Both natural gas and coal are doomed as feedstock for electricity generation in the U.S., overlooked but inevitable victims of the Clean Air Act, warned Christopher Guith, U.S. Chamber of Commerce senior vice president of policy for the Institute of 21st Century Energy. It’s only a matter of when, not if.

“[The Environmental Protection Agency] has to go after natural gas; that’s how the Clean Air Act works,” he said, referring to a recent change in the 1970 law that adds greenhouse gases to the list of pollutants specifically targeted.

Speaking at Hart Energy’s DUG Eagle Ford conference, Guith said, “We are now on a path where, at some point in the future, we will no longer use coal or natural gas to produce electricity.”

The Clean Air Act, enacted by Congress under the Nixon administration, was designed to target air pollutants harmful to the human body. However, following a Supreme Court decision during the Bush administration, and implemented by the Obama administration, beginning in 2011 the EPA is now mandated to eliminate greenhouse gas emissions as well, specifically CO2.

And the Clean Air Act is a zero-sum game.

“The Clean Air Act is designed to focus on a specific pollutant, then keep ratcheting down that pollutant until it is eradicated,” said Guith.

That is in spite of the fact that modern technology has created an overabundance of natural gas supply and is an “obviously natural choice” as an electricity feedstock.

“That has been turned on its head” with the implementation of Clean Air Act regulations. Already, onerous regulations are squeezing coal-fired power plants into oblivion. Natural gas electrical generators are next, he forewarned.

“At the end of the day, methane is still a fossil fuel. For the Clean Air Act to work, it has to go after methane too. It’s a certainty because that’s how the Clean Air Act works. Natural gas will start to feel a pinch in a very short time frame—2025 to 2030 at the latest.”

He makes the point that President Obama has been very clear that natural gas is a bridge fuel only. “That means there is an end to it.”

Guith said, “No one can say how long it will take, but it is an absolute inevitability that we’re on this course that we can’t divert from unless Congress changes the Clean Air Act. We will no longer use coal or natural gas for our electricity sector.”