If you are going to decarbonize concrete, you have two choices. You can try to reinvent the entire chemistry of cement, or you can find a way to use the existing, sprawling, and stubbornly cheap concrete industry. CarbonBuilt, a spinout from UCLA, is betting on the second path. Its pitch is a retrofit that fits into a standard concrete block plant in about six months, swapping out half the cement for a proprietary binder and injecting captured CO2 into the curing process [Carbon Leadership Forum, August 2023]. The result, the company says, is a block that meets all the same specs but carries up to 70% less carbon [GlobeNewswire, September 2024]. The unit economics of climate tech are rarely this straightforward.
A retrofit, not a revolution
The core of the bet is a technology called Reversa, a binder made primarily from upcycled industrial byproducts. At a partner plant, CarbonBuilt's team installs equipment to inject dilute CO2 streams,often sourced directly from a nearby industrial flue gas,into concrete masonry units as they cure. The chemical reaction permanently mineralizes the carbon dioxide while also replacing up to 50% of the Portland cement, the most carbon-intensive ingredient [carbonbuilt.com, retrieved 2024]. This retrofit approach is the company's entire commercial wedge. Instead of building billion-dollar greenfield plants, it partners with existing manufacturers, investing capital to upgrade their lines. For its first commercial partner, Blair Block in Alabama, the retrofit investment was approximately $2 million [carbonbuilt.com, April 2024]. That line is now producing thousands of tons of concrete each month [GlobeNewswire, September 2024].
The team behind the chemistry
The science comes from Gaurav Sant, a civil and environmental engineering professor at UCLA and the founder of CarbonBuilt. Sant leads the university's Institute for Carbon Management and spent years developing the underlying mineralization process [Los Angeles Business Journal, October 2021]. To turn the lab work into a business, the company brought in operators with industrial and financial scale. Michelle Hellums Carvin, the CEO, and Soham Badheka, the CFO, have backgrounds that span Goldman Sachs, startups, and scaled manufacturing [Connecticut Innovations, retrieved 2024]. Brian Bush, the chief manufacturing officer, adds decades of concrete production experience. It is a team built to navigate the gritty realities of heavy industry, not just the elegance of a chemical formula.
Traction in tons and partnerships
CarbonBuilt's commercial footprint is taking shape through a mix of owned operations and partnerships. The flagship is the retrofitted line at Blair Block in Alabama, which the company says enables the annual production of about 2.3 million standard concrete blocks with a carbon footprint reduced by over 80% [GlobeNewswire, April 2022]. Those blocks are already being used in municipal projects across the state [blairblock.com, retrieved 2026]. The company has also opened its first fully-owned manufacturing facility in Danielson, Connecticut, where it is producing low-carbon masonry units [carbonbuilt.com, December 2025]. On the demand side, the company has attracted buyers looking for verified carbon removal, including Shopify and Stripe, who purchase the carbon-removal services associated with the blocks [carbonbuilt.com, retrieved 2024]. A collaboration announced with Meta in late 2024 aims to accelerate production and upgrade additional plants, though the financial terms were not disclosed [GlobeNewswire, September 2024].
| Partner/Project | Location | Role | Key Metric |
|---|---|---|---|
| Blair Block | Childersburg, Alabama | First commercial retrofit | ~2.3M blocks/year capacity [GlobeNewswire, April 2022] |
| Owned Facility | Danielson, Connecticut | Fully-owned production plant | Producing low-carbon CMUs [carbonbuilt.com, December 2025] |
| Meta | Not disclosed | Production acceleration partner | Collaboration to upgrade plants [GlobeNewswire, September 2024] |
The crowded field of clean cement
The ambition to clean up concrete has spawned a long list of well-funded competitors, each with a different technical angle. CarbonBuilt's retrofit-for-masonry model exists within a noisy landscape of startups aiming to decarbonize one of the world's dirtiest industries.
- Biomason & Minus Materials: These companies grow or formulate cement-like binders biologically or chemically, often for specialized applications rather than bulk commodity production.
- Brimstone & Sublime Systems: These are among the ventures attempting to reinvent cement chemistry itself, creating entirely new processes to make low-carbon ordinary Portland cement (OPC) or alternatives.
- Fortera & Blue Planet: Similar to CarbonBuilt, these companies focus on carbon mineralization, but often with different process pathways or target products.
CarbonBuilt's answer to this crowd is its focus on concrete masonry units (CMUs),the humble concrete block. It is a specific, high-volume product with a relatively simple production process, making it an ideal first beachhead for a retrofit model. The company's third-party validation confirms its blocks meet the critical ASTM C90 standard, the industry benchmark for compressive strength and durability [National Carbon Capture Center, December 2021]. The risk is that by starting with blocks, it may be perfecting a solution for a segment that larger reinventions could eventually render obsolete.
The math on a ton of concrete
The ultimate test for any green concrete is whether it can match the price of the dirty stuff. CarbonBuilt does not publicly disclose its production costs, but the structure of its model offers some clues. The retrofit capex is measured in millions, not tens of millions. The binder uses low-cost industrial byproducts. And the process can use low-concentration CO2 that is expensive for other carbon-capture schemes to handle. A back-of-the-envelope calculation on the Blair Block line is illustrative. The retrofit cost roughly $2 million for a line producing about 2.3 million blocks annually [carbonbuilt.com, April 2024][GlobeNewswire, April 2022]. If a standard 8-inch block weighs around 30 pounds, that's roughly 34,500 tons of annual capacity. Spread the capital cost over a conservative ten-year life, and the retrofit adds maybe $6 to $7 per ton of concrete. For CarbonBuilt to win, the premium for its low-carbon block,and any carbon credit revenue,must cover that delta and then some. The incumbent it must beat isn't another startup; it's the century-old, brutally efficient economics of ordinary Portland cement.
Sources
- [Carbon Leadership Forum, August 2023] CarbonBuilt | https://carbonleadershipforum.org/carbonbuilt/
- [GlobeNewswire, September 2024] CarbonBuilt collaborates with Meta to accelerate production of ultra-low carbon concrete | https://www.globenewswire.com/news-release/2024/09/24/2952124/0/en/carbonbuilt-collaborates-with-meta-to-accelerate-production-of-ultra-low-carbon-concrete.html
- [carbonbuilt.com, retrieved 2024] About CarbonBuilt | https://www.carbonbuilt.com/about
- [carbonbuilt.com, April 2024] Invested approximately $2 million to retrofit one of Blair Block’s four production lines | https://www.carbonbuilt.com/about
- [Los Angeles Business Journal, October 2021] CarbonBuilt Raises $10 Million in Series A Funding | https://labusinessjournal.com/technology/carbonbuilt-raises-10m-series-funding-co2-concrete/
- [Connecticut Innovations, retrieved 2024] Connecticut Innovations post on leadership | https://www.linkedin.com/posts/connecticut-innovations_big-news-from-connecticut-innovations-we-activity-7371027457702780928-6plv
- [GlobeNewswire, April 2022] CarbonBuilt agreement with Blair Block | https://www.globenewswire.com/news-release/2022/04/26/2429861/0/en/CarbonBuilt-and-Blair-Block-Announce-Agreement-to-Produce-Ultra-Low-Carbon-Concrete-Masonry-Units.html
- [blairblock.com, retrieved 2026] Blair Block projects | https://www.blairblock.com
- [carbonbuilt.com, December 2025] Owned facility in Danielson, CT | https://www.carbonbuilt.com/about
- [National Carbon Capture Center, December 2021] Reversa technology validation | https://www.nationalcarboncapturecenter.com/