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

• Published in: Environmental science & technology 2024-09, Vol.58 (35), p.15539-15550
• Main Authors: Zhang, Mingyang, Vimont, Isaac J., Jordaan, Sarah M., Hu, Lei, McKain, Kathryn, Crotwell, Molly, Gaeta, Dylan C., Miller, Scot M.
• Format: Article
• Language: English
• Subjects: Air Pollutants - analysis; Air Pollution; Atmosphere - chemistry; Emission inventories; Emissions; Energy and Climate; Environmental Monitoring; Ethane; Ethane - analysis; Greenhouse gases; Natural Gas; Supply chains; United States
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/acs.est.4c00380

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.