Operational strategy of high rate anaerobic digester with mixed organic wastes: effect of co-digestion on biogas yield at full scale.

The present research work is aimed at providing an economically feasible solution for the farmers to exploit the mixed organic wastes (MOW) as resources for the generation of biogas based electrical power and utilize the same for irrigation purpose to reduce the dependence on electricity board. A full scale biomethanation plant has been installed based on anaerobic gas lift reactor (AGR) technology to analyse, understand the operational parameters of anaerobic digestion and assess the performance of a high rate biomethanation plant by co-digesting the MOW such as poultry litter (PL), cattle manure (CM) and napier grass (NG) at ambient temperature. The biomethanation plant was incorporated with inline pre and post-processing unit assembly. The plant was fed with 1000 kg of MOW per day having 250 kg of total solids, about 178-200 kg of volatile solids and operated continuously for 52 weeks under ambient temperature. Electrical power generated (84.5-104 kWh/day) from biogas (65-80 m3/day) containing methane (40-48 m3/day) was used for operating the water pumps for agricultural purpose and the digestate (115-130 kg/day) was exploited as organic manure for growing crops in the same field. Napier grass was grown in the same land and other feedstocks were procured from the nearby area at the cost of $10-$15 per ton. Around 6 acres of land was being cultivated using the biogas based power generated from the MOW that was being used for growing vegetables and maize.

Exploitation of rapid acidification phenomena of food waste in reducing the hydraulic retention time (HRT) of high rate anaerobic digester without conceding on biogas yield.

The aim of the present work was to study and infer a full scale experience on co-digestion of 1000kg of FW (400kg cooked food waste and 600kg uncooked food waste) and 2000L of rice gruel (RG) on daily basis based on a high rate biomethanation technology called "Anaerobic gas lift reactor" (AGR). The pH of raw substrate was low (5.2-5.5) that resulted in rapid acidification phenomena with in 12h in the feed preparation tank that facilitated to obtain a lower hydraulic residence time (HRT) of 10days. At full load, AGR was fed with 245kg of total solids, 205kg of volatile solids (167kg of organic matter in terms of chemical oxygen demand) which resulted in the generation of biogas and bio manure of 140m3/day and 110kg/day respectively. The produced biogas replaced 60-70kg of LPG per day.