HOUSTON — National methane emissions are up to 75 percent higher than the Environmental Protection Agency has previously estimated, according to a study to be published Friday.
The study accounted for methane leaking from natural gas processing plants, wells and other infrastructure. Methane is a potent greenhouse gas that has a warming effect about 30 times that of carbon dioxide.
The research, which will be published in the journal Science, involved seven universities, three government agencies and other groups, according to the journal. The study did not involve new data collection, but reviewed existing research.
The study was funded by the nonprofit Novim through a grant from the Cynthia and George Mitchell Foundation, according to a press release on the philanthropy’s website. George Mitchell was the innovator behind modern hydraulic fracturing.
“Atmospheric tests covering the entire country indicate emissions around 50 percent more than EPA estimates,” said a statement from the lead author of the study, Adam Brandt, an assistant professor of energy resources engineering at Stanford University. “And that’s a moderate estimate.”
Methane emissions are between 25 percent and 75 percent higher than EPA estimates because the agency does not take into account natural seepage and has not gained a clear picture of leaks from natural gas infrastructure, according to the study.
“We find measurements at all scales show that official inventories consistently underestimate actual (methane) emissions, with the natural gas and oil sectors as important contributors,” the study said.
Because of natural gas facility leaks, diesel may be a more climate-friendly fuel when it comes to vehicles, since its total life-cycle emissions have a lower impact on global warming than that of natural gas used for transportation, according to the study. That’s because natural gas can leak at several points before it is delivered to vehicles, the study said.
The study found that methane leaks from natural gas wells, pipelines, storage tanks and processing facilities are a major concern, although they happen at a low frequency. An analysis of from 75,000 infrastructure components found that 58 percent of all methane leaked came from 0.6 percent of possible sources, the study said.
Those “superemitters” are a major part of the problem, said Francis O’Sullivan, director of research at the Massachusetts Institute of Technology’s energy initiative and an author of the study.
“We can develop more cost effective more technically effective sensing technologies,” O’Sullivan said. “It should be possible to identify much more rapidly these superemitters and if one was able to do that you could very significantly address the problem.”
Despite current leak problems, natural gas remains a better option for power plants than coal, the study said.
The foundation said:
Even though the gas system is almost certainly leakier than previously thought, generating electricity by burning gas rather than coal still reduces the total greenhouse effect over 100 years. Not only does burning coal release an enormous amount of carbon dioxide, mining it releases methane.
Perhaps surprisingly though, 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. For natural gas to beat diesel, the gas industry would have to be less leaky than the EPA’s current estimate, which the new analysis also finds quite improbable.