On a beach in the Caribbean, a nonprofit called Project Vesta will soon begin testing a radical new way to fight climate change that involves spreading ground-up olivine—a cheap green mineral—over the sand, where ocean waves will break down the mineral, which in turn will pull CO2 from the air.

“Our vision is to help reverse climate change by turning a trillion tons of carbon dioxide into rock,” says Tom Green, executive director of Project Vesta. The idea is to speed up a natural process that normally takes place very slowly, over geological time. “When rain falls on volcanic rocks, those rocks dissolve a little bit, and it triggers a chemical reaction that pulls carbon dioxide out of the atmosphere and into the water as a molecule called bicarbonate,” Green says.

Grinding up olivine, and then spreading it on beaches where ocean waves can further break it down, triggers the same chemical reaction that pulls CO2 out of the air. In the water, marine organisms use the bicarbonate to build shells, and it will eventually end up as limestone on the floor of the ocean.

Past studies have theorized that the process works, but until now, no one has attempted to actually do it on beaches. And it doesn’t come risk free. There are potential ecological challenges that could come from spreading a rock on beaches where it wouldn’t naturally exist.

Some critics raise the possibility that the olivine could release heavy metals such as nickel, although Green says that nickel released into the water is not bioavailable, meaning that it shouldn’t impact marine species. But the initial pilot will closely monitor metal concentrations in the water, sand, and tissues of local organisms, as it seeks to fully understand all of the impacts of the intervention.