Cutting-Edge Projects Aim to Decarbonize US Cement Emissions

New innovations are yielding promising technological solutions for cement production, which has historically been considered one of the most challenging of the heavy industrial sectors to decarbonize.

As a key ingredient in concrete, the primary material in our roads, bridges, homes and offices - and the second-most consumed material on the planet - cement's massive scale makes it responsible for 8% of global carbon dioxide (CO2) emissions and about 1.5% of U.S. emissions.

Reducing, avoiding or eliminating cement emissions is a difficult puzzle to piece together given the extremely high heat requirements and CO2-producing chemical reactions of its production process, coupled with the material's low price and the industry's small profit margins. Meeting the U.S.'s net-zero goals of eliminating climate-harming emissions by 2050 will require the cement sector to decarbonize a lot faster than the current rate, according to the U.S. Department of Energy (DOE).

Fortunately, recent DOE funding is laying the foundation for new projects across the U.S. that aim to produce low-carbon cement (also known as green cement). However, to scale the cutting-edge technologies being demonstrated in these projects, the U.S. will need to implement additional policies that will incentivize and facilitate their widespread adoption throughout the cement sector.

Several cement masons and concrete finishers pour fresh concrete on a bridge in Seattle, Washington. Cement, an ingredient in concrete, is the second-most consumed material on the planet. Photo by Sonja Blom / Alamy.

U.S. Investment in Abating Cement Emissions

As part of a recent push to decarbonize U.S. heavy industry, the DOE is investing $6.3 billion in 33 projects across eight industries to demonstrate cutting-edge decarbonization technologies. This Industrial Demonstrations Program (IDP), managed by the DOE's Office of Clean Energy Demonstrations (OCED), is by far the largest government investment to substantially reduce greenhouse gas (GHG) emissions from industry, the third highest emitting sector in the U.S. These government investments will also be matched by over $14 billion in private funding.

As of 2022, the U.S. has 91 operating cement plants that are responsible for 68 million metric tons (Mt) of direct CO2 emissions - the emissions equivalent of around 16 million gas-powered cars - annually.

DOE's IDP awards, which are still under negotiation, will grant up to $1.6 billion - the greatest share of the total funding - to six projects in the cement sector, which are expected to avoid 4 million tons of CO2 emissions annually.

Beyond the IDP, DOE and private sector funders have also made smaller investments in projects geared toward researching, developing and demonstrating (RD&D) innovative methods to reduce emissions from cement production. Based on WRI analysis of green cement projects in the U.S., there's nearly $65 million worth of government funding devoted to additional RD&D projects in the cement sector. It's also likely that private funding far exceeds direct public investments for these projects.

Types of Cement Decarbonization Technologies

The potential decarbonization solutions cement producers are pursuing range from more established options, such as lowering the amount of clinker in cement (clinker is a precursor material in cement and its production accounts for 85% of emissions from cement production), to technologies that reinvent cement as we know it. There isn't one solution that will get us to zero-emissions cement - multiple technologies, such as blended cements, novel cements, carbon capture and sequestration and carbon mineralization, will need to be deployed in tandem across the sector to rapidly scale the availability of low-carbon or near-zero cement. And the technologies themselves will need certain infrastructure and regulatory support such as readily available clean electricity and permits for CO2 transport and sequestration.

Low-Carbon Cement Commercial Demonstration Projects

Sources: Department of Energy, company websites, company outreach conversations and authors' analysis.

*Summit's four projects are projected by DOE to meet 2% of U.S. cement demand by 2030, (averaging 600 Kt/yr of cement per project). Applying the U.S. average emissions intensity (0.75 t CO2/t cement), Summit's plants would emit 1.8 Mt CO2 without reductions. DOE estimates a reduction of 1.1 Mt CO2 from the projects, suggesting a 61% reduction of estimated emissions.
Note: More information on these projects and the feasibility studies/pilot projects is available at this table and in the map below.

Blended Cements

One of the fastest and cheapest ways to cut U.S. cement and concrete emissions is to make cements with less clinker. Cement producers can do this by incorporating substitute materials, called supplementary cementitious materials (SCMs), to make blended cements. Because the United States uses more clinker in its cement than most other countries, this option is considered a particularly low-hanging fruit.

Half of the IDP-funded cement projects will demonstrate the potential of these lower-carbon alternatives to conventional cement. For example, the Roanoke Cement Company in Virginia will replace much of its clinker with SCMs. It estimates emissions reductions of 83% compared to the commonly used Ordinary Portland Cement (OPC). Denver, Colorado-based Summit Materials, another awardee, will construct four plants to produce enough blended cement to satisfy 2% of U.S. cement demand by 2030.

Due to its low-cost relative to other decarbonization pathways, many other non-IDP projects are geared toward production of blended cements for significant emissions reductions. The Ash Grove Cement Company, in Overland Park, Kansas, has been awarded more than $4 million from the DOE Industrial Efficiency and Decarbonization Office to develop low-carbon, circular practices in the cement industry by converting sediment waste from further up the cement supply chain into SCMs. The company estimates this process will reduce cement's carbon intensity by up to 70%.

Even with blended cements, demand for clinker will remain. Thus, the cement industry will need to find solutions that eliminate emissions from the remaining clinker production. This is where innovative processes that are less technologically ready must be developed and scaled.

Novel Cements

One option is to develop new methods and products that avoid the process emissions from clinker production entirely by using different raw materials that don't contain carbon. Two startups will be awarded substantial DOE funding through the IDP to construct small-scale commercial plants to demonstrate the feasibility of these innovative processes at scale.

One of them, Sublime Systems from Somerville, Massachusetts, uses an electrochemical process in electricity-powered electrolyzers to turn carbon-free rocks into an alternative cement that is as durable as OPC. It is developing a plant in Holyoke, Massachusetts, which will begin producing 30 kilotons (Kt) of cement per year in 2026 and plans on constructing a megaton scale plant in a yet to be determined location by 2028.

The other startup slated to receive IDP funding, the Oakland, California-based Brimstone, produces OPC also using non-carbonate rock with a different process that doesn't release CO2 when transformed into cement. Brimstone's plant, which is still in its planning phase, is expected to have a production capacity of 140 Kt of cement per year.

By switching to non-carbonate rocks as feedstocks, these startups' production methods will avoid the process emissions of conventional cement production. They will still require clean energy - to power electrolysis in Sublime's case and heat kilns in Brimstone's - to completely decarbonize. Electricity from renewables and low-emission thermal energy powered by technologies such as thermal heat batteries will enable these companies to produce near-zero emissions cements at scale.

Another approach already being deployed by a privately-funded California startup named Fortera involves recirculating CO2 from the clinker kilns of its partner, CalPortland, to make 15 Kt of novel cement and SCM products through carbon mineralization at its plant in Redding, California. Fortera recently broke ground on an additional plant where they will scale this process to produce an estimated 400 Kt of low-carbon cement per year with 70% fewer emissions than conventional cement production.

Carbon Capture and Sequestration

Aside from novel and blended cements, carbon capture can be used to stop CO2 emitted during conventional production from entering the atmosphere. Once the CO2 is captured, it can be injected and permanently sequestered deep underground.

Cement production is one industrial sector in which carbon capture is expected to play a critical role in decarbonization. Unlike the power sector, which has cheaper and more efficient decarbonization options like renewables, the combination of process emissions and high heat requirements leaves conventional cement production without widely available decarbonization alternatives to carbon capture and sequestration (CCS) for deep decarbonization.

The U.S. government, industry associations, international organizations, civil society and cement companies themselves agree: a significant scale up of CCS is needed to decarbonize the cement industry. The unique importance of this technology for cement decarbonization is reflected in the fact that the only two IDP projects involving CCS are in the cement sector. One project is Heidelberg Materials' cement plant in Mitchell, Indiana - one of the largest operating cement plants in the U.S. This plant has the benefit of being located above geologic formations that are ideal for carbon sequestration. When its CCS system is fully operational, 95% of the CO2 generated at the facility - up to 2 million tons - will be captured and injected far below the Earth's surface per year.

National Cement Company's plant in Lebec, California, plans to utilize waste-biomass for fuel, shift to blended cements and install carbon capture and sequestration, with the goal of achieving net-zero emissions. Photo by National Cement Company of California.

Several other cement companies are seeking to retrofit their facilities with carbon capture systems, taking advantage of dedicated grants for carbon capture retrofits from DOE. For example, the Swiss-based Holcim, one of the largest cement companies in the world, has received DOE funding to conduct front-end engineering design (FEED) studies into carbon capture on two of its U.S. cement plants in Colorado and Missouri, the latter of which is the largest cement plant in the U.S.

Carbon capture can also be deployed alongside other decarbonization technologies to achieve near- or net-zero emissions at cement plants. This is the National Cement Company's plan for their plant in Lebec, California. The company could be awarded up to $500 million through the IDP to continue developing a combination of retrofits on the plant, including increasing its use of waste-based biomass to replace fossil fuels and continuing its switch to blended cement production. The plant will also install a CCS system to reduce its remaining emissions. If all goes to plan, the Lebec plant will be producing cement with net-zero emissions by 2031.

Carbon Mineralization

Carbon dioxide can also be utilized in concrete as a method of technological carbon removal. For instance, CO2 captured from industrial plants or direct air capture facilities can be mineralized in concrete just as Fortera does with cement, preventing it from entering the atmosphere. Companies like Solidia Technologies, CarbonCure and Blue Planet are developing technologies for mineralizing carbon in concrete and aggregates to mitigate some of the overall emissions from cement production downstream of the cement plant.

Challenges that New Cement Technologies Must Overcome

The evolving landscape of U.S. cement decarbonization projects represents promising momentum. But they face hurdles that need to be overcome for successful deployment. Challenges include lack of permits and infrastructure for CO2 transport and sequestration, market acceptance of novel and blended cements, and access to clean energy. The timelines of large industrial projects like these and future availability and acceptance of low-carbon cement are therefore subject to some unpredictability.

Once operational, however, these first-of-a-kind cement plants will play a vital role in demonstrating to cement producers, cement consumers and financiers the technical and economic viability of these decarbonization technologies at the commercial scale.

Policy Support Needed for Scaling Technologies

Despite the unprecedented scale of these green cement projects, they will likely only supply around 5% of the 120 million tons of cement annually consumed in the U.S. once deployed. Additional policies and incentives to facilitate their widespread adoption will be needed.

Government RD&D grants for low-carbon cement production, like the IDP or those proposed in the recent bipartisan Concrete and Asphalt Innovation Act, can accelerate the improvement of some of these technologies, making them appear less risky. In doing so, they serve a vital function in carrying emerging technologies across what's known as the investment "valley of death," a phrase used to describe how the diffusion of emerging technologies can be stymied from a lack of funding.

However, to support a rapid scale-up and adoption of cement decarbonization technologies, federal and state policymakers should adopt the next generation of additional policy measures such as the following:

• Demand-side Policies: Governments can demonstrate there is a market for low-carbon products through green public procurement, advanced market commitments and similar policies.
• Tax Subsidies: Tax credits can provide incentives for low-carbon production and investment.
• Market-based Policies: Policies like a Low-Carbon Product Standard, the proposed Clean Competition Act or an industrial sector-wide cap-and-trade program can provide incentives for companies to meet or exceed emissions intensity benchmarks.

Adding these policies to the mix would accelerate the growth of a vibrant and self-sufficient low-carbon cement industry - a necessity if the U.S. is to achieve its net-zero goals by mid-century - while allowing U.S. businesses to benefit from being a "first mover" in green cement production.

Analysis for this article was primarily based on information from public online sources such as the Department of Energy and company websites, and was supplemented with information after contacting several of the companies featured in this article.