Heirloom Carbon

Heirloom Carbon Technologies is a San Francisco-based direct air capture company that uses limestone's natural CO2-absorbing properties to pull carbon dioxide permanently out of the atmosphere. Their process accelerates a geological phenomenon that normally takes thousands of years into a 3-day cycle: calcium oxide powder absorbs CO2 from ambient air, becomes limestone, gets heated in a renewable-energy-powered electric kiln to release the captured CO2, and repeats. The captured CO2 is then stored permanently underground or embedded in concrete. Founded in 2020, Heirloom opened America's first commercial DAC facility in Tracy, California in November 2023 and has raised over $354 million to expand capacity toward their goal of removing 1 billion tons of CO2 by 2035.