Introduction and summary
As policymakers around the world work to reduce carbon emissions, it is essential they address the second-most widely used material after water: concrete.1 The cement and concrete industry is a massive contributor to climate change, responsible for 8 percent of carbon dioxide (CO2) emissions worldwide.2 If the cement and concrete industry were a country, it would rank as the world’s fourth-largest emitter, following the United States, China, and India.3
Despite cement’s overwhelming presence, the world has been relatively slow to address its decarbonization. Like the rest of the industrial sector, the cement industry is often questionably labeled “hard to abate,”4 because emissions result from the chemical process that creates cement and the fossil fuels needed to reach high temperature heat. Cement cannot be decarbonized by simply switching to clean energy, leaving emissions to remain consistently high over the past decade while progress in the power and transportation sectors has soared ahead.5 However, after years of research and development spurred by federal funding and incentive policies, dozens of companies have begun investing in new low-emission cement and concrete manufacturing technologies.
After years of research and development spurred by federal funding and incentive policies, dozens of companies have begun investing in new low-emission cement and concrete manufacturing technologies.
New companies like Brimstone, Sublime Systems, and Chement have invented ways to create entirely emission-free cement, and existing facilities around the world are already adopting other alternative methods that can cut emissions nearly in half—such as limestone calcined clay cement (LC3). Meanwhile, some working facilities have turned to carbon capture and storage (CCS) to capture up to 100 percent of their emissions in the next decade, with two of the biggest projects—Holcim’s Ste. Genevieve plant and Heidelberg Materials’ Mitchell plant—located in the United States. Finally, multiple U.S. companies have invented cement-free and emission-free concretes, such as C-Crete Technologies and Prometheus Materials.
Federal funding has supported many of these new projects to demonstrate technical and commercial viability. In March 2024, the U.S. Department of Energy’s Office of Clean Energy Demonstrations (OCED) allocated $1.6 billion for six cement and concrete decarbonization projects that will avoid a total of 4 million metric tons of carbon dioxide emissions annually.6 These grants were a part of the OCED’s Industrial Demonstrations Program, funded by the Infrastructure Investment and Jobs Act (IIJA) and the Inflation Reduction Act (IRA). In addition to these significant funding opportunities, further ambitious policymaking will be necessary to bring low-emission technologies to the scale needed to completely transform the cement and concrete industry.
What is the difference between cement and concrete?
Cement is an ingredient of concrete. When activated with water, cement acts as the binding material that holds concrete together. Most concrete mixes are about 7 to 15 percent cement, combined with sand, gravel, and water.7
Cement production is responsible for about 88 percent of the CO2 emissions associated with concrete production.8 The 98 cement facilities in the United States produce at a large scale, in contrast to the 8,500 concrete plants that typically mix in small-scale quantities for use locally.9
Background
Cement and concrete have been in use for thousands of years and remain as critical today as they were in ancient times. Ninety-five percent of hydraulic cement produced in the United States today is ordinary portland cement (OPC), developed in the early 1800s, which emits nearly a pound of CO2 for every pound of cement produced.10 While the world has made a small improvement in the average carbon intensity of cement production, this progress has been offset by increased demand. The result is that carbon emissions from the global cement industry have more than doubled since 2000.11 Global cement production has grown exponentially, largely driven by the growth and urbanization of China, which saw a 100-fold increase in cement production from 1970 to 2020. Other countries, including India and Indonesia, have seen similar but less dramatic growth in production over this period of modernization and infrastructure expansion.12 It is expected that the growth of India and Indonesia may eventually reach the dramatic levels of China,13 and by 2050, global cement production is expected to increase by 12 to 23 percent as economies continue to grow, especially in Asia.14
88%
The percentage of CO2 emissions cement is responsible for in concrete production
Simply reducing demand will not solve this problem, as concrete is already less emissive and less expensive than alternative building materials such as clay bricks.15 All told, the reduction rate of cement carbon intensity is well off track to meet the goal of net-zero carbon emissions by 2050. It would need to see an annual decrease of 4 percent through 2030 in order to be compatible with not exceeding 1.5 degrees Celsius of global warming.16
In addition to carbon emissions, cement production emits air pollutants with adverse health effects, including particulate matter, sulfur dioxide, nitrogen dioxide, ground-level ozone, lead, and carbon monoxide.17 Pollutants from cement facilities are responsible for premature deaths as well as respiratory and cardiac damage.18 In fact, an analysis by Sierra Club estimates that reducing emissions of particulate matter and its precursors from cement production could avoid up to 400 deaths a year in the United States.19
Why is cement production so emission-intensive?
Today, 95 percent of hydraulic cement produced in the United States is ordinary portland cement, produced by combining limestone (calcium carbonate) with silicate-containing materials such as sand and shale in a kiln.20 The kiln heats these materials to up to 3,000 degrees Fahrenheit, causing the chemical reaction of calcination to fuse them into portland cement clinker.21 This process is responsible for 51 percent of cement emissions, as CO2 is released from limestone during calcination.
The remaining emissions come from the combustion of fuels—typically, coal, natural gas, municipal solid waste, or biomass—to heat the kiln as well as the electricity used for mining and to power machinery.22
The Department of Energy (DOE) estimates that 40 percent of domestic cement emissions could be abated by 2050 using technologies and approaches that are ready to be deployed and are economically viable.23 These measures include energy and material efficiency, the use of alternative low-emission fuels, and cement clinker substitution. The remaining 60 percent will be possible through technologies currently under development that still must be demonstrated at a commercial scale, including many of the innovative ideas highlighted in this report. Some of these developments are already well underway, notably reducing the amount of clinker in cement.24
U.S. government support and policy for reducing cement and concrete emissions
Public policy has been and will continue to be essential to enabling low-emission technologies to make the jump from scientific discovery to commercially available products and, eventually, industrywide transformation. The projects highlighted below are largely the result of years of government funding to offset research and development costs, as well as policies such as green public procurement that guarantee demand.
Research, development, and demonstration funding
In the United States, the Department of Energy has a long history of supporting research, development, and demonstration for industrial decarbonization. It has allocated billions of dollars in industrial decarbonization grants and has contributed to research through the national laboratories. For example, the DOE’s Sandia National Laboratories collaborated on the CEMEX and Synhelion pilot to replace the use of fossil fuels with concentrated solar thermal energy in clinker production.25
Progress on industrial decarbonization was dramatically accelerated with the passage of the IIJA and IRA. These monumental laws led to the creation of the DOE’s Office of Clean Energy Demonstrations, which has already distributed $1.6 billion in grants for cement and concrete decarbonization.26 The DOE found that among economic sectors, the industrial sector would see the second-largest reduction in emissions as a result of decarbonization policies in the IIJA and IRA.27 The department estimates that to bring key cement and concrete technologies to scale and reach full decarbonization of the industry, a total investment of $5 billion to $20 billion by 2030 and $60 billion to $120 billion by 2050 will be necessary.28
While the federal funding allocated to industrial decarbonization has helped spark progress, if the industrial sector is going to reach net zero by 2050, the United States will need to allocate five to 10 times more funding than what was generated from the IIJA and IRA.29 Moving forward, public funding should be prioritized for technologies that will be freely shared and have the potential for “spillover,” acknowledging that companies and countries should work toward the common goal of achieving a net-zero cement and concrete industry. An excellent model of this is limestone calcined clay cement, which was developed with support from the Swiss government but shared with companies worldwide. Now, more than 50 countries are either producing or conducting research and development on LC3.30
Public procurement
The federal government can leverage its immense purchasing power to ensure sufficient demand for low-emission cement and concrete products. In 2021, the Biden administration launched the Federal Buy Clean Initiative to promote the use of low-carbon American-made construction materials. The Inflation Reduction Act then provided $4.5 billion to the General Services Administration (GSA), the Environmental Protection Agency, and the Department of Transportation to identify and procure clean construction materials for federally funded construction projects.31 Combined, these efforts led to the federal government’s first “Buy Clean” standard for low-carbon concrete. It was issued by GSA, which manages federal building and construction projects.
The Biden administration built on the work of multiple states that had previously developed Buy Clean and other green public procurement policies, helping expand these policies by launching the Federal-State Buy Clean Partnership in 2023, in which 13 states committed to supporting the procurement of low-carbon materials in state-funded projects.32
Projects leading on cement and concrete decarbonization
Achieving the full transformation of the cement industry necessary to address the climate crisis will require a variety of different technologies, suitable for the varying needs and available resources in different parts of the world. The following sections highlight some of the cutting-edge projects working toward this goal, including low-emission cement production, carbon capture and storage for cement facilities, and low-emission concrete production.
The emissions reductions reported by the companies have not been independently verified.
New low-emission ways to produce cement
Innovative cement companies
The following projects demonstrate the range of new technologies that eliminate emissions from cement production. Many of these solutions include low-emission substitutions for the highly emissive limestone or clean energy alternatives to replace fossil-fuel-powered kilns.
Brimstone
The most emission-intensive part of cement production is the calcination process of limestone. California-based company Brimstone completely cut these emissions by replacing limestone with carbon-free calcium silicate rock.33 This widely available rock contains magnesium. When extracted, magnesium residue permanently captures atmospheric CO2, allowing the resulting cement to be deeply decarbonized across a range of traditional and clean energy scenarios and carbon-negative when exclusively using clean energy.34 In 2020, Brimstone received its initial federal funding, a $500,000 award, from the DOE’s Advanced Research Projects Agency – Energy.35 In March 2024, Brimstone was awarded up to $189 million from the DOE’s OCED Industrial Demonstrations Program to construct a commercial-scale demonstration plant that will prevent 120,000 metric tons of CO2 emissions annually.36
Sublime Systems
Cement emissions are mainly a result of the fossil fuels typically used to power a high-temperature kiln and the emissions released from the calcination process of limestone. Sublime Systems, a Massachusetts-based company, has eliminated both these emission sources to create cement that approaches “true” zero carbon.37 The process also avoids nitrogen oxides (NOx), sulfur oxide, aerosols, and combustion-related particulate emissions.38
Sublime develops cement using noncarbonate materials in an electrolyzer powered by renewable energy. Rather than producing lime using limestone—an intermediary step of traditional cement making—Sublime’s process can make lime from a wide variety of calcium-bearing inputs, such as silica, magnesium, iron, and aluminum. The company says this feedstock flexibility will help make the technology easier to use in different areas of the world. Sublime’s main cement product uses reactive silica, which can be obtained from a wide variety of low-cost, abundant natural minerals or industrial waste materials.39 In January 2024, the DOE’s Industrial Efficiency and Decarbonization Office selected Sublime for a $6.7 million grant—one of 49 projects working to reduce industrial greenhouse gas emissions.40 And in March 2024, Sublime was awarded up to $86.9 million from the DOE’s OCED Industrial Demonstrations Program to build a new cement facility in Holyoke, Massachusetts.41
Applicants to all funding opportunities made available in the IIJA and IRA, including the Industrial Demonstrations Program, are required to submit a community benefits plan (CBP). CBPs are developed jointly by the project developer and community organizations to outline the developer’s commitments to community priorities such as job creation, local hiring preferences, environmental justice priorities, and actions that reduce air and water pollution.42 In developing their application, Sublime selected Holyoke for their first plant using screening tools created through Justice40, an initiative to direct 40 percent of benefits from some federal investments to underserved communities. Sublime also signed a strategic partnership agreement with the United Steelworkers, which represents half of unionized cement workers nationwide, regarding the up to 90 ongoing jobs the plant will create. In addition, Sublime’s CBP includes a program to prepare local residents for career opportunities in STEM.43
Cambridge Electric Cement
Another innovative cement-making process was inspired by a common recycling method used by the steel industry. The researchers at the University of Cambridge who launched Cambridge Electric Cement recycle concrete waste from the demolition of old buildings into a slag-forming addition that can replace ordinary portland cement.44 They discovered that the chemical composition of used cement is nearly identical to the lime-flux used in the steel recycling process and that they could use the same electric arc furnaces used in steelmaking—powered by renewable energy—to produce zero-emission clinker for cement.45
Fortera
California-based company Fortera takes a different approach to low-emission cement production. Their ReCarb process captures CO2 kiln exhaust from the limestone-to-lime conversion process and mineralizes it into a cementitious material.46 In doing so, Fortera generates cement with 70 percent less CO2, while the remaining 30 percent is abated when the process is powered by clean energy. In addition to their cement replacement product, Fortera offers ReAct Blend, which other cement producers can add to their product to reduce overall emissions.47
Limestone calcined clay cement
A type of low-emission cement already being used in projects around the world is limestone calcined clay cement (LC3), which was conceptualized in 2005 at the École Polytechnique Fédérale de Lausanne (EPFL). LC3 replaces half of the clinker used in ordinary portland cement with a blend of limestone and calcined clay, thereby reducing up to 40 percent of CO2 emissions.48
LC3 is one example of a blended cement, meaning it replaces a portion of clinker with supplementary cementitious materials (SCMs)—mainly suitable clays—to reduce the overall emissions of the resulting cement and concrete.49 Other blended cements utilize industrial byproducts such as fly ash—a byproduct of coal-fired power plants—or slag, a byproduct of steel production. However, the already limited availability of these materials is expected to decline further, raising costs.50 LC3 has the advantage of being widely available and affordable in the majority of countries.51 It can be produced using existing equipment, and the materials are abundant enough that LC3 can be produced in 75 percent of current cement plants worldwide.52 The EPFL shared the technology for LC3 freely so that it could be accessible to all cement companies, leading to current projects in Cuba, Colombia, Ghana, Malawi, and India.53 By the end of 2025, the use of LC3 is expected to have saved 45 million tons of CO2, and the developers of the technology believe it can prevent up to 500 million tons by 2030 if the cement industry widely adopts it.54
LC3 provides an opportunity for low-income countries to take immediate action to lower their cement emissions, particularly in the Global South, where the majority of new construction will occur in the coming decades. In most of Africa, suitable limestone to manufacture clinker is not available, but the most suitable clay types for LC3 are. Producing LC3 will, therefore, reduce not only CO2 emissions but also the need to import clinker, helping lower costs.55
While financing the development and commercialization of more ambitious solutions, high-income countries should support the widespread use of LC3 and other near-term decarbonization solutions in low-income nations through international financing.
Widespread adoption of LC3 would have a large cumulative impact on reducing emissions worldwide, but it should be viewed as a low-cost, market-ready technology that can be widely implemented now—until technologies and processes that approach emission-free production are affordable in all countries. Companies can also immediately switch to LC3 in tandem with other emission-reducing technologies in order to make their operations fully carbon-neutral, as the National Cement Company of California’s Lebec plant plans to do by using LC3, fuel-switching, and CCS.56 This strategy would reduce the total CO2 emissions that must be captured and stored, thereby cutting costs.
Higher-income countries have the responsibility to strive for zero-carbon technological breakthroughs through domestic policy support and should take on the higher, first-mover costs. Companies in high-income countries can utilize the policy support available to them to pursue rapid decarbonization and should not settle for the 40 percent emissions-reduction LC3 offers. Yet while financing the development and commercialization of more ambitious solutions, high-income countries should support the widespread use of LC3 and other near-term decarbonization solutions in low-income nations through international financing.
Carbon capture and storage for cement
There are multiple decarbonization strategies for cement facilities, such as implementing energy efficiency measures, using alternative low-carbon raw materials, or electrifying operations. However, the difficulty of abating process emissions from cement-making could make carbon capture and storage a common and effective solution to achieve net-zero carbon emissions from cement. In fact, the DOE estimates that CCS will have the largest impact on reducing emissions from the cement sector, cutting 65 percent of CO2 emissions by 2050.57 Estimates vary, however: The Global Cement and Concrete Association (GCCA) predicts that carbon capture will account for only 36 percent of CO2 emission savings in 2050.58
The world’s first industrial-scale CCS project at a cement plant is Heidelberg Materials’ Norcem Brevik plant in Norway.59 The project will capture 50 percent of the plant’s emissions starting in 2024, using amine-based post-combustion capture, a commercially available technology that has been used in the petroleum sector since 1996.60 Heidelberg plans to use the same technology to capture close to 100 percent of CO2 emissions at their Mitchell plant in Indiana and their Slite cement plant in Sweden, each of which will capture 2 million tons of CO2 emissions annually by 2030.61
The French company Air Liquide developed CrycocapTM FG technology, which captures CO2 from flue gases.62 Many cement plants plan to use this technology to capture 100 percent of their emissions by 2027 or 2028, including Equiom’s K6 project in France and Holcim’s Ste. Genevieve plant in Missouri, its Go4ECOPlanet project in Poland, and its GO4ZERO in Belgium.63
Nearly all the cement facilities highlighted above plan to use permanent geologic storage for their captured carbon dioxide. After the CO2 is captured and separated from the other gases produced at the facility, it is compressed to a liquid form for transportation. It is then transported by pipeline or ship for offshore storage and pumped more than 800 meters underground into a porous rock. The storage site must have a dense rock layer above called a “caprock” to keep the CO2 in place to ensure it does not affect the surrounding environment. Over time, the carbon dioxide turns to solid minerals bound within the rock, preventing leakage.64 In basalt reservoirs, mineralization takes place over roughly two years, a significantly shorter time period than those of other storage options.65
As long as a storage site is carefully chosen for its highly impermeable caprocks, geological stability, and effective trapping mechanisms and is consistently monitored, the likelihood of CO2 leakage is extremely low.66 One study suggests that even in the worst-case leakage scenario, more than 99.9 percent of CO2 would be contained in storage sites for more than a hundred years, making the storage system an effective climate solution.67 However, if leakage were to occur, it could leak into groundwater and have negative effects on plants and subsoil animals.68 Yet this scenario is less likely when CO2 is stored offshore, as most of the European projects highlighted above plan to do.69
Does carbon capture reduce conventional air pollution?
In addition to capturing CO2, installing CCS at cement plants decreases air pollution, reducing the public health effects cement plants pose to their surrounding communities. A Clean Air Task Force study found that an amine-based carbon capture system could reduce particulate matter emissions by more than 90 percent and nearly eliminate sulfur dioxide emissions. For the cement plants they studied, reducing particulate matter emissions would reduce the annual mortality rate of neighboring communities as well as save the communities up to $138 million in annual health benefits.70
To address other air pollutants not covered by CCS, including nitrogen oxides and organic compounds, companies can consider technologies such as the DeCONOx gas reduction process used by the Kirchdorfer Zementwerk plant in Austria.71 This technology breaks down pollutants, reducing NOx by up to 90 percent and carbon monoxide and volatile organic compounds by up to 99 percent.72
While adding carbon capture to existing plants allows companies to keep the rest of their process the same, retrofitting an existing plant to add carbon capture is usually just as expensive as creating a new CCS plant altogether. Additional high costs are associated with the transport and storage of the CO2. Many companies have taken advantage of government funding opportunities to avoid having this retrofit double the price of cement.73 In the United States, for example, the DOE provided funding for CCS through programs such as OCED, the Office of Fossil Energy and Carbon Management, and the Carbon Storage Assurance Facility Enterprise (CarbonSAFE) initiative. Projects such as the Mitchell cement plant in Indiana, Heidelberg Materials’ largest carbon capture project to date, have received millions of dollars in funding from all three programs.74
Similar programs exist in Europe, including the EU Innovation Fund which has granted hundreds of millions of dollars to CCS projects in Belgium, Bulgaria, France, Germany, Greece, and Poland.75 The program is funded by polluters paying for their greenhouse gas emissions via the Emissions Trading System, a cap-and-trade system that applies to all energy sectors and manufacturing facilities in the European Union.76 The EU Innovation Fund has contributed 1.9 billion euros to cement and lime projects so far, more than 80 percent of which has gone to cement CCS projects.77
New low-emission ways to produce concrete
Since cement is responsible for about 88 percent of the CO2 emissions associated with concrete production, an effective way to reduce concrete emissions is to reduce or replace concrete’s cement portion.78 The projects in Figure 5 show a range of low-emission alternatives to cement, including materials that absorb CO2.
Companies can stretch cement further by adding other ingredients known as supplementary cementitious materials.79 This is the approach of Terra CO2, which makes SCMs from widely available silicate-based raw materials, thereby reducing 70 percent of the CO2 and 90 percent of the NOx emissions associated with traditional concrete.80
C-Crete Technologies is doing the same, using a cement-free binder that uses different local materials as feedstocks.81 Not only does their manufacturing process produce almost no CO2, but the resulting concrete also absorbs CO2 from the air, so that the company is carbon-neutral when first formed and carbon-negative over the years. In 2023, C-Crete was awarded $950,000 from the DOE to expand the types of materials it can use for its SCM, as well as $2 million from the DOE’s Office of Fossil Energy and Carbon Management to accelerate production.82
Canadian company CarbonCure created a technology for concrete producers that injects captured CO2 into concrete during mixing, where the CO2 becomes chemically converted into a mineral. This not only eliminates carbon emissions but also makes the concrete stronger. It can be retrofitted into existing concrete plants and has already been used to save more than 450,000 tonnes of CO2.83
In addition to the emissions reductions that concrete companies can achieve by reducing the percentage of cement used, the construction industry can make a significant impact by simply using less concrete. The GCCA estimates that efficiency in design and construction alone could reduce CO2 emissions by 22 percent globally by 2050.84
Producer commitments
Many of the companies working toward lowering their carbon emissions have joined together to meet shared decarbonization goals. The most ambitious network is the newly formed Decarbonized Cement and Concrete Alliance (DC2), a coalition of companies with innovative ultra-low-carbon, carbon-neutral, and carbon-negative cement and concrete technologies.85 Members include many of the companies highlighted above, such as Brimstone, CarbonBuilt, Chement, Fortera, Prometheus Materials, Sublime Systems, and Terra CO2. DC2 will work to shape U.S. policies that expedite the use of new low-carbon cement and concrete products in public infrastructure, such as advocating for public procurement programs, expanding tax credits, and implementing stronger emission standards.86
In Europe, the Alliance for Low-Carbon Cement and Concrete has the goal of a zero cement and concrete emissions value chain by 2040 and plans to work with target EU policy, standards, and market actors. Its members include some of the companies mentioned above: Fortera, Sublime Systems, and Terra CO2.87
The Global Cement and Concrete Association represents 80 percent of the global cement industry volume outside of China, including some of the companies highlighted above, such as CEMEX, Heidelberg Materials, and Holcim. Its members have committed to producing carbon-neutral concrete by 2050. The GCCA developed a road map to achieve this goal, with the largest percentage of emissions reduced through carbon capture utilization and storage, increased efficiency in design and construction, increased efficiency in concrete production, and savings in clinker production.88
Conclusion
Within the cement and concrete industry, companies and scientists are working hard to develop new low- and zero-emission manufacturing processes that have the potential to transform this highly polluting industry. Bringing these innovative solutions to the scale necessary to reach net-zero emissions by 2050 will require further research, development, and ambitious investments and policies worldwide.
The United States has made progress in funding innovative solutions that eliminate both process emissions released in limestone calcination and energy-associated emissions. While only a few of these companies are currently producing at a commercial scale, their progress shows multiple technology pathways to decarbonize the sector, and the DOE grants allocated in the past few years will help accelerate their operations and keep costs competitive. In addition, policymakers should enact and expand policies to reduce emissions from cement and concrete, including public procurement policies such as “Buy Clean,” tax policies that incentivize clean materials, and standards for carbon intensity or embodied emissions of cement products.
Yet as the federal government pursues zero-emission technologies for widespread use in the longer term, it should continue to invest in carbon capture and storage to cut emissions at existing facilities in the short term. For low-income countries where CCS presents a cost barrier, the United States should support the adoption of LC3 through collaborative international financing and the utilization of multilateral platforms to encourage technical capacity support and rapid technology deployment.
The climate crisis cannot be solved without eradicating emissions from heavy manufactured goods such as cement. With each year and every forward-thinking policy and investment, the pathways to achieving this become clearer. Now is the time to invest more and push for deeper ambition from countries and companies around the world to rapidly reduce emissions from the cement and concrete sector.
Acknowledgments
The author would like to thank Mike Williams, Shannon Baker-Branstetter, and Jasia Smith of the Center for American Progress; Scott Shell of ClimateWorks Foundation;* Ash Lauth of Industrious Labs; and Simon Brandler of Brimstone for their review of and input on this report. The views expressed in this report are solely attributable to the author.
*Author’s note: Scott Shell is an architect and respected expert in low-carbon and sustainable architectural design, including green cement. He currently serves as a program strategist at ClimateWorks Foundation, which has previously supported CAP. Scott contributed editorial review and input for this report in his capacity as a subject matter expert.