Enhancement of Biogas Generation by Addition of Lipase in the Co-Digestion of Tannery Solid Wastes

Co-digestion studies were carried out for biogas generation using fleshings as the primary substrate and a mixture of primary and secondary sludge generated during the treatment of tannery wastewater as the co-substrate. Steapsin, a commercial grade lipase, was added to enhance the hydrolysis in anaerobic co-digestion. The lipase dosages used were ranging between 0.25 and 1.0 g for a volatile solids input of 7.5 g. The performance of the co-digestion was assessed from the volume of biogas generated. Experimental results revealed an optimum lipase dosage of about 0.75 g. At this dosage, the biogas generation was observed to increase by about 15% compared to that in the control without adding lipase. Further, the digestion with lipase addition was observed faster since the digestion period was reduced about 30%. This means that the capacity of the digester could also be reduced about 30% leading to savings in its installation cost.