Bury or Burn North America MSW? LCAs Provide Answers for Climate Impacts & Carbon Neutral Power Potential

Abstract

This study uses life cycle assessment (LCA) to compare climate impacts of landfill (LF) and waste-to-energy (WTE) for disposal of municipal solid waste (MSW). To avoid possibly arbitrary assumptions about landfill gas (LFG) capture rates, the study develops a crossover function for LFG capture that indicates the capture rate at which LF and WTE breakeven for climate impacts. Above the crossover rate LF is better for the climate; below WTE is superior. Base case and sensitivity analyses show how this crossover rate is affected by waste composition, electricity conversion efficiency, heat capture, scrap metal recovery, greenhouse gas (GHG) intensity of displaced power, and LCA time horizon. In general, crossover rates are in the 50% to 70% range. Notable exceptions include much higher crossover when WTE has high heat recovery, and much lower crossover for low carbon displaced power. The study also compares GHG emissions for electricity generated by WTE, captured LF methane, coal and natural gas, and concludes that none are carbon neutral. Further, the study tentatively suggests that MSW is a particularly carbon intensive fuel due to GHGs avoidable when readily recyclable materials in MSW are used in manufacturing new products rather than used to generate electricity.