Understanding Trends in Methane Emissions from Landfills through Repeat Aerial Surveys

Abstract

Landfills contribute 18% of all anthropogenic methane emissions in the US. While prior work has shown that official inventories underestimate landfill methane emissions compared to measurements, no systematic study of the spatiotemporal variation in landfill emissions exists. In this work, we report on results from quarterly, source-resolved, aerial methane measurements across 46 landfills in the Appalachian Basin. While total landfill emissions were found to be consistent across all surveys, we observe significant variability in emissions from individual landfills, with total annual emissions of 76028 ± 1437 t per year. Local rainfall events up to a week before surveys resulted in approximately 29% higher emissions. We see that methane emissions can be empirically predicted based on the annual rate of bulk waste disposed, providing an independent method to validate field measurements. In addition, landfills with renewable natural gas facilities were the highest emitters but had the lowest emissions intensity (per metric ton of bulk waste disposed). We estimate a mean measurement-informed landfill gas collection efficiency of 53 ± 1.9%, significantly lower than the mean reported value of 81%. Our findings underscore the need to update reporting methods that account for measured data to improve the accuracy of landfill methane emissions.