Evaluation of Biogas Production from Solid State Anaerobic Digestion of Municipal Sewage Sludge

Due to the increasing consumption of fossil fuels in the world as well as their increasing cost and environmental impacts, the great need and interest to replace them with renewable energy resources has increased. Anaerobic digestion is a biochemical process that is able to convert almost all kinds of multi-dimensional biodegradable organic matters under anaerobic conditions to biogas. According to water content, anaerobic digestion methods are classified as wet and solid state. The solid-state anaerobic digestion has been claimed to be advantageous over liquid AD for a number of reasons including smaller reactor volume, lower energy requirements for heating and minimal material handling. In this paper, biogas production from solid state anaerobic digestion of municipal sewage sludge was studied. A series of single-stage batch mesophilic (37 ± 1oC) anaerobic digestions were performed at a total solids concentration of 20% in 1 liter reactor volume. The evaluation of municipal sewage sludge characteristics showed that this substrate has a good potential for solid state anaerobic digestion (Total solids, volatile solids and C/N ratio were obtained 25.7%, 50.7% and 11.7, respectively). The biogas yield was achieved 362 ml/g VS, which methane content of biogas was 213 ml (58.8%). The volatile solids reduction, a significant parameter to measure productivity of anaerobic digestion, was obtained to be 63.7%.