Two companies said they have devised a way to pull carbon dioxide emissions out of the sky and trap the CO2 in concrete after demonstrating the first-of-its-kind technique in San Jose, Calif.

Heirloom Carbon Technologies Inc. and CarbonCure Technologies Inc. announced the success of the project Feb. 3. The project was the first to permanently store CO2 extracted by direct air capture into concrete; the demonstration took place at a Central Concrete Supply Co. Inc. facility.

Central Concrete, a Vulcan Materials Co. subsidiary, will use the material for construction projects in the Bay Area.

Direct air capture refers to nascent technologies that extract CO2 from the atmosphere as a tool that may help reverse climate change. The captured carbon is then stored underground or converted into other products, allowing the capturer to receive tax credits in the U.S.

California-based Heirloom uses limestone to pull CO2 from ambient air and breaks the stone down in a kiln, separating the gas from the waste rock. The recent demonstration project paired Heirloom's direct air capture process with CarbonCure's mineralization technology, which involves mixing CO2 into wastewater that was used to clean out concrete trucks. Once combined, the CO2 reacts with the residual cement, forming a "CO2-treated slurry" that can be used in new concrete mixes, according to a press release.

"This is the start of something big," Julio Friedmann, chief scientist at Carbon Direct Capital Management LLC, said in a tweet about the Feb. 1 demonstration. Carbon Direct, a private equity company that invests in climate technology, has a stake in both Heirloom and CarbonCure, according to S&P Global Market Intelligence data.

"Cement [and] concrete are huge emissions sources with very few options and no substitutes for abatement," Friedmann added.

Robert Niven, chair and CEO of CarbonCure, also touted the project's implications, both for direct air capture development and the decarbonization of the building sector. "This demonstration project is a global milestone for carbon removal technology that confirms concrete's enormous potential as a climate solution that can permanently store carbon in our most essential infrastructure — from roads and runways to hospitals and housing," Niven said in a statement.

Direct air capture starts to commercialize

The demonstration project is the latest success story in the development of technology-based carbon dioxide removal, or CDR. The phrase is used to distinguish from nature-based CDR, such as planting trees.

Such technologies remove CO2 at a massive price premium. As of Feb. 3, technology-based carbon credits were selling at $128 per tonne of CO2 removed, compared to $12.10 for nature-based credits, according to S&P Global Platts' basket pricing assessments.

But industry experts said engineered approaches to CDR are more reliable than nature-based approaches, which are temporary and require more land. A recent report called investment in technology-based CDR an "urgent priority" for countries to meet the temperature goals of the Paris Agreement on climate change.

The U.S. government has also sought to spur private-sector investment in direct air capture, allocating $3.5 billion to the U.S. Energy Department to deploy the infrastructure at scale thanks to the bipartisan infrastructure law of 2021.

Spokesperson Alexa Dennett said Heirloom is confident that it has the "fastest path" to remove CO2 for less than $100 per tonne. Unlike other direct air capture developers, Heirloom's core ingredient is limestone, keeping primary input costs between $10-$50 per tonne, Dennett added.

Meanwhile, CarbonCure's CO2-to-concrete technology could allow some of those costs to be recouped.

"On average, concrete producers see a net neutral economic impact from the use of our technologies and are also able to benefit from the growing demand for green construction materials from the public and private sectors," Dennett said.

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