Carbon-Neutral Cement Firm Gets Crucial Certification

Brimstone, which claims to make portland cement in a carbon-negative process, announced that it obtained third-party ASTM C150 certification, an industry requirement. The company said that the certification “validates that the cement Brimstone produces is ordinary portland cement, the type of cement used in virtually all construction today.”

“Cement production is a substantial driver of climate change, accounting for 7.5% of global CO2 emissions and 5.5% of total greenhouse gas (GHG) emissions,” it said. “The Brimstone process is carbon-negative across a range of energy scenarios, providing a pathway to eliminate this footprint.”

Key to the process is a significant change in making cement. Rather than using limestone, which releases CO₂ in the manufacturing process, Brimstone replaces the mineral with carbon-free calcium silicon rock. The company has claimed that the result is chemically and physically identical to conventional portland cement while remaining cost-competitive.

The use of such a cement could help improve carbon ratings for new construction buildings, affecting ESG ratings for investors and regulators.

“Our process produces two core products used in concrete: ordinary portland cement and supplementary cementitious materials (SCM),” the company’s website says. “Today, cement and SCM are made from different processes and sourced from different locations. Our rock contains all the minerals necessary to make both cement and SCM from one process in one location.”

Brimstone says that its manufacturing process pulls carbon from the air because the rock contains magnesium in addition to calcium, silicon, iron, and aluminum. The magnesium allows the process to permanently, creating a carbon-negative final product.

The ASTM C150 certification covers eight different types of portland cement. Brimstone did not mention for which type it received certification.

Cement and concrete have been thorny problems for the building industry. Researchers have tried reformulations and addition of other materials like plastics to add strength. A recent paper in Scientific Reports described incorporating cleaned used disposable diapers to replace some of the sand used in concrete.

“At Brimstone, we believe decarbonizing cement relies on three essential principles: producing the exact same trusted material, at much lower carbon, and at equal or lower cost to other options,” the release quoted Brimstone co-founder and CEO Cody Finke as saying. “Not only will our process slash carbon emissions and compete on price, we’ve now proven that it delivers the exact same material relied on by engineers and builders worldwide — and without forcing millions of construction workers to get retrained to use a new material.”

Brimstone says that it expects to sell its portland cement and SCM at conventional prices.

“The company was founded in 2019 at Caltech by Cody Finke and Hugo Leandri with the mission to decarbonize cement production this century, which is responsible for 7.5% of global CO2 emissions today. The company is backed by leading climate investors, including Breakthrough Energy Ventures, DCVC, Collaborative Fund, Fifth Wall, S2G Ventures, Amazon Climate Pledge, Acceler8, Gatemore, Impact Science Ventures, Osage University Partners, and SystemIQ.”