Most of the built environment today is made at least partially from concrete, making it the second most-used substance on earth after water. But making concrete emits almost as much carbon dioxide as cars, because its main ingredient, cement, is made from limestone. Limestone naturally consists of about 50% CO2 by weight.
Brimstone Energy, a California-based startup, is one of several companies trying to reduce the carbon emissions from the production of cement, which accounts for about 8% of global carbon emissions. Brimstone is using a different rock but producing standard, so-called ordinary Portland cement. Brimstone is using a calcium silicate rock that is even more abundant than limestone and uses patented technology to remove the calcium. Unlike limestone, however, the silicate rock contains no CO2, so there are no such emissions associated with the production process. Last July it received certification that its product is essentially the same as Portland cement.
"People already know how to build with it, so construction will not be delayed. People already know how to specify it, that way there are not safety concerns," said Brimstone Co-founder and CEO Cody Finke.The company is still in the early stages, with a pilot plant now in the works, but Finke says once scaled, the cement will be cheaper to produce than what's out there now.
In addition to Breakthrough, Brimstone investors include DCVC, Collaborative Fund, Fifth Wall, S2G Ventures, and Amazon's Climate Pledge Fund. The company has raised $60 million so far.