U.S. Ethane Emissions and Trends Estimated from Atmospheric Observations.

Oil and natural gas (O&G) production and processing activities have changed markedly across the U.S. over the past several years. However, the impacts of these changes on air pollution and greenhouse gas emissions are not clear. In this study, we examine U.S. ethane (CH) emissions, which are primarily from O&G activities, during years 2015-2020. We use CH observations made by the NOAA Global Monitoring Laboratory and partner organizations from towers and aircraft and estimate emissions from these observations by using an inverse model. We find that U.S. CH emissions (4.43 ± 0.2 Tg·yr) are approximately three times those estimated by the EPA's 2017 National Emissions Inventory (NEI) platform (1.54 Tg·yr) and exhibit a very different seasonal cycle. We also find that changes in U.S. CH emissions are decoupled from reported changes in production; emissions increased 6.3 ± 7.6% (0.25 ± 0.31 Tg) between 2015 and 2020 while reported CH production increased by a much larger amount (78%). Our results also suggest an apparent correlation between CH emissions and CH spot prices, where prices could be a proxy for pressure on the infrastructure across the supply chain. Overall, these results provide insight into how U.S. CH emissions are changing over time.