Brimstone receives ASTM certi­fi­ca­tion for its OPC: can now replace 98% of world’s cement

As venture capitalists dedicated to supporting industry-disrupting, deep-tech solutions to global challenges, we’re thrilled to celebrate a significant achievement of one of our portfolio companies, Brimstone.

Brimstone has just received third-party certi­fi­ca­tion that its cement meets or exceeds ASTM C150 standards for ordinary portland cement (OPC), becoming the first and only ultra-low carbon, carbon-neutral or carbon-negative cement to meet this critical and universally accepted industry requirement. 

The certi­fi­ca­tion means Brimstone is now poised to not only disrupt a centuries-old building tradition but also decarbonize the global construc­tion industry, which is one of the biggest producers of greenhouse-gas emissions. At full-scale deployment, Brimstone’s manu­fac­turing process could eliminate well over 2 billion metric tons of carbon dioxide (CO₂) emissions each year. 

To understand how that’s possible, it helps to have a few key data points that speak to the size and scale of the global cement industry, its carbon footprint, and the signif­i­cance of ASTM C150.

• In 2020, the world produced 4.2 billion metric tons of cement—over half a metric ton for each person on the planet. It’s the most widely used material on Earth after water, and serves as the binding agent in concrete. Portland cement is used in more than 98% of global concrete production, and is what builders typically require for construction projects.
• Unfor­tu­nately, cement manu­fac­turing is also one of the biggest sources of human-made greenhouse-gas emissions (more below about why this is). In 2021, the cement industry produced nearly 2.9 billion metric tons of carbon dioxide (CO₂), accounting for ~8% of global, human-produced CO₂ emissions. To put it another way, if the global cement industry were a country, it would be the third-largest CO₂ emitter after China and the United States.
• The spec­i­fi­ca­tions and require­ments outlined in ASTM C150 are considered benchmarks for quality assurance and performance evaluation of OPC, which is why ASTM C150 is recognized and used as a standard for OPC worldwide.

But how exactly does Brimstone’s process work, and how can it produce cement without emitting CO₂? Here’s a quick chemistry explainer: since OPC was first developed early in the 19^th century, its production has relied on the process of heating limestone (CaCO₃) in kilns to access lime (CaO). This emits substantial amounts CO₂ into the atmosphere. These emissions stem from two sources: the release of CO₂ trapped within the limestone due to the applied heat, and the combustion of fossil fuels to provide thermal energy to the kiln.

Brimstone’s cement presents a trans­for­ma­tive solution. Instead of relying on carbon-heavy limestone, Brimstone uses a carbon-free calcium-silicate rock — so no CO₂ is released to access lime. Brimstone’s manu­fac­turing actually goes a step further in addressing cement’s carbon footprint by generating magnesium compounds that permanently absorb CO₂. This means Brimstone’s process can be entirely carbon-negative—meaning it pulls CO₂ from the air instead of putting it in. While the exact emissions depend on what energy types are available to power the process, they would always be substan­tially lower-carbon and often carbon-negative — even if clean energy is not yet available in a region.

By becoming the first and only company to develop a carbon-negative process for making industry-standard OPC, Brimstone has eliminated the regulatory hurdles to industry adoption while solving cement’s climate problem. 

Brimstone’s achievement showcases the trans­for­ma­tive potential of deep-tech innovation in addressing global sustain­ability challenges, but it’s only the beginning. Brimstone is now moving to scale up its technology: with a pilot plant in Nevada underway and site selection for a commercial-scale facility, the company is actively pursuing part­ner­ships and nego­ti­a­tions for offtake agreements. We at DCVC are excited to support both Brimstone and the construc­tion industry in making significant strides toward achieving climate goals using the company’s break­through carbon-negative process for making OPC.

Rachel Slaybaugh is a Partner at DCVC.