Quantifying Methane and Ozone Precursor Emissions from Oil and Gas Production Regions across the Contiguous US

We present an updated fuel-based oil and gas (FOG) inventory with estimates of nitrogen oxide (NO_x) emissions from oil and natural gas production in the contiguous US (CONUS). We compare the FOG inventory with aircraft-derived ("top-down") emissions for NO_x over footprints that account for ∼25% of US oil and natural gas production. Across CONUS, we find that the bottom-up FOG inventory combined with other anthropogenic emissions is on average within ∼10% of top-down aircraft-derived NO_x emissions. We also find good agreement in the trends of NO_x from drilling- and production-phase activities, as inferred by satellites and in the bottom-up inventory. Leveraging tracer-tracer relationships derived from aircraft observations, methane (CH₄) and non-methane volatile organic compound (NMVOC) emissions have been added to the inventory. Our total CONUS emission estimates for 2015 of oil and natural gas are 0.45 ± 0.14 Tg NO_x/yr, 15.2 ± 3.0 Tg CH₄/yr, and 5.7 ± 1.7 Tg NMVOC/yr. Compared to the US National Emissions Inventory and Greenhouse Gas Inventory, FOG NO_x emissions are ∼40% lower, while inferred CH₄ and NMVOC emissions are up to a factor of ∼2 higher. This suggests that NMVOC/NO_x emissions from oil and gas basins are ∼3 times higher than current estimates and will likely affect how air quality models represent ozone formation downwind of oil and gas fields.