Technology for utilising non-edible oilseeds as renewable energy resources for rural communities

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Worldwide concerns over energy and environmental issues have necessitated research into regenerative energy and biomass resources such as oilseeds have become attractive for investigation as fuels. Non-edible oils from Carapa procera and Jatropha curcas have been extracted by aqueous and mechanical pressing methods and evaluated as fuels. Oil contents of Carapa and Jatropha oilseeds were (62.95 ± 0.82) % and (30.95 ± 0.85) % respectively. Pre-conditioning of Carapa oilseeds via moderate heating at 100°C for 6 hours was found to improve oil yields over higher temperatures (i.e. 180°C for 2 hours). Mechanical pressing of Carapa and Jatropha oilseeds using a portable hand-operated mini-screw press yielded better results than aqueous methods. Employing a meal to water ratio of 1:3 and boiling for 2½ hours yielded the highest amount of oil (i.e. 32.57 ± 1.42% efficiency) which was not significantly different (p> 0.05) from traditional processing methods (25-35%). Gradual heating during aqueous extraction was noted to improve oil yields over rapid heating and the probable influence of lipase enzymes in aqueous extraction has been implicated. Calorific values of Carapa and Jatropha oils were 41.27 MJ/KG and 39.6 MJ/KG respectively and these were comparable to values for diesel (i.e. 40.0 MJ/KG) and kerosene (i.e. 41.5 MJ/kg). Viscosity of Carapa oil was however high and indicative of probable problems of flow and atomization in diesel-type engines or lanterns (with respect to wick capillarity). Carapa oil was found to contain over 60% saturated fatty acids. Phospholipids contents of all extracted Carapa oils were rather low. Implication of lipases in the research revealed that lipases could be utilized to reduce the large molecular structures of the vegetable oils to improve flow characteristics although the use of lipases as viscosity reducers would be expensive.
A thesis submitted to the University of Science and Technology in fulfilment of the requirements for the award of the Degree of Master o Philosophy in Biochemistry, 1993.