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Brimstone processBrimstone—
Brimstone process
Courtesy of Brimstone · Press kit, editorial use (opens brimstone.com)

Brimstone process

by BrimstoneUS

PilotStage 3 of 5

Pilot operations; first commercial plant in planning.

Updated 10 Dec 2025Checked 25 Sep0 updates this week

Milestones

Next · First commercial plant
  1. Selected for DOE award of up to $189MMar 2024Complete.
  2. Metals co-production roadmap announced2 Dec 2025Complete.
  3. First commercial plantNowCurrent milestone.

Most important updates

  • 10 Dec 2025
  • Mar 2024

Current obstacles

  • Many products, many marketsProfits depend on selling several side products, each with its own market and approval process.

Physics limits

  • Cement clinker still needs 1,450 °CRock CO2 is avoided, but forming clinker needs ~1,450 °C, and fuel for that heat causes ~40% of cement's CO2 unless it is electrified or captured.
  • Silicate rock is poor in calciumBasalt-type rocks hold roughly 10% calcium oxide versus ~55% in limestone, so several times more rock must be mined and processed per tonne of cement.

How it works

4 parts
Anorthosite, a calcium-bearing silicate rock with no carbonate in it: rocks of this kind replace limestone as Brimstone's source of calcium
Anorthosite, a calcium-bearing silicate rock with no carbonate in it: rocks of this kind replace limestone as Brimstone's source of calciumPhoto: James St. John · CC BY 2.0 (opens commons.wikimedia.org)
Rock

Calcium from silicate rock

Brimstone starts with calcium silicate rock, which holds calcium but no carbonate, so there is no CO2 locked inside to release.

Leach

Dissolve and separate

Crushed rock is dissolved and its calcium, silica, aluminium, magnesium and iron are split into separate streams.

Clinker

Ordinary portland cement

The calcium and silica are made into standard portland cement, chemically the same as today's, so no new building codes are needed.

By-products

Alumina and metals too

Side streams give alumina for aluminium, plus magnesium and other metals, spreading costs over several products.

Update log

2 updates

Wed 10 Dec 2025

  • Minor: PressOther

Mar 2024

  • Minor: PressFunding

About Brimstone

The team behind Brimstone process

Brimstone

Limestone-free portland cement, alumina

Brimstone (Oakland, founded 2019) makes ordinary portland cement from calcium silicate rock instead of limestone, avoiding the CO2 from baking limestone. It also makes alumina, and in December 2025 outlined plans to add metals.

  • Its cement is chemically ordinary portland cement, so no new building codes are needed.
  • Selected in 2024 for a DOE award of up to $189M, which it later lost in 2025 cancellations.
  • Pitches itself as a rock refinery: cement plus alumina and critical metals from the same rock.

brimstone.com (opens brimstone.com)Company profile →

Founded
20197 yrs
Headquarters
United States
Status
Private
Valuation
private
Works in
MaterialsClean cement
Coverage
1 program · 2 updateslatest 10 Dec 2025checked 25 Sep
People
Cody Finke (opens brimstone.com)Co-founder & CEO
Primer