Emissions of Methane, Ethane, and VOCs from the Denver-Julesburg Basin from airborne studies in 2023: Improved Quantification with Independent Wind Observations

Oil and natural gas (O&G) operations emit substantial methane (CH 4 ), ethane (C 2 H 6 ), and other volatile organic compounds (VOCs), yet their fluxes and trends remain uncertain. We conducted airborne mass balance measurements of CH 4 and C 2 H 6 in the Wattenberg Field of the Denver-Julesburg Basin during four flights in October -November 2023. An updated framework integrates mobile lidar wind profiles with modeled winds to better resolve wind speed and planetary boundary layer height, two dominant sources of uncertainty, improving confidence in derived fluxes. Expanded VOC analysis distinguishes agricultural CH 4 emissions from concentrated animal feeding operations (CAFOs), assessing acetic acid (CH 3 COOH) temperature sensitivity following freezing conditions and ethanol as a potential CAFO tracer. CH 3 COOH shows temperature sensitivity, but enhancements remain sufficient, supporting its use as a robust CAFO tracer. Tracer analysis using C 2 H 6 and CH 3 COOH attributes 66 +/- 17% of CH 4 emissions to O&G sources, with the remainder dominated by CAFOs. Total CH 4 emission rates in 2023 (26.0 +/- 7.5 t hr -1 ) are consistent with prior measurements from 2012—2023 despite increased O&G production, while C 2 H 6 emission rates (3.2 +/- 0.6 t hr -1 ) have declined. Production-normalized CH 4 and C 2 H 6 emission intensities have decreased substantially since earlier studies, although most of the decline occurred before 2021, with little change observed between 2021 and 2023. Expanded flights, coverage, and platforms improve confidence in emission intensity estimates.