Bio-methanisation of Jatropha curcas defatted waste

Abstract

The study deals with the use of Jatropha curcas defatted waste as an alternative feed in biogas plant for its bio-methanisation. As it remains as defatted cake after the extraction of non-edible oil from Jatropha seeds, it cannot be used directly for any purpose due to presence of toxic substance called ‘curcin’. This toxin renders it unsafe for the animal feed and other purposes. It contains 5.73% nitrogen, 1.5% phosphorus and about 1% potassium. On the basis of its chemical composition, its application as substrate to the biogas plant can be a sustainable alternative as compared to the other applications of Jatropha press cake. The study was conducted on a floating drum type biogas plant. It was observed that the biogas plant, initially charged with pure cattle dung, when gradually replaced withJatropha oil cake (0 - 100%), it increased the biogas production up to approximately 25% in reasonable time duration. A significant increase in the percentage of nitrogen, phosphorus and potassium during the bio-fermentation process invokes the use of the effluent slurry as organic manure. Simultaneous reduction in the amount of the oil (5.67 to 3.95%) sustains the possibility of degradation of oil during methanisation. The plant has showed higher biogas yields at low temperatures also. Therefore, Jatropha defatted waste can successfully be used as a adduct as well as substrate in already running cattle dung based biogas plant to get high yield of biogas in comparison to cattle dung feed. Key words: Jatropha oil cake, biogas production, gas yield, pragati biogas pla.