America's Natural Gas System's Leaks Go Underreported

Organizations such as the Environmental Protection Agency (EPA) have been underestimating US methane emissions from the natural gas industry, a thorough investigation revealed.

Methane leaks are important because methane is a potent greenhouse gas - about 30 times more impactful than carbon dioxide. The study, published in the journal Science, synthesizes findings from more than 200 studies surrounding gas production.

"People who go out and actually measure methane pretty consistently find more emissions than we expect," said the lead author of the new analysis, Adam Brandt, an assistant professor of energy resources engineering at Stanford University. "Atmospheric tests covering the entire country indicate emissions around 50 percent more than EPA estimates," said Brandt. "And that's a moderate estimate."

Methane emissions are estimated by multiplying the estimated leak amount from a particular source by the number of that source type in the region. The EPA does not include natural methane sources, like wetlands and geologic seeps in its estimates.

The analysis finds that powering trucks and buses with natural gas instead of diesel fuel probably makes the globe warmer, because diesel engines are relatively clean. To beat diesel the gas industry would have to become less leaky, which the new analysis also finds quite improbable, according to a press release announcing the findings.

"Fueling trucks and buses with natural gas may help local air quality and reduce oil imports, but it is not likely to reduce greenhouse gas emissions. Even running passenger cars on natural gas instead of gasoline is probably on the borderline in terms of climate," Brandt said.

The natural gas industry, the analysis finds, must clean up its leaks to really deliver on its promise of less harm. Fortunately, most of the emissions can be blamed on a few easily fixable leaks. One earlier study examined about 75,000 components at processing plants. It found some 1,600 unintentional leaks, but just 50 faulty components were behind 60 percent of the leaked gas.

"Reducing easily avoidable methane leaks from the natural gas system is important for domestic energy security," said Robert Harriss, a methane researcher at the Environmental Defense Fund and a co-author of the analysis. "As Americans, none of us should be content to stand idly by and let this important resource be wasted through fugitive emissions and unnecessary venting."