Methane Production and Waste Stabilization in Anaerobic Co-Digestion of Food Waste, Biosolids and Used Cooking Oil

Restaurants, food processing industries and café kitchen generate significant amounts of food waste (FW) and waste cooking oil. Septage treatment also generates large amount of biosolids. This study explores the application of anaerobic process, which generates methane, a renewable energy resource, to these wastes. The performance of batch anaerobic co-digestion of food waste, biosolids and waste cooking oil at varying waste ratio, namely 0, 30, 50 and 70 mass percent volatile solids (VS) was determined. The seed sludge used was a combination of cow rumen obtained from a slaughterhouse and pig manure. The waste mixture that did not contain waste oil yielded the highest amount of methane (61.5 mL g-1 VS), showed the highest VS destruction (48.51%) and rate of hydrolysis (first-order rate constant of 0.187 d-1). Rates of hydrolysis and methane production, methane yield and methane content of the biogas produced were lower at higher amounts of oil added but constant amount of seed sludge. Nevertheless, the mixture containing 70% waste oil produced 9.54 mL g-1 VS. Compared with other simple means of disposal, this method of the three kinds of wastes is a promising energy-generating option for treating food waste.