Measurement of methane emission rates from several landfill sites in Indiana, USA using an aircraft-based platform

Landfills are one of the most important anthropogenic sources of methane with global emission estimates ranging from 500 - 800 MtCO2-eq/yr. However, because of the spatial inhomogeneity and large areal extent of landfill sites, previous estimates of methane emissions from direct, small-scale surface enclosure techniques varied over seven orders of magnitude. As a diffuse methane source, it is a challenge to obtain an average flux estimate for a given landfill site. Here we present methane emission rates from several landfill sites in Indiana, USA estimated using a whole landfill measurement technique. Using cavity ring-down spectroscopy and a mass balance approach, methane plumes from the landfill are measured downwind of the field site with an aircraft-based platform. By flying perpendicular to the prevailing wind direction, the mobility of the aircraft allows for multiple horizontal transect measurements at various altitudes up to the top of the convective boundary layer to rigorously intercept and quantify the methane plume. In this work, we will discuss our unique measurement technique as well as investigate the relationship between the measured methane emission rates to the reported annual disposal rates in these landfill sites.