Official tallies of how much methane leaks into the atmosphere have “consistently underestimated” the amount that has seeped from pipelines, wells, processing plants and other gas facilities during the past 20 years, a new study has found.
About “50 percent more” natural gas is leaked into the atmosphere than the Environmental Protection Agency estimates, according to a 16-person research team from the United States and Canada, which analyzed 200 studies, measurements and predictions, and published its findings in the journal Policy Forum on Thursday.
"People who go out and actually measure methane pretty consistently find more emissions than we expect," Adam Brandt, an assistant professor at Stanford University and the paper’s lead author, said in a statement. "Atmospheric tests covering the entire country indicate emissions around 50 percent more than EPA estimates. And that's a moderate estimate."
The EPA’s estimates may be low, in part, because oil-well and -processing facilities are not required to participate in EPA emissions surveys, the researchers explained, and because EPA estimates do not include abandoned oil and gas wells.
Nonetheless, while the country’s gas system “is almost certainly leakier than previously thought,” burning natural gas instead of coal to generate electricity will still reduce greenhouse gas emissions over 100 years, Brandt and his team found.
The study did find, though, that replacing diesel trucks and buses with others that burn natural gas actually likely contributes more to global warming, because diesel engines already run relatively cleanly.
"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,” Brandt stated. “Even running passenger cars on natural gas instead of gasoline is probably on the borderline in terms of climate.”
For natural gas to perform better than diesel, the country’s gas system would need to be less leaky than EPA estimates, which the paper found “quite improbable,” according to a statement distributed by Stanford University.
Most of the gas leaks that were found came from just a small group of sources, the research team said: one of the studies it examined found that of 1,600 unintentional leaks that were found at processing plants, more than half came from just 50 faulty components – out of 75,000 components total.
"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."