Low-Carbon Transition in the Cement Industry

The low-carbon transition in the cement industry is the coordinated transformation of the world’s cement production so that its direct carbon dioxide emissions fall by about 24 percent below their current levels by 2050, even while the world’s construction economy demands roughly 12 percent more cement than it produces today. That target, developed by the International Energy Agency (IEA) together with the Cement Sustainability Initiative (CSI), the global effort of 24 major cement producers with operations in more than 100 countries that collectively account for about one-third of the world’s cement production, is the subject of the Technology Roadmap document held in the Complete Cement Technical Package. This complete technical guide explains the roadmap in full: the sources of the cement industry’s emissions, the four great levers of the reduction (energy efficiency, alternative fuels, the reduction of the clinker-to-cement ratio, and the emerging innovative technologies including carbon capture, use and storage), the regional pathways, the policy and finance requirements, and the action plan to 2030.

The cement industry faces a harder decarbonisation problem than almost any other industry, because roughly half to two-thirds of its direct CO2 emissions are not energy emissions at all: they are the chemical emissions of the calcination reaction itself, the release of the carbon dioxide from the limestone when it becomes lime. No fuel switch, no efficiency gain and no renewable electricity can eliminate those process emissions, which is why the roadmap’s conclusion is unromantic and decisive: the full decarbonisation of cement requires the deployment of carbon capture at scale, supported by every other lever, and the transition must begin now because the plants being built today will still be running in 2050. This guide gives the engineer, the manager and the policy maker the complete technical map of that transition: the numbers, the levers, the technologies and the milestones.

1. The Roadmap and Its Partners: IEA and the Cement Sustainability Initiative

The Technology Roadmap for the low-carbon transition of the cement industry was prepared jointly by the International Energy Agency and the Cement Sustainability Initiative, the global effort of 24 major cement producers with operations in more than 100 countries. The partnership brought together the two institutions that could make the roadmap credible: the IEA, which examines the full spectrum of energy issues (oil, gas, coal, renewables, electricity markets, energy efficiency and access to energy) and advocates the policies that enhance the reliability, affordability and sustainability of energy in its member countries and beyond, and the CSI, whose member companies account for about one-third of the world’s cement production and range in size from large multinational corporations to small local producers.

• The business case: the CSI companies believe there is a strong business case for the pursuit of sustainable development, and the roadmap is the collective expression of that belief, built on the real production data, the technology costs and the project experience of the industry.
• The policy context: the roadmap responds to Goal 13 of the United Nations 2030 Agenda for Sustainable Development, adopted in September 2015, which calls for urgent action to combat climate change, and to the Paris Agreement architecture that followed.
• The methodology: the roadmap uses a bottom-up approach to explore a possible transition pathway based on least-cost technology analysis for the cement industry, identifying the combination of technologies that delivers the required emissions reduction at the lowest total cost rather than the cheapest per unit of each individual technology.
• The target: the least-cost pathway reduces the direct CO2 emissions of the industry by 24 percent below the current levels by 2050, an ambitious but practical, realistic and achievable reduction, and the outlined transition is designed to be both economically and regulatory-supported.

The institutional design of the roadmap is part of its message: the reduction target is not an external imposition but an industry-endorsed engineering pathway, and its feasibility rests on the explicit statement that the transition can only be attained with a supportive regulatory framework and the coordinated action of the producers, the governments and the finance community.

2. Where the Emissions Come From: The Carbon Anatomy of Cement

The design of any decarbonisation strategy must begin with the carbon anatomy of the process, and the cement industry’s anatomy is unusual. The direct CO2 emissions of a cement plant arise from three sources of very different characters:

• The calcination process emissions: the decarbonation of the limestone (calcium carbonate converting to calcium oxide and carbon dioxide, CaCO3 becoming CaO plus CO2) releases roughly half to two-thirds of the direct CO2 of the plant, about 0.5 tonnes of CO2 per tonne of clinker from the chemistry alone; these are process emissions that no fuel change can remove.
• The fuel combustion emissions: the kiln system burns the fuel that heats the material to the 1450 degrees Celsius of the burning zone, and the combustion of the coal, pet coke, gas and alternative fuels adds roughly a third to two-fifths of the direct emissions, about 0.3 tonnes of CO2 per tonne of clinker at the typical specific fuel consumption of 3.5 to 4 GJ per tonne.
• The indirect electricity emissions: the grinding, the fans and the auxiliaries consume electricity, roughly 90 to 120 kilowatt-hours per tonne of cement in a modern plant, and the emissions of that electricity depend on the grid that supplies the plant, outside the direct accounting of the process.

Emission source	Share of direct CO2	Typical magnitude	Lever that attacks it
Calcination process emissions	~50-60 percent	~0.5 t CO2 per tonne of clinker	Clinker substitution, carbon capture
Fuel combustion (kiln system)	~30-40 percent	~0.3 t CO2 per tonne of clinker at 3.5-4 GJ/t	Energy efficiency, alternative fuels
Indirect electricity (grinding, fans)	Indirect, grid-dependent	90-120 kWh per tonne of cement	Mill efficiency, renewable electricity

This anatomy dictates the strategy: the efficiency and the alternative fuel levers attack the fuel emissions, the clinker substitution lever attacks the process and the fuel emissions together (each tonne of clinker avoided avoids both the calcination and the fuel CO2), and only the carbon capture technologies attack the calcination emissions directly. Because the process emissions dominate, the roadmap’s own analysis is explicit that the industry cannot reach its long-term goals through the traditional levers alone, however far they are pushed.

3. The Vision and the Target: 24 Percent Below Current Levels by 2050

The roadmap’s vision is quantified with precision: the direct CO2 emissions of the cement industry fall by 24 percent below the current levels by 2050 while the cement production continues to grow. The numbers of the vision deserve to be stated exactly as the roadmap frames them:

• Production growth: the world’s cement demand grows by roughly 12 percent between the baseline year and 2050, driven by the urbanisation of the developing world, the infrastructure renewal of the developed world and the growth of the global middle class.
• The 24 percent reduction: against that growing production, the direct emissions fall by 24 percent below the current levels, which in absolute terms means the emissions intensity of the product falls by far more than 24 percent, because the same total reduction is spread over a larger tonnage.
• The intensity translation: the intensity of the direct emissions per tonne of cement must fall from about 0.6 tonnes of CO2 per tonne of cement toward roughly 0.4 tonnes by 2050, a drop that combines every lever of the roadmap.
• The ambition note: the roadmap notes explicitly that the 24 percent pathway, while ambitious, is not the full decarbonisation of the industry; deeper reductions are possible only with the deployment of the carbon capture and the novel cements at a scale and a pace beyond the least-cost pathway.
• The milestone logic: because the cement plants have service lives of decades, the decisions of the 2020s (the kiln rebuilds, the capacity expansions, the fuel switches and the efficiency retrofits) lock in the emissions of the 2040s, which is why the roadmap’s milestones to 2030 matter as much as the 2050 target.

The vision is therefore a managed decline of the emissions intensity against a growing market: the industry that achieves the roadmap does not shrink; it transforms, and the transformation is the subject of the four levers that follow.

4. Lever One: Improving Energy Efficiency

The first lever of the roadmap is the classical efficiency programme of the industry: the reduction of the thermal energy per tonne of clinker and the electrical energy per tonne of cement. The efficiency agenda is well mapped and partially exhausted, but its remaining potential is still significant:

• The thermal baseline: the global average thermal energy intensity of clinker production stands in the region of 3.5 to 3.9 GJ per tonne, against the best available technology of approximately 3.0 to 3.3 GJ per tonne, so the closure of the gap is worth roughly 15 to 20 percent of the thermal fuel consumption of the lagging plants.
• The electrical baseline: the grinding dominates the electricity of the plant, and the modern closed-circuit mills with the high-efficiency separators, the vertical roller mills and the roller presses have cut the finish grinding energy from above 40 kilowatt-hours per tonne toward the mid-twenties; the remaining gains come from the process optimisation and the waste heat recovery.
• The installation sweep: the dry process with the preheater and the precalciner, the heat recovery from the cooler, the oxygen and combustion optimisation, the online quality control that stabilises the burning, and the waste heat recovery power generation are the established efficiency measures whose application the roadmap extends to the whole world’s plant fleet.
• The economic position: the efficiency measures are the cheapest and most mature of the levers, with the shortest paybacks, and the roadmap assigns them the role of the immediate, bankable reductions while the deeper technologies mature.

The efficiency lever is the foundation of the transition because it is the only lever whose every tonne of reduction also saves the producer money, which is why the roadmap treats it as the default action of every plant and every new investment, and why the laggard plants (particularly the older wet and semi-wet lines that still operate in some regions) are the first target of the global programme.

5. Lever Two: Switching to Alternative Fuels

The second lever replaces the fossil fuels of the kiln with alternative fuels: the wastes and the biomass whose combustion either avoids the fossil carbon entirely (the biomass fraction) or displaces the fossil fuel that would otherwise be burned elsewhere (the waste fraction). The alternative fuel agenda is one of the industry’s great success stories and one of its most contested practices:

• The thermal substitution rate (TSR): the share of the kiln’s thermal energy supplied by the alternative fuels; the global average remains modest, of the order of 5 to 10 percent, while the leading European industries reach 50 to 70 percent and beyond, so the roadmap’s pathway pushes the global average substantially upward through the period to 2050.
• The fuel families: the alternative fuels of the cement industry are the treated municipal solid waste and the refuse-derived fuel, the waste tyres, the waste oils and solvents, the plastics and the biomass streams (wood, agricultural residues, sewage sludge), each with its calorific value, its moisture and its chlorine, sulfur and heavy metal content to be managed.
• The kiln as the thermal reactor: the cement kiln is uniquely suited to the waste combustion: the flame temperature exceeds 2000 degrees Celsius in the burning zone, the residence time and the alkaline environment neutralise the acid gases and retain the heavy metals in the clinker, and the ash of the waste becomes part of the raw meal.
• The quality constraints: the alternative fuels bring the volatile cycles (chlorine, sulfur, alkalis) that threaten the kiln operation and the product quality, and the roadmap’s engineering content treats the pre-processing, the feeding points, the bypass and the fuel quality control that make the high substitution rates safe.

The alternative fuel lever attacks the fuel emissions directly and is nearly carbon-neutral in its biomass fraction, but its ceiling is set by the availability and the quality of the waste streams, not by the technology; the roadmap therefore treats the TSR growth as an important but bounded contribution, fully exploited where the waste logistics and the regulation allow, and complemented by the other levers where they do not.

6. Lever Three: Reducing the Clinker-to-Cement Ratio

The third lever reduces the clinker content of the cement: every tonne of clinker that is replaced by a supplementary cementitious material (SCM) removes both the calcination CO2 and the fuel CO2 of that tonne, which makes the clinker substitution the most powerful of the conventional levers. The roadmap’s analysis of the lever covers the materials, the limits and the economics:

• The baseline and the target: the global average clinker-to-cement ratio stands in the region of 0.65, and the roadmap’s pathway reduces it to the range of 0.60 to 0.65 by 2050, a modest percentage change with a large absolute effect because it applies to the world’s more than 4 billion tonnes of annual cement production.
• The classic SCMs: the granulated blastfurnace slag, the fly ash from the power plants, and the natural and artificial pozzolans are the established materials, already used at substantial ratios in the leading markets; their availability is constrained by the declining production of the blast furnaces and the coal power plants, which the transition itself accelerates.
• The calcined clays: the calcined clay pozzolans, particularly the clay-lime systems of the LC3 family, are the roadmap’s answer to the SCM scarcity: the clays are abundant worldwide, the calcination can use the waste heat or the alternative fuels, and the clay- limestone blends can replace a third or more of the clinker while maintaining the performance.
• The limestone filler: the interground limestone addition, standardised in the modern portland-limestone cements with the limestone contents up to 15 percent and beyond, contributes the immediate, cheap clinker reduction that every plant can adopt.
• The quality engineering: the substitution is bounded by the performance: the setting, the strength development, the durability and the carbonation behaviour of the blended cements are the engineering constraints, and the roadmap’s content treats the mix design, the fineness optimisation and the standards work that carry the higher substitution ratios.

The clinker substitution lever is the industry’s own direct reduction tool: it needs no new infrastructure, it lowers the cost and the energy of the product, and it recycles the materials that would otherwise be waste. Its ceiling is the availability of the quality SCMs and the acceptance of the standards and the markets, which is why the roadmap combines it with the standards modernisation and the calcined clay development as the twin tracks of the same lever.

7. Lever Four: The Emerging and Innovative Technologies

The fourth lever is the frontier: the carbon capture, use and storage (CCUS) technologies and the novel binding materials that address the calcination emissions directly. The roadmap’s treatment of this lever is the heart of its honesty, because it names the technology that nothing else can replace:

• The post-combustion capture: the amine and the membrane-based processes that strip the CO2 from the kiln exhaust gas of the existing plants; the technology is the retrofit-friendly option, but its energy penalty (of the order of 30 percent of the plant’s fuel consumption in the classical amines) is the price of the flexibility.
• The oxyfuel combustion: the kiln burns in an oxygen-rich atmosphere instead of air, producing an exhaust gas that is almost pure CO2 ready for purification, compression and storage or use; the oxyfuel route is the leading option for the new and the rebuilt lines, with the demonstrations now operating at commercial scale in the industry.
• The calcium looping: the twin-fluidised-bed process in which the lime sorbent captures the CO2 from the kiln gas and is regenerated in a second vessel, a technology with the natural synergy to the cement process because the spent sorbent is the raw meal itself; the calcium looping is a leading candidate for the deep retrofit of the large plants.
• The use of the CO2: the captured carbon dioxide finds its uses in the chemicals, the enhanced curing of the concrete products and the mineralisation routes, generating the revenue streams that offset part of the capture cost while the permanent storage (the geological storage) is developed at the scale the volumes demand.
• The alternative binders: the spotlight of the roadmap falls on the alternative binding materials for the cements: the calcined clay-limestone systems, the alkali-activated and geopolymer materials, the belite-rich and the other low-temperature clinkers, and the magnesium-based binders, each with its performance, its durability evidence and its standards gap to close before the market scale is possible.

The roadmap’s least-cost analysis shows the innovative technologies entering the pathway in force after the early 2030s and carrying a growing share of the reduction toward 2050, because their cost curves fall with the deployment. The message to the industry is unambiguous: the conventional levers alone can carry the industry roughly half of the way; the rest of the journey requires the capture and the novel materials, and the plants that do not begin their capture journeys in the coming decade will not be able to complete them by 2050.

8. The Regional Pathways: Where Each Lever Counts Most

The roadmap is a global pathway built from regional realities, because the cement industry’s emissions are heavily concentrated and the levers play differently in each region:

• China: the world’s largest producer, with a modern and recently expanded fleet; its pathway is dominated by the efficiency closure, the alternative fuel growth and the clinker reduction, with the capture arriving on the large new lines.
• India: the second largest market, growing rapidly; its pathway carries the greatest tension between the demand growth and the emissions, and the efficiency and the clinker reduction levers carry the early burden, with the calcined clays particularly promising in the Indian raw material base.
• The OECD economies: the mature, stable markets where the alternative fuel substitution has already reached the high rates and the clinker factors are already low; their remaining levers are the deep efficiency, the capture retrofits and the novel materials, and their producers are the technology leaders of the transition.
• The Middle East and Africa: the rapidly urbanising markets with the modern plants and the growing demand; their pathway combines the efficiency, the alternative fuels (where the waste infrastructure develops) and the clinker substitution, with the capture arriving later at the scale the region’s plants demand.

The regional structure of the roadmap explains its policy content: a global target expressed in percentages translates into very different national programmes, and the international collaboration the roadmap demands is precisely the mechanism by which the technology, the finance and the capacity of the leaders reach the laggards.

9. Policy, Finance and International Collaboration

The roadmap is explicit that the technology pathway is necessary but not sufficient: the transition can only be attained with a supportive regulatory framework and the finance to carry the capital costs. The policy and finance architecture the roadmap lays out covers:

• The carbon pricing: a meaningful and predictable price on the carbon emissions is the master instrument, because it converts the emissions reduction from a cost into a revenue and ranks the levers by the true economics; the roadmap examines the carbon pricing architectures that respect the international trade exposure of the industry.
• The standards and the public procurement: the cement standards that admit the blended and the low-carbon products, and the public procurement that specifies them, create the market pull that the technology push needs; the roadmap’s standards agenda includes the performance-based specifications that reward the low-clinker and the novel products.
• The investment requirements: the roadmap estimates the additional investment the pathway demands and identifies the finance channels: the corporate capital, the development finance for the emerging markets, and the climate finance instruments that carry the early capture projects through their demonstration phase.
• The innovation support: the capture technologies and the novel binders are at the demonstration and the early deployment stages, and the public support for the demonstration plants, the pilot programmes and the research is the bridge between the laboratory and the market.
• The international collaboration: the roadmap’s action plan is built on the cooperation of the producers, the governments and the international organisations: the technology sharing, the harmonised accounting, the capacity building and the joint demonstration projects that the global nature of both the industry and the climate problem demands.

This architecture is the roadmap’s answer to the political economy of the transition: the technology is ready and the industry is willing, but the price signals, the standards and the finance must be aligned, and the alignment is a task of policy as much as of engineering.

10. The Action Plan to 2030 and the Milestones

The roadmap translates the vision into an action plan with explicit milestones to 2030, the decade whose decisions lock in the emissions of 2050. The milestones of the plan include:

• The efficiency floor: the universal deployment of the best available thermal and electrical efficiency on every new plant and every major retrofit, closing the gap between the world average and the best practice.
• The fuel and clinker agenda: the sustained growth of the alternative fuel substitution and the reduction of the clinker factor toward the roadmap range, supported by the standards modernisation and the SCM quality systems.
• The capture demonstrations: the commercial-scale demonstrations of the oxyfuel, the calcium looping and the post-combustion capture in the cement industry, so that the cost and the reliability data exist when the deployment wave begins.
• The novel materials programme: the validation and the standardisation of the calcined clay and the other low-carbon binders, bringing the new products to the market acceptance and the specification status.
• The policy environment: the establishment of the carbon pricing, the standards and the finance instruments in the major producing regions, and the international frameworks that carry the technology to the emerging markets.

The milestone logic is the roadmap’s discipline: every milestone is measurable, dated and assigned, and the reviews of the progress are the mechanism by which the industry and its partners hold themselves to the pathway. The action plan is not a forecast but a commitment, and the roadmap’s own framing makes the consequence explicit: the decisions of this decade decide whether the 2050 target is reached or missed.

11. The Role of Concrete and the Demand Side

The roadmap does not confine itself to the production side, because the demand side of the concrete economy participates in the transition. The demand-side agenda of the roadmap includes:

• Material efficiency in construction: the design that uses less concrete per building (the optimised sections, the high-strength grades, the reuse of the structures) reduces the cement demand without reducing the service; the roadmap treats the demand-side savings as a legitimate part of the least-cost pathway.
• Concrete durability and service life: the concrete that lasts twice as long halves the cement needed over the century; the durability agenda (the mix design, the protection, the maintenance) is therefore a carbon agenda.
• The urban planning dimension: the compact cities, the public transport and the building stock strategies shape the construction demand of the coming decades, and the roadmap positions the cement industry within that broader urban transition.
• The CO2 uptake of concrete: the recarbonation of the concrete structures over their lives reabsorbs a fraction of the process emissions, and the roadmap acknowledges the accounting of this uptake in the lifecycle view of the product.

The demand-side treatment completes the roadmap’s logic: the transition is not only a question of how the cement is made but also of how the concrete is designed, used and maintained, and the least-cost pathway draws on both sides of the equation.

12. Frequently Asked Questions

Why can the cement industry not simply switch to renewable energy?

Because roughly half to two-thirds of the direct CO2 emissions of a cement plant are not energy emissions: they are the process emissions of the calcination reaction, the release of the CO2 from the limestone itself when it converts to lime. No fuel switch or renewable power can remove those chemical emissions, which is why the roadmap’s long-term pathway depends on the carbon capture technologies for the process stream.

What is the roadmap’s 2050 target in plain numbers?

The direct CO2 emissions of the cement industry fall by 24 percent below the current levels by 2050 while the cement production grows by about 12 percent over the same period. In intensity terms, the emissions per tonne of cement fall from roughly 0.6 tonnes of CO2 toward about 0.4 tonnes, combining the four levers of the pathway.

Which lever is the most powerful?

Per tonne of material, the reduction of the clinker-to-cement ratio is the most powerful of the conventional levers, because each tonne of clinker avoided removes both the calcination CO2 and the fuel CO2 of that tonne. Over the full pathway, however, the carbon capture technologies carry the largest share of the reduction toward 2050, because only capture addresses the process emissions of the remaining clinker.

What are the four levers of the roadmap?

The four levers are: improving energy efficiency (thermal and electrical); switching to alternative fuels (waste and biomass, raising the thermal substitution rate); reducing the clinker-to-cement ratio (slag, fly ash, limestone, calcined clays); and deploying the emerging and innovative technologies, above all the carbon capture, use and storage and the novel low-carbon binders.

What is the alternative fuel thermal substitution rate and where does it stand?

The thermal substitution rate is the share of the kiln’s thermal energy supplied by the alternative fuels instead of the fossil fuels. The global average remains in the range of 5 to 10 percent, while the leading European industries reach 50 to 70 percent and beyond; the roadmap’s pathway grows the global average substantially through the period to 2050, bounded by the availability and the quality of the waste streams.

Which carbon capture technologies suit the cement industry?

The three leading families are the post-combustion capture (the solvent processes retrofitted to the existing plants), the oxyfuel combustion (the kiln burning in oxygen to produce a concentrated CO2 stream, the leading option for the new lines) and the calcium looping (the lime sorbent cycle with the natural synergy to the cement raw meal). The captured CO2 is then used or stored geologically.

13. Conclusion and Summary

The low-carbon transition in the cement industry, as framed by the IEA-CSI Technology Roadmap, is a managed, quantified transformation: the direct CO2 emissions fall by 24 percent below the current levels by 2050 against a 12 percent growth of the production, combining four levers in a least-cost pathway. The energy efficiency lever closes the gap between the world average and the best available technology; the alternative fuel lever raises the thermal substitution rate toward the levels the leading regions already achieve; the clinker-to-cement ratio lever replaces the clinker with the slag, the fly ash, the limestone and the calcined clays; and the innovative technology lever brings the carbon capture, use and storage and the novel binders to the market from the 2030s onward, because the calcination process emissions can be removed by no other means.

The roadmap is equally explicit about the non-technical pillars: the carbon pricing, the standards and the public procurement, the investment and the finance, and the international collaboration that carries the technology to every producing region. The action plan to 2030 sets the milestones (the efficiency floor, the fuel and clinker agenda, the capture demonstrations, the novel materials programme and the policy environment) whose outcomes decide the 2050 target, and the demand-side agenda of the material-efficient and durable concrete completes the least-cost picture. The transition is ambitious, practical, realistic and achievable with a supportive regulatory framework, and the full document, with its data, its modelling and its action plan, is available in the Complete Cement Technical Package for every engineer and manager engaged in the decarbonisation of the industry.

This file is part of the Complete Cement Technical Package (931 files) available from cementequipment.org. Respective rights holders; library copy for the licensed single user.