President Trump told a crowd in the coal mining-heavy state of West Virginia on Thursday that he had fulfilled his campaign promise to end the “the war on beautiful, clean coal,” adding that “we are putting our coal miners back to work.”

“I made you a promise during the campaign . . . and as you’ve seen, I’ve kept that promise,” Trump said. “We’ve stopped the [Environmental Protection Agency] intrusion. American coal exports are already up.”

But at the same time, the Trump administration is pushing measures that would slow the development of what is often referred to as “clean coal.” Also called carbon capture and storage, clean coal involves taking carbon dioxide emissions from power plants and either storing them underground or using them for another purpose, like oil and gas extraction. The “storage” aspect keeps the emissions from contributing to man-made climate change.

Trump’s budget proposal, released in May, would slash the budget of an Energy Department program working on clean coal by 55%. (Congress will almost certainly restore some of that funding when it passes a budget).

More broadly, Trump’s wider rollbacks of environmental regulations and his decision to withdraw from the Paris Agreement on climate change has weakened the primary justification for so-called clean coal. Because coal coupled with capture and storage technology would be far more expensive than other energy sources, clean coal only makes sense in the U.S. if the country has policies compelling power providers to move away from fossil fuels. Without such measures, companies lack incentive to invest.

Trump has long promised to revitalize the number of coal mining jobs available in the U.S. The industry currently employs around 50,000 people, down from nearly 90,000 in 2011 and more than 200,000 in the 1980s. Indeed, analysts say Trump’s initiatives—most importantly, undoing the President Obama’s Clean Power Plan—will bring short-term relief for the ailing coal industry, which has faced years of decline largely thanks to competition from cheap natural gas. But data from the U.S. Energy Information Administration suggests that U.S. coal production will ultimately level off in the coming decades as other energy sources continue to become less expensive. Trump may be able to save jobs in the immediate future, but even he can’t fight raw economics.

Few issues today are as politically polarizing as climate change. Yet clean coal research and development has drawn bipartisan support. A range of carbon capture measures currently before Congress are backed by lawmakers on both sides of the aisle, including a measure to allow tax-exempt bonds for carbon capture facilities and an expanded tax credit for capturing carbon. “When utilities, coal companies, and environmental groups come together to support your bill,” Senator Heidi Heitkamp, a North Dakota Democrat, said last year in a statement endorsing a measure to boost the tax credit, “you know you’re onto something that could work.” The Trump administration has declined to endorse such measures in the past; the White House did not reply to a request for comment from TIME.

To be sure, clean coal technology has faced several significant roadblocks this year. Most visibly, the Southern Company—a utility operating in the Southeast U.S.—abandoned an attempt to implement it after spending billions on a Mississippi power plant. The company ultimately converted the project into a natural gas facility, citing a need to “manage costs.”

Trump’s apparent lack of support for clean coal technology comes despite his repeated use of the phrase on the campaign trail and while in office. One possible explanation: While energy experts and others in the field understand “clean coal” to mean carbon capture, it’s possible Trump is using it with a different intention — or just to give a positive spin on the coal industry more broadly. “We’re going to have clean coal—really clean coal,” the President said as he signed a measure in March that could lead to the repeal of the Clean Power Plan. “I will cancel job-killing restrictions on the production of American energy, including shale energy and clean coal,” he vowed in a November post-victory video.

Clean coal also suffers from a practical disconnect in the Trump era. Trump and many in his administration have expressed skepticism at the very science of climate change, a stance that has been reflected in White House policy decisions. Spending money on clean coal technology makes little sense if the U.S. doesn’t feel pressure to reduce its carbon emissions. Several Republicans and coal industry supporters made exactly that argument as Trump weighed whether to leave the Paris deal earlier this year.

“The U.S. should use its seat at the Paris table to defend and promote our commercial interests, including our manufacturing and fossil fuel sector,” U.S. Rep. Kevin Cramer, a North Dakota Republican who advised Trump on energy policy during the campaign, wrote in a letter to the President earlier this year. “We should work closely with our allies to develop, deploy, and commercialize cleaner technologies to help ensure a future for fossil fuels within the context of the global climate agenda.”

Ultimately, clean coal offers an opportunity, however small, for the coal industry to survive as the world moves away from high-polluting energy sources. But without carbon capture technology, power suppliers will simply look elsewhere as the price of other energy sources continue to plummet in comparison.

Get our Politics Newsletter. The headlines out of Washington never seem to slow. Subscribe to The D.C. Brief to make sense of what matters most. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Write to Justin Worland at justin.worland@time.com.