Modelling the Kinetics of Biogas Generation from Mesophilic Anaerobic Co-Digestion of Sewage Sludge with Municipal Organic Waste

Abstract

This work investigated the effect of municipal organic waste as co-substrate in the anaerobic digestion of industrial sewage sludge for efficient and high biogas production. The biogas experiments were carried out in two different 30 L anaerobic digesters D1 and D2 which contained sewage sludge and mixture of sewage and municipal organic waste, respectively and were incubated for 25 days at ambient mesophilic temperatures (28 ^oC to 32 °C). The results showed that co-digestion of sewage sludge with municipal organic waste as co-substrate reduced start-up time for biogas generation and increased biogas yield by 132% as compared to sewage sludge alone. Peak biogas production was obtained for both digesters at pH of 6.85 and 7.85 as well as temperature of 30 and 31.5^oC, respectively. Modelling study revealed that exponential plot simulated better than the linear plot, the biogas production rates in digester D1 (sewage sludge) and D2 (mixture of sewage sludge and municipal organic waste), respectively. Logistic growth model and modified Gompertz plot showed better correlation of cumulative biogas production than exponential rise to maximum plot. These results show that biogas production can be enhanced efficiently through co-digestion process.

Keywords: Anaerobic digestion; Biogas; Municipal waste; Sewage sludge; Kinetic model.