One of the unknowns on fracking is now becoming a bit clearer as natural-gas drilling sites do not seem to be leaking as much methane into the atmosphere as the federal government and critics had believed, a study said.

The study is likely to ease some concerns about the impact of natural-gas extraction on the climate. Researchers at the University of Texas at Austin published the study Monday in the Proceedings of the National Academy of Sciences.

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Measuring emissions at 190 sites, the study found less “fugitive methane” than previous work by the Environmental Protection Agency (EPA) and some university researchers, which relied on estimates. Methane, the primary ingredient in natural gas, is a strong greenhouse gas.

Critics of fracking continue to say large amounts of methane leak from gas drilling sites, with some suggesting the problem was so great it would be better for the environment to burn coal instead of natural gas.

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More studies need to occur before researchers can say definitively that producing and burning natural gas is better for the environment than using coal to generate electricity.

But the measurements of gas emissions found that wells emitted about 20 percent less greenhouse gases than the EPA estimated, which is less than the amount emitted by burning coal. The study also found much higher-than-expected leakage from pneumatic switches, which turn equipment on and off at well sites.

David Allen, a chemical engineering professor at the University of Texas and lead researcher, said he believed the better data will help guide policy makers.
“If the goal is to reduce emissions, a critical first step is to know what the emissions are,” he said.

Nine large fossil fuel companies, including Exxon Mobil Corp., Royal Dutch Shell PLC, Anadarko Petroleum Corp. and Pioneer Natural Resources Co. contributed about $250,000 to fund this study, as did the nonprofit Environmental Defense Fund.

University of Texas officials said the research was independent and the 14 authors declared “no conflict of interest” in the paper. However, a university spokesman said he was looking into a report that one of the authors worked for a petroleum engineering firm.

After the study published, Physicians, Scientists & Engineers for Healthy Energy, a group critical of fracking, called the study “fatally flawed” by the small sample size and oil-industry influence. The UT researchers say their methodology was independent and sound.

The study also found the extra equipment used in “green completions” was effective at capturing methane gas that could go into in pipelines and sold, eliminating venting into the atmosphere. “For those wells with methane capture or control, 99 percent of the potential emissions were captured or controlled,” the paper said.

The federal government will require green completions for all natural gas wells beginning in January 2015. The rule doesn’t require such equipment on fracked wells in North Dakota, Texas and elsewhere that produce mostly crude oil.

The amount of methane leakage has been a source of significant controversy. In 2011, Cornell University scientists suggested the EPA estimates were far too low, and natural-gas production wasn’t helping slow carbon emissions. Their assertion fell under attack by other scientists, but little data was available until this new paper.

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