Municipal solid waste landfills as geothermal heat sources

Abstract

It is well established that ground-source heat pumps (GSHPs) require less external energy input than conventional heating and cooling systems for buildings because they exchange heat with the subsurface soil and rock, which has a steady temperature compared to that of the outside air. To address barriers to implementation for GSHPs, incorporation of heat exchangers into civil engineering infrastructure is being investigated to reduce installation costs. Of these infrastructures, municipal solid waste (MSW) landfills may be a potential source of heat for GSHPs due to their elevated temperatures associated with the long-term, exothermic decomposition of organic materials within the waste. To assess this potential, this paper provides a review of studies focused on characterization of the thermal resource of landfilled MSW. Further, the potential impacts of heat exchange on rates of methane generation, hydraulic performance of landfill liners, and clogging of leachate collection systems are evaluated. Based on landfill construction requirements and different approaches for GSHP installation used in practice, configurations for geothermal heat exchangers in landfills are proposed for different landfill operational and closure scenarios. An economic analysis of geothermal heat exchange in MSW landfills indicates that they are expected to provide an accessible and sustainable thermal energy resource.