Anaerobic co-digestion of cafeteria, vegetable and fruit wastes for biogas production

Abstract

Biogas, a renewable, efficient and carbon-neutral form of energy source, could be a very well substituent of fossil fuels which are depleting very fast. Here we reported to determine the optimal biogas production from variable mixing ratios and methane yields without bacteria inoculums added using batch anaerobic digesters at mesophilic conditions. The digestion was carried out in 200 L polypropylene digesters. The mixing ratio used were CW:VW:FW (0.5:1.0:1.5, 1.0:1.5:0.5, 1.5:0.5:1.0 and 1.0:1.0:1.0) for cafeteria waste (CW), vegetable waste (VW) and fruit waste (FW) respectively. The results showed that the co-digestion significantly influenced the biogas production and methane yield. The maximum biogas yield was obtained to be CW:VW:FW (0.5:1.0:1.5, 1.0:1.5:0.5, 1.5:0.5:1.0 and 1.0:1.0:1.0) were 33.92, 35.52, 36.55 and 43.87 L/day, at the 25th, 24th, 24th, and 21th day respectively. The higher cumulative biogas yields were obtained from the CW:VW:FW (1.0:1.0:1.0) mixture ratio than those from the CW:VW:FW (1.5:0.5:1.0, 1.0:1.5:0.5, and 0.5:1.0:1.5). The average methane yield from CW:VW:FW (0.5:1.0:1.5, 1.0:1.5:0.5, 1.5:0.5:1.0 and 1.0:1.0:1.0) were 59.95%, 60.07%, 61.41%, and 63.61%, respectively. The biogas and methane yields obtained in this work for the cafeteria (CW), vegetable (VW) and fruit wastes (FW) mixture were in the order of (1.0:1.0:1.0 > 1.5:0.5:1.0 > 1.0:1.5:0.5 > 0.5:1.0:1.5). Thus, optimum mixing ratio suggested by the study which gave maximum yields within 35 day hydraulic retention time for biogas production which holds promise for the future energy crisis recovery.