In recent years, the biggest U.S. energy story by far has been the surge of gas production from shale rock, thanks to a new drilling technique known as “fracking.” Rigs have cropped up in backyards across the Northeast, as 11,400 new wells get drilled each year. Dirt-cheap natural gas is elbowing coal plants out of business and bringing jobs back to once-decaying states like Ohio.

A gas flare at a fracking site in Bradford County, Pennsylvania. (Reuters)

And, as calls grow for fracking oversight, there are questions about how strictly the Environmental Protection Agency will clamp down. On Wednesday, the EPA finalized its first-ever rules on air pollution from natural gas wells and offered hints of its approach on this — the government plans to tread quite cautiously.

Typically, a fracking well is developed in two stages. First, the drillers use high-powered injections of water, chemicals and sand to crack the underground shale rock and release the gas. Then, there’s a process known as “flowback” in which gas and other chemicals rise to the surface. This second stage, which can take anywhere from 3 to 10 days, can lead to the release of heat-trapping methane and “volatile organic compounds” such as benzene into the air. The latter can produce smog and create various health problems.

The newest EPA rules will regulate these volatile organic compounds, but they’ll also give the industry more time to comply than had been previously proposed. For the next two years, all gas producers will have to at the very least burn or flare their wasted gas, which will reduce hazardous compounds by 95 percent. Then, starting in 2015, all gas producers will have to undertake a more comprehensive strategy known as “green completion,” in which they capture leaked and vented gas in order to resell it. (About half of drilling companies already do some version of this, so they won’t be affected by the rules.)

Environmentalists had asked the EPA to require “green completions” as soon as possible — indeed, the original draft of the EPA’s rule would have done just that. But industry groups like the American Petroleum Institute had requested a delay, so that they could have time to acquire equipment and train workers. In the end, the EPA sided with industry on this question. They did not, however, leave air-pollution regulations to the states, another big industry request.

“Overall, EPA has made some important adjustment in the rules,” the American Petroleum Institute’s Howard Feldman told Bloomberg. “Most of the changes were constructive.”

The ultimate goal, said EPA air quality chief Gina McCarthy in a call with reporters, was to control volatile organic compounds “without slowing natural gas production.” To underscore the point, she opened her remarks by declaring that “natural gas is key to the country’s clean energy future.”

If that sounds like a banal statement, it’s not. In recent months, many green groups have agonized over whether natural gas really is the key to the country’s clean energy future — whether, for instance, it actually produces less carbon pollution than coal. Scientists from the Environmental Defense Fund and elsewhere recently published a study in the Proceedings of the Natural Academies of Science looking at this question in some depth. The answer, they argued, all hinges on how much methane leaks out from the production process.

As long as the rate of methane leakage from fracking stays below 3.2 percent, the paper suggested, then natural-gas power plants will produce fewer greenhouse-gas emissions than coal plants do. According to the EPA, the current leakage rate is around 2.4 percent, although this number continues to be debated (thanks to patchy data). But, the paper argues, it’s unlikely that natural-gas vehicles would be better for the climate than conventional gasoline automobiles unless the industry can whittle leakage down to 1.6 percent.

While the EPA’s new air-pollution rules don’t address methane directly, many of the techniques used to capture air toxins would curb methane leaks. Even flaring reduces methane’s global-warming impact to some extent by converting it into carbon dioxide, a less potent (though still important) greenhouse gas.

Still, groups like the Natural Resources Defense Council are pushing the EPA to regulate methane directly, arguing that there are a slew of proven technologies to limit methane leaks from natural gas production.