Evaluation of biomethane potential of waste algal biomass collected from eutrophied lake: effect of source of inocula, co-substrate, and VS loading

Present study used sequential optimization of inoculum, co-substrate, and volatile solid (VS) loading rate to enhance biomethanation of waste algal biomass (HL) collected from eutrophied Hauz Khas lake, India. The mixed algal biomass was rich in lipids (45% TS) with a C/N ratio of 10.08 and 88% VS. Higher methane yield (279 mLg(-1) VSfed) was observed using inoculum from algae-cattle dung based biogas plant compared to 170-200mLg(-1) VSfed using other inocula (from sewage sludge, Jatropha/ Karanja cake and cattle dung based plant). Biomethane yield was further enhanced (312 mLg(-1) VSfed) by co-digestion with cattle dung (HL+CD) as compared to 282 mLg(-1) VSfed for HL+WAS (waste activated sludge). Further, VS loading of 5gVSL(-1) gave highest methane yield of 315 mLg(-1) VSfed, while a decrease (240 and 224 mLg(-1) VSfed) was observed at 10 and 15gVSL(-1), respectively.