Microsoft-Backed Start-Up Heirloom Uses Limestone To Capture CO2

California-based startup Heirloom is using limestone to capture CO2 from the atmosphere to reduce carbon emissions and prevent the worst effects of global warming. CNBC reports: CO2 naturally occurs in limestone. Heirloom removes that CO2 by heating the limestone into a powder and stores the extracted CO2 underground. The remaining powder is then thirsty for more CO2. Heirloom spread that powder out on trays, with a robot determining location for maximum CO2 absorption. A process that naturally takes years is reduced to just three days. Once the powder is full, the process starts again. Heirloom's approach is relatively cheap compared with other types of carbon capture and removal and highly scalable, which made it attractive to investors like Microsoft. "We identified that Heirloom's enhanced mineralization approach used widely available materials as passive airflow technologies, [which] means it has a potential to reach a low cost trajectory that's really been a challenge to this industry as a whole," said Brandon Middaugh, director of the climate innovation fund at Microsoft. Heirloom says it plans to deploy its first site next year and aims to remove 1 billion tons of CO2 by 2035. It also sells carbon credits, which allow companies to offset their own CO2 emissions. Buyers include Microsoft, Stripe, Shopify and Klarna.

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