Vegetable oil as fuel for diesel engines
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CTA. 1993. Vegetable oil as fuel for diesel engines. Spore 46. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/49173
There is little new about the idea of using vegetable oil as engine fuel, but for a long time technical problems and the low price of petroleum-based fuels have meant that the idea has not been pursued in practice. However, a German project in Mali...
There is little new about the idea of using vegetable oil as engine fuel, but for a long time technical problems and the low price of petroleum-based fuels have meant that the idea has not been pursued in practice. However, a German project in Mali has recently been advocating the use of physic nut oil in diesel engines. Such a scheme would bring benefits in the fields of ecology, economics and energy. The physic nut tree (Jatropha curcas) grows abundantly throughout the Sahel. The inhabitants of the region use its seeds and leaves medicinally and plant it as hedges and windbreaks around their gardens and fields. The physic nut tree, which is a member of the Euphorbiaceae family, thrives on poor soil even in times of drought because of the water-retaining fibres in its roots, trunk and branches. Since 1987 the Agricultural Machinery Service in Mali and the Special Energy Programmes of the Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ) have been researching the possible use of the physic nut's oil rich seeds as diesel engine fuel. The multi-use physic nut The physic nut is adaptable and does well on marginal land where other crops are not viable, and it can be used in reafforestation schemes As well as being used as a windshied, it is also a protection against rainwater erosion mainly because its shallow roots slow the surface run-off and aid the infiltration of the water into the soil. In areas inhabited by nomadic herdsmen, the physic nut tree is used to make enclosures. The smell and taste of the toxin (curcin), which is present in the leaves, deters animals. Hedges therefore stay intact and cattle are prevented from getting out and grazing on crops. This reduces the frequency of clashes between farmers and pastoralists. Electric fencing is too expensive for small-scale farmers, but the physic nut tree is a more shall adequate solution. In the southern region of Mali which is managed by the Compagnie Malienne des Textiles (CMDT), around 5000km of physic nut hedges were planted in 1992 and an increase of 4000km per annum is envisaged. The hedges protect the leguminous crops planted on fallow land to improve impoverished soil. Peasant farmers are in favour of schemes which promote the physic nut. The slump in agricultural prices on world markets has meant that cotton and groundnut growers are taking a keen interest in whatever might widen their income base. The women who harvest the seeds are strongly in favour, since profits are two or three times higher than for sheabutter and the harvest takes place after the rainy season, when other work in the fields is over. Put a physic nut in your tank! Over and above all these advantages, the physic nut seeds contain oil which is light enough to be used as motor fuel, and which has an energy value only 3% less than diesel. It was used in Europe during World War 11, but was soon forgotten in the general euphoria over the subsequent cheap petrol prices. In developing countries physic nut oil has much to recommend it, especially in rural areas. It means local people can be independent of power stations for energy for their mills, generators or motorpumps; and if imported petroleum products are not being bought, valuable foreign exchange is saved for other purposes. The machinery needed to extract the oil from the seed is neither sophisticated nor expensive. Small and simple turnscrew presses for semi-industrial use can be made locally which will extract eight litres per hour; hydraulic manual presses for small scale operations produce five to ten litres per day. Already engines designed to run on vegetable oil are in use. Is it viable? In African countries which do not produce petrol, and in rural areas away from main transport routes, feasibility studies have demonstrated that physic nut oil is cheaper than diesel. In Mali, after deducting capital repayments for the motor and the press and the costs of maintenance, seed and labour, physic nut oil is fetching 163.4 FCFA per litre in the areas where it is produced, against 300 FCFA per litre of diesel. Summing up the benefits, Reinhard Henning of GTZ says: 'This project will create a new economic activity which will eventually change not only the face of the countryside, but also social practices and energy consumption.' For more information contact: Reinhard K Henning Deutsche Gesellscaft fur Technische Zusammenarbeit (GTZ) 6 GMBH Postfach 5180 6236 Eschborn 1 GERMANY or GTZ BP 100, Bamako, MALI