Characterizing the spatiotemporal variability in methane emissions from a large municipal solid waste landfill in Québec, Canada

Landfills contributed 18% of anthropogenic methane (CH4) emissions in Canada in 2023. Regulatory efforts have been implemented to reduce these emissions by 50% by 2030 relative to 2019 levels. A comprehensive understanding of the spatiotemporal variability of landfill CH4 emissions is required to support the effective implementation of these policies. In this study, we investigated the spatiotemporal variability of CH4 emissions at a large municipal solid waste landfill in Sainte-Sophie, Québec, Canada, from May to July 2022. We used four measurement methods covering different spatial scales from point to facility levels: static chambers (point scale), eddy covariance and semiconductor sensors (landfill section scale), and mobile concentration surveys (facility scale). Multi-scale measurements identified CH4 emission hotspots in the active section and intermediate cover area, as well as near the leachate treatment facility in the landfill. At the facility scale, an average emission rate of 14,000 ± 5,100 kg day-1 from the entire landfill was estimated using a backward Lagrangian stochastic model. At the section and point scales, we characterized spatiotemporal CH4 emission patterns and identified several CH4 emission hotspots and key drivers. No pronounced temporal patterns of CH4 emissions were observed over the two-month study period. The findings highlight that identifying key emission hotspots at the facility scale, followed by continued monitoring at finer spatial scales, is essential for effectively characterizing CH­4 emissions. Such efforts can support the effective implementation of the regulatory frameworks aimed at mitigating CH4 emissions from landfills.