A review of LCA assumptions impacting whether landfilling or incineration results in less greenhouse gas emissions

Abstract

One common life cycle assessment (LCA) focus is to understand whether landfill or municipal solid waste incineration (MSWI) treatment is more environmentally favorable. Past studies have focused on evaluating which disposal treatment method had the least greenhouse gas (GHG) emissions footprint and in most cases MSWI treatment was more favorable. Surprisingly, several studies reported contrasting results where landfilling was more GHG emissions favorable than MSWI. Here, we compiled numerous peer-reviewed papers and identified which key LCA assumptions resulted in a paper reporting landfill or MSWI treatment to be more favorable. The assumptions related to landfill gas management, specifically, a high gas collection (>75%) and landfill gas-to-energy recovery efficiency (>90%) were reported as crucial for landfilling to be more favorable. The MSWI treatment assumptions of including energy recovery offsets from when energy is produced from incinerated waste and used to replace fossil fuel-based energy sources was key for MSWI to be more favorable. The review findings provided a general insight on key assumptions, however we aimed to understand which specific assumptions had the greatest influence on results. To do so, we used the review findings to tailor an LCA analysis where we assessed whether landfilling or MSWI was more GHG emissions favorable based on changing waste stream composition, landfill gas management, and energy grid. An aggressive gas collection management (collecting gas early and long with gas-to-energy), a waste stream with more plastic (>40%), and a more fossil-based energy grid (>50%) favored landfilling.