Developing Measurement-InformedMethane EmissionsInventory Estimates at Midstream Compressor Stations

Natural gas transmissions and storage compressor stations account for the largest share of anthropogenic methane (CH₄) emissions in New York State (NYS). Yet, NYS’s CH₄ emissions inventory is based on measurements that are a decade old and potentially unlikely to be representative of NYS operations. Here, we present results from a comprehensive, multiscale aerial CH₄ measurement campaign across all NYS transmission and storage compressor stations. We find a skewed emissions distribution, with 20% of stations accounting for 74% of total CH₄ emissions. Emissions at engine-driven compressor stations are, on average, 3–4× higher than emissions at turbine-driven compressor stations, thus demonstrating the need for separate emissions factors for engine- and turbine-drive compressor stations. Overall, measurement-informed emissions inventory from midstream transmission and storage compressor stations in NYS is 72% and 69% lower than the current NYS inventory, respectively. We estimate updated emissions factors of 464 [95% CI: 162–920] metric ton (MT) CH₄/station/yr and 139 [97, 191] MT CH₄/station/yr for engine- and turbine-based transmission compressor stations, respectively. Similarly, we estimate an updated emissions factor of 413 [164, 733] MT CH₄/station/yr for engine-based storage compressor stations. These updated emissions factors, along with improved activity data, enable effective reconciliation of NYS inventory with measured emissions.