Canada’s landfill methane inventories: The challenge of accurate modeled and measurement-based emissions

We present a measurement-based assessment of methane emissions from 42 landfills across diverse climatic regions in Canada. Our findings reveal that emission rates predicted by the First-Order Decay (FOD) model used by Environment and Climate Change Canada at the visited sites are substantially higher than most measured emission rates, on average by a factor of 3, particularly for cold and arid climates typical of the Canadian prairie provinces (by a factor of 13 on average). Bias-corrected measurement rates aligned more closely with values reported to the Canadian Greenhouse Gas Reporting Program. Compared with the amounts estimated by the FOD model, our measurement-based estimates show greater variation with climate change. At some warmer, wetter sites, measured rates exceeded FOD-modeled estimates, underscoring the influence of climate on landfill methane dynamics and on FOD model behavior. We also found that measurement-based estimates yield more realistic methane collection effectiveness values than those implied by Canada’s FOD-based inventories. Our results suggest that the current FOD inventory model parameters—that include decay rates and oxidation assumptions—should be refined to better reflect site-specific conditions and climate variability across Canada.