to nitrogen (C/N) ratios, volatile fatty acids, and trace elements, reinforcing the importance of regular waste characterization and co-digestion to ensure stable digester performance. The absence of inhibitory elements such as chromium suggests that the feedstocks used were environmentally safe. The resulting digestate was nutrient-rich, supporting its potential as a biofertilizer for circular nutrient recycling.

These findings highlight the viability of anaerobic digestion as a circular economy solution for simultaneously addressing Kenya’s organic waste burden, promoting renewable energy and organic fertilizer access, and reducing greenhouse gas (GHG) emissions, particularly methane from landfills, open dumping, and livestock manure. The study recommends further work on seasonal waste characterization, digester sizing, emissions reduction analysis, and economic feasibility to guide implementation and scale-up. Transforming organic waste into a valuable resource that advances a circular bioeconomy and sustainable food, and energy systems aligns with Kenya’s climate goals under the Nationally Determined Contributions (NDCs), the Bioenergy Strategy, and the National Climate Change Action Plan (NCCAP 2023–2027).