Thermal Conductivity of Municipal Solid Waste from In Situ Heat Extraction Tests

Given that municipal solid waste (MSW) in landfills can reach temperatures greater than 50 degrees C that may be sustained for several decades due to methanogenic bacteria activity, the generated heat is an alternative energy source that can be exploited for direct heating of nearby infrastructure or for augmenting industrial processes. However, in situ measurements of MSW thermal properties are needed to properly design heat extraction systems for landfills. In this study, the spatial and temporal evolution of the waste temperatures in a new MSW landfill cell in Santee, California, were monitored over 13 months. After the temperatures reached stable values, a 17-day heat extraction thermal response test was performed on serpentine geothermal heat exchangers that were installed at three elevations in the cell during waste placement. Because the serpentine segments were separated from each other to minimize thermal interference during the heat extraction test, the pipes were assumed to represent line heat sinks. The values of effective thermal conductivity estimated from infinite line source analyses ranged from 0.86 to 1.32 W/m degrees C, which are consistent with values on the higher range of those from laboratory tests on MSW. (c) 2020 American Society of Civil Engineers.