Natural geological processes have been regulating Earth’s climate for millions of years. Accelerated versions of these processes are now being promoted as technologies to draw down carbon from the atmosphere—and some are rapidly moving from concept to real-world deployments.

Two such technologies are known as enhanced weathering, which speeds up the chemical breakdown of certain rocks, and ocean alkalinity enhancement, which increases the ocean’s natural ability to remove carbon dioxide from the air.

Startups backed by tech companies including Google and Microsoft are already applying these technologies in field trials. Investment in the sector is rising rapidly, with large-scale trials underway and carbon credits beginning to appear on voluntary markets.