BIOGAS PRODUCTION FROM JATROPHA-CURCAS PRESS-CAKE

Seeds of the tropical plant Jatropha curcas (purge nut, physic nut) ar e used for the production of oil. Several methods for oil extraction h ave been developed. In all processes, about 50% of the weight of the s eeds remain as a press cake containing mainly protein and carbohydrate s. Investigations have shown that this residue contains toxic compound s and cannot be used as animal feed without further processing. Prelim inary experiments have shown that the residue is a good substrate for biogas production. Biogas formation was studied using a semicontinous upflow anaerobic sludge blanket (UASB) reactor; a contact-process and an anaerobic filter each reactor having a total volume of 110 L. A max imum production rate of 3.5 m(3) m(-3) d(-1) was obtained in the anaer obic filter with a loading rate of 13 kg COD m(-3) d(-1). However, the UASB reactor and the contact-process were not suitable for using this substrate. When using an anaerobic filter with Jatropha curcas seed c ake as a substrate, 76% of the COD was degraded and 1 kg degraded COD yielded 355 L of biogas containing 70% methane.