https://archive.ph/rgrNI https://archive.ph/rgrNI subtitle: "Deal with Heirloom Carbon is one of largest ever purchases of carbon-removal credits" Excerpt: '

https://archive.ph/rgrNI https://archive.ph/rgrNI subtitle: "Deal with Heirloom Carbon is one of largest ever purchases of carbon-removal credits" Excerpt: 'Founded in 2020, Heirloom hopes to use the Microsoft deal to raise money from investors to build its first large-scale project later this year. The startup will have to contribute funding equivalent to the government grants for the Louisiana effort, which will take much longer. Limestone naturally absorbs carbon. Heirloom accelerates the natural process so it takes days instead of years. To remove carbon from the air, the company warms up crushed limestone in a kiln heated to about 1,650 degrees Fahrenheit and powered by renewable electricity. That heat separates the carbon dioxide, which is stored underground or in concrete, and leaves a chemical powder called calcium oxide. That powder is then combined with water to become calcium hydroxide and spread onto trays the size of large desks or picnic blankets. Outside, the calcium hydroxide puffs up like a cookie in the oven as it absorbs carbon dioxide over about three days. The resulting limestone can go back into the kiln to restart the cycle.'