EPA officials have known for some time that leaks from natural gas pipelines and other infrastructure are a major source of methane emissions.

Now, a recent study of methane leaks in cities in the Northeast shows that these leaks put out twice the amount of gas as the EPA thought.

Methane is a powerful greenhouse gas — many times more powerful than carbon dioxide. It is also the main ingredient in the natural gas that we use for heating and cooking.

Some of these leaks can’t be helped, expert Eric Kort told Living Lab Radio on Tuesday. Kort is an associate professor of atmospheric, oceanic, and space sciences at the University of Michigan and the co-author of a survey of methane leaks published in July.

“It's simply difficult to take such large volumes of gas, pull them out of the ground in one place, process them to make it more pure methane than what comes out of the ground, transport it along hundreds and thousands of miles of pipelines. ... You will inevitably lose some along such a system,” Kort said.

But there are systemic problems that could be corrected, he said.

“Some of it is likely related to just old infrastructure and some of it is related to not knowing where the emissions or losses are,” he said. “And some of it is the economic incentive doesn't line up.”

For example, in some places it could cost a company $100,000 to repair a leak. But the leak only loses $100 worth of gas each year, so it doesn’t make financial sense for the company to fix it, Kort said.

“And then there's another economic element, which is that often the people that are responsible for the loss of the gas often don't own that gas and maybe are not incentivized to not lose it,” he said.

Kort studied the methane leaks by equipping an aircraft with instruments that measure methane, carbon dioxide, carbon monoxide, and ethane. His team flew the plane over Washington D.C., Baltimore, Philadelphia, New York City, Providence, and Boston.

“We were able to look at multiple gases to identify that most of that methane that we saw indeed was coming from natural gas systems and not from systems like landfills,” Kort said.

The results could be seen as discouraging news, but Kort doesn’t see it that way. Rather, it’s the low-hanging fruit of carbon reduction, he said.

“I actually tend to think of this work and these findings as more providing really appealing mitigation opportunities,” he said.

“We could actually reduce emissions that have significant climate impact in a more efficient way that does not require large structural changes.”