Elon Musk is putting up $100 million as part of a new X Prize Foundation competition focused on carbon removal technology. The contest, announced Monday morning, will run for four years and is open to teams around the globe.

Fifteen teams will be selected for the competition within 18 months. They will each get $1 million, and 25 separate $200,000 scholarships will be given to student teams who enter. The grand prize winner will be awarded $50 million, second place will receive $20 million, and third place will get $10 million.

Winners will have to “demonstrate a solution that can pull carbon dioxide directly from the atmosphere or oceans and lock it away permanently in an environmentally benign way,” according to the X Prize Foundation. Judges will be looking for solutions that could remove one ton of CO2 per day that can scale to gigaton levels. Full competition guidelines will be published on April 22nd.

“We want to make a truly meaningful impact. Carbon negativity, not neutrality,” Musk says in a statement. “This is not a theoretical competition; we want teams that will build real systems that can make a measurable impact and scale to a gigaton level. Whatever it takes. Time is of the essence.”

Musk first announced that he was donating money towards a prize in January, not long after he passed Amazon CEO Jeff Bezos to become the richest person in the world. When that happened, the Tesla and SpaceX CEO asked his millions of Twitter followers for “ways to donate money that really make a difference.” The $100 million is coming from Musk’s own foundation. This donation roughly doubles the amount he has publicly given away to date through the Musk Foundation.

Carbon removal technology is an expensive idea that’s still unproven at scale, with options ranging from funding reforestation projects to physically pulling the greenhouse gas out of the air. But it’s become fashionable as the world heats up. It’s especially popular among major corporations. Last year, Stripe made it possible for businesses that use its payment processing platform to funnel portions of their proceeds towards the development of carbon removal tech.

Perhaps most notably, Microsoft announced in 2020 that it wanted to capture the equivalent of all the carbon dioxide it’s ever emitted. The company pledged $1 billion toward the effort.

Last month, we got the first glimpse at the slight progress Microsoft has made toward that goal. The company purchased contracts to capture 1.3 million metric tons of CO2, or just 11 percent of its total emissions for 2020 alone.