These Startups Are Solving The Hard Problem Of Decarbonizing Cement

Stopping cement production would have the same effect on civilization's carbon footprint as taking all the world's cars off the road.

An enormous amount of cement—around four billion metric tons—is produced each year, pumping a nearly equal mass of carbon dioxide—around 3.4 billion metric tons—into the atmosphere during its manufacture.

There are two strategies to lower cement's carbon footprint:

This offers an overview of a few of the companies engaged in the cement replacement pathway; an upcoming will offer a brief overview of companies in the aggregate capture pathway, and I plan to do further research and writing on this industry next year.

Replacing cement is not a trivial undertaking.

The process of manufacturing ordinary portland cement from limestone and clay and mixing OPC with aggregate to make concrete for use in large construction projects has two centuries' worth of research and practice behind it. Because the properties of OPC concrete are so well known, engineers and architects are wary of innovations that have not been certified by the ASTM, a globally-recognized standards body.

Herein lies the quandary. Carbon dioxide generation is intrinsic to the process of manufacturing OPC due to the chemical reaction that breaks limestone down. ASTM C150 cement is difficult to manufacture without releasing CO2.

Eco Material Technologies , a company previously featured in this column , was formed when the MIT spinout Green Cement merged with the ash mining firm Boral Resources in a 2022 deal worth $755 million . EMT is the company furthest along the low-carbon cement commercialization pathway.

Eco Material produces supplemental cementitious material by mechanically and chemically treating waste ash recovered from coal-fired power plant landfills. Using coal ash as an SCM is a longstanding practice in the cement business, but Green Cement's process replaces most or all cement with its proprietary treated binder, reducing carbon emissions of C150 cement to nearly nothing in the best case.

Eco Material just released its 2023 sustainability report , and the findings are impressive. According to the report, the company recycled or diverted over 10 million tons of landfill ash for use in low-carbon cement. EMT's SCMs lowered CO2 emissions by nearly 6 million metric tons, the carbon footprint of providing power to over 769,000 homes for a full year.

Terra CO2 is a Colorado-based company that announced a $46 million Series A funding round led by Bill Gates's Breakthrough Energy Ventures and LenX, homebuilder Lennar's corporate VC arm, in 2022.

Terra's management team consists of construction material industry veterans like CEO Bill Yearsley, whose vision is to produce SCM from various widely available feedstocks instead of recycled ash or steel slag, another common SCM input. Terra has said that its newest SCM will replace 100% of OPC in concrete mixtures, bringing the carbon footprint of a structure built with this material to nearly zero.

In addition to a Canadian R&D facility where Terra runs feedstock tests, it has been running a small pilot plant for about four years in Colorado, which it scaled up to a 1-ton-per-day facility in 2022.

Terra won the CleanTech Breakthrough Awards program's 2024 Decarbonization Solution of the Year in April, and is in the final stages of building a 30-ton-per-day commercial facility in the Dallas-Fort Worth area. Yearsley believes that Terra's high-yield process, its ability to serve as a drop-in solution for existing supply chains, and wide feedstock accessibility make its low-carbon cement particularly attractive.

Carbon Limit is a Florida-based company that replaces high-carbon-footprint OPC with a proprietary SCM that continues to sequester CO2 from the air after installation. The company just announced it is releasing an SCM binder that improves the solar reflectance of concrete while reducing its carbon footprint by up to 40%.

This product, which the company calls CoolCrete , is important in mitigating the urban heat island effect that makes our cities—especially low-income areas with fewer shady mature trees and cooling greenspaces—less livable in a post-climate world.

Brimstone , an Oakland, California-based start-up, caused a splash in the investment world after raising $55 million in a Series A round led by Breakthrough Energy Ventures and DCVC, a well-known "deep tech" venture capital fund, in April 2022.

Brimstone's technology uses a geopolymer , a cementitious material composed of ferro-silico-aluminate compounds, which requires less heat to produce than it takes to break down limestone and does not release carbon dioxide during production.

Geopolymer cements are usually activated in an aqueous solution that is either alkaline or acidic. Brimstone's binder material also includes magnesium, which sequesters carbon dioxide after the concrete is installed.

There is tremendous investor interest in solving the hard problem of decarbonizing cement, as indicated by the magnitude of funding for such ventures. One look at the Keeling Curve , a daily record of global atmospheric carbon dioxide concentration, should tell you that this interest comes not a moment too soon.

Intelligent investors take note.