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

Abstract

We present an updated fuel-based oil and gas (FOG) inventory with estimates of nitrogen oxide (NOx) emissions from oil and natural gas production in the contiguous US (CONUS). We compare the FOG inventory with aircraft-derived (“top-down”) emissions for NOxover 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 NOxemissions. We also find good agreement in the trends of NOxfrom 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 NOx/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 NOxemissions are ∼40% lower, while inferred CH4and NMVOC emissions are up to a factor of ∼2 higher. This suggests that NMVOC/NOxemissions 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.