Aerial Estimates of Methane and Carbon Dioxide Emission Rates Using a Mass Balance Approach in New York State

Abstract. Accurate greenhouse gas (GHG) emissions inventories are vital for climate mitigation as they can identify areas of need and ensure effective policy and regulation in reducing GHG emissions. Several studies have shown that self-reporting GHG inventories are undercounting methane emissions across all anthropogenic sectors showcasing an increasing need to validate the inventory with direct measurements. This study carried out aerial observations and emission rates of methane and carbon dioxide across multiple sectors in New York State (NYS). Emission rates were calculated for each of the sources using a mass balance method and were subsequently compared to the 2021 Environmental Protection Agency GHG Reporting Program (EPA GHGRP) Inventory. Landfills were the source of the highest observed methane emission estimates, ranging from 161–3440 kg/hr. There was also significant variation in observed emissions within facilities between seasons indicating a significant influence from meteorology. Observed carbon dioxide emission estimates were dominated by combustion facilities followed by landfills. Comparisons with the inventory show that methane emissions averaged over ten observed landfills are underestimated by a factor of 2. However, out of the ten landfills, five landfills had observed methane emission estimates significantly higher than the inventory value, four landfills had an inventory value within the uncertainty range of the observations, and one landfill observed emission estimate was markedly lower than the reported inventory estimate. Seneca Meadows Landfill was the highest emitter from the measurements and was ~4.3x higher than what was reported to the 2021 EPA GHGRP Inventory. The difference in emissions between landfills could be due to operational differences or waste quantities. NYS can use this information to inform the NYS GHG Inventory and improve emission estimation methodologies to better depict actual emissions.