Global warming potential implications of US waste LCA assumptions: A perturbation-based approach for decision support

Waste management decision makers often rely on LCA findings to determine effective strategies to reduce environmental impacts, of which climate change mitigation has become centerstage. The complexity of conducting an LCA for waste management decision making is typically simplified using comprehensive models developed for wide region (e.g., United States, United Kingdom, Denmark) containing geographic and temporal metadata particular to the region. The aims of this study are to: 1) determine hotspot assumptions triggering the greatest sensitivity to the global warming potential (GWP) indicator for the management of various waste components in the US; and 2) inform on data collection approaches decision makers may use to improve their waste LCA by applying the findings of the first aim to a US context. A perturbation analysis was conducted for several recycling, landfilling, and combusting parameters using the Solid Waste Optimization Framework (SWOLF) Model. For landfilling, critical assumptions included landfill gas management factors such as lifetime gas collection efficiency, the type of gas management employed, and the bulk decay rate. In recycling, the most influential factor was the material substitution ratio. For combustion, key parameters were the avoided emissions from the electrical grid mixture and the types of metals recovered from the ash. Whenever data is available it should be supplemented in place of defaults to reduce uncertainty in waste LCA tools, especially the parameters highlighted that have influential impacts on results.