Study finds super-emitters responsible for nearly 40% of methane emissions in five U.S. basins

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Research demonstrates how the coordinated use of multiple remote observing systems enables more complete greenhouse gas quantification over high-emitting regions.

September 13, 2022—Pasadena, CA—A study released today by Carbon Mapper, University of Arizona, NASA’s Jet Propulsion Laboratory (JPL), Arizona State University, and Environmental Defense Fund (EDF) shows that strong methane point sources contribute an average of 40% of total emissions across multiple basins in the U.S., revealing that a small number of emitters account for a disproportionately high fraction of emissions. The ability to quantify the regional impact of super-emitters (point sources that emit greater than 22 pounds or 10 kilograms of methane per hour)—and precisely determine their causes can improve the accuracy of emissions accounting and inform strategies for timely methane emissions mitigation.

Published today in the Proceedings of the National Academy of Sciences, the research is a key milestone in bridging the gap between research and operations of a global tiered observing system for methane. A tiered system involves the coordinated application of multiple technologies to observe and analyze methane emissions across a range of scales.

The team mapped five regions from 2019-2021 including the southern San Joaquin Valley in California, Uinta basin in Utah, Denver-Julesburg basin in Colorado, the Permian basin in Texas and New Mexico, and key sections of the Marcellus shale in Pennsylvania. Researchers used a tiered observing system to quantify the net regional emissions, as well as the contributions from over 3,000 individual high emission point sources.

“This study exposes the diversity of methane emission distributions both spatially and by sector across the U.S., offering a glimpse into the improved methane detection we can expect in the coming years thanks to the deployment of new satellites,” said Dr. Daniel Cusworth, Project Scientist with Carbon Mapper and lead author. “This multi-tiered observing approach demonstrates and reinforces the potential value of a more sustained and comprehensive assessment of methane sources.”

Researchers used airborne imaging spectrometers to pinpoint super-emitters by imaging invisible methane plumes at high resolution.

“Arizona State University’s Global Airborne Observatory (GAO), which is one of the imaging spectrometers used in this study, can pinpoint methane sources to within 15 feet while flying at 18,000 feet. When methane emission plumes are detected, we can then use a high-resolution imagery to relate the plumes to individual pieces of equipment,” said Greg Asner, professor and director of the Center for Global Discovery and Conservation Science, in the Julie Ann Wrigley Global Futures Laboratory at ASU.

The research team used the high-resolution data from the GAO and NASA JPL’s Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG) to attribute emissions to major sectors—including key oil and gas production segments, wet manure management from animal feedlots, large landfills, and coal mine venting—and assessed their intermittency by sampling each area several times, in some cases spanning intervals from months to years. The team then contextualized these emissions by comparing them with total basin methane derived from Sentinel 5p satellite observations.

They discovered that across all basins and time periods, super-emitters make up on average 40% of each basin’s total observed methane emissions. This occurs in both oil and gas dominant basins such as the Permian, but also in basins where other emissions sectors play an equivalent or larger role.

“These findings drive home the need for swift action to advance strong methane rules in the U.S., which should tackle pollution from practices like routine flaring—a common source of super-emitters from oil and gas facilities” said David Lyon, Sr. Scientist at Environmental Defense Fund, and study co-author. “This study shows that states that have established leading methane rules like Colorado and California appear to have a lower frequency of super-emitters, underlining the importance of strong nationwide rules from EPA.”

Additional key findings are as follows:

• Multiple surveys of each region revealed a population of both persistent (long-lived) emissions and intermittent (short-lived) emissions, each contributing roughly equally to total emissions. Long-lived sources may be indicative of undetected leaks as well as known, intentional releases (e.g., permitted coal venting). Short-lived sources may be indicative of expected releases (e.g., temporary maintenance) or intermittent malfunctions. Quantifying super-emitter persistence is an important factor for observing system design since infrequent measurements would not be able to distinguish between these modes and potentially over- or under-estimate average emission rates.
• Gathering pipelines made up 23% of point source emissions and were the second largest source of emissions. These pipeline emissions are highly variable in their oil and gas contribution across basins and even within basins over time, suggesting a priority area for greater observation and mitigation.
• In the surveyed area of the Marcellus basin in southwestern Pennsylvania, 58% of the observed methane in the region was attributed to point sources—primarily persistent coal mine ventilation. Coal mine venting in many cases is an expected and permitted operation but it’s important to understand the sector’s impact on regional and national greenhouse gas emissions.

“There is a critical need for persistent, open-source monitoring of methane emissions at local and regional scales around the world to guide mitigation efforts and ensure accurate accounting, particularly given international commitments under the Global Methane Pledge and new policies in the U.S. like methane provisions in the recently enacted Inflation Reduction Act and pending EPA rulemaking,” said Riley Duren, CEO of Carbon Mapper and Research Scientist with the University of Arizona who served as Principal Investigator for a series of NASA-funded projects that culminated in this study. “We look forward to applying the lessons learned from this study as new complementary satellite programs join the expanding global methane monitoring system of systems next year.”

Download the full study at https://www.pnas.org/doi/10.1073/pnas.2202338119.

About Carbon Mapper

Carbon Mapper is a non-profit organization focused on facilitating timely action to mitigate greenhouse gas emissions. Its mission is to fill gaps in the emerging global ecosystem of methane and CO₂ monitoring systems by delivering data at facility scale that is precise, timely, and accessible to empower science-based decision making and action. The organization is leading the development of the Carbon Mapper constellation of satellites supported by a public-private partnership composed of Planet Labs PBC, NASA’s Jet Propulsion Lab, the California Air Resources Board, the University of Arizona, Arizona State University, and RMI, with funding from High Tide Foundation, Bloomberg Philanthropies, The Grantham Foundation, and other philanthropic donors. Learn more at carbonmapper.org and follow us on Twitter @carbonmapper.

About the University of Arizona

The University of Arizona, a land-grant university with two independently accredited medical schools, is one of the nation’s top 50 public universities, according to U.S. News & World Report. Established in 1885, the university is widely recognized as a student-centric university and has been designated as a Hispanic Serving Institution by the U.S. Department of Education. The university ranked in the top 20 in 2020 in research expenditures among all public universities, according to the National Science Foundation, and is a leading Research 1 institution with $761 million in annual research expenditures. The university advances the frontiers of interdisciplinary scholarship and entrepreneurial partnerships as a member of the Association of American Universities, the 66 leading public and private research universities in the U.S. It benefits the state with an estimated economic impact of $4.1 billion annually.

About Arizona State University

Arizona State University’s Global Airborne Observatory (GAO) is owned and operated by the Center for Global Discovery and Conservation Science at Arizona State University. The GAO is made possible by support from private foundations, visionary individuals, and Arizona State University. ASU ranked No. 1 “Most Innovative School” in the nation by U.S. News & World Report for seven years in succession, has forged the model for a New American University. ASU is a comprehensive public research institution, measured not by whom it excludes, but by whom it includes and how they succeed; advancing research and discovery of public value; and assuming fundamental responsibility for the economic, social, cultural, and overall health of the communities it serves.

About NASA Jet Propulsion Laboratory (JPL)

JPL is a federal-funded research and development center managed by Caltech for NASA. Since the start of the Space Age, JPL has developed and launched robotic missions to explore the solar system and beyond. NASA-JPL missions also monitor Earth from land, air, and space with a fleet of satellites and airborne and ground-based observation campaigns, collecting long-term data records that contribute to understanding and protecting our home planet.