Anaerobic two stage degradation pattern of fermentable components of municipal solid waste

With increased contribution of household and kitchen wastes in overall MSW and its preferred conversion by biomethanation there is a need to study decomposition rates and kinetics, ‘leachate potential’ and related issues– especially to promote decentralized treatment. Anaerobic digestion characteristics of ten predominant types of the fermentable components (fruits, vegetables and their mixture) commonly found in urban solid waste in Bangalore were examined under lab conditions by monitoring biogas production in micro-digesters at room temperatures (25±3°C). The rate of decomposition, the pattern of fit and extent and rate of biogas production from these potential feedstocks are analyzed to understand the degradation kinetics. All feedstocks showed a two stage linear fit for gas production comprising of a rapid initial phase lasting 10-20days accounting for >70% gas production followed by a slower second phase. Degradation could be predicted using a two stage linear fit transiting from initial to a second stage at an appropriate unique transition point, yet similar amongst fruits or vegetables. The need for large aceticlastic capability (rapid initial degradation) thus becomes a criteria for biomethanation process of such feedstocks.