Brimstone

Why it's on ClimateTicker

Brimstone targets one of the hardest-to-abate emissions sources—ordinary portland cement, responsible for roughly 7.5% of global CO2—by substituting carbon-free calcium silicate rocks for limestone, eliminating calcination process emissions and generating CO2-absorbing magnesium byproducts that make the process net carbon-negative across a wide range of energy mixes. Third-party ASTM C150 certification of its cement and IEA recognition add credibility, but the company remains pre-commercial and has not yet proven its process at industrial scale, with its planned first plant still in site-selection and the key $189M DOE grant cancelled in 2025. Investors should treat the technology thesis as scientifically well-grounded but subject to material scale-up, financing, and execution risk.