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 (C₂H₆) emissions, which are primarily from O&G activities, during years 2015-2020. We use C₂H₆ 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. C₂H₆ emissions (4.43 ± 0.2 Tg·yr^-1) are approximately three times those estimated by the EPA's 2017 National Emissions Inventory (NEI) platform (1.54 Tg·yr^-1) and exhibit a very different seasonal cycle. We also find that changes in U.S. C₂H₆ 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 C₂H₆ production increased by a much larger amount (78%). Our results also suggest an apparent correlation between C₂H₆ emissions and C₂H₆ 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. C₂H₆ emissions are changing over time.