Effects of Temperature and Organic Loading Rates on the Biogas Yield of MSW Anaerobic Digester

The amount of municipal solid waste (MSW) generated in Iran is around 60000 ton/day of which more than 70% is organic wastes. The objective of this study was to optimize the applications of anaerobic digestion for the treatment of municipal organic wastes. In order to obtain basic design criteria for anaerobic digester of MSW, the effect of different organic loading rates (OLR) and digesting temperatures were investigated. The study was made at pilot scale using 701 reactor. In the first part of the investigation, the digester was operated at different organic feeding rates of 1.4, 2 and 2.75 kg VS/(mo.d). The biogas produced had methane composition of 49.7-64% and biogas production rates of 0.12-0.4 m/ (kg VS). The reactor showed stable performance with highest biogas production (0.4m'/kg VS) and VS reduction of around 88% during loading rate of 1.4 kg VS/(m'.d). VS removal and methane concentration in biogas was decreased when the organic loading rate was increased. In the second part of the investigation, digester temperatures were set between 25-34°C. Digestion with temperature in these range resulted in biogas yield of 0.23-0.33 m biogas/ kg VS, with a methane content in the biogas of 52.4-62.6%. The methane content and yield decreased with reduction of digestion temperature. However this reduction was almost negligible from 34°C to 30°C. Based on the data obtained from this study, organic loading rates of 1.4 kg VS/ (m'.d) and temperature in the range of 30-34°C is suggested as a base for design purpose.