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Cleaning up concrete

Concrete is an integral part of modern construction, used in almost every structure, from bridges and office blocks to housing and stadiums. Whilst being incredibly important, its production has a big environmental impact.

"When making cement you start with limestone: that limestone is crushed and heated in a kiln well over 1,000 degrees," Robert Niven, CEO of CarbonCure, told CNBC's Sustainable Energy.

"Every molecule of limestone is actually broken in half," Niven added. "One half forms clinker, which is cement, and the other half is released into the air to cause climate change through the release of CO2."


CarbonCure's big idea is to retrofit concrete plants with technology that can recycle waste CO2 during production and produce greener, cleaner concrete.

Rather than being released into the atmosphere, the CO2 is locked in to the concrete.

"We actually use CO2, which is normally a greenhouse gas, and put that to work by injecting it into concrete manufacturing," Niven added, going on to explain that this helped to make the concrete stronger.

The process has several steps. CarbonCure say that when CO2 is added to the concrete during the mixing process it reacts with water, forming carbonate ions, which subsequently react with calcium ions released by the cement.

A "limestone like" material is formed and dispersed in the mix "in the form of nanomaterials."

A school in Halifax, Nova Scotia was one of the first places to utilize CarbonCure's "concrete masonry units." Going forward, Niven had a positive outlook.

"The ultimate goal for CarbonCure is to be part of the solution to provide a net zero carbon concrete," he said. "We actually want to make a concrete that heals rather than harms the environment," he added.