Microsoft has paid to have 12,000 tons of carbon dioxide (CO2) removed into the open ocean over the next two years, by “ocean health” company Running Tide.

Running Tide offers carbon capture and removal by deploying floating buoys containing limestone, which boosts the ocean’s alkalinity, and algae which then grows and captures more carbon, before sinking to the deep ocean, where gravity and water pressure hold the biomass. The captured carbon is trapped in a slow cycle that Running Tide says will keep it locked up for thousands of years.

More on Running Tide’s work with Microsoft here.