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Does natural gas really cause less global warming than coal? We’re about to find out

The hydraulic fracturing (“fracking”) of rocks deep underground to extract their tightly held reserves of oil and gas is controversial for its impact on the environment, particularly water sources. But it’s been an article of faith that the ensuing boom in natural gas production is good for climate change. Natural gas-fired power plants emit about half as much carbon dioxide as coal.

But there’s a wild card. It’s methane, a byproduct of the production and use of natural gas. Over a 100-year period, methane in the atmosphere traps over 20 times as much heat as the same weight of carbon dioxide. And no-one really knows how much methane is escaping at the thousands of production wells sprouting across the US. So no-one knows the break-even point at which these fugitive methane emissions from natural gas exceed the carbon savings from replacing coal.

A paper published last year by the Proceedings of the National Academy of Sciences (PNAS) said that better data were needed. “There have been all these studies that have come out about the emissions rates for all parts of natural gas production but none of them were based on going out and actually measuring the emissions,” says Fred Krupp, president of the Environmental Defense Fund (EDF). “Having a debate about fracking without real data is silly.”

That’s about to change. Krupp’s green group last year joined with the University of Texas at Austin and nine big gas producers—including Chevron, Shell and ExxonMobil’s XTO Energy—to measure methane emission rates at the companies’ shale gas wells in the US. David Allen of the University of Texas, who led the fieldwork and data analysis, told Quartz that the results have already been submitted to a scientific journal, and will become public when it publishes the paper.

West Virginia University is leading another EDF-backed study that will measure methane leaks from natural gas-powered vehicles. A host of corporations are sponsoring the project; with the US awash in a sea of cheap natural gas, energy producers see transportation as a big potential market.

In 2009, the US Environmental Protection Agency estimated that there is about a 2.4% leakage rate of natural gas during production and transportation. The authors of the PNAS paper concluded that rates would need to fall below to 1.6% for natural-gas-powered cars to have less effect on climate change than those running on gasoline. For trucks, total methane emissions would have to be cut by two-thirds.

“At current leakage rate estimates, converting a fleet of heavy duty diesel vehicles to natural gas would result in nearly 300 years of climate damage before any benefits were achieved,” stated the paper.

Additional EDF-sponsored studies, set to be completed by the end of 2013, will measure methane emissions from other stages of natural gas production, including leaks from transcontinental and local pipelines. “We’ll get a better understanding where there are fugitive emissions escaping and where can we capture them and put them to work,” says Krupp.

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