Incorporating Thermal Effects in Modeling of MSW Landfills

Abstract

Heat is one of the primary byproducts of biodegradation of municipal solid waste (MSW). Biodegradation of MSW in landfills induces changes in physical properties, mechanical response of MSW, and flow of leachate within the MSW pore spaces. Moreover, biodegradation of MSW in landfills is temperature dependent and consequently the engineering properties of MSW are all influenced by waste temperatures. Thus, landfills are complex systems with interrelated processes and it is crucial to account for all these interdependencies to accurately predict the coupled behavior of MSW. In this study, a coupled-thermo-hydro-bio-mechanical model was formulated that incorporates the effect of temperature on heat generation and biodegradation of MSW. The model integrates a two-phase flow hydraulic model, a plane-strain formulation of the Mohr-Coulomb mechanical model, a first order decay biodegradation model, and a one-dimensional heat conduction model with temperature-dependent heat generation. Numerical simulations were carried out using a typical landfill configuration with leachate injection simulating a bioreactor landfill. The simulations were carried out with and without temperature effects to determine the influence of temperature on MSW behavior. The results indicate a significant influence of temperature on the MSW response (degradation and settlement) and underscore the importance of incorporating thermal effects in numerical modeling of MSW landfill systems.