Mechanistic model For electricity generation via biomethane production through anaerobic digestion of organic fraction of municipal solid waste generated In Sri Lanka

Abstract

Waste management practices such as open dumping and composting are widely used for the management of municipal solid waste (MSW) in Sri Lanka. Severe socio-economic and environmental problems occur due to open dumping of major fraction of MSW. Anaerobic digestion is a sustainable waste management strategy to manage organic fraction of MSW (OFMSW). In order to evaluate the feasibility of this strategy, a mechanistic model was developed using a steady state anaerobic digestion model which was modified using improved Chen–Hashimoto kinetic equations. It was applied to treat OFMSW generated in open dumping site at Karadiyana in Sri Lanka. The daily MSW arrival to the site is 550 tons/day and input OFMSW slurry to the anaerobic bioreactor contained of total solids 70 g/l, volatile solids 55.6 g/l, carbohydrates 58.5%, proteins 13% and lipids 3%. According to the mechanistic model, minimum payback period of 1.79 years was achieved when anaerobic bioreactor operated in continuously fed mode at operating temperature of 40°C and hydraulic retention time of 11.28 days. The volatile solid reduction efficiency of 76.62%, methane yield of 0.26 m³ per kg of volatile solids added, electricity generation of 10.31 W per kg of OFMSW per day and carbon dioxide generation of 0.21 kg per kg of OFMSW were achieved at these optimized process conditions. The model was limited to apply for continuously fed anaerobicbioreactors operated at temperature ranging from 30°C to 40°C.