Coal and gas-fired power plants would have to eliminate nearly all their climate-warming carbon dioxide emissions in just a little over a decade, under proposed regulations issued today by the Environmental Protection Agency.

Owners of those plants have been allowed to spew climate-warming carbon dioxide and other greenhouse gasses into the atmosphere for more than a century. If these proposed regulations are finalized, they would come close to putting a stop to that practice.

"The EPA's proposed rule sends an unequivocal signal to American power plant operators: the era of unlimited carbon pollution is over," wrote Dan Lashof, U.S. Director at the World Resources Institute, in a statement responding to the proposal.

The regulations are based on technologies that capture and then store deep underground 90% of carbon dioxide from coal and gas-fired plants. But some facilities that plan to shut down in coming years or that operate at less than 20% of their capacity would be subject to less stringent requirements. Those could include adding cleaner hydrogen to natural gas to limit its climate-warming effects.

Environmental groups welcomed the rules, which are almost certain to face opposition and a legal challenge from the fossil fuel industry and its allies.

"EPA's proposal relies on proven, readily available technologies to limit carbon pollution and seizes the momentum already underway in the power sector to move toward a cleaner future," said EPA Administrator Michael Regan.

The EPA projects the rules would avoid up to 617 million metric tons of carbon dioxide through 2042. The agency says that's the equivalent to the annual emissions of 137 million passenger vehicles, or about half of the cars on the road today.

Regan says the regulation would also bring health benefits by reducing other air pollutants, such as particulate matter, sulfur dioxide and nitrogen oxide. The EPA projects that in 2030, the proposed rules would prevent 1,300 premature deaths, more than 800 hospital and emergency room visits and more than 300,000 cases of asthma attacks. While the rules could increase electricity prices a "negligible" amount, the agency values the net climate and health benefits would be up to $85 billion.

The regulations also would help the U.S. meet its obligations under the 2015 Paris climate agreement, and they would be crucial in meeting President Biden's goal of zeroing out carbon pollution from the electricity sector by 2035.

A climate regulation nearly a decade in the making

Power plants are the second biggest source of climate-warming greenhouse gas emissions in the country, according to the EPA, behind transportation.

The newly proposed rules would help the country get closer to the Biden administration goal of reducing greenhouse gasses 50 to 52% by 2030, based on 2005 emissions. Other initiatives to hit that goal include rules that will require more cars to be electric, tighter energy efficiency standards for appliances and switching buildings from gas to electric.

According to the Supreme Court's landmark 2007 Massachusetts v. EPA decision, the EPA is required to regulate carbon dioxide and other greenhouse gas emissions under the Clean Air Act.

In 2014 the Obama administration proposed its "Clean Power Plan" aimed at cutting carbon dioxide emissions from power plants 32%, from 2005 levels, by 2030. That plan faced legal challenges and never went into effect. Still the country met that goal well before 2030, as coal-fired power plants were replaced by natural gas plants that emit less climate pollution than coal. Despite fast growth of climate-friendly wind and solar power, about 60% of the country's electricity still comes from fossil fuels.

President Biden came into the office with the most ambitious plan to address climate change of any major party candidate in U.S. history, with a goal for the country to stop adding carbon dioxide to the atmosphere by 2050.

Scientists say that's what's needed to limit warming to 1.5 Celsius (2.7 degrees Fahrenheit) over pre-industrial levels and avoid the worst effects of climate change. Global average temperatures have already risen about 1.1 degrees Celsius.

The new EPA rules were shaped by legal battles. Last year, the Supreme Court restricted the agency's options for regulating power plant emissions. Justices said that without a specific law, the agency cannot force the entire power generation industry to move away from fossil fuels toward less-polluting energy sources.

"It told EPA some things it could not do, but it also told EPA the path that's open, under the law," says David Doniger of the Natural Resources Defense Council.

The proposed rules set emission limits for power plants and then let power plant owners decide how they'll meet the requirements, which could include shutting down their facility. The EPA concludes technologies, such as carbon capture and storage, that have been too expensive in the past are now more affordable, especially with tax credits available under the climate-focused Inflation Reduction Act that was passed last year.

Still, the coal industry may have the most to lose under this proposal. There are currently 158 active coal power plants, according to the Sierra Club. Despite the EPA's analysis, the National Mining Association says carbon capture technology is not yet "technically and fully economically demonstrated." The organization called for a "carbon capture moonshot."

The coming legal fight

Criticism from the coal industry and its allies came even before the proposed rules were announced, some of it from within President Biden's own party.

"This Administration is determined to advance its radical climate agenda and has made it clear they are hell-bent on doing everything in their power to regulate coal and gas-fueled power plants out of existence," said Sen. Joe Manchin, D-W.Va., in a statement released by his office. In addition to representing a state where coal remains a powerful business, Manchin's family owns a coal company. Manchin said he would oppose the Biden administration's EPA nominees until the White House halts "their government overreach."

Coal remains a major industry in West Virginia and preserving coal-fired electricity is a priority for many people there. State regulators recently approved a $3 million per month surcharge on customers' bills to keep a coal plant from shutting down at the end of May. Customers will pay the subsidy even if the plant doesn't generate electricity, though it will keep the facility's 146 employees on the payroll.

West Virginia Attorney General Patrick Morrisey, who's also running for governor, led a legal challenge by states opposed to the 2015 Clean Power Plan. He's expected to lead a similar legal challenge to these rules, once they are finalized next year.

The regulations also could face opposition from the natural gas industry, which has sought to preserve its role in electricity generation. The American Petroleum Institute, in comments submitted before the rule was released, urged "EPA to consider the essential role gas-fired generators will continue to play in complementing renewables," and asked for "significant compliance flexibility."

Critics also argue the regulations will force coal and gas-fired power plants to shut down and leave the grid vulnerable to blackouts. But EPA Administrator Regan says this issue was considered. He recently signed a memorandum of understanding with the Department of Energy that is aimed at keeping the grid reliable and stable.

Even if the regulation survives an expected court challenge and takes effect, a future administration could change it. In 2019 former President Trump replaced the Obama-era Clean Power Plan with his much weaker Affordable Clean Energy rule. That means these rules likely will become an issue in the upcoming 2024 presidential election campaign.