Microsoft’s Remarkably Big Bet on Carbon-Absorbing Rocks

Microsoft has made a significant investment in Heirloom Carbon, a startup that has developed a method to absorb carbon dioxide (CO2) from the air using crushed rocks. Under the deal, Microsoft will pay Heirloom to capture 315,000 metric tons of carbon from the atmosphere over the next decade. This amount is equivalent to about 75% of the carbon emissions Microsoft produced in 2022. Heirloom’s process begins with limestone, which is heated to release carbon dioxide, leaving behind calcium oxide. The remaining powder is then spread on trays and exposed to the air, allowing it to absorb even more carbon. The partnership highlights the confidence Microsoft has in Heirloom’s unique approach and contributes to Microsoft’s goal of becoming carbon negative by 2030 and removing historic emissions by 2050.

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