Aerial estimates of methane and carbon dioxide emission rates using a mass balance approach in New York State

Abstract. Accurate greenhouse gas (GHG) emission 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, showing 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 to 3440 kg h−1. There was also significant variation in observed emissions within facilities between seasons, indicating a significant influence from meteorology. Variation in estimated measured emissions between different landfills could be due to operational differences. Observed carbon dioxide emission estimates were dominated by combustion facilities, followed by landfills. Comparisons with the inventory show that methane emissions averaged over 10 observed landfills are underestimated by a factor of 2. However, of the 10 landfills, 5 had observed methane emission estimates significantly higher than the inventory value, 4 had an inventory value within the uncertainty range of the observations, and 1 had a landfill-observed emission estimate that was markedly lower than the reported inventory estimate. Seneca Meadows Landfill was the highest emitter from the measurements and was ∼ 4.3× higher than the annual average estimate that was reported to the 2021 EPA GHGRP Inventory. NYS can use this information to inform the NYS GHG Inventory and improve emission estimation methodologies to better depict actual emissions. The two datasets described in this paper are published on PANGAEA. The raw dataset can be found at https://doi.org/10.1594/PANGAEA.979845 (Catena and Smith, 2025a). The emission rate dataset can be found at https://doi.org/10.1594/PANGAEA.979843 (Catena and Smith, 2025b).