Heirloom’s technology hinges on a simple bit of chemistry: Limestone, one of the most abundant rocks on the planet, forms when calcium oxide binds with carbon dioxide. In nature, that process takes years. Heirloom speeds it up.
At the California plant, workers heat limestone to 1,650 degrees Fahrenheit in a kiln powered by renewable electricity. Carbon dioxide is released from the limestone and pumped into a storage tank.
The leftover calcium oxide, which looks like flour, is then doused with water and spread onto large trays, which are carried by robots onto tower-high racks and exposed to open air. Over three days, the white powder absorbs carbon dioxide and turns into limestone again. Then it’s back to the kiln and the cycle repeats.