A single study — no matter how scientific, thorough and rigorous — probably wouldn’t silence all critics, but the natural gas industry has a powerful new defense against those who warn about the dangers of methane emissions at well sites.A study from the University of Texas at Austin, done in partnership with the Environmental Defense Fund and published last week in a peer-reviewed scientific journal, says methane emissions during the crucial period of well completions are a tiny fraction of earlier estimates.Methane leaks from pneumatic valves and other well equipment during production are significantly higher than estimated. Still, overall emissions are in line with recent projections from the Environmental Protection Agency.All of that is crucially important for Tarrant County, where Barnett Shale natural gas wells have been a part of life for a decade. Drilling and completion work here have dropped off dramatically with the decline of natural gas prices, but it’s still very active in south Texas and other areas where punching new wells is more economical.And even more important, the study findings go a long way to confirming the environmental impact of natural gas as better than coal for fueling power-generating plants.Methane emissions from natural gas wells are “one of the most hotly debated issues in environmental science and policy today,” said Mark Brownstein, associate vice president and chief counsel of the U.S. Climate and Energy Program at the Environmental Defense Fund.EDF’s participation lent a great deal of credibility to the study, which was done with the cooperation of nine energy companies, including Fort Worth’s XTO Energy, an ExxonMobil subsidiary.Methane released during the completion phase of the drilling process, in which fluids used in hydraulic fracturing are brought back out of the well, has been a key point of the environmental controversy. The study found that so-called “green completion” equipment and procedures reduce methane emissions by 99 percent.Total completion emissions are 97 percent lower than estimates released by the EPA in April.Equipment leaks show that there are “many further opportunities to reduce emissions,” Brownstein said.Overall, that’s powerful good news for the natural gas industry.