From the hum of machinery to the dust in the air, cement plants are places you expect permanence—and resistance to change. Yet this year, in laboratories and boardrooms alike, something quietly shifted. In the fight against climate change, the building blocks of our world may be about to change too.
Cement’s Carbon Burden
Cement is everywhere: in buildings, roads, skyscrapers. Yet it carries a hidden cost. Globally, production of Ordinary Portland Cement (OPC) is responsible for about 7.5-8% of all carbon dioxide emissions.
Central to that burden is the use of limestone: when it’s heated in kilns (in a process called calcination), it releases CO₂. Then there is the energy required—very high temperatures, often from burning fossil fuels.
Because of those deep, embedded emissions, cement is what many experts call a “hard-to-abate” industry. It’s inexpensive, well entrenched in building codes, and the scale of cement needed globally grows with infrastructure demand. Thus innovations must not only reduce emissions, but also work with existing standards and systems.
Brimstone’s Breakthrough: Rock Instead Of Limestone
In Oakland, California, a company called Brimstone Energy has been quietly rethinking cement from the ground up—and from the rock out. Instead of limestone, which carries built-in CO₂, Brimstone’s process starts with calcium-silicate rocks—common, abundant, and crucially, carbon-free feedstock.
Here’s how their method stands out:
- Their process yields industry-standard OPC that meets the ASTM C150 specifications (the benchmark in the US for Ordinary Portland Cement). This means the resulting cement can be used in most concrete applications without rewriting rulebooks.
- They also co-produce supplementary cementitious materials (SCMs) from the same feedstock. SCMs help reduce the amount of clinker (the high-carbon component of cement) needed in concrete mixes.
- Further, their Rock Refinery process includes smelter-grade alumina, which is important for aluminum production, another high-volume industrial use. Co-products help spread cost and reduce waste.
Proof In The Lab And Amazon’s Bet
Passing standards on paper is one thing; proving performance is another.
- In recent tests developed with Amazon, Brimstone’s OPC was put through “slab mix” designs similar to what Amazon uses in its building projects. The concrete made with Brimstone’s cement showed comparable compressive strength, workability, and met all ASTM C150 requirements. In simpler terms: it behaves like regular cement.
- Amazon, satisfied with those initial results, entered into a commercial agreement to reserve annual volumes of Brimstone’s cement and SCMs—pending the successful completion of extended tests over the coming years. These tests will include checking durability, resistance to sulfate attack, and other environmental stresses across diverse mix designs.
Cody Finke, Brimstone co-founder and CEO, explained that Brimstone had developed a more efficient, economical, and sustainable process for producing industry-standard materials that can be used today with known testing programs, allowing for fast market adoption.
Asad Jafry, Amazon’s Director of Global Energy, Sustainability & Automation, added that the results were encouraging and showed the potential for Brimstone’s innovative materials to scale across Amazon’s building portfolio and reduce the carbon footprint of concrete.
The Fourth Point: Scale, Cost, Regulatory Alignment
This is where the story becomes both hopeful and practical.
Scale and cost: Brimstone is no longer just a lab startup. They aim to build a commercial-demonstration plant with capacity to produce over 100,000 metric tons per year of decarbonized OPC, SCM, and alumina. This scale is meaningful—not gigaton scale yet, but significant enough to test supply chains, logistics, and cost models.
Their technology promises competitive pricing at scale by co-producing several valuable materials, using feedstocks that are widespread, and using existing standards so that infrastructure, workers, and markets don’t need radical retooling.
Regulation and standards: Because Brimstone’s cement meets ASTM C150, it can slot into existing codes and specifications. That’s a huge advantage. Often, newer or alternative cements struggle to be accepted by building inspectors, codes, and engineers because of unfamiliar performance. Brimstone’s approach sidesteps that barrier.
Challenges ahead:
- Even though performance in lab tests is promising, long-term durability in varied climates (freeze/thaw cycles, chemical or salt exposure, etc.) remains to be demonstrated fully.
- Raw material availability and mining operations: although calcium silicate rocks are said to be abundant and geographically widespread, ensuring supply chains are sustainable will be essential.
- Energy input: even with carbon-free feedstocks, some heating and processing is needed. The source of that energy—whether renewable or fossil-based—will determine the net climate benefit.
Why This Suggests Hope
Here’s what makes this more than just another green startup:
- Compatibility: The ability to use existing standards and practices means builders don’t have to relearn everything, and regulations don’t have to be rewritten.
- Private sector pull: Big players like Amazon making commercial agreements signal that demand is there, pulling investment and encouraging others to follow.
- Economic leverage: Because Brimstone co-produces alumina and SCMs, there is revenue from multiple sources, cushioning cost risks.
- Carbon avoidance, possibly removal: By avoiding emissions from limestone and using feedstocks that may sequester CO₂ or avoid producing it, the net carbon footprint is significantly reduced.
Looking Forward: What The Next Few Years Will Tell Us
The journey from promising test results to widespread adoption is long—but we can already mark key milestones to watch for:
- Durability and environmental testing – how the cement performs under real-world stressors over time.
- Full cost analyses at scale – whether Brimstone’s cement can compete on price once logistics and energy costs are included.
- Regulatory approvals and code updates globally – crucial for adoption outside the US.
- Community and environmental impact – assessing mining practices, local effects, and sustainability of feedstock sourcing.
- Scaling supply chains – ensuring transport, material availability, and manufacturing infrastructure can support demand.
Conclusion: Building A New Foundation
Brimstone’s work embodies a rare combination of innovation and realism. It isn’t a distant idea—it is meeting recognized standards, striking deals with big customers, planning a demonstration plant, and designing its process for adaptability.
Change in heavy industry often moves slowly. But this could be one of those turning points where what’s possible becomes what’s practical. If Brimstone and its partners succeed, every concrete slab, bridge span, or data center built with this new cement could represent not just progress—but a new foundation for a more sustainable built world.
