Life Cycle Assessment of Biogeochemical versus Conventional Soil Landfill Cover: Sensitivity and Uncertainty Analyses

Municipal solid waste landfills are the third-largest anthropogenic source of methane (CH4) emissions in the United States, contributing significantly to climate change. Although engineered landfills utilize gas collection and soil cover systems, fugitive emissions of landfill gas, including CH4 and CO2, persist. To mitigate these emissions, an innovative biogeochemical cover (BGCC) system was developed. The BGCC integrates a biochar-based biocover layer that enhances CH4 oxidation, overlaid with basic oxygen furnace (BOF) slag to capture CO2 and H2S via mineral carbonation and sulfidation mechanisms, respectively. A previous baseline life cycle assessment (LCA) evaluated the environmental sustainability of the BGCC system, but it did not explore parametric uncertainties or conduct sensitivity analysis with different variables. This study expands upon that by conducting a LCA of the BGCC and conventional soil cover (SC) systems, incorporating (1) a baseline case where materials such as BOF slag, biochar, and sand are locally sourced; (2) a sensitivity analysis to identify parameters most influencing the environmental performance of the BGCC system; and (3) an uncertainty analysis to assess the robustness of the estimated environmental impacts. Results show that the BGCC system outperforms the SC system across all environmental impact categories in the baseline case. Notably, the BGCC system offers 4.5 times higher global warming mitigation potential than the SC system. The CH4 oxidation rate was identified as the most sensitive parameter. However, increasing the transportation distance of BOF slag beyond 200 km may offset BGCC’s benefits in certain impact categories. The uncertainty analysis revealed high variability in fossil fuel depletion, smog formation, and acidification impacts. Nonetheless, over 90% of simulations indicated greater negative impacts for the SC system. Overall, the BGCC system demonstrates substantially higher environmental sustainability than SC systems, driven by its superior performance in mitigating greenhouse gas emissions and leveraging waste-derived materials for beneficial reuse.