CarbonCure brings home Heirloom Direct Air Capture carbon dioxide

CarbonCure Technologies, Halifax, Nova Scotia, and its concrete producer licensees will mineralize and permanently store atmospheric carbon dioxide from Heirloom Carbon Technology Direct Air Capture (DAC) assemblies under a two-year agreement. The plan advances the DAC-to-concrete storage pathway demonstrated earlier this year at the Central Concrete Supply Co. headquarters plant in San Jose, Calif. 

Based in Brisbane, Calif., Heirloom Carbon Technology has refined in short order a process entailing chemical phases similar to those in lime or portland cement production: Limestone is broken down into calcium oxide rock and CO2 gas using heat from a renewable-energy powered, electric kiln. The calcium-based material is spread onto vertically stacked trays where it acts like a sponge, pulling CO2 from the air before it is returned to the kiln and the process repeats. The captured CO2 gas is then permanently and safely stored underground or, when used in CarbonCure operations, embedded in concrete. 

The DAC method has garnered the attention of carbon management-minded parties no less than Microsoft, which in September enlisted Heirloom to deliver 315,000 metric tons of CO2 removal—one of the largest such contracts to date. That award followed Heirloom’s Notification of Selection from the U.S. Department of Energy for a proposal tied to the Infrastructure Investment & Jobs Act’s Regional DAC Hubs program in Louisiana. Separately, Heirloom and CarbonCure await DOE word on participation in a DAC Hub project in Illinois.

The CarbonCure announcement set the table for Heirloom’s dedication of the first DAC technology installation in the United States to capture CO2, permanently sequester it, and fulfill commercial removal purchases. The Tracy, Calif. facility runs on renewable energy sourced from a local utility, Ava Community Energy. It demonstrates the rapid pace at which the Heirloom process and business plan—from gram-sized lab sample testing to metric ton-scale field deployment—have progressed since the company’s 2020 founding. 

By harnessing the power of algorithms to increase the capture capacity of easy-to-source materials like limestone, and scaling with modularity, the Heirloom technology represents one of the lowest cost pathways to permanent CO2 removal. Company officials aim to remove 1 billion tons of CO2 from the atmosphere by 2035. That volume represents 20 percent of current annual U.S. emissions and 10 percent of the yearly global carbon removal that climate observers envision by 2050.

“The capacity of our limestone-based technology to capture CO2 from the air has gone from 1 kilogram of CO2 to up to 1 million, or 1,000 metric tons, in just over two years,” Heirloom CEO and Co-Founder Shashank Samala noted at a mid-November Tracy facility dedication ceremony, where Department of Energy Secretary Jennifer Granholm topped the guest list. 

CarbonCure concrete plants will provide a CO2 destination for the Heirloom DAC method, which loops 1) calcium carbonate through phases where it is transformed to 2) calcium oxide, then hydrated to form 3) calcium hydroxide, ready to absorb CO2 and revert to 4) calcium carbonate. A vertical electric kiln separates the compound, conveys captured CO2 to storage, and returns calcium oxide to the loop. 

The charter Heirloom Carbon Technology facility in California’s Central Valley has a carbon dioxide capture capacity upward of 1,000 metric tons per year. It will deliver net removals to initial Heirloom CO2 removal credit buyers, including Microsoft, Shopify, Stripe and Klarna. The limestone-bearing trays at the heart of the process, coupled with racks and transfer devices, mimic the pallet, roller conveyor, lowerator/elevator, kiln relay and wet-to-dry side sequences typical of concrete masonry building or hardscape unit production.