There are two ways to go about it. They’re both somewhat feasible and a little complicated. Both also require a knowledge of U.S. land law.

The United States is one of very few nations in the world where mineral rights—the ability to mine an area—can be privately held. (In most nations, these rights are public or royal.) But U.S. rights differ depending on where you are. East of the Mississippi, a property owner typically controls not only the land that they have a deed to, but also the rights to mine any minerals beneath that land. In Appalachia, in particular, many property owners can and do sever those mineral rights from their surface rights and sell them to private companies. Rights get severed by coal seam, so it’s possible for multiple companies to own rights for one location, as long as they hold rights to different depths.

“If you ask someone to build a property map of mineral rights in West Virginia, you have to specify which coal seam, because each coal horizon can have a separate owner on the exact same lat-lon coordinates,” says Frost. “As you go up and down the mountain, you can run into different ownership.”

But west of the Mississippi, things work different. Especially in Montana and the Mountain West, the government mostly holds mineral rights. That’s because, when the Wilson administration began parceling out public land there in 1916, it realized that mineral rights were a lucrative business and retained them for itself. The Bureau of Land Management now manages those rights, as well as the rights under land that has never left the federal government’s ownership. Today, the country’s major Western coal deposits—almost 90,000 square miles—are administered by the Bureau of Land Management.

Two different mineral regimes: two different forms that Frost’s plan could take.

In Appalachia, no one would have to give a climate-concerned billionaire permission to buy up coal. In fact, Bill Gates or someone else could start buying coal there “tomorrow,” he says.

“The coal industry employs ‘land guys’ who play a lot of golf with other land guys and strategically assemble viable mining units out of the parcels they can stitch together. A shrewd buyer of retirement coal would apply the same skills, but from the angle of ‘sterilizing’ as much nearby coal as possible,” he wrote to me in an email.

He calls these sterilizing buyers “green-hat land guys.” Were a billionaire inclined to hire them, now would be an especially good time. Natural gas has pushed the cost of fossil fuels too low for the old giants to survive. Nearly every major Appalachian coal company has collapsed or filed for bankruptcy this year, and the major national and international banks have fled the industry.

Despite that ease, Appalachia isn’t the ideal place to sequester carbon underground. Unless the government changed the tax code, the tracts of unmined coal would continue to be a taxable resource, their price fluctuating with the commodity. There would be no tax benefit to keeping the coal out of the market in perpetuity. In fact, the locked-away seams would present a perpetual tax liability.