From Grey to Green: Low‑Carbon Cement Revolution

Why Cement Needs a Revolution

Cement is the backbone of modern civilisation. The world produces more than four billion tonnes of concrete each year and consumption is expected to jump by almost 50 % by 2050 as population growth and urbanisation drive demand. Unfortunately the process of making cement, the key ingredient in concrete, emits huge amounts of greenhouse gases. Cement production accounts for 7–8 % of global anthropogenic CO₂ emissions and more than three per cent of global energy consumption. Ninety per cent of concrete’s emissions come from the cement itself; producing one tonne of ordinary Portland cement releases roughly one tonne of CO₂. With global warming accelerating and governments adopting net‑zero targets, the cement industry has become a focal point for decarbonisation. This blog explores emerging technologies, policy drivers and practical steps to transition from grey cement to a green, low‑carbon future—without naming any competitor brands.

The Anatomy of Emissions – How Cement is Traditionally Made

To understand the opportunities for change, we first need to understand where the emissions originate. Traditional cement is manufactured by quarrying limestone, sand and clay; grinding them into a fine powder; then heating the mixture in a kiln at temperatures above 1 400 °C to form clinker. The calcination of limestone (CaCO₃) releases CO₂ to produce lime (CaO), and this chemical reaction alone generates about 60 % of cement’s emissions. The remaining 40 % comes from burning fossil fuels to achieve the high kiln temperatures and from ancillary processes. Once clinker is produced, it is mixed with gypsum and ground to make cement, which is then combined with sand and gravel and mixed with water to form concrete. Each tonne of ordinary Portland cement therefore emits about a tonne of CO₂, making the sector one of the hardest to decarbonise.

Beyond the chemistry, demand is surging. Global consumption of cement is expected to increase from 4.2 billion to 6.2 billion tonnes by 2050, driven largely by economic growth in developing regions. The United States alone produces roughly 91 million tonnes of cement annually, with 92 plants contributing 4.4 % of the nation’s industrial emissions and 1.1 % of total U.S. emissions. The combination of growing demand and high carbon intensity underscores the urgency of finding sustainable alternatives.

Clinker substitutes and novel chemistries

Replacing or reducing clinker content is one of the most effective ways to lower cement’s carbon footprint. Researchers and manufacturers are exploring several alternatives.

Limestone calcined clay cement (LC³)

Limestone calcined clay cement (LC³) is currently one of the most promising low‑carbon formulations. It combines clinker with calcined clay, limestone and gypsum, reducing both energy use and emissions. LC³ can reduce concrete emissions by up to 40 % and is up to 25 % more cost‑effective than ordinary Portland cement. It also uses widely available clay reserves and can be manufactured in existing kiln infrastructure with modest modifications. A Colombian plant producing LC³ has achieved a 30 % reduction in energy consumption and halved its carbon output. Ghana is constructing what will be the world’s largest calcined‑clay cement facility, expected to substitute 30–40 % of clinker and cut emissions by 40 %. Government studies in the United States suggest that shifting half of public cement procurement to LC³ could cut 7.3 million tonnes of CO₂ annually—about 9 % of the U.S. cement sector’s emissions. When both public and private markets adopt LC³, the emissions reduction could reach 15.9 million tonnes per year.

Bio‑cement and algae‑grown limestone

Researchers are also exploring biological routes to produce cement. Microalgae called coccolithophores can precipitate calcium carbonate, creating biogenic limestone. By substituting conventional limestone with algae‑grown limestone, scientists project potential savings of up to 2 gigatons of CO₂ and the ability to pull additional CO₂ from the atmosphere. Start‑up companies have already demonstrated masonry blocks made from bio‑cement with compressive strengths comparable to conventional concrete. However, this technology is still at an early stage: scaling up the production of algae, securing consistent supply, and ensuring cost competitiveness remain major hurdles.

Electric recycled cement

Another emerging solution reimagines cement as part of the circular economy. Researchers from Cambridge University discovered that the chemistry of recycled cement is similar to lime flux used in steelmaking. They propose crushing end‑of‑life concrete, separating the cement paste, and using it as a flux in electric arc furnaces (EAFs). When the steel melts, the flux forms a slag that can be cooled and ground into new cement. This approach has the potential to produce up to a billion tonnes of recycled cement annually by 2050. It also leverages existing steel infrastructure and could be carbon‑neutral if EAFs are powered by renewable electricity. Pilot projects have shown that this method may produce 30 tonnes of recycled cement per hour. Challenges include ensuring renewable power supply, developing supply chains for concrete waste, and achieving the necessary temperatures.

Alternative chemistries and electrolysis

Beyond these three headline approaches, new chemistries are gaining momentum. Innovative processes are emerging that produce lime using electrolysis, eliminating CO₂ emissions associated with calcination. Others recapture CO₂ from kiln exhaust and route it back into the process to create additional cement, achieving up to a 70 % reduction in carbon emissions and eliminating feedstock waste. There are also pilot plants replacing limestone entirely with calcium silicate rock, which avoids CO₂ emissions from calcination and promises production of more than 140 000 tonnes per year with significant CO₂ avoidance. These technologies are still in demonstration phases and require substantial capital, but they represent pathways for zero‑emission cement in the medium term.

Energy Efficiency and Alternative Fuels

While novel chemistries evolve, immediate reductions are achievable through plant upgrades and fuel switching. A case study from a European plant shows that artificial intelligence (AI) and advanced process control can optimise kiln operations and cut emissions by around 2 %. Efficiency measures such as modern dry kilns, improved grinding technology, and waste heat recovery have largely been implemented in the U.S., leaving limited gains, yet process optimisation continues to yield savings.

Switching fuels delivers larger reductions. Alternative fuels—ranging from agricultural residues to used tyres—now power up to 60 % of European cement kilns, and some facilities operate on nearly 100 % alternative fuels. These fuels generally add $5–10 per tonne to production costs but can achieve significant CO₂ reductions. Electrification of kiln heating is at an earlier stage (technology readiness level ~3), yet when combined with pre‑calcined raw materials it can cut emissions by 40–87 %. However, electrification could increase operating costs by 27–45 % and depends on access to low‑cost renewable power.

Plant owners are also integrating renewable energy into their operations, powering grinding mills and auxiliaries with solar or wind. Waste‑heat recovery systems generate electricity from the high‑temperature exhaust gases, lowering both emissions and energy costs. Advanced kiln designs and firing techniques can further reduce fuel consumption. These measures, combined with alternative fuels, are crucial for decarbonising existing plants while more disruptive technologies mature.

Carbon capture, utilization and recarbonation

Even with efficiency improvements and alternative chemistries, the cement sector will continue to emit CO₂ because of the fundamental chemistry of clinker production. Carbon capture, utilisation and storage (CCUS) is therefore seen as indispensable for achieving net‑zero. Experts estimate that more than half of the sector’s emissions reductions will depend on a mix of fuel switching, decarbonised power and CCUS. However, CCUS is capital‑intensive and requires a robust logistics network to transport and store CO₂, making deployment challenging. The world’s first capture facility specifically designed for cement opened in China in 2024 with a capacity of 200 000 tonnes of CO₂ per year. Point‑source capture is commercially available today, while direct air capture remains costly and is unlikely to be adopted widely until the 2040s.

Carbon utilisation offers an attractive alternative. One approach injects captured CO₂ into fresh concrete where it mineralises, strengthening the material and cutting emissions by 3–5 %. Another strategy uses mineral carbonation to produce aggregates or building blocks, effectively turning CO₂ into a valuable resource. Both methods require reliable CO₂ supply and rigorous quality control to ensure the structural integrity of the products.

Finally, cement itself can reabsorb CO₂ during its service life and after demolition. Concrete naturally carbonates when lime in the cement reacts with atmospheric CO₂ to form calcium carbonate. At end‑of‑life, crushing the concrete increases the surface area and accelerates this recarbonation process. Studies estimate that up to 25 % of the CO₂ emitted during cement manufacture can be reabsorbed when crushed concrete is exposed to air for several months. Properly sorting demolition waste and allowing stockpiles of crushed concrete to sit before reuse are simple practices that maximise this carbon sink. While recarbonation alone cannot offset all emissions, it forms an important part of a circular strategy.

Policy Drivers and Market Realities

Decarbonising cement is not just a technical challenge; it requires supportive policies and investment. In the United States, government procurement accounts for nearly half of cement demand. Researchers estimate that if public projects mandate LC³ and other low‑carbon cements for 50 % of their concrete purchases, annual emissions could fall by 7.3 million tonnes, equivalent to taking 1.7 million cars off the road. Extending this procurement to private projects could double the impact. Such mandates create demand for low‑carbon products and give manufacturers confidence to invest in new plants.

Financial requirements are significant. Industry analysts calculate that $20 billion of cumulative investment is needed by 2030 to develop low‑carbon cement solutions, rising to $60–120 billion by 2050. Currently only 3 % of global cement production is low‑carbon. Low‑carbon cement costs between $65 and $130 per tonne, roughly 75 % higher than conventional cement. These premiums reflect the higher capital costs, new raw materials and additional processing. Without regulatory incentives—such as carbon pricing, tax credits or public procurement standards—few producers will risk investing in low‑carbon technologies. Policy frameworks must therefore establish a market for sustainable cement and reward early adopters.

Alongside market incentives, design standards and building codes must evolve to allow the use of new materials. For example, new national standards for LC³ in India provide guidelines for production and testing, clearing the way for broader adoption. Environmental Product Declarations, performance‑based specifications and digital design tools can help project owners compare embodied carbon and choose low‑carbon options. Public‑private collaboration is essential to align specifications, streamline permitting and enable infrastructure for CO₂ transport and storage.

Polygonmach’s Role in the Low‑Carbon Revolution

As a manufacturer of asphalt and concrete plants, Polygonmach stands at the centre of this transformation. The company designs integrated batching systems, mixing equipment and material‑handling solutions that can be adapted to new low‑carbon cements and alternative fuels. By incorporating calcined‑clay calciners, modular grinding units, and flexible dosing systems, Polygonmach’s plants allow operators to blend supplementary cementitious materials—such as calcined clay, natural pozzolans and recycled cement—without disrupting production. Advanced automation and process‑control software ensure consistent quality and optimise energy use, aligning with the AI‑enabled efficiency gains demonstrated in European plants.

Polygonmach also offers alternative‑fuel ready kiln burners and waste‑heat recovery systems that enable customers to substitute fossil fuels with biomass, refuse‑derived fuels or other renewable sources, replicating the 60 % alternative fuel share achieved in Europe. For clients pursuing electrification, Polygonmach designs equipment that can integrate electric heating elements or plasma torches, prepared for the eventual roll‑out of renewable‑powered kilns. In regions with abundant solar or wind resources, the company can help integrate onsite renewable generation into cement and concrete operations, reducing dependence on grid electricity and improving resilience.

In addition, Polygonmach acknowledges the importance of carbon capture and utilisation. While full‑scale CCUS may be beyond the scope of most current plants, the company designs its facilities with the flexibility to retrofit future capture equipment or mineralisation modules. It also provides equipment for crushing and screening of demolition concrete, enabling clients to implement recarbonation and circular‑economy strategies. By combining technological innovation with a commitment to sustainability, Polygonmach positions itself as a partner for contractors, precast producers and infrastructure developers seeking to decarbonise their supply chains.

Practical Steps for Industry Professionals

To accelerate the low‑carbon cement revolution, sector professionals can take the following actions:

• Optimise design and reduce material use. Utilise digital design tools and structural optimisation to minimise concrete volumes. Case studies show that lean design saved 40 % and 24 % of concrete in two landmark towers.

• Adopt supplementary cementitious materials. Specify cements with reduced clinker content such as LC³, natural pozzolans, calcined clays or recycled cement. Evaluate locally available SCMs like fly ash and slag but recognise that these industrial by‑products may be limited as coal plants and blast furnaces retire.

• Switch to alternative fuels and renewable energy. Work with suppliers to source biomass, agricultural residues or industrial waste as kiln fuels; invest in electrification where feasible; and integrate onsite solar, wind or waste‑heat recovery to power grinding and auxiliary systems.

• Plan for carbon capture and recarbonation. Design new plants and retrofits with space and interfaces for future carbon‑capture units; experiment with mineralisation in concrete mixing; and develop practices for sorting and storing demolition concrete to maximise recarbonation.

• Leverage procurement and certification. Encourage clients and government agencies to include low‑carbon cement in procurement specifications. Demand Environmental Product Declarations to compare embodied carbon. Support policy frameworks—such as tax credits, carbon pricing or clean procurement standards—that reward low‑carbon products.

• Partner with innovative suppliers. Engage manufacturers like Polygonmach that are investing in flexible plants, alternative fuels and advanced process control. Collaborative R&D and pilot projects can accelerate the deployment of new technologies and create competitive advantages.

Looking Ahead – From Grey to Green

The transition to low‑carbon cement is both a technological and societal challenge. Demand for concrete will continue to rise as billions of people seek housing, infrastructure and resilient communities. Without intervention, cement emissions will rise from today’s 2.6 gigatonnes per year to an even greater share of the global carbon budget. Yet solutions exist across the value chain. LC³ and other clinker substitutes can cut emissions by up to 40 %, bio‑cement offers a pathway to carbon‑negative materials, electric recycled cement could close the loop, alternative fuels already power 60 % of some regional kilns, and carbon capture can abate the remaining emissions. When combined with better design and recarbonation, up to 25 % of emissions may be reabsorbed. Achieving these gains will require investment, supportive policies and cooperation across government, industry and academia.

Polygonmach and other forward‑thinking manufacturers are ready to support this revolution. By embracing innovation, flexible plant design and sustainable practices, the construction sector can transform concrete from a climate liability into a cornerstone of a low‑carbon future. The journey from grey to green begins today; those who act early will not only help the planet but also gain competitive advantage in the markets of tomorrow.