Canadian start-up CarbonCure developed a system that injects CO2 into the concrete when it’s being mixed, sequestering it when it hardens while also reducing the need for cement.

Concrete is the most abundant artificial material on earth, but the production of its main ingredient, cement, has a huge carbon footprint. Cement functions as a glue to hold the other ingredients of concrete together. To make cement, calcium carbonate, also known as limestone, is heated, which releases massive amounts of carbon dioxide into the atmosphere. Cement is responsible for 7 per cent of global greenhouse emissions, the second largest industrial source.

CarbonCure came up with a method to trap CO2 emission forever, while also reducing the need for cement to make strong concrete. The system takes captured CO2 and injects it into concrete during the mixing phase. The carbon dioxide reacts with the concrete, turning into a mineral. When the concrete hardens, the carbon is sequestered forever, even if the building is torn down.

The main advantage of this method is of course that since the CO2 is trapped, it can’t be released into the atmosphere, adding to global warming. In addition, the carbon makes the concrete stronger, reducing the need for cement.

CO2, when released, can be captured. Companies that use the CarbonCure system can buy it from, for instance, fertiliser plants, but because the concrete needs less cement, the costs even out.

The method is currently being used its largest project as of yet, to construct a building in Atlanta, US, which will be opened in 2019. The 33,500 sq metre (360,000 sq ft) office building will save 0.6 million kilograms (1.5 million pound) of CO2 from being released into the air, the same amount 800 acres of forest would sequester in a year.

Other companies that use CO2 to make greener concrete include Carbicrete, which doesn’t use cement at all, and Carbon Upcycling with their CO2NCRETE, about which you can read more here.

Photos: CarbonCure / Circe Denyer