Finite-Element Modeling of Landfills to Estimate Heat Generation, Transport, and Accumulation

Abstract

In North America, temperatures nearing 100°C have been reported in several municipal solid waste landfills. However, the temporal and spatial-dependent processes that result in excessive heat accumulation are not well understood. The objective of this study was to develop a transient finite-element three-dimensional model that incorporates gas-liquid-heat reactive transfer in a landfill with biotic and abiotic reactions and spatially dependent heat transfer processes to better understand heat generation, accumulation, and propagation. The model incorporates gas-liquid-heat reactive transfer with aerobic and anaerobic biological reactions, anaerobic metal corrosion, and ash hydration and carbonation. Increasing boundary temperature, biological reaction rates, and landfill height increase the maximum temperature in the central region of a landfill, whereas the impact of thermal properties of municipal solid waste (MSW) is small. Simulation results predict that placement of ash near the corner of a landfill reduces the size of the elevated temperature region relative to placement in the landfill center. Mixing heat-generating wastes (ash or Al) with MSW decreases maximum temperatures but results in elevated temperatures over a larger fraction of the landfill volume relative to segregated ash disposal.