An analysis of previously reported data alongside new airborne measurements suggests that the annual methane leaks from the US oil and gas industry are 60% higher than officially estimated levels.

Methane, a primary component of natural gas and a potent greenhouse gas, has a warming effect over 20 years more than 80 times that of carbon dioxide. Scientists say these unaccounted methane emissions could have significant impacts on climate and the economy. It's estimated that the lost natural gas alone amounts to $2 billion annually.

Published on June 21 in the journal Science, this analysis is one of the most comprehensive studies to date on methane production in the US oil and gas industry, reinforcing previous findings that emissions exceed government estimates. This study suggests a need for improved regulations to curb methane emissions from the oil and gas industry—regulations that the current US President, Donald Trump, is attempting to roll back.

After evaluating measurements from over 400 well pads across six oil and gas fields and dozens of midstream facilities, this research found that the US oil and gas supply chain emits approximately 13 million tons of methane annually, significantly higher than the Environmental Protection Agency's (EPA) estimate of 8 million tons per year.

Ramon Alvarez, lead author of the study and an atmospheric chemist at the nonprofit Environmental Defense Fund in Austin, Texas, suggests that this discrepancy may stem from the fact that EPA's emission assessments overlook potential methane leak sources, such as faulty equipment in oil and gas facilities.

Scientists believe methane in the atmosphere contributes to about 25% of global warming. Alvarez stated, "That's a big number."

Alvarez noted that uncontrolled methane emissions from the oil and gas industry could erode the potential climate benefits of using natural gas. While burning natural gas releases far less carbon dioxide and other toxic pollutants than coal, the methane emissions issue from the oil and gas sector might somewhat diminish the emission advantage of natural gas.

This latest study comes after the EPA announced a one-year delay in regulations to limit methane emissions from the oil and gas industry. These regulations were introduced under former US President Barack Obama and were set to take effect by 2019.

Before 2012, methane leakage rates reported in the US ranged from 1% to 8%, with a lack of consensus prompting scientists to better characterize these rates over the subsequent years. Alvarez and his team compiled data from these studies—many of which quantified methane emissions at individual facilities and validated these measurements using aircraft sampling. The regions studied represent approximately 30% of US natural gas production.

Researchers then inferred nationwide methane leakage. Their conclusion was that methane emissions in 2015 were about 60% higher than EPA's greenhouse gas inventory—compared to EPA's estimated leak rate of 1.4%, the actual leakage rate should be 2.3%. Alvarez explained, "Natural gas isn't going from the well into the pipeline; it's leaking out of vents or other openings in the system, and that results in a lot of methane emissions."

"This is important work," said Shane Murphy, an atmospheric scientist at the University of Wyoming in Laramie. "They're taking all of these disparate measurement approaches and pulling them together into a more quantitative result."

Daniel Zimmerle, an energy researcher at Colorado State University in Fort Collins, believes these findings reduce uncertainty in US methane emissions. He said, "I think it's now in the right range. But I'd be surprised if this were the final word on the topic."

Robert Howarth, a geoscientist at Cornell University in Ithaca, New York, stated that the 2.3% leak rate is concerning due to methane's warming potential. However, he cautioned that this study might underestimate the actual methane leakage rate. Howarth pointed out that researchers collected a range of measurement data, including some obtained with instruments that often yield lower values, according to the inventors of those instruments.

Additionally, Howarth noted that researchers didn't focus on emissions from gas distribution systems entering urban areas, which recent studies suggest are also quite substantial. He believes that while the study authors make "optimistic assumptions," the research "casts further doubt on the wisdom of continuing to use natural gas."

However, Alvarez remains optimistic. With a significant portion of these leaks likely due to equipment malfunctions, he sees a "huge opportunity" to reduce methane emissions by developing systems to quickly detect faults in oil and gas facilities and identify overlooked pathways for greenhouse gases entering the atmosphere.

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