Biogas production by two-stage thermophilic and mesophilic biodigestion of kitchen waste

Abstract

The present research work focuses on the biogas production from kitchen waste generated at the NIT hostels and to investigate the effects of the key process parameters like pH and temperature, by operating a pilot scale setup in two stage thermophilic and mesophilic digestion conditions. In 1st experimental setup, a comparison of the digestion of food wastes in small scale was done. In this experiment three setups were operated in mesophilic, thermophilic and two stage mesophilic and thermophilic conditions respectively. The comparison of kitchen waste digestion in case of two stage setup was found to be 30% faster than mesophilic setup in terms of total solids and carbohydrates degradation over the operation period of 20 days. The biogas production initially was found to be 40% faster in case of two stage setup than the mesophilic setup. In 2nd experimental setup the pilot scale setup was based on two stage thermophilic and mesophilic digestion process and operated as a batch reactor. In batch condition, maximum of 7.45 Liters biogas was produced from the digestion of 6 kg of food wastes in 25 days. The initial total solid content of the waste slurry was measured to be 10.27% which was reduced to 5.51% on 25th day. The initial total carbohydrate and volatile fatty acid concentration was 61.2 g/L and 2475.5 mg/L respectively. After 24 days of digestion, the total carbohydrate concentration was decreased to 22.3 g/L, whereas volatile fatty acid concentration was increased to 4954 mg/L. The project work signifies that the kitchen waste can be used as a potential source for biogas production using two stage digestion process and thus effective waste management can be achieved.