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Terra CO2 says its Texas factory will cut carbon and cost from cement

The startup is building its first large-scale plant to turn common rocks into cement additives that can reduce cement’s hefty carbon footprint without raising costs.
By Jeff St. John

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A truck pours concrete on to a test roadway in Minnesota.
Concrete made with startup Terra CO2’s low-carbon supplementary cementitious material being poured for a test roadway in Minnesota. (Terra CO2)

How can we decarbonize the most widely used material on earth?

That’s the enormous question Bill Yearsley, a 40-year veteran of the construction materials industry and CEO of Terra CO2 Technology, thinks he has an answer to.

The Golden, Colorado–based company has devised a method to turn some of the world’s most abundant and commonly used minerals into a drop-in replacement for the additives used in cement production.

Using widely available materials is crucial, he said, because the type of raw materials used can end up being the deal-killer for a lot of technologies” in the cement decarbonization space.

There are a lot of novel technologies out there that work, and work fine. But they’re not scalable, they’re not commercially viable — and usually it’s because the feedstock is not available in full volume, or not available where it’s needed.”

On Tuesday, Terra CO2 announced its first big step in bringing its technology to commercial scale — plans for a facility in Texas capable of producing up to 240,000 metric tons per year of its supplementary cementing material (SCM). Construction is set to start next year, and Asher Materials, a subsidiary of Texas-based asset management firm Instar Holdings, has agreed to buy and operate the plant once it’s built.

Cement and concrete production are responsible for 8 percent of human-caused carbon dioxide emissions worldwide, and novel SCMs like Terra’s offer one path to reducing that massive carbon footprint. SCMs lower emissions from concrete production because they reduce reliance on Portland cement — by far the most common type of cement made today and also the driver of concrete’s carbon impact. The production of Portland cement requires super-high temperatures that are achieved by burning fossil fuels, and the carbon-rich limestone used in its production also leaks CO2 into the air.

Major cement and concrete companies such as Cemex and Holcim already use millions of tons of SCMs today, mostly fly ash from coal plants and slag from steel mills, both to reduce their concrete’s carbon footprint and to strengthen the material. But the same climate imperatives that are pushing the cement industry to cut its carbon emissions are also driving the closure of coal plants and steel blast furnaces, making these components less ubiquitous and more expensive to get.

Terra CO2’s SCM, by contrast, is made from a variety of silicate rocks, including granite, basalt, alluvial sand and gravel, glacial flood gravel and clay-sand mixtures.

The reason we focused on silicate rock is twofold,” Yearsley said. One, silica rock for the most part doesn’t have any embodied CO2.” That’s in contrast to limestone, the primary ingredient of Portland cement, which by weight is about 50 percent embodied CO2” — carbon that’s released into the atmosphere when it’s processed into clinker, the precursor to Portland cement.

The other reason we chose silicate rock is they’re approaching 90 percent of the earth’s crust,” he said. We can for most cases work with existing construction aggregate mines — the sand and rock quarries that exist in most urban environments.”

Terra CO2 puts these rocks into a reactor that heats them to their melting point, yielding glassy powders that can replace 25 to 40 percent of the Portland cement needed for different mixes of concrete. The company estimates that every ton of cement replaced by Terra’s SCM results in 70 percent lower carbon-dioxide emissions compared to pure Portland cement. Right now the reactors run on fossil fuels, but if a reliable source of clean-electricity-powered high heat becomes available, the process could become completely carbon-free, he noted.

Other SCMs can yield similar reductions in carbon emissions. But because Terra CO2’s approach uses widely available silicate rocks that don’t need to be transported far from where they’re mined before they’re blended into cement or concrete, for the most part, we are the same price — and in some cases, cheaper — than the traditional SCMs like fly ash,” Yearsley said. And that’s without green incentives.”

Avoiding the green premium for concrete 

Cutting the carbon impact of such a huge industry will take innovative technologies — but because concrete and cement are commodities produced and sold with tight profit margins, they also require technologies that can offer established industry giants a way to cut costs and improve performance at the same time.

Cement is quite cheap relative to the amount of emissions” it puts out, according to Ian Hayton, a senior associate leading materials and chemical research at Cleantech Group, a U.K.-based research and consulting firm. If you address these emissions, it costs money, and your product will increase in price. And cement is a commodity…[so] anything you do to add cost will reduce your competitiveness.”

Most early-stage efforts for reducing the carbon emissions of cement and concrete have been designed to fit easily into the industry’s existing processing and manufacturing methods, he noted.

One example is CarbonCure, a Canadian startup that injects carbon dioxide captured from other emitting sources into concrete, which both strengthens the concrete and stores the carbon, preventing it from entering the atmosphere. This practice can reduce the carbon footprint of concrete by roughly 5 to 15 percent, and it is relatively simple to integrate into how concrete is produced today. That’s allowed the company to scale up to more than 5 million truckloads of concrete delivered to date across more than 30 countries.

Low-carbon SCMs tend to be the next step for cement-makers trying to cut their carbon emissions, Hayton said. The key factors for successful SCMs are, first, being able to meet government and industry standards for strength and durability of the cement they produce, and second, being widely and cheaply available.

On the first front, Terra CO2 has earned approval from ASTM International, a nonprofit standards-setting body, for varieties of SCMs the company produces from various rock feedstocks. Terra CO2 has also tested cement and concrete using varying proportions of its SCMs in sites from roadways in Minnesota to buildings in Texas.

On the second front, the silicate rocks that Terra CO2 uses to make SCMs are already more widely and cheaply available than traditional materials, Yearsley said — and that’s only growing more pronounced.

Fly ash is already supply-distressed now,” he said. By the end of the decade, it’s going to go away. And blast furnace slag is going away as well. […] The way we make steel is changing fast. If we can’t find a scalable and viable SCM for the future, understanding the traditional ones are going away rapidly, the only alternative for concrete-making is going back to full Portland cement — which will increase the industry’s carbon footprint substantially.”

Even while these traditional SCMs remain available, they’re becoming increasingly hard to find in certain regions, which forces cement and concrete users to pay higher costs to transport them to where they’re needed, he noted. These products are all sold by the ton, and every mile you move it makes you less competitive, with less margin,” he said. Today, they’re railing fly ash into Denver from 1,000 miles away.”

Terra CO2 facilities, by contrast, can be located close to sources of silicate minerals and to the panoply of concrete ready-mix providers that serve regional construction markets, he said. The company now operates a test reactor in Vancouver, Canada and a larger-scale reactor in Golden, Colorado.

Terra CO2 has lined up roughly $160 million in commitments from project finance partners to fund two commercial-scale plants using its reactor technology, he said. Those partners include Breakthrough Energy Catalyst, a Bill Gates–founded entity that’s pledged $1.5 billion for hard-to-decarbonize industries including steel, aviation and cement manufacturing, and which is bringing in capital for roughly half the cost of the first plant,” he said.

Terra CO2 is also lowering the cost of its first plant by securing Asher Materials as a buyer of the facility once it’s complete, he noted. We’ve got to build and commercialize it — there’s technology risk there. But once we build it, we have a definitive binding agreement with a buyer. That’s enabled us to bring in bank debt on the first project, which normally you can’t do.”

Jonathan Green, founder of Asher Materials’ parent company Instar Holdings, said in a Tuesday statement that he sees this first plant laying the groundwork for building a progressive network of these advanced processing facilities across Texas.”

Competing low-carbon cement alternatives

Hayton highlighted a number of companies other than Terra that aim to displace more and more Portland cement with their novel SCM formulas. The higher the proportion of SCM, the lower the carbon impact of the cement, with a complete replacement of Portland cement being something of a holy grail for decarbonizing the industry.

Cement-makers such as Heidelberg Materials and Hoffmann Green Cement Technologies are pursuing one SCM option known as calcined clays. This material is widely available in Asia and Africa, but not as much in North America and Europe, making it less suitable for those markets, Yearsley said.

And Terra isn’t alone in pursuing silicate-based rocks as both a near-term feedstock for SCMs and potentially a way to someday completely replace Portland cement.

Brimstone, an Oakland, Calif.–based startup, has developed a process to convert basalt rock into ordinary Portland cement, and it recently earned third-party certification that its product meets ASTM standards. It’s planning to build a pilot plant in Nevada to test its production methods before building a commercial-scale facility.

Today, Terra CO2 offers two varieties of SCM — one that can be used to replace about 25 percent of the Portland cement in concrete mixes, and another that can replace up to 40 percent. Yearsley said the higher proportions are enabled both by being able to produce an engineered SCM” from its reactors and through the use of additives that improve the performance of its materials.

To take a supplemental cement up to 40 percent — and in time, potentially up to 50 percent — on a steady, reliable basis, nobody’s done that before. We think we’re there,” he said. Terra CO2’s first large-scale plant will be something of a test on that front. Today, the company runs different samples of silicates through its pilot plant and subjects the output to examination via X-ray diffraction and test mixes of concrete in its lab to ensure the SCM product can meet ASTM specifications, he said.

If that goes well, we’ll take a full truckload to our pilot plant and make a full batch,” he said. Usually it’s our potential customers who want to check it in their labs, pour concrete with it.”

Terra CO2 has raised about $61 million in venture capital to date, with investors including U.K.-based mining firm Rio Tinto, the venture arm of U.S.-based homebuilder Lennar Corp. and Bill Gates–founded Breakthrough Energy Ventures. BEV is a big backer of low-carbon cement, with investments in Brimstone Energy, CarbonCure, Ecocem and Solidia as well as Terra CO2.

Other approaches that promise a completely zero-carbon replacement for Portland cement are in a more experimental phase and would require retooling the cement industry to bring to scale. Some examples include startups such as Sublime Systems and Chement, which are developing electrochemical processes to replace the high-heat methods used to make cement. More esoteric concepts include using living organisms to grow” cement.

A lot of the other emerging technologies, they’re scientists trying to work out of labs and eventually commercialize,” Yearsley said. He sees future promise in that kind of work, but with their outsized emissions, the concrete and cement industries also need technologies that can provide guaranteed emissions reductions — right now.

Jeff St. John is director of news and special projects at Canary Media. He covers innovative grid technologies, rooftop solar and batteries, clean hydrogen, EV charging and more.