Biogas production potential of jatropha seed cake

Jatropha seed cake (JSC) was anaerobically digested at different total solid contents (TS) and carbon to nitrogen (C:N) ratios in batch type digesters with 40 days hydraulic retention time (HRT). Biogas production from kg of TS was found to be maximum i.e. 0.17 m(3) at 20% TS of JSC slurry followed by 15%, 25% and 10% TS in that order as compared to 0.166 m(3) in case of cow dung (CD) slurry alone. Higher gas production from JSC slurry was observed when the carbon to nitrogen ratio (C:N) ratio was between 22:1 to 27:1 (by adding different quantity of paddy straw). Further gas production from kg of TS of the mixture of JSC and CD was higher than that produced from JSC/CD slurry alone and was maximum when JSC percentage in the mixture was within 25%. The Nitrogen content in the biodigested JSC slurry was increased by 5.9% as compared to JSC alone and its use as fertilizer produced better growth of maize and tomato crops.