CHICAGO - The US oil and gas industry emits 13 million metric tons of methane from its operations each year, nearly 60 percent more than current estimates, according to a national study involving University of Michigan (UM) researchers.

The study, posted on UM website Thursday, estimates that the current leak rate from the US oil and gas system is 2.3 percent, as against the Environmental Protection Agency's current inventory estimate of 1.4 percent.

The percentages may seem small, but the volume represents enough natural gas to fuel 10 million homes, with lost gas worth an estimated 2 billion dollars, the researchers say.

"This work pulls together an extensive set of analyses done in the last five years to determine our current best estimate of methane emissions from the oil and gas sector in the US," said study co-author Eric Kort, UM assistant professor of climate and space sciences and engineering.

Methane is a highly potent greenhouse gas, with over 80 times the warming impact of carbon dioxide over the first 20 years after it is released.

"This is by far the most comprehensive body of research of its kind," said EDF chief scientist and co-author of the study Steven Hamburg. "Reducing methane emissions from the oil and gas sector is the fastest, most cost-effective way we have to slow the rate of warming today."

The study has been published in the journal Science.