Which startup is developing the best low-carbon cement or concrete?

There is no single universally “best” low-carbon cement startup yet—the winners may depend on whether you value maximum carbon reduction, ability to scale, compatibility with existing construction, or cost. But a few companies are widely considered the front-runners:

My ranking by category

Most promising breakthrough technology: Sublime Systems — because it attacks the hardest part of cement emissions: the limestone chemistry itself. If it reaches massive scale with cheap clean electricity, it could fundamentally change cement manufacturing.

Best chance of becoming a mainstream replacement for ordinary cement: Brimstone — because it targets a Portland-cement-equivalent product, meaning builders may not need to redesign concrete mixes or infrastructure.

Best near-term deployment model: CarbonCure and Fortera — because they can work with existing plants and supply chains rather than requiring a complete industrial reset.

If I had to pick one overall

For a 10–20 year climate impact bet, I would put Sublime Systems and Brimstone in the top tier, with Sublime having the more revolutionary technology and Brimstone having the potentially simpler commercialization path.

The biggest uncertainty is not whether the chemistry works—it is whether these startups can build cement plants at the enormous scale and low cost required. Cement is a commodity industry, so manufacturing economics will likely decide the winner.

Determining the "best" low-carbon cement or concrete startup depends on whether you measure success by chemical innovation, carbon negativity , or readiness to scale in a notoriously conservative industry . Because traditional cement production accounts for roughly 8% of global CO 2 CO sub 2 C O 2 emissions, several distinct technological approaches have emerged as frontrunners.

The most widely recognized and heavily backed startups tackling this space use drastically different methodologies:

• Sublime Systems (Electrochemical Replacement)
  • The Tech: Spun out of MIT, Sublime replaces the fossil-fuel-burning kiln and limestone calcination process with an electrochemical approach that makes true zero-emission cement at ambient temperatures.
  • Why it stands out: It creates a drop-in replacement for traditional Portland cement that matches its chemical performance without the massive carbon footprint. It has achieved major industry milestones, including standard compliance testing approvals.
• Brimstone (Alternative Chemistry & Carbon-Negative Potential)
  • The Tech: Brimstone makes a cement chemically identical to ordinary Portland cement, but uses calcium silicate rocks instead of limestone.
  • Why it stands out: Because their raw materials don't release CO 2 CO sub 2 C O 2 from calcination the way limestone does, and because their process yields magnesium and other supplementary materials that can trap carbon, it is one of the few processes certified as carbon-negative overall.
• CarbonBuilt (Carbon Mineralization in Concrete)
  • The Tech: Rather than focusing purely on the cement powder, CarbonBuilt manufactures concrete blocks by injecting captured CO 2 CO sub 2 C O 2 directly into a novel mixture, permanently mineralizing the gas inside the block.
  • Why it stands out: It dramatically reduces (and in some cases eliminates) the need for traditional cement binders while turning waste carbon dioxide into a structural asset, achieving a 7 0%--1 0 0% reduction in embodied carbon for concrete units.
• Terra CO 2 CO sub 2𝐂𝐎𝟐 (Scalable Supplementary Materials)
  • The Tech: Terra CO 2 CO sub 2 C O 2 creates alternative Supplementary Cementitious Materials (SCMs) using a wide variety of local silicate rocks and industrial byproducts.
  • Why it stands out: As traditional fly ash and slag (byproducts of coal and steel) become scarce, Terra CO 2 CO sub 2 C O 2 provides a scalable, locally sourced alternative that drops the carbon footprint of the final mix by up to 7 0% and integrates smoothly into existing concrete supply chains.
• CemVision (Upcycled Waste Binders)
  • The Tech: Based in Europe, CemVision replaces limestone-heavy clinker with recycled by-products from mining and industrial waste streams.
  • Why it stands out: They have secured strong backing and validation from major traditional building material giants, aiming for an ultra-low carbon binder that can be deployed at scale quickly.

If you want to narrow this down, let me know:

• Are you looking at this from an investment/market adoption perspective?
• Or are you evaluating a specific project where you need a commercial-ready product?

If I had to pick one startup today, I’d put Sublime Systems at the top—but there’s an important distinction between best technology and best near-term business.

My 2026 ranking

🥇 Why I favor Sublime

Sublime attacks the hardest part of cement's emissions problem: the chemistry itself.

Traditional cement requires heating limestone, which releases CO₂ even if the kiln is powered by zero-carbon energy. Sublime uses an electrochemical process to produce cement from non-carbonate feedstocks, potentially eliminating both the process emissions and much of the high-temperature energy requirement. The Decarbonized Concrete Coalition cites a preliminary independent LCA showing >93% CO₂ reduction.

It's also moving beyond laboratory science: Sublime is building a 30,000-ton/year commercial facility in Massachusetts, with Holcim investing and reserving output while partnering on future facilities.

That's a particularly important signal because cement is an extremely conservative industry: a technology can have fantastic theoretical economics but still fail if it can't meet ASTM specifications, work in existing concrete mixes, and get accepted by contractors and engineers.

🥈 Brimstone may ultimately be even bigger

Brimstone has an elegant proposition: use calcium-silicate rock instead of limestone and manufacture ordinary Portland cement, rather than asking the construction industry to adopt an unfamiliar binder.

Its process also produces supplementary cementitious material and alumina as co-products. Brimstone has completed pilot work and is advancing toward a manufacturing facility in Nevada.

The attraction is enormous: if you can make essentially the same cement using a radically lower-carbon process, adoption could be much easier. The catch is that Brimstone is earlier in commercialization than Terra and Sublime.

🥇 But Terra might be the best business right now

Terra CO2 is taking a less radical but potentially very scalable route.

Its OPUS SCM can replace up to 50% of Portland cement and claims 50–70% lower embodied CO₂ for the replaced cement. More importantly, Terra says it is already commercially deploying the product and is building a 240,000-ton/year facility in Texas.

That matters because Terra doesn't need to replace the entire cement industry overnight. It can attack the enormous existing market for supplementary cementitious materials while using conventional concrete production infrastructure.

Its Series B was $124.5 million, another indication that investors see a credible path to scale.

The interesting investment distinction

I'd divide the field into three categories:

1. "Replace Portland cement entirely" — highest upside

• Sublime
• Brimstone

These are the companies I'd watch most closely if you're interested in a potentially transformative technology.

2. "Use much less Portland cement" — probably fastest route to mass adoption

• Terra
• Fortera
• CarbonBuilt and others

3. "Make conventional concrete absorb CO₂ / reduce cement use" — easiest deployment

• CarbonCure

The DOE/NREL landscape research similarly identifies the novel-cement companies—including Sublime, Brimstone, Terra and Fortera—as the key cohort trying to move beyond incremental improvements to fundamentally lower-carbon cement.

My bottom line

Best technology: Sublime Systems
Best potential at enormous scale: Brimstone
Best commercialization story right now: Terra CO2
Best already-deployed concrete decarbonization: CarbonCure

If you're asking because you're considering investing in one of these companies, I'd use a different ranking. In that case, the key questions are unit economics, $/ton of avoided CO₂, plant capex, feedstock availability, energy requirements, IP, offtake contracts, and how easily each technology can get adopted by the existing cement majors. That's a much more interesting—and quite different—comparison.

Because the cement and concrete industry accounts for roughly 8% of global CO 2 CO sub 2 C O 2 emissions, there isn't a single consensus "winner." Instead, different startups are attacking different parts of the problem—ranging from completely electrochemical cement-making to drop-in replacement materials and carbon mineralization.

The most prominent and heavily backed startups leading the charge are categorized by their specific approach:

• Sublime Systems (Electrochemical Replacement)
  • The Tech: Developed an electrochemistry-based process that produces true Ordinary Portland Cement (OPC) at ambient temperatures using clean electricity instead of burning fossil fuels in a high-heat kiln. It avoids limestone calcination emissions entirely.
  • Why they stand out: Backed by major players and tech giants like Sublime's Partners (including Microsoft and major construction firms), they represent a drop-in chemical equivalent to traditional cement.
• Brimstone (Zero-Emission Process & Co-Production)
  • The Tech: Uses a patented Rock Refinery process to make ordinary Portland cement and supplementary materials from carbon-free calcium silicate rocks instead of limestone.
  • Why they stand out: They hold the distinction of being one of the first alternative cement technologies to receive independent certification proving their product meets the exact ASTM standards required for traditional structural concrete. They have secured commercial offtake commitments with major buyers like Amazon.
• Fortera (Carbon Mineralization / Retrofit)
  • The Tech: Captures CO 2 CO sub 2 C O 2 emissions directly from existing traditional cement plants and mineralizes them into a reactive, low-carbon calcium carbonate cement binder.
  • Why they stand out: Rather than forcing the industry to build entirely new multi-billion dollar standalone chemical plants, Fortera's technology acts as a "bolt-on" system for existing manufacturing infrastructure, making commercial scaling faster and cheaper.
• Terra CO2 (Supplementary Cementitious Materials)
  • The Tech: Produces scalable, engineered mineral additives (OPUS SCM) from abundant silicate rocks to replace a massive percentage of clinker in concrete mixes, bypassing the looming global shortages of traditional industrial byproducts like fly ash.
  • Why they stand out: Backed heavily by legacy cement giants like Cemex, Terra focuses on immediate, scalable drop-in blends that reduce emissions by up to 7 0% without requiring changes to how construction sites mix concrete.
• CarbonBuilt (Carbon-Negative Concrete Blocks)
  • The Tech: Focuses on the concrete manufacturing side rather than just the cement binder, injecting and permanently mineralizing captured CO 2 CO sub 2 C O 2 into the concrete curing process.
  • Why they stand out: Their process significantly reduces or eliminates the need for traditional high-carbon cement in precast concrete blocks while economically storing CO 2 CO sub 2 C O 2.

If you want to narrow this down, let me know if you are looking at this from an investment angle , an architectural specification/purchasing angle , or if you want a deeper dive into the chemistry and physics of one specific approach.

Because traditional cement manufacturing is responsible for roughly 8% of global carbon emissions, dozens of innovative startups are racing to reinvent the material. There isn't a single consensus "best" startup because they use radically different technological approaches—some replace the kiln, some replace the rock feedstock, and others inject or mineralize carbon into the final mix.

The frontrunners leading the industry, categorized by their technological approach, include:

1. Eliminating Kilns & Thermal Emissions (Electrochemical)

• Sublime Systems (Somerville, MA): Pioneered an electrochemical process that operates at ambient temperatures to extract reactive calcium, completely eliminating the need for fossil-fuel-fired kilns and limestone calcination (the two biggest drivers of cement emissions). They produce true ASTM-compliant cement and have secured prominent commercial testing and procurement partnerships.

2. Kicking Limestone Out of the Mix (Alternative Feedstocks)

• Brimstone (Oakland, CA): Takes a unique approach by using calcium-bearing silicate rocks (like basalt) instead of limestone. Because these rocks contain no carbon, the chemical process releases zero process-related CO 2 CO sub 2 C O 2 from the source material, while co-producing standard ordinary Portland cement and valuable industrial byproducts.
• Fortera (San Jose, CA): Captures and reuses CO 2 CO sub 2 C O 2 directly at existing cement plants to manufacture a novel supplementary cementitious material and mineral binder from reactive calcium carbonate, effectively bridging traditional manufacturing with low-carbon outputs.

3. Scalable Supplementary Cementitious Materials (SCMs)

• Terra CO 2 CO sub 2𝐂𝐎𝟐 Technology (Golden, CO): Focuses on replacing clinker by engineering low-carbon SCMs from widely available silicate rocks. Their locally producible alternatives directly combat the dwindling global supply of traditional industrial waste byproducts like fly ash.

4. Carbon Curing & Sequestration

• CarbonCure Technologies (Dartmouth, Canada): A mature market leader that retrofits existing concrete mixing plants with technology to inject recycled CO 2 CO sub 2 C O 2 into fresh concrete. The CO 2 CO sub 2 C O 2 instantly mineralizes into calcium carbonate, permanently trapping the gas while boosting compressive strength—allowing producers to reduce the amount of carbon-heavy cement used in the mix.

If you're looking into a specific application—such as structural pouring, precast blocks , or investing/partnering —let me know, and I can give you more details on which of these companies fits that specific use case.

If I had to pick one startup with the strongest overall shot at transforming cement, I’d pick Sublime Systems.

But there are several credible contenders, and “best” depends on whether you care most about maximum CO₂ reduction, near-term scalability, cost, or drop-in compatibility.

1. 🥇 Sublime Systems — my overall winner

Sublime Systems has perhaps the most compelling fundamental technology.

Instead of heating limestone to ~1,450°C in a kiln, Sublime uses electrochemistry at much lower temperatures to produce cement. That matters because conventional cement has two major emissions sources: burning fuel and, more importantly, the CO₂ chemically released when limestone is converted to lime. Sublime avoids the latter altogether.

Its screening LCA estimated about 72 kg CO₂ per tonne of cement, versus roughly 922 kg/t for U.S. average Portland cement—a claimed reduction of more than 90%.

The particularly interesting thing is that it isn't merely a cement additive: it aims to produce a replacement cement capable of making conventional concrete.

Sublime is also getting serious industrial validation. Holcim has invested in the company and agreed to take a significant share of output from its first commercial facility while collaborating on future large-scale plants.

The catch: scaling electrochemical cement manufacturing to millions of tonnes/year is still a huge industrial challenge, and the economics depend heavily on cheap, clean electricity.

---

2. 🥈 Brimstone — potentially the most disruptive

Brimstone takes a different route.

The fundamental problem with Portland cement is limestone: roughly half the limestone's mass escapes as CO₂ during calcination. Brimstone instead uses calcium silicate rock, which doesn't contain that embedded CO₂. It can therefore make ordinary Portland cement rather than asking builders to adopt a fundamentally different binder.

That's an enormous advantage if it works economically at scale.

Brimstone's process also produces supplementary cementitious material and alumina as co-products, potentially improving the economics of the overall process.

The downside is that Brimstone still requires high-temperature processing, whereas Sublime's process fundamentally eliminates the kiln. Its large demonstration plant is also less mature than some competitors. WRI lists a planned 140,000-ton/year demonstration project.

If Brimstone can hit its cost and scale targets, though, it could be enormous because it potentially produces cement that fits existing specifications and infrastructure.

---

3. Terra CO₂ — probably the most interesting right now

Terra CO₂ is taking a more pragmatic approach.

Its OPUS SCM is a low-carbon cementitious material that can replace up to 50% of Portland cement in appropriate applications. Terra says it produces 50–70% less CO₂ per tonne of Portland cement replaced.

That's less revolutionary than Sublime or Brimstone, but it has an important advantage: you don't have to replace the entire cement industry overnight.

Terra is building a 240,000-ton/year commercial facility in Cleburne, Texas, with product expected to ship in 2027.

It has also raised more than $250 million, according to the company.

For an investor or construction company wanting something that can actually get into concrete mixes relatively soon, Terra is exceptionally interesting.

---

4. Fortera — underrated because it's already doing it

Fortera uses CO₂ mineralization to make cementitious material.

This is significant because Fortera isn't merely at the laboratory stage. Its Redding, California facility is already producing low-carbon cement, and WRI reports roughly 70% lower emissions than conventional cement for the process. A larger facility is planned at approximately 400,000 tonnes/year.

I'd put Fortera ahead of some flashier startups on technology readiness, even if I think Sublime has a more transformative underlying process.

---

The important distinction

There are actually three different bets here:

A. "Let's reinvent cement."
→ Sublime / Brimstone

B. "Let's dramatically reduce the amount of Portland cement needed."
→ Terra CO₂

C. "Let's capture/mineralize CO₂ or otherwise clean up existing concrete production."
→ Fortera / CarbonCure

For context, the U.S. Department of Energy's industrial-demonstration portfolio includes major projects from Brimstone, Fortera and Sublime, reflecting the government's view that multiple technological pathways are worth pursuing.

My ranking

If I were evaluating these as venture-scale climate technology investments, I'd roughly rank them:

1. Sublime Systems — highest technological upside
2. Brimstone — potentially enormous if the economics work
3. Terra CO₂ — best combination of scalability + near-term adoption
4. Fortera — strongest evidence of actual industrial deployment
5. CarbonCure — excellent incremental solution, but less transformative

The really interesting investment question isn't necessarily “who makes the greenest cement?” It's “who can produce low-carbon cement at the same delivered cost, performance, and reliability as Portland cement?” That's where the winner of this market will likely emerge.

If I had to pick one startup today, I’d put Brimstone at the top—with Sublime Systems a very close second.

The important distinction is “best technology” vs. “closest to mass deployment.”

🥇 Brimstone — my overall pick

Brimstone is trying to make ordinary Portland cement without limestone. Instead, it uses calcium-rich silicate rocks and a different refining process. That matters enormously because it potentially eliminates the process emissions created when limestone is heated.

Its cement is designed to meet the existing ASTM C150 Portland-cement standard, meaning the ambition is essentially drop-in replacement rather than inventing a new type of concrete.

The U.S. Department of Energy has selected Brimstone for up to $189 million toward a commercial-scale demonstration plant expected to produce about 103,000 tonnes/year of cement and SCMs, while avoiding more than 77,000 tonnes of CO₂/year.

A 2026 peer-reviewed study also supports the underlying silicate-rock approach, finding potential advantages in energy and economics versus conventional limestone-based production.

Why I like it: if it works economically at scale, it attacks the fundamental source of cement's emissions rather than merely compensating for them.

---

🥈 Sublime Systems — arguably the most exciting technology

Sublime Systems uses an electrochemical process rather than a conventional fossil-fueled kiln. It can produce cement at much lower temperatures and avoid the CO₂ released by limestone calcination. Its cement is designed as a drop-in replacement for ordinary Portland cement.

Sublime has raised more than $200 million and is developing a 30,000-ton/year commercial facility in Holyoke, Massachusetts, following its pilot operation.

Why I like it: the technology could ultimately produce genuinely near-zero-carbon cement if supplied with clean electricity.

Big question: economics and scaling the electrochemical process to the enormous volumes required by the global cement industry.

---

🥉 Terra CO₂ — perhaps the best near-term deployment bet

Terra CO2 takes a somewhat different route. Its OPUS SCM product can replace up to 50% of Portland cement, with the company targeting 50–70% lower embodied CO₂. Its technology is designed to work with existing cement-production infrastructure rather than requiring an entirely new cement plant.

Terra is building its first full-scale commercial facility in Cleburne, Texas, which gives it an interesting advantage in deployment risk.

Why I like it: it may be easier for incumbent cement producers to adopt than a completely new cement-making process.

---

My scorecard

There are also interesting companies attacking the concrete side rather than cement itself—such as carbon-mineralization and CO₂-curing approaches—but I think the biggest prize is still replacing the conventional Portland-cement manufacturing process, because cement is responsible for the overwhelming majority of concrete's embodied carbon.

Bottom line:
Brimstone is my #1 startup to watch in 2026. Its combination of a potentially very large emissions reduction, conventional Portland cement as the end product, abundant raw materials, and substantial DOE backing gives it an unusually compelling risk/reward profile. Sublime is the one I'd watch most closely technologically, while Terra CO₂ may have the easiest commercialization path.

Brimstone · Sublime Systems · Terra CO₂ 

There is no single "best" startup because the race to decarbonize cement—which accounts for roughly 8% of global CO 2 CO sub 2 C O 2 emissions—is divided into very different technological approaches. Instead of a clear winner, a few frontrunners stand out based on their chemistry, scalability, and major corporate backing.

1. Completely Eliminating Kilns & Limestone

Traditional cement releases massive amounts of CO 2 CO sub 2 C O 2 because limestone must be heated to extreme temperatures (1500∘C 1500 raised to the composed with power C 1 5 0 0∘C ), releasing the carbon locked inside the rock.

• Sublime Systems (USA): Pioneers an electrochemical process operating at ambient temperature to make true Ordinary Portland Cement (OPC) without using fossil-fuel kilns or limestone calcination. Backed by major players like Holcim and a major procurement agreement with Microsoft, they represent a holy-grail approach to zero-emission cement chemistry, though scaling up remains capital-intensive.
• Brimstone (USA): Takes a different chemical route by using non-carbonate calcium silicate rocks (like basalt) instead of limestone. Because their source rock contains no carbon, it avoids process emissions entirely, and their process co-produces supplementary cementitious materials (SCMs) alongside standard cement. They have secured commercial volume commitments from companies like Amazon.

2. Retrofitting Existing Infrastructure (Lower Capital Hurdle)

Building brand-new multi-billion-dollar cement plants from scratch takes decades. Some startups focus on dropping solutions into existing manufacturing lines.

• Fortera (USA): Uses a re-carburization process that captures CO 2 CO sub 2 C O 2 emissions from traditional cement plants and mineralizes them into a cementitious powder. Their commercial plant in California operates adjacent to a traditional cement factory, proving a viable "bolt-on" retrofit model with 7 0% fewer emissions.
• Terra CO 2 CO sub 2𝐂𝐎𝟐 (USA): Focuses on scaling up alternative Supplementary Cementitious Materials (SCMs) derived from abundant silicate rocks to replace a vast majority of the carbon-heavy clinker in concrete mixes. They are actively expanding their R&D and production footprints to combat global fly-ash shortages.

3. Fixing the Concrete Mix & Curing Process

• CarbonCure Technologies (Canada) & CarbonBuilt (USA): Rather than just focusing on the cement binder, these companies inject captured CO 2 CO sub 2 C O 2 directly into concrete during the mixing or curing process. The CO 2 CO sub 2 C O 2 permanently mineralizes into calcium carbonate inside the concrete, increasing structural strength while trapping the carbon forever and reducing the need for heavy cement content.

If you're looking into this for a specific project or investment, let me know:

• Are you more interested in zero-emission chemistry (substitutes for Portland cement) or carbon-curing/capture tech that works with existing concrete?
• Are you evaluating them from a technical readiness, commercial scaling , or investment perspective?

There is no single "best" startup because the race to decarbonize cement and concrete (which accounts for roughly 8% of global C O 2 cap C cap O sub 2 C O 2 emissions) is split into completely different technological approaches. Instead of one winner, a few frontrunners stand out based on their chemistry, scaling milestones, and major commercial backing from tech giants and building conglomerates.

The top contenders leading the industry take distinct approaches:

• Sublime Systems (Electrochemical Process)
  • The Tech: An MIT spinout that uses an electrochemical process to make cement at ambient temperatures, completely eliminating the need for fossil-fuel-fired kilns and limestone calcination (the two biggest sources of traditional cement emissions).
  • Why they are a leader: They produce an exact drop-in replacement that meets standard performance specs (ASTM C1157) and have achieved high-profile pilot pours for data center campuses, backed by major commercial interest.
• Brimstone (Alternative Raw Materials)
  • The Tech: Instead of using calcium-heavy limestone (which releases C O 2 cap C cap O sub 2 C O 2 when heated), Brimstone uses calcium-bearing silicate rocks like basalt that contain zero carbon. Their process co-produces ordinary Portland cement and supplementary cementitious materials (SCMs) without the emissions tied to traditional limestone.
  • Why they are a leader: They secured significant commercial offtake and reservation agreements with major buyers like Amazon for their low-carbon output.
• Fortera (Carb Upcycling & Coral-Inspired Chemistry)
  • The Tech: Takes cues from coral reefs to capture C O 2 cap C cap O sub 2 C O 2 from a cement plant's own kiln and mineralize it into a reactive calcium carbonate binder. It functions as a "bolt-on" technology that integrates directly into existing cement manufacturing infrastructure.
  • Why they are a leader: Fortera has outpaced many peers in commercialization, moving from pilot phases to operating commercial-scale facilities alongside traditional cement giants like CalPortland.
• Terra C O 2 cap C cap O sub 2𝐂𝐎𝟐 (Supplementary Cementitious Materials)
  • The Tech: Focuses on solving the looming global shortage of fly ash (a byproduct used to lower concrete's carbon footprint) by engineering alternative SCMs from widely available silicate rocks.
  • Why they are a leader: They offer a practical, scalable drop-in material that can replace large portions of traditional clinker without requiring a total redesign of cement-making kilns.

Are you looking at this from an investment angle , a construction/procurement perspective , or out of general technical curiosity ? I can dive deeper into the specific unit economics or regulatory hurdles of whichever approach interests you most.

There is no single clear winner yet—the “best” low-carbon cement startup depends on what you value: deep decarbonization potential, scalability, commercial readiness, or compatibility with today’s construction industry. The strongest contenders are:

My ranking by category

Most promising long-term breakthrough:
🥇 Sublime Systems
Its process attacks the core chemistry problem: conventional cement releases CO₂ because limestone itself contains carbon. Eliminating limestone is a more fundamental solution than simply capturing emissions later.

Best chance of near-term industry adoption:
🥇 CarbonCure
It fits into existing concrete supply chains, which is a huge advantage. The cement industry changes slowly, so “drop-in” solutions may win even if they are less theoretically perfect.

Best “replace Portland cement at scale” bet:
🥇 Brimstone
The ability to make a familiar Portland-type cement from non-carbonate rock could be a major advantage if costs and manufacturing scale work out.

Best investment-style shortlist:

• Sublime Systems — highest technical upside
• Brimstone — strongest industrial replacement thesis
• Terra CO₂ — strong commercialization momentum
• CarbonCure — strongest current deployment
• Fortera — strongest retrofit/transition pathway

The big challenge is that cement is a commodity industry: a technology that cuts emissions by 90% but costs 30% more may struggle, while a technology that cuts emissions by 50% and works in existing plants could dominate. The eventual winner may not be the “greenest” chemistry—it may be the one that can produce billions of tons of cement at competitive cost.

If I were building a climate-tech portfolio, I would probably treat Sublime, Brimstone, and CarbonCure as the three most strategically interesting bets, but for different reasons.