Updated

The government is losing tens of millions of dollars in potential royalties from energy companies that let immense volumes of natural gas escape into the atmosphere, congressional investigators said in a new report.

The Government Accountability Office report says about 50 billion cubic feet of natural gas has been needlessly lost every year during production on federal lands. That translates into $23 million annually in lost revenues.

But more than just royalties are at stake: The lost gas is equivalent to the annual greenhouse gas emissions of more than 3 million cars.

"You'd much rather capture gas and use it for productive purposes rather than releasing it into the atmosphere," the GAO's Frank Rusco said Tuesday. "They could do so either for environmental reasons or because they should be getting (royalties) from this gas."

Rusco said technology to capture the escaping gas is available and economical. He faulted the Interior Department for lax regulations on the issue and said the agency had greatly underestimated how much gas escapes from storage tanks and leaking equipment.

Interior spokeswoman Kendra Barkoff said the agency was reviewing the GAO report, which was released publicly Monday.

Most natural gas produced in the U.S. comes from five states — Louisiana, Texas, Oklahoma, New Mexico and Wyoming. But demand for the fuel is booming, in part because it offers an alternative to more polluting coal. Drilling has been expanding in Colorado, Montana, Utah and other Western states in recent years.

Kathleen Sgamma, government affairs director for the Western Energy Alliance, said the industry is moving forward on its own to install equipment that captures escaping natural gas.

"Interior could much better spend its time pursuing actual job creation and significant economic development if it removes some of its barriers to onshore oil and gas development," she said.

Sgamma added that GAO's estimate of $23 million in lost royalties was "pretty minuscule" compared with $2.7 billion in onshore federal oil and gas revenues in fiscal year 2010. Also, because the GAO report was based in part on 2006 data, Sgamma said it failed to reflect the industry's recent progress to curb emissions.

But environmentalists who want strict limits on greenhouse gas emissions seized on the GAO report as validating their position.

"It's confirmation of the work we've been doing," said Erik Schlenker-Goodrich, an attorney with the Western Environmental Law Center. "We've known all along there are significant opportunities here to safeguard the climate, produce more royalties for government and produce more gas for consumers."

In Montana, North Dakota, South Dakota and New Mexico, groups including WildEarth Guardians and Earthworks have pushed the Interior Department to consider greenhouse gas emissions whenever public lands are leased for energy development.

The Interior Department's Bureau of Land Management has resisted calls for change, saying the emissions from gas produced on leased federal lands are impossible to link directly to climate change.