The Environmental Protection Agency (EPA) today proposed limits on carbon pollution from new fossil fuel power plants. The move, if successful, would be the first major step by the U.S. government to limit greenhouse gas emissions from the power sector. For the first time, plants would be required to capture some of the carbon dioxide gas produced by burning fossil fuels in addition to finding ways to produce less of the gas in the first place.

The regulations, which are a key element of President Barack Obama’s second term climate plan, include separate limits for power plants fueled by coal and natural gas. Coal plants would have to limit their carbon dioxide pollution to about 500 kilograms per megawatt hour of producing power; that's a 30% to 50% greater reduction than required by existing rules, EPA says. Power plants powered by natural gas, which produce less carbon pollution per unit of energy produced, would be limited to a little more than 450 kilograms per megawatt hour.

“By taking commonsense steps to limit carbon pollution from new power plants, we can slow the effects of climate change and fulfill our obligation to ensure a safe and healthy environment for our children,” EPA Administrator Gina McCarthy said in a statement released today.

Opposition to the new regulations is expected to be fierce, with the energy industry and its allies on Capitol Hill reacting strongly today. “The proposed standards would require the use of expensive new technologies that are not commercially viable,” said Representative Fred Upton (R-MI), chair of the Energy and Commerce Committee of the U.S. House of Representatives, in a statement. “We are the Saudi Arabia of coal, but this impractical rule restricts access to one of our most abundant, affordable, and dependable energy sources.”

The EPA received a whopping 2.5 million comments on the first version of the rules, released last year, before pulling them to work out some procedural issues.

Some experts think that the new rules could help efficiently transition the U.S. economy to a lower carbon future. "The agency’s proposed rule is very flexible," says John Thompson, an analyst with Clean Air Task Force, a Boston nonprofit. He cites the fact that power plants will be allowed to phase in emission reductions over 7 years, if they agree to slightly more stringent standards.

Another flexibility that EPA included is that new plants would be required to capture some, but not all, of their carbon pollution. Advocates for reducing emissions from the power sector have argued that such “carbon capture and storage” (CCS) technologies will be essential to combating climate change, but CCS research and development is still in its very early days. Even more importantly, the power industry is turning to natural gas for generating electricity, suggesting that the market for building coal-fired power plants with carbon capture equipment could be decades off. “This rule is really not about ending coal, it's about starting carbon capture,” Thompson says.

The Obama administration is also working on new emissions regulations that would apply the existing fleet of power plants in the United States, but a draft isn’t expected until next year.