Waste-composition-dependent ‘HBM’ model parameters based on degradation experiments

Abstract

Municipal solid waste (MSW) is biodegradable in landfills under anaerobic conditions. The evolution of the hydro-biochemical-mechanical (HBM) processes during degradation is investigated first through experiments and subsequently through modelling. Three well-characterised MSW specimens from US landfill sites with significantly different waste compositions ranging from ‘waste-rich’ to ‘soil-rich’ were degraded in large-scale experimental set-ups that enabled simultaneous characterisation of the processes with time. The closely monitored processes are subsequently modelled using a two-stage anaerobic degradation model which is incorporated in the HBM model. This allows an assessment of model performance as a function of waste composition and derivation of waste-composition-dependent model parameters. The model performed fairly well in capturing the biochemical and physical behaviours. An increase in biodegradable material in waste specimen corresponds to an increase in anaerobic activity (volatile fatty acids and methanogenic biomass accumulation), a higher rate of organic fraction depletion, an increase in settlement and an increase in methane production. However, the model is found to significantly overpredict methane production for all the specimens.