Drilling and fracking for natural gas do not seem to spew immense amounts of the greenhouse gas methane into the air, as has been feared, a study says.
The findings bolster a big selling point for natural gas - that it's not as bad for global warming as coal. And they undercut a major environmental argument against fracking, a process that breaks apart deep rock to recover more gas.
But the study, mostly funded by energy interests, doesn't address fracking concerns about potential air and water pollution.
The results, which generally agree with earlier US Environmental Protection Agency estimates, were published by the Proceedings of the National Academy of Sciences.
About 90 per cent of the study funding came from nine energy companies that drill for natural gas with the rest coming from an environmental group.
But study authors said they controlled how the research was done and how the wells were chosen for study. And even Robert Howarth of Cornell University, one of the scientists who first raised the methane leak alarm, called the results "good news".
However, Howarth, who didn't participate in the study, cautioned that the results may represent a "best-case scenario".
It might be, he said, that industry can produce gas with very low emissions, "but they very often do not do so. They do better when they know they are being carefully watched".
The study found that during the process of extracting natural gas from the ground, total leakage at the study sites was 0.42 percent of all produced gas.
Additional leaks occur in the second half of the process - delivery from wells to homes and power plants.