Dartmouth, N.S.-based CarbonCure Technologies has collaborated with Heirloom and Central Concrete Supply Company to store atmospheric carbon dioxide in concrete for the first time using direct air capture (DAC).

Heirloom says it runs the only operational DAC facility in the United States at its Brisbane, Calif. headquarters, while CarbonCure used its reclamation method to inject the carbon dioxide (CO2) into process wastewater at a Central Concrete plant in San Jose.

The concrete produced was used in a variety of projects in the Bay Area.

“Through this demonstration project (we) collaborated with Heirloom because while it's important to take that CO2 from the atmosphere, it's equally important to (be) permanently stored somewhere, and at the moment, the main available storage solution in North America is concrete,” Reilly O’Hara, a carbon finance manager for CarbonCure, told SustainableBiz.

“It's really the only storage solution that is online right now that can handle the quantities of CO2 that will be pulled from the atmosphere in the next few years in the near term. So we partnered with Heirloom to demonstrate that it was feasible, that concrete can serve as a viable and important storage solution for direct air capture of CO2.”

About CarbonCure

Founded in 2012, CarbonCure’s investors include Breakthrough Energy Ventures, Amazon, Microsoft, BDC, Carbon Direct and Mitsubishi Corporation. It is also listed in the Cleantech 100 Hall of Fame, having been featured seven times on the top-100 list.

Its reclaimed water process is a more recent development, compared to its original injection process by which CO2 is injected into a ready mix and converted into a mineral.

The company’s technologies are operational in hundreds of plants in over 30 countries, it says, and have generated nearly 250,000 tonnes of CO2 savings to date.

In June 2022, CarbonCure announced participation in a U.S. Department of Energy study on DAC-to-concrete with the University of Illinois, Los Angeles-based Carbon Capture Inc. and Ozinga.

The DAC-concrete process

CarbonCure’s technology injects CO2 into recycled water collected from the cleaning of concrete trucks. When injected, the CO2 reacts with cement in the water and mineralizes, permanently storing the CO2 and stabilizing the cement for reuse. That CO2-treated slurry is then used in new concrete mixes.

"(The water) is filled with cementitious materials and other solids. There are a range of concrete producers that use what's called a reclaimer, sort of a giant vat. It's used to separate solids from water into aggregates and clarified water, and then reuse materials into future uses of concrete,” O’Hara explained.  

“But reuse of those elements is quite difficult because there are native performance attributes that are associated with the water chemistry and the makeup of those different elements are separated out.”

CarbonCure’s process, which won the 2021 Carbon XPRIZE, stabilizes the cementitious materials in the wash water, allowing more water to be reused and reducing the amount of cement required for future batches. 

The manufacture of cement accounts for approximately eight per cent of global greenhouse gas emissions.

The company's goal is to remove 500 million metric tonnes of carbon emissions annually. Without divulging specifics, O’Hara said CarbonCure is continuing to discuss opportunities with companies that are capturing atmospheric CO2.

“We continue to be optimistic in achieving that milestone, that's a key part of our mission. And part of the pathway that will enable us to achieve that milestone is really the design and deployment of new commercial technologies. So that's one reason why the reclaimed water system is so exciting,” O’Hara said. 

“It has the potential to mineralize increasing volumes of CO2 in concrete, and then also stack with our existing technologies to offer yet another technological solution for concrete producers that are looking to generate CO2 savings.”

The CarbonCure-Heirloom collaboration

The collaboration took “in the order of months,” but was aided by how both companies share investors in Carbon Direct and Breakthrough Energy Ventures.

“There are a number of DAC technologies that exist in very early stages, but very few direct air capture technologies are pulling meaningful levels of CO2 from the atmosphere at this moment,” O’Hara said. “So when you look across the landscape of direct air capture companies, and you look to storage solutions that utilize significant quantities of atmospheric CO2, Heirloom is the leader in that area.”

Central Concrete has partnered with CarbonCure many times in the past, and was the first in the Bay Area to utilize CarbonCure's technology. CarbonCure's website states Central Concrete has saved the equivalent of 14,194 acres of trees in CO2 emissions.

Heirloom’s location was also convenient for CarbonCure as its second reclaimed water deployment is in San Jose.

While other companies do capture atmospheric CO2 in a number of ways, not all have the necessary supply, unlike Heirloom. The collaboration managed to capture dozens of kilograms of CO2, and inject them into concrete. 

Heirloom’s DAC process breaks down limestone into calcium oxide, which then acts like a sponge to pull CO2 from the air. Normally, it is then stored underground.

According to O’Hara, billions of tonnes of CO2 could be captured via DAC by 2050.

The Global Cement and Concrete Association's industry roadmap predicts carbon capture, utilization and storage will account for 36 per cent of the industry's emissions reductions needed to reach net-zero by 2050.