The EPA has a plan to eliminate climate pollution from power plants, but will it survive in court?

The Environmental Protection Agency proposed by far the largest-ever climate change regulation in U.S. history on Thursday, when it unveiled a proposal to require a 90% reduction in carbon dioxide emissions from the largest power plants by 2040.

Electricity generation is the nation's second-largest source of those planet-warming emissions, after transportation, accounting for one-quarter of the total. Swiftly cutting climate pollution from power plants is crucial to meeting President Biden's pledge to cut U.S. emissions by 50% by 2030.

“EPA is delivering on its mission to reduce harmful pollution that threatens people’s health and wellbeing,” said EPA Administrator Michael Regan in a statement on Thursday.

The EPA's announcement enraged coal industry advocates like Sen. Joe Manchin, D-W.Va., who preemptively announced Wednesday that he would oppose all nominees to EPA positions requiring Senate confirmation "until they halt their government overreach."

"This Administration is determined to advance its radical climate agenda and has made it clear they are hellbent on doing everything in their power to regulate coal and gas-fueled power plants out of existence," Manchin said in a statement.

EPA regulations are complicated, and the legal disputes over them are even more so, but Yahoo News is here to guide you through the morass. These are the answers to all your questions about how the new rule would work, when it would take effect and whether it will hold up in court.

How does the new rule work?

Existing coal-fired power plants would have to slash emissions by 90% by 2030 or commit to taking the plant out of service before 2040. For gas-fired plants, the larger, frequently operating facilities — known as “base load” plants — would be required to reduce emissions by 90% by 2035, or by 2038 if they’re adding hydrogen to the gas. (The rules are stricter for coal than for gas because coal creates more carbon dioxide and other pollutants when burned.)

The standards follow the legal requirement that the EPA set an emissions standard based on the "best available control technology," which it determined to be capturing CO2 from the smokestack and storing it underground, a system known as carbon capture and storage, or CCS.

States and the energy utilities they regulate don’t necessarily have to add CCS to all of their coal or base load gas plants: They could instead shut some of them down, replace them with cleaner energy sources — including blending hydrogen with natural gas, for which there are subsidies in the 2022 Inflation Reduction Act — or use them less frequently.

What are the benefits?

The EPA estimates that through 2042, the rule would reduce carbon emissions by the equivalent of taking 137 million passenger vehicles off the road for one year. By speeding up the shift away from coal, it also would cut particulate matter, sulfur dioxide and nitrogen oxide. By 2030 alone, the agency projects that it would prevent roughly 1,300 premature deaths, more than 300,000 cases of asthma attacks and 66,000 lost workdays. The health benefits would be worth an estimated $85 billion through 2042.

What are the drawbacks?

Given the costs and technical challenges associated with CCS, it’s likely that many power plants would shut down rather than adopt the technology. Critics contend that this will increase the cost of electricity and reduce reliability.

The EPA counters that the declining cost and rapid growth of wind and solar power production — combined with growing battery storage capacity — mean that the industry can switch to renewables without meaningfully increasing costs.

“We’re looking at a negligible impact on electricity prices,” Regan said in a press call that preceded the announcement, adding that average national prices are projected to be just 0.24% higher in 2035 over the expected baseline.

The Inflation Reduction Act includes subsidies for CCS that the EPA notes will make it more economical. But the EPA is also tightening the vise on coal through strengthened regulations of other pollutants such as coal ash and mercury.

Could it be stronger?

Environmentalists think so, because gas-fired “peaker” plants, which are turned on at times of high demand, are exempt from the emissions reduction requirements. The proposal would cover only about 55% of carbon emissions from power plants, according to Evergreen Action power sector policy lead Charles Harper, and green groups are planning to advocate in the coming public comment period for the proposal to be expanded to cover more plants.

“We’ll advocate for more of the fleet to be covered, that is a concern,” Harper said in a Thursday press briefing. “We think EPA can and should regulate the entire fleet.”

Will it hold up in court?

After the rule is finalized, expert observers say that some fossil-fuel-producing and Republican-led states will likely sue to block it by arguing that CCS isn't actually practical to require. The Supreme Court's 2022 ruling in West Virginia v. EPA, in which the court ruled that the Obama administration's Clean Power Plan went beyond the agency's authority, is unlikely to pose a problem for this plan, because this one — unlike the Obama-era proposal — sets a standard based only on technology that can be used at a power plant.

However, opponents will argue that CCS doesn’t meet the Clean Air Act’s definition of “best available technology,” which has to be “adequately demonstrated.”

“EPA faces two big legal problems here,” Jeff Holmstead, head of the environmental strategies group at the law firm Bracewell, told Yahoo News in an email. “First, there isn’t a single commercial-scale gas-fired power plant anywhere in the U.S. — or as far as I know, anywhere in the world — that uses CCS to control its emissions. This fact alone could make it hard for EPA to convince the courts that CCS has been adequately demonstrated for gas-fired power plants.

“And second,” he continued, “by giving these plants until 2035 to begin operating with CCS, EPA is acknowledging that it won’t actually be feasible to use CCS to reduce CO2 emissions from these plants for another 12 years. This tends to undercut the argument that CCS has been adequately demonstrated.”

Proponents of the plan note that CCS is being used in some industrial facilities that use the captured carbon for profitable purposes, like extracting oil from hard-to-reach locations, but it hasn't made economic sense for power plants because anything that costs money doesn't make sense unless it's required or incentivized.

“The companies will try to make it sound like it has to be used for dozens and dozens of plants for dozens and dozens of years before you can say it is adequately demonstrated, and if that were true, we still wouldn’t have scrubbers for sulfur [systems that remove sulfur dioxide emissions] on power plants, because back in the day there were only a few scrubbers,” David Doniger, senior strategic director of the climate and clean energy program at the Natural Resources Defense Council, told Yahoo News. “The companies always said you haven’t demonstrated [that] they operate all the time, they break down. EPA said the technology is adequately demonstrated and these problems can be solved.

“When you stop and think about it, the reason the companies haven’t used these technologies is that it’s easier and cheaper to dump an unregulated pollutant into the atmosphere,” Doniger added. “But when there were sulfur limits, the companies simply started to use the scrubbers on a much more widespread basis.”

Doniger noted that courts typically defer to the agencies on matters of economic and technical modeling and expertise.

Some environmental law experts believe that the regulations actually had to identify CCS as the best available technology because of the subsidies in the Inflation Reduction Act and the 2021 infrastructure law, which includes money for building the pipeline network to move captured carbon to underground storage sites.

“In light of those two game-changing pieces of legislation being enacted, they had to move in this direction,” said Kevin Poloncarz, co-chair of the environmental and energy practice group at the law firm Covington & Burling, where his clients include energy utilities. “The Clean Air Act is necessarily technology-forcing.”