Brimstone's one-rock process aims to replace limestone in cement — and co-produce critical minerals

Brimstone's pilot line in Oakland is built around a single swap: instead of pulling cement from limestone, the company pulls it from calcium-silicate rock, then keeps the same feedstock in the reactor to refine alumina, the smelter-grade feedstock for aluminum. The chemistry is the unusual claim. Conventional cement production is responsible for about 8% of global CO2 emissions, most of it released when limestone is heated to drive off carbon.

Brimstone, founded in 2019, says its Portland-cement output generates roughly 60% lower greenhouse-gas emissions than the conventional route, a figure that comes from the company and has not been independently verified. A third-party industry program certified the Portland-cement chemistry in 2023, and the company's published patent record and a continuation filing cover the non-limestone route and are public.

The more aggressive pitch is the second product. Brimstone disclosed in early 2025 that its process can also yield smelter-grade alumina, and expanded the claim late last year to include steel, magnesium, titanium, and other critical minerals from the same feedstock. CEO Cody Finke pegs the combined output market at $2.4 trillion globally, a figure that is his framing, not an independent market assessment.

The Department of Energy selected Brimstone for a $189 million Industrial Demonstrations Program award negotiation, part of a wider effort to decarbonize cement and concrete. The award is a negotiation, not yet a disbursement, and the program's project page names National Cement Company of California as the industrial partner. Separately, ARPA-E funds a related program on co-generating low-energy, CO2-free hydrogen and ordinary Portland cement from calcium-rich basalts, the same feedstock family Brimstone is using.

The policy logic is the part most wire coverage skips. Cement is the binding constraint on cheap, low-carbon construction, and the metals on Brimstone's list are inputs to nearly every manufactured good a growing economy needs. Today, most of those metals are refined in China, and the Department of Defense and the Department of Energy have flagged the concentration as a national-security vulnerability. A cement plant that also produces alumina, magnesium, and titanium in the same reactor would not just lower emissions. It would add domestic mineral capacity inside a project the government is already paying to build.

The 2023 third-party certification covers Portland-cement chemistry only. The alumina disclosure is roughly a year old, and the broader multi-mineral pitch is months old. Brimstone has not yet published commercial-scale production data for the metal suite. If the metal chemistry does not extend past pilot scale, the doubled-output story collapses to a single-cement decarbonization story.

Brimstone says the first commercial plant is targeted for the mid-2020s. Whether the same silicate rock that yields low-carbon cement also yields smelter-grade alumina at scale is the question the next eighteen months of pilot data, and the federal award negotiation, are designed to answer.