The ​‘clean cement’ projects getting $1.5B in Biden admin funds

Cement-making accounts for roughly 8 percent of global human-caused carbon emissions — an enormous climate footprint that will take nothing short of a full transformation to curb.

This week, the U.S. cement industry got a big jolt of federal funding to help it along that path. On Monday, the Biden administration announced $6 billion in investment for 33 demonstration projects aimed at decarbonizing heavy industrial sectors. Among them, six projects set to receive a collective $1.5 billion are seeking to slash the carbon impact of cement — and each project is going about it in a different way.

That’s because cement — the gluey powder that’s mixed with sand, gravel and water to form concrete, the most widely used material on earth — represents a particularly complex emissions problem that no one technology on its own can solve.

About 40 percent of the industry’s emissions come from burning fossil fuels in kilns used to make cement. Scaling up cost-effective alternatives to reach the super-hot temperatures required is challenging in its own right, particularly for an industry that churns out more than 4 billion metric tons of product per year.

But the other 60 percent of emissions from cement-making come from the chemical process of breaking down limestone, the core precursor material for almost all cement made today, into its constituent parts of calcium oxide and CO₂. That process can’t be decarbonized simply by switching fuels.

The U.S. Department of Energy — the source of this week’s industrial decarbonization grants — estimated in a report last year that roughly one-third of the cement industry’s emissions can be eliminated using established technologies and processes by the early 2030s. Major cement-makers in the U.S. and around the world are already using these approaches, which the DOE also estimates will actually help the industry save around $1 billion per year.

But the remaining two-thirds of cement’s emissions will be harder and more expensive to reduce, the DOE wrote in its report, requiring investments of a cumulative $5 billion to $20 billion by 2030 and between $60 billion and $120 billion by midcentury. For an industry that made just under $15 billion in sales last year and competes on very tight margins, that’s a hefty burden.

Eliminating that share of cement emissions will require alternative materials, alternative chemistries, alternative processing methods, or capturing and sequestering the carbon dioxide before it reaches the atmosphere — all viable pathways that face their own unique challenges.

That’s why government backing like that announced this week — which will be matched by equal or larger investments from the companies that won the awards — is vital to getting first-of-a-kind cement decarbonization projects off the ground.

Here’s a breakdown of the projects that won awards and the particular technology pathways they’re exploring.

Making ordinary Portland cement from different kinds of rocks 

Nearly all the cement made today is Portland cement, a material invented in 1824 that relies on carbon-rich limestone as a key ingredient. But what if cement could be made from minerals that aren’t packed full of carbon that escapes into the atmosphere?

That’s the goal of Brimstone, an Oakland, California–based startup that’s developing a way to convert calcium-bearing silicate rocks into Portland cement. These rocks are rich in the key cement-making ingredient of calcium oxide but free of carbon atoms.

Brimstone was approved for a DOE grant of up to $189 million to build its first-of-a-kind commercial-scale demonstration plant for its technology. That plant will be capable of producing 140,000 metric tons per year of this carbon-free Portland cement, along with supplementary cementing materials — alternatives to clinker, the precursor material for cement, that can bulk up a cement mix — that will avoid more than 120,000 metric tons of carbon dioxide emissions per year compared to standard Portland cement production.

Last year, Brimstone earned third-party certification verifying that its Portland cement is structurally and chemically identical to conventional supplies — an important finding for companies leery of replacing tried-and-true cement mixes with novel formulas.

But in an industry like cement, where almost all new facilities are financed by existing producers, ​“obtaining capital for a first-of-a-kind commercial-scale plant is challenging,” Cody Finke, Brimstone’s co-founder and CEO, said in an email. The new DOE funding ​“greatly accelerates the path to market for our deeply decarbonized cement,” allowing the company to start building its first pilot plant in 2025 while it starts to plan and design its first commercial-scale plant in 2027 or 2028.

Making cement from electricity 

Getting the carbon out of the minerals going into cement kilns is one way to cut carbon. Another way is to switch out fossil-fuel-burning cement kilns with a process that uses electricity to do the same work.

That’s the goal of Sublime Systems, an MIT spinout that’s developed an electrolytic technology similar to those used to produce clean hydrogen to make cement in a way that doesn’t emit carbon and runs at close to room temperature. Sublime’s electrolyzer uses electricity to extract calcium from calcium silicate materials and then precipitate that calcium in a form that can be used to make its final cement product.

Sublime has also earned an industry designation finding its product meets certain performance-based standards for hydraulic cement, and in late 2022, it finished a pilot plant that can produce up to 100 metric tons of cement per year. Its new DOE grant of up to $87 million will fund its first commercial-scale plant in Holyoke, Massachusetts, capable of producing tens of thousands of tons of its cement per year.

“Access to sufficient capital for industrial-scale demonstrations is the single biggest obstacle preventing breakthrough innovations from reaching the scale humanity needs to combat the climate crisis,” Sublime CEO and co-founder Leah Ellis said in a statement. ​“The Department of Energy has cleared this obstacle.” The company plans to begin construction of its Holyoke plant in 2025 and start producing cement in 2026.

Using clays to lower the carbon footprint of cement 

Supplementary cementing materials (SCMs) that reduce the proportion of high-emissions clinker needed in cement mixes are the chief ingredient in the lower-carbon cement blends now available around the world. But the most commonly used SCMs today are fly ash from coal plants and slag from steel mills — two materials that are limited in supply, expensive to transport and expected to decrease in availability as the power and steel sectors decarbonize.

Calcined clays, a form of naturally occurring minerals, are a promising alternative SCM already used by major cement producers such as Heidelberg Materials, Holcim and Hoffmann Green Cement Technologies to reduce up to half of the clinker in certain cement blends. So-called LC³ (limestone calcined clay cement) can be produced with emissions up to 40 percent lower than Portland cement.

The challenge for introducing LC³ into new markets and for new uses is in testing the strength, durability and suitability of new mixes made from distinct sources of calcined clays available in different parts of the world. Two of the projects funded by DOE’s newly announced grants are aimed at expanding the scope of these cements in parts of the country where they aren’t yet in wide use.

Roanoke Cement Company in Troutville, Virginia was awarded up to $61.7 million to use locally available clay types to reduce carbon emissions and establish markets for LC³ cement in its region. And Summit Materials was awarded up to $215.6 million to build ​“calcination” facilities in Maryland, Georgia and Texas, with the goal of reducing 1.1 million metric tons of CO₂ emissions per year.

Carbon capture and multitechnology approaches

Alternative chemistries, alternative cement-making methods and new sources of supplementary cementing materials are all valuable options for cutting cement’s carbon footprint. But even if they can compete on cost with standard Portland cement, it’s likely that construction-industry buyers will be slow to purchase them instead of old-fashioned Portland cement. The DOE suggests these alternatives could ​“face a ~10–20+ year adoption cycle to be accepted under widely used industry standards.”

The planet doesn’t have that long to wait to decarbonize cement production, however — and that’s focused many of the industry’s biggest players and government programs on carbon capture, utilization and sequestration (CCUS) as a vital near-term path. DOE’s Liftoff report cites industry and research studies indicating that CCUS could account for more than half of the industry’s potential to reduce carbon emissions by midcentury — if it can cost-effectively scale up to match the industry’s enormous emissions challenge.

CCUS is the focus of the two largest DOE grants for cement decarbonization projects, each up to $500 million. The first is for Heidelberg Materials, which is planning to capture at least 95 percent of the carbon dioxide — quite a high capture rate for today’s technologies — from its newly retrofitted plant in Mitchell, Indiana, one of the country’s largest cement production sites.

If successful, it would capture 2 million tons of CO₂ per year from the plant and store it in geologic formations beneath the plant property.

One of the biggest challenges of CCUS is building the pipelines and wells needed to sequester carbon dioxide deep underground where it can’t escape back into the atmosphere. The biggest U.S. cement CCUS projects, such as the Mitchell plant and two projects with Holcim at plants in Florence, Colorado and Bloomsdale, Missouri, are conveniently nearby underground geological formations that could house large amounts of captured CO₂ for centuries. These and other carbon-sequestration plans still face years of work to determine that they’re safe and to secure permits to undertake that work.

The second award of up to $500 million is for the National Cement Company of California, which is taking up a multitechnology approach to its goal of producing ​“carbon-neutral cement” at its plant in Lebec, California. That project will implement CCUS, and it will also use calcined clay to produce lower-carbon LC³ cement. It will also replace fossil fuels for its kilns with locally sourced agricultural waste such as pistachio shells, which embed the carbon dioxide that trees have previously absorbed from the atmosphere.

None of these awards are final yet — each project must go through contract negotiations, and the companies involved must commit to supplying an equal or greater amount of matching funds. Designing and building each project could take years. And each will need to secure commitments from buyers willing to use the cement it produces.

But if successful, these projects could help provide a blueprint for building a future with much lower-carbon cement — or even ​“net-negative” cement, as DOE’s announcement describes its longer-term vision.