Enhancement of biogas production from organic fraction of municipal solid waste using acid pretreatment

Anaerobic digestion of organic fraction of municipal solid waste (OFMSW) is a potential and economic technique for harnessing bioenergy from Indian municipal solid waste. Pretreatment before anaerobic digestion has been known to improve biodegradability of substrate and enhance biogas production. In this study, the effectiveness of acid pretreatment in enhancing the hydrolysis of complex organic matter and ensuing biogas generation from OFMSW was studied using one strong and one weak acid. Acid pretreatment (pH 6–pH 1) of OFMSW was carried out using hydrochloric acid (HCl) and acetic acid (CH3COOH) for 24 h before batch anaerobic digestion assays with cow dung as inoculum. Increase in biogas yield ranged between 13.2 and 28.9% as compared to untreated OFMSW after pretreatment with HCl, whereas the same varied between 8.2 and 16% in case of CH3COOH pretreatment. The highest biogas yield (389.4 ml/gVS) with methane content of 68.3% was obtained after pretreatment with HCl at pH 3, whereas for CH3COOH, the highest yield (350.2 ml/gVS) with 67.4% methane was observed after pretreatment at pH 1. OFMSW characteristics after each pretreatment step and their variation during the course of anaerobic digestion were also studied. An economic evaluation of all pretreatment scenarios was performed; out of which, pretreatment of OFMSW with HCl at pH 4–pH 6 yielded positive results in terms of net revenue gains.