Comparison of Landfill Methane Emission Quantification Using Multiple Observation Methods

Quantifying facility-level methane (CH₄) emissions is an important task for measuring progress toward net zero and carbon emission reduction targets. Landfills are a significant source of anthropogenic CH₄ emissions in Canada. Quantifying Canadian landfill emissions is also critical for validating assumptions in bottom-up inventory calculations but is a challenging task because of their variability in emissions sources and complex topography on and near landfill sites. We compare CH₄ emissions estimates for seven different emissions quantification strategies and platforms at a large landfill in Southern Ontario, Canada. We compare ground-based, aircraft-based, and satellite-based remote sensing techniques in addition to ground-based stationary, mobile, and aircraft-based in situ observation strategies across a 3.5-year period, including a 28-month deployment of a low-precision sensor network for continuous monitoring. Each methodology quantified a large range of emissions rates that vary by 1 order of magnitude for the site (∼200-2000 kg·h^-1), and the average estimated emissions rates agree within uncertainty. We find that the remote sensing methods have a higher empirical minimum detection limit and are sufficient for quantifying 20-50% of all Canadian landfill sites, while ground-based in situ methods have detection limits suitable for quantifying emissions from the majority of accessible landfill sites.