Evaluation of GHGSat Methane Emission Estimations of South Side Landfill in Indianapolis, Indiana

As global methane (CH4) continues to grow, accurate quantification of CH4 emission sources has become a high priority for climate management. Urban CH4 emissions in the US could potentially account close to 20% of the national CH4 anthropogenic emissions. While isolated insitu urban CH4 emissions quantification projects have been successful, they require sophisticated planning and prolonged analyses. Such studies are imperative, but they cannot easily operate in every city. An ability to quantify the magnitude of CH4 point sources in a variety of cities with a satellite could support wide scale urban CH4 emissions quantification. Whole-earth scanning satellite instruments such as the TROPOMI and GOSAT are too coarse and noisy to provide meaningful measurements over cities with mid-strength emissions and most point-source emissions in general. It may be possible to address this deficiency utilizing a product with the high spatial resolution of 30-50 m from a private company GHGSat Inc. These sensors are specifically designed to identify and quantify CH4 emissions from diverse types of point sources of varying intensities. In this work we analyze a year (05/2023-05/2024) of GHGSat scans over South Side Landfill in downtown Indianapolis, Indiana and assess the instruments’ accuracy and precision with respect to prior estimations. The results indicate that the data are helpful for estimating landfill’s emissions (~750 kg/hr ± 200 kg/hr) over months-to-a-year time frame but may not be appropriate for identifying daily or even seasonal variations with any trustable degree of certainty, at least not in an urban environment.