CHARLESTON, W.Va. -- U.S. emissions of the powerful greenhouse gas methane are considerably higher than previous official estimates, according to a new review of more than 200 earlier studies.
Among other findings, the study, published Friday in the journal Science, concludes that switching buses and trucks from traditional diesel fuel to natural gas could make climate change worse.
While burning natural gas produces less carbon dioxide, leaks of methane during the drilling and production process complicate the equation, according to the study by scientists from Stanford University and a collection of other institutions.
"People who go out an actually measure methane pretty consistently find more emissions than we expect," said lead author Adam Brandt, an assistant professor of energy resources engineering at Stanford.
"Atmospheric tests covering the entire country indicate emissions around 50 percent more than EPA estimates," Brandt said. "And that's a moderate estimate."
Results of the research will continue a growing debate as the Obama administration promotes the use of natural gas -- generally thought to be a cleaner alternative to coal -- as part of a plan to combat potentially devastating impacts of global warming.
Three years ago, the issue of methane emissions from the gas boom gained much more attention with the publication of a study by a team of Cornell University researchers led by ecology professor Robert Howarth. That study reported that natural gas could be just as bad as -- or worse than -- coal for global warming, especially if the issue is examined on the short time frame in which some scientists believe action is needed to curb global warming.
Since then, industry officials have harshly criticized Howarth's study, and there's been a lively debate in scientific journals about his results and about the many variables used to estimate methane emissions from the country's shale-gas boom.
The new Science paper says that while the natural gas system creates more methane emissions 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, the study said.
Still, the analysis found that powering trucks and buses with natural gas -- a strategy promoted in West Virginia by the industry, local officials and the Tomblin administration -- probably makes the globe warmer.
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.
"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.
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.