Brimstone, an Oakland-based startup founded in 2019, is developing a cement-making process that swaps conventional limestone for silicate rock. Because limestone releases carbon dioxide when heated, the standard process accounts for roughly 8% of global CO2 emissions. Brimstone says its approach cuts that pollution about 60% and has already earned third-party certification for its Portland cement.
The company also claims the same silicate rock can yield smelter-grade alumina, steel, magnesium, titanium, and other critical minerals in a single refinery. That lets Brimstone tailor its message to the politics of the day: under the Biden administration it highlighted the climate benefit, while under the Trump administration it emphasizes domestic mineral production and national security. CEO Cody Finke calls it a "generational company" that could create an "industrial revolution."
Those claims remain unproven at scale. Brimstone has no commercial facility, and the Trump administration revoked a $189 million grant for its planned demo plant in Reno, Nevada, though Finke says talks to restore funds are ongoing. The company expects to start operating that Reno plant in 2028, initially producing cement, supplementary materials, and alumina; full output of steel and titanium would require another factory likely in the next decade.
Brimstone has lined up supply deals with Amazon for cement and with Century Aluminum for alumina, and even if the broader mineral ambitions fall short, the cement process itself could be a meaningful climate win. But observers remain skeptical about whether the economics of extracting so many materials from one rock will work.