Optimization of process parameters for enhanced biogas yield from anaerobic co-digestion of OFMSW and bio-solids

The effects of mesophilic anaerobic co-digestion (AcoD) of organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) on enhancement of biogas production were investigated under different types of sludge combinations (primary sludge PS, waste-activated sludge WAS and mixed sludge MS), varying mixing ratios of OFMSW and MS (50:50, 70:30, 80:20, 90:10, v/v) and varying total solid TS concentrations (6, 9, 12, 15%). The co-digestion of OFMSW with MS resulted in the biogas yield of 138 mL/gVS over mono-digestion of OFMSW (39 mL/gVS). Co-digestion of OFMSW + PS and OFMSW + WAS yielded biogas of 107 and 129 mL/gVS, respectively, which is less than that of OFMSW + MS (138 mL/gVS), respectively. The co-digestion of OFMSW with MS showed a 2.5 times increase in biogas yield over OFMSW digestion alone and 23% and 7% higher biogas yield than OFMSW + PS and OFMSW + WAS, respectively. The highest biogas yield of 967 mL/g VS was observed at TS concentration of 9% and OFMSW to the MS mixing ratio of 80:20, respectively. The biogas yields at different TS percentages were modelled using Gompertz and Logistic models and fitted well.