Carbon dioxide (CO2) sequestered from the atmosphere via direct air capture (DAC) has been permanently stored in concrete for the first time.
When injected, the CO2 immediately reacts with cement in the water and mineralises, permanently storing the CO2 and stabilising the cement for reuse. The CO2-treated slurry is then used in new concrete mixes.
The CO2 is permanently sequestered in the concrete as calcium carbonate and will not be returned to the atmosphere for centuries, even if the concrete is demolished, Heirloom said.
The start-up currently runs what it says is the only operational DAC facility in the US. It uses limestone, which is inexpensive and abundant, to pull CO2 from the air.
The limestone is then broken down into calcium oxide rock and CO2 gas using heat from a renewable energy-powered electric kiln.
The calcium oxide 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 begins again. The captured gas is typically then stored underground on a permanent basis.
“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,” said Robert Niven, chair and CEO of CarbonCure Technologies. “We’re thrilled to be collaborating with Heirloom and Central Concrete on this ground-breaking world first.”
Shashank Samala, CEO of Heirloom, said: “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 toward that future and shows the promise of DAC technologies combined with smart, permanent methods of sequestration.”
The most aggressive emissions reduction projections from the UN Intergovernmental Panel on Climate Change will require the removal of between six and 10 billion tons of CO2 per year by 2050 to stick to the 1.5˚C warming pathway.
However, the UK’s Climate Change Committee recently said that carbon offsets such as this are being used by firms to mask insufficient efforts being made toward eliminating their own emissions.
Last month, US researchers said they had developed a cost-efficient method to capture CO2 and convert it into methanol.