As the world gathers at COP28 to discuss ways to decarbonise the global economy, a new technology is helping concrete, long considered one of the world’s most carbon-intensive building materials, eliminate embodied carbon on an enormous scale.
Developed by CarbonCure, the technology is retrofitted into concrete plants, allowing producers to inject captured carbon dioxide (from the air) into fresh concrete during mixing.Â
Once injected, the carbon dioxide reacts with the concrete mix and becomes a permanently embedded mineral – like a rock, meaning that it will never return to the atmosphere.Â
It also increases the concrete’s compressive strength, enabling producers to optimise cement content and reduce carbon emissions without impacting the concrete’s performance.
According to Robert Niven, CEO of CarbonCure, the technology “demonstrates the very near-term opportunity for carbon removal, not just this decade but over the next few months. Ours is a climate solution that puts captured CO2 to good use, permanently storing it and using it to build greener homes, highways, high-rises and more.”
CarbonCure has loft ambitions and claims “it’s on a mission to make concrete a climate solution by reducing and removing 500 million metric tons of carbon dioxide from the atmosphere.”
The last few months have been a busy time for Mr Niven, who has negotiated carbon credit agreements with global accounting giant Deloitte and has expanded into Asia-Pacific, Africa and North America.
In February, CarbonCure, its US Partner Heirloom and concrete producer Central Concrete, made history after successfully demonstrating for the first time the ability to capture carbon dioxide from the atmosphere and permanently embed it into concrete.
At the time, Julio Friedmann, a scientist working on the project, said, “The development was a landmark day for carbon reduction.
Because concrete is so widely used, it has great potential for absorbing carbon dioxide if the process works and goes global. “The thing about direct air capture and concrete is it’s a big prize together,” he said.
However, capturing and locking down carbon globally will be challenging, with companies needing to build expensive plants capable of capturing millions or billions of tons a year.
“To remove a billion tons from the air, we need in the order of mid-hundreds of billions of dollars,” Heirloom CEO Shashank Samala told Reuters earlier this year, who expects funders of solar, buildings, transmission towers to finance carbon infrastructure, too.
He also said the price of carbon needs to fall. The US government and industry see US $100-a-tonne carbon dioxide as a reasonable price for broad deployment, and whilst Heirloom charges $1,000 now, Samala expects that to drop to the $100-a-tonne baseline by the time his projects are soaking up millions of tons a year.
Concrete is also controversial: it is the most used building material in the world, and it accounts for about 8% of global carbon dioxide emissions, including those of its main binding agent, cement.Â
CarbonCure’s most-used technology cuts that by about 5%, said CarbonCure CEO Rob Niven. The new one using wastewater could cut a further 5%-10%.
That still leaves it a huge net emitter with a difficult path to zero emissions without raising prices.
However, concrete’s ubiquity is attractive because there are few places to hold carbon dioxide securely.Â
“It is a thoughtful way to get around the current bottleneck of storage for DAC,” said Anu Khan, deputy director of science at climate advocacy group Carbon180.
“The thing about concrete is there are no substitutes,” Niven said. Technology can find new binding agents and new ingredients. “We just have to clean it up,” he said.
