Among all uses, the use of CO2 in concrete appears to be perhaps the most promising. 30 billion tons of concrete are produced every year worldwide (and about 4 billion tons of cement).
And not just scale, it is also a great material to store CO2. When CO2 is incorporated into concrete, it’s literally piped into the mix and the natural tumbling motion of churning concrete is all the energy that’s needed to transform the CO2 into a calcium carbonate, a substance that doesn’t just act as filler but also actively strengthens the concrete mix. More calcium carbonate also means the concrete needs less cement in its mix, which means less energy needed for its production and less CO2 emissions.
Interestingly, even the concrete that we use today captures a reasonable amount of CO2 over its lifetime - some estimates suggest it could about 30% of the total CO2 emissions during its production. But this is over its lifetime - we want things faster, don't we!
Studies suggest that curing of cement with CO2 (instead of water) could capture CO2 that is 25-30% the weight of concrete - now, assuming these numbers stand on large scales, we are talking about a possible 7-8 billion tons of CO2 being sequestered in concrete if all concrete were to be cured by CO2 instead of water. That's massive.
Companies such as Carbon Upcycling Technologies are looking to expand into the carbon-capture field. The company uses some of the carbon emissions produced by a natural gas power plant in southeast Calgary to produce an additive that makes concrete more durable. "We put the CO2 and powder feedstock into our reactor that's pressurized with CO2. It spins and then, at the end, you have a product that has carbon dioxide captured in the product," said Natalie Giglio, a business associate with Carbon Upcycling Technologies.
https://www.cbc.ca/news/canada/calgary/carbon-upcycling-technologies-co2-carbon-sink-1.6110999
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