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 (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 NOx over footprints that account for similar to 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 similar to 10% of top-down aircraft-derived NOx emissions. We also find good agreement in the trends of NOx 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 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 NOx emissions are similar to 40% lower, while inferred CH4 and NMVOC emissions are up to a factor of similar to 2 higher. This suggests that NMVOC/NOx emissions from oil and gas basins are similar to 3 times higher than current estimates and will likely affect how air quality models represent ozone formation downwind of oil and gas fields.

Automated summary

This study provides an updated fuel-based oil and gas inventory, estimating NOx emissions from production in the contiguous US, and compares it with aircraft-derived emissions. The research shows good agreement between the bottom-up inventory and top-down aircraft-derived NOx emissions. It also suggests that NMVOC/NOx emissions from oil and gas basins may be three times higher than current estimates, potentially affecting how air quality models represent ozone formation downwind of oil and gas fields.