Anaerobic Digestion of aqueous Jatropha seed oil extraction residues and phorbol ester degradation

Abstract

Aqueous Jatropha Oil Extraction Residue (AJOR) is a byproduct from a novel technique for Jatropha seed oil extraction. Its potential for biogas production, its effects on process stability and the reduction of toxic phorbol esters were investigated. AJOR had a total solid and volatile solid content of 24.3% and 92% and contained 35.5% of crude protein and 17.5% of crude fat, based on total solids. The specific methane yield was measured with the Hohenheim Biogas Yield Test at 406 LCH4 kg−1VS. In continuous digestion, 405 LCH4 kg−1VS was reached, but was accompanied by an excessive volatile organic acids to total inorganic carbon ratio at an organic loading rate of 2.64 kgVS m−3 d−1. After a reduction of the organic loading rate to 1.7 kgVS m−3 d−1, the specific methane yield amounted to 440 LCH4 kg−1VS and the fermentation process became stabilized. Phorbol esters per FM decreased by 97–98%.