Biogas Production Through Dry Anaerobic Digestion Of Waste Sludge

Abstract

A single stage pilot scale anaerobic reactor of 50 Litter volume was constructed to conduct dry anaerobic co-digestion of sludge and rice husk. Reactor was started with batch start-up phase followed by semi-continuous phase. Total solid content and C: N ratio of waste mixture used in this research was maintained at 15% and 30 respectively. Mesophilic temperature range was maintained in reactor. Effect of variation in organic loading rates of biogas production was examined in semi-continuous phase. For this purpose the reactor was operated at OLR of 2, 4, 6 and 8 kg VS/m 3 /d. Results revealed that in comparison of OLR 2, 4 and 8 OLR 6 had higher biogas production rate. Average specific biogas yield of 142 L/kg/VS with %VS removal of 63% was achieved. For OLR 2, 4 and 8 these were 113, 94, 115 and 76, 61, 47%.Reactor performance decreased with at OLR 8 due to Volatile fatty acids accumulation and inhibition of biogas production. Thus based on biogas production and stability of anaerobic reactor, OLR 6 kg VS/m 3 /d was considered to be most optimum for dry anaerobic codigestion of waste sludge and rice husk.