Seasonal landfill methane emissions driven by temperature and pressure

More than a quarter of anthropogenic global warming has been attributed to
methane growth in the atmosphere. Landfills account for 17 % of estimated
methane emissions in the United States of America (USA), according to the
Environmental Protection Agency (EPA), but studies show that many
landfills emit more than reported. We developed a novel method to
calculate monthly methane emissions from an active landfill using
atmospheric methane mixing ratios observed from a single tower in New
Jersey, USA. The tower method provides two and a half years of
semi-continuous measurements and therefore observes more of the
variability of methane emissions and lacks the sampling bias present in
other methods. Time-specific comparison of tower-based methane emissions
against those observed from summertime aircraft sampling and year-round
mobile ground-based platforms showed good agreement. Estimated methane
emissions for 2023 were five times greater than those reported to the EPA.
We observed a strong seasonality in methane emissions, with a peak in the
winter and a minimum in the summer. This seasonal cycle was driven by a
strong negative dependence on air temperature and the change in
atmospheric pressure. Our results highlight the importance of observations
in non-ideal weather conditions (such as declining pressure and
near-freezing temperatures) when methane emissions are largest. We suggest
that this methodology could be applied to other suitable landfills to
improve estimates of methane emissions.