The U.S. oil and gas industry is responsible for emitting 3 times more methane than current government estimates, according to a new study. Those emissions cost $9.3 billion annually because of their effects on global warming and air quality, the authors estimated.
The study, published in Nature, used aerial surveys to track methane emissions from oil and gas fields, pipelines, processing facilities, and more in six fossil fuel–producing regions of the United States. It adds to a growing body of evidence indicating that methane emissions are far higher than previously thought.
Methane is a potent greenhouse gas, often calculated to be 28 times more powerful than carbon dioxide (though some studies say it could be even more powerful), and is responsible for around a third of human-caused global warming to date.
Curtailing these emissions has been a focus of recent regulatory efforts, such as the Global Methane Pledge, signed by more than 150 countries that agreed to reduce methane emissions by 30% by 2030. The U.S. EPA also recently unveiled new rules, set to take effect in May, that aim to cut 58 million tons of methane emissions over the next 15 years.
Historically, getting a handle on where methane emissions are coming from has proven to be difficult. It’s only in the past decade or so that new technologies such as ground-based surveys, specialized satellites, and aerial survey techniques have allowed researchers to begin to pinpoint methane sources.
Those efforts were “really eye-opening for the scientific and policy community,” said methane data scientist Evan Sherwin from Lawrence Berkeley National Laboratory, especially given that the data pointed to a small number of very large emitters making up much of the methane released. Sherwin is lead author of the new paper, which was supported by Stanford University’s Department of Energy Science and Engineering and funded by the Stanford Natural Gas Initiative, which is supported by the fossil fuel industry.
Getting a Grip on Methane
For a more comprehensive look at methane emissions, Sherwin and his colleagues took data from 15 aerial surveys completed between 2017 and 2021, covering almost a million oil and gas sites across six regions of the United States.
The surveys covered just a portion of the country’s onshore oil and gas production. Even so, the results were striking.
Combining their measurements with estimates from sources too small to be detected from above, the researchers found that the surveyed regions emit about 6.2 million tons of methane per year, or about 3% of total fossil fuel production from those sites, far more than previously thought. That amounts to about a billion dollars in losses for fossil fuel companies and a large chunk of total U.S. methane emissions.
“One big takeaway is that this is a pretty solvable problem.”
Most methane emissions came from a small number of sources within the production and processing supply chain. In California’s San Joaquin Valley, fewer than 1% of sites release more than half the measured methane emissions.
“It’s way more concentrated than we thought,” Sherwin said.
Sources of methane emissions include flares that blow out, allowing the gas to escape rather than being burned, as well as pressure release valves on oil tanks, according to Sherwin. But ultimately, he said, methane escapes during every stage of the oil and gas supply chain. He estimates that about half of methane emissions from oil and gas production come from midstream infrastructure, which includes compressor stations, gas processing plants, and pipelines.
Though these sources are troubling, they are also likely to be relatively easy to fix. “One big takeaway is that this is a pretty solvable problem, at least a great chunk of it,” Sherwin said.
Geography Matters
The researchers also found big differences in methane release between regions. In the Denver-Julesburg Basin, centered in eastern Colorado, slightly more than 1% of total oil and gas production was released as methane. In the New Mexico portion of the Permian Basin, methane release rates were almost 10% of total production. The difference comes down to several factors, such as the type of fossil fuel produced and the productivity of the well site.
The true magnitude of emissions is likely higher, Sherwin cautioned. The researchers were conservative in their estimates, including the fraction of methane found in oil deposits and the amount of methane released from smaller sources.
Another difficulty in getting an estimate is that many large point sources, such as blown-out flares, are transient. So surveys taken at two different times could find varying amounts and sources of methane. Aerial surveys are important because they can be repeated, Sherwin said.
Better Methane Data Still Needed
Aerial surveys also have their drawbacks, said Ritesh Gautam, an atmospheric scientist with the Environmental Defense Fund (EDF). The aerial survey platform used in the study can’t capture smaller sources (though some others can), he said, meaning aerial-only surveys will miss some emissions.
“Flying over an area or flying over sites does not always mean that you’re measuring emissions from it,” Gautam said. He added that some recent studies indicated that the methods of estimating smaller emissions sources, such as that used by Sherwin and his coauthors, may be underestimating methane release.
“While the study makes an important contribution towards characterizing high-emitting point sources, we need more direct measurements and observations for characterizing the total regional emissions,” Gautam said.
For a true picture of global methane emissions, scientists will need to combine ground, aerial, and satellite surveys for a more cohesive look, Gautam said. That could be on the horizon, as new satellites such as EDF’s MethaneSAT enter operation and as methane surveys expand.
Action on methane emissions from both the fossil fuel industry and governments has been slow to ramp up, though it’s now gaining momentum. With potential gains for both fossil fuel companies and society at large for doing so, the incentives may be aligned for real action to take place.
—Nathaniel Scharping (@nathanielscharp), Science Writer