Critics of the natural gas extraction technique known as fracking have long criticized it for leaking too much methane — a potent greenhouse gas — into the atmosphere during the extraction process. The Environmental Protection Agency recently estimated that natural gas operations emitted about 145 million metric tons of methane in 2011, making it the biggest source of these emissions in the country.

 

Now a new study, sponsored by the Environmental Defense Fund (EDF) and nine energy petroleum companies, finds that emissions may be lower than previously thought, at least during part of the extraction process. According to the study (pdf), published in the Proceedings of the National Academy of Sciences, the average methane emissions from the well completion flowbacks at 190 natural gas sites ranged from 0.01 metric tons to 17 metric tons.