To remedy this, scientists from the University of Colorado have come up with a surprising solution: plankton.
More specifically, they are using coccolithophorids, micro-algae with a very resistant mineral shell, which contains calcium carbonate.
This material is precisely what could replace the main ingredient of cement, made of limestone and clay and heated at very high temperatures to harden.
“Global cement production accounts for 7% of annual greenhouse gas emissions in large part through the burning of quarried limestone,” explains researcher Wil Srubar, associate professor in civil, environmental and architectural engineering at the University of Colorado, and lead principal investigator on the project.
The research team found that replacing quarried limestone with a biologically-grown plankton-based alternative would allow for carbon-neutral manufacturing of portland cement, the most common type of cement.
In fact, the amount of carbon dioxide released into the atmosphere during the manufacturing process would be equal to the amount previously captured by the coccolithophorids.
“If all cement-based construction around the world was replaced with biogenic limestone cement, each year, a whopping two gigatons of carbon dioxide would no longer be pumped into the atmosphere and more than 250 million additional tons of carbon dioxide would be pulled out of the atmosphere and stored in these materials,” explains Wil Srubar.
And, according to the researcher, this “could theoretically happen overnight, as biogenic limestone can ‘plug and play’ with modern cement production processes.”
The international construction industry is experimenting with various solutions to help make construction materials “greener.” The Canadian company CarbonCure, for example, is on a mission to decarbonise concrete production.
To do this, it is working on a unique and particularly innovative technology that consists of injecting recycled CO2 directly into concrete.
Recovered from other industries, such as ethanol and fertiliser plants, this CO2 is intended to reduce the amount of cement needed to make concrete.