Main image: Heirloom

CarbonCure Technologies in Canada worked with Californian start-up, Heirloom, to inject carbon dioxide (CO₂), which has been isolated from the atmosphere via direct air capture (DAC), into concrete.

Direct air capture

Using cost-effective and readily available limestone to pull CO₂ from the air, Heirloom currently runs the only operational DAC facility in the United States of America (USA). The limestone is broken down into calcium-oxide rock and CO₂ gas, using heat from a renewable energy-powered electric kiln. Spreading the calcium oxide onto vertically stacked trays, it acts like a sponge, pulling CO₂ from the air before returning to the kiln, where the process begins again.

CO stored in concrete

Captured CO₂ is usually stored underground on a permanent basis, but in this case, by injecting the gas into recycled water at the manufacturer, Central Concrete’s, plant, it has been permanently stored in concrete for the first time. Through this process, the CO₂ reacts with cement in the water and mineralises, permanently storing the CO₂ in the concrete as calcium carbonate and stabilising the cement for reuse in new concrete mixes.

Heirloom states that the CO₂ will not be returned to the atmosphere, even if the concrete is demolished. The demonstration project used 30kg of captured CO₂, which is equivalent to the exhaust pipe emissions of driving a car for approximately 120km.

CO and global warming

“This demonstration project is a global milestone for carbon removal technology, which 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,” said Robert Niven, chairperson and chief executive officer of CarbonCure Technologies. “We are thrilled to be collaborating with Heirloom and Central Concrete on this groundbreaking world first.”

Shashank Samala, chief executive officer of Heirloom, says: “The science is clear: In order to reach climate goals, we must remove billions of tons of already emitted CO₂ from the atmosphere each year. This is an important step towards that future and shows the promise of DAC technologies combined with smart, permanent methods of sequestration.”

The United Nations Intergovernmental Panel on Climate Change requires the removal of six to ten billion tons of CO₂ per year by 2050 to limit global warming to the 1,5°C temperature threshold.

Issue: Removal and storage of CO₂ to limit global warming.
Solution: Capture and use of CO₂ in the manufacture of concrete, as an alternate means of storage.

Full acknowledgement and thanks go to https://eandt.theiet.org/ for the information used in this article.

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