Numerical modeling of coupled biochemical and thermal behavior of municipal solid waste in landfills

Abstract

A coupled bio-thermal (BT) model is proposed and validated for the prediction of long-term biochemical and thermal behavior of municipal solid waste (MSW) in landfills. The biochemical and thermal behavior of the waste was modeled using a two-stage anaerobic degradation model and diffusive heat transport model, respectively. A temperature function that accounts for the inhibitory effect of non-optimum temperatures on the microbial growth was proposed to simulate the coupled effects of biochemical and thermal behavior of waste in landfills. Six numerical simulation cases representing conventional and bioreactor landfill conditions were performed on a typical full-scale landfill cell model to determine the spatial and temporal variation in the long-term biochemical and thermal characteristics of waste in landfills. The results from the numerical analyses show that incorporating the effect of temperature of waste in the modeling of biodegradation of waste in landfills plays a significant role in realistically predicting the long-term biochemical and thermal regime in MSW landfills. The proposed BT model captures the key trends in the landfill gas (LFG) production and waste temperatures typically observed in actual full-scale landfills. Elevated waste temperatures were predicted especially in the bioreactor landfill cases suggesting that rapid decomposition of waste induces high heat generation rates; however, the elevated temperatures were short-lived.