Authors and contributors
Araceli Fernandez Pales
Pharoah Le Feuvre
IEA (2019), "Tracking Industry", IEA, Paris https://www.iea.org/reports/tracking-industry-2019
Reducing CO2 emissions while producing enough cement to meet demand will be very challenging, especially since demand growth is expected to resume as the slowdown in Chinese activity is offset by expansion in other markets.
Key strategies to cut carbon emissions in cement production include improving energy efficiency, switching to lower-carbon fuels, reducing the clinker-to-cement ratio and advancing process and technology innovations. The latter two contribute the most to direct emissions reductions in the Sustainable Development Scenario (SDS).
Demand for cement in the construction industry drives production, and thus it is an important determinant of cement subsector energy consumption and CO2 emissions.
Initial estimates suggest that cement production returned to 4.1 gigatonnes (Gt) globally in 2018, a 1% increase following annual declines of 1% during 2014‑17.
China is the largest producer of cement, accounting for close to 60% of global production, followed by India at 7%.
Without efforts to reduce demand, annual cement production is expected to grow moderately to 2030. Production is likely to decline in China in the long term, but increases are anticipated in India, other developing Asian countries and Africa as these regions develop their infrastructure.
Adopting material efficiency strategies to optimise the use of cement would help reduce demand along the entire construction value chain, helping to cut CO2 emissions from cement production.
Lower cement demand can be achieved through actions such as optimising the use of cement in concrete mixes, using concrete more efficiently, minimising waste in construction, and maximising the design life of buildings and infrastructure. Material efficiency efforts have gained increasing support in recent years.
Globally, the energy intensities of thermal energy and electricity have continued to gradually decline as dry-process kilns – including staged preheaters and precalciners (considered state-of-the-art technology) – replace wet-process kilns, and as more efficient grinding equipment is deployed.
The thermal energy intensity of clinker is estimated to have fallen to 3.4 GJ/t on average globally in 2017, representing an annual decrease of 0.4% since 2014.
Fossil fuels continue to provide the majority of energy in the cement sector, with alternative fuels such as biomass and waste accounting for only 6% of thermal energy used in 2017.
In the SDS, the thermal energy intensity of clinker production declines by 0.5% per year to a global average of 3.2 GJ/t of clinker, and the electricity intensity of cement production falls by 0.5% to 85 kWh per tonne of cement.
Progress is particularly needed in the Eurasian region (Russia and the Caspian countries), which has the highest thermal energy intensity of clinker production (5.4 GJ/t), primarily due to the continued use of wet-process kilns. (Beyond process technology choice, regional factors affect the thermal intensity of clinker, such as moisture content and burnability of raw materials, typical clinker composition and average capacity of cement plants.)
The share of alternative fuels increases to 18% by 2030 in the SDS. There is considerable regional variation, with the European Union accounting for almost 50% of the share.
Clinker is the main ingredient in cement, and the amount used is directly proportional to the CO2 emissions generated in cement manufacturing, due to both the combustion of fuels and the decomposition of limestone in the clinker production process.
From 2014 to 2017, the clinker-to-cement ratio increased moderately by 0.5% per year, reaching 0.66 in 2017; this rise was the main reason for the increase in direct CO2 intensity of cement over the period.
Although China has one of the lowest clinker-to-cement ratios globally, a local shortage of other cementitious materials caused China's clinker-to-cement ratio to rise from 0.57 to 0.60 during 2014‑17, driving the global increase.
In the SDS, the clinker-to-cement ratio falls to a global average of 0.64 by 2030 owing to greater use of blended cements and clinker substitutes, including industrial by-products such as blast furnace slag and fly ash.
In the long term, however, alternative clinker replacements that are widely available – such as calcined clay in combination with limestone – will become more important, as the decarbonisation of power generation as well as iron and steelmaking will reduce the availability of these industrial by-products.
CCUS will be crucial to reduce cement sector CO2 emissions, particularly the process emissions released during limestone calcination. While current commercial deployment of CCUS is limited, there have been a number of innovation efforts underway in recent years, including:
- Between 2013 and 2016, chemical absorption, the most advanced post-combustion CO2 capture technology, was successfully trialled in a cement plant in Brevik, Norway, and became operational in a cement plant in Texas, United States.
- In Dania, Denmark, oxy-fuel capture was successfully piloted in a kiln precalciner. A first demonstration project of oxy-fuel capture technologies is planned in Europe, but funding uncertainty makes realisation unlikely before 2020. Carbon capture technologies other than post-combustion and oxy-fuel are also being explored.
- Direct separation, which captures process CO2 emissions by applying indirect heating in the calciner, is being piloted at a cement plant in Belgium (2017‑20).
- The CLEANKER project is developing pre-commercial demonstration of a calcium looping carbon capture process at a cement plant in Vernasca, Italy.
To be on track to achieve SDS decarbonisation, oxy-fuel carbon capture technologies in cement production should be demonstrated at commercial scale by 2030. It will also be necessary to gain experience in large-scale post-combustion capture technologies.
Alternative binding materials could also be key to reduce cement production emissions, particularly process emissions. They rely on raw materials or mixes different from those of ordinary Portland cement (OPC) clinker, and are currently at various stages of development.
Several alternative binding materials are currently commercially available, although their use so far has been relatively limited to niche applications.
Barriers to wider market deployment are related to technology and raw material costs, technical performance, range of possible market applications and standardisation levels for the materials. Continued innovation could further develop and advance opportunities to deploy these materials.
Other innovative processes also offer cement decarbonisation potential. The European Cement Research Academy has established a pre-competitive research project dedicated to energy-efficient grinding in the cement industry, which involves equipment suppliers and other cross-sectoral stakeholders.
In Sweden, cement producer Cementa (a subsidiary of Heidelberg Cement) and energy producer Vattenfall are working together on the CemZero project to explore opportunities to electrify cement production (Cementa, 2019; Bioenergy International, 2019).
Electrifying production would reduce emissions by using low-emissions electricity and by facilitating the capture of process CO2 emissions (i.e. emissions from limestone decomposition during clinker production).
The feasibility study, completed in early 2019, showed that electrified cement production is technically possible and likely cost-competitive with other options to substantially reduce emissions. The next step will be an in-depth study on how to construct a pilot plant.
Policy and private sector efforts are facilitating reductions in energy use and emissions in key cement-producing economies.
- As part of its 13th Five-Year Plan (2016-20), China aims to reduce the thermal energy intensity of clinker production to 3.07 GJ/t clinker on average by 2020, which would shrink the gap between the current level and best available technology thermal energy performance by two-thirds.
- Between 2011 and 2015, 85 cement plants in India participated in the first cycle of Perform, Achieve, Trade (PAT), a market-based mechanism to improve energy efficiency. They achieved energy demand reductions equivalent to 9% of India’s 2014 cement sector energy consumption, and the cement sector is now involved in the second PAT cycle, with higher targets and coverage.
- In Europe, the mandate to develop cement standards within the European Committee for Standardisation was recently widened to allow possible low-carbon alternatives to OPC clinker that rely on different raw materials or mixes.
- In 2015 in the private sector, 18 key cement companies developed the shared objective to reduce their CO2 emissions by 20-25% from the business-as-usual level by 2030, equivalent to 1 GtCO2.
Nevertheless, further policy efforts across all countries will be required to achieve necessary cement sector decarbonisation.
Decarbonisation of the cement sector is challenging due to the relatively few emissions mitigation options currently available and the limited economic incentives to reduce emissions in the absence of strong carbon pricing policies.
Energy efficiency can be accelerated through collaborative efforts among industry, public sector and research partners to share best practices on state-of-the-art technologies and to develop plant-level action plans that would increase the speed and scale of technology deployment.
Ensuring efficient equipment operation and maintenance would also help guarantee optimal energy performance, as would the use of energy management systems.
Furthermore, ensuring efficient equipment operation and maintenance will help guarantee optimal energy performance. This can be reinforced by implementing energy management systems.
The cement industry can also take advantage of opportunities for industrial symbiosis – including using the waste or by-products from one process to produce another product of value – to help close the material loop, reduce energy use and reduce emissions in the case of carbon capture and utilisation.
Examples include using steel blast-furnace slag in cement production and waste from other industries as alternative fuels for cement production.
Greater uptake of alternative fuels can be facilitated by redirecting waste from landfills to the cement sector and by co‑ordinating the supply of sustainably sourced biomass across sectors to enable cost-competitive access for the cement sector.
Accelerating innovation and deployment of innovative low-carbon technologies – particularly CCUS and alternative binding materials – will be key to reduce cement production emissions after 2030; RD&D over the next decade is therefore imperative.
Increased support for RD&D is needed from governments and financial investors, particularly to advance the large-scale demonstration and deployment of technologies that have already shown promise.
Private-public partnerships can help, as can green public procurement, which generates early demand and can enable producers to gain experience and bring down costs.
Government co‑ordination of stakeholder efforts can also direct focus to priority areas and avoid overlap.
Governments may also need to develop or modify regulations to facilitate technology uptake. For example, shifting from prescriptive to performance-based design standards (e.g. within building codes) would stimulate uptake of lower-carbon blended cements and cements that include alternative binding materials.
Policy makers can promote CO2 emissions reduction efforts by adopting mandatory reduction policies, such as a gradually increasing carbon price or tradeable industry performance standards that require average CO2 intensity for production of each key material to decline across the economy and permit regulated entities to trade compliance credits.
Adopting these policies at lower stringencies within the next three to five years will provide an early market signal, enabling industry to prepare and adapt as stringency increases over time. It can also help reduce the costs of low-carbon production methods, softening the impact on cement prices in the long term.
Complementary measures may be useful in the short to medium term, such as differentiated market requirements, that is, a government-mandated minimum proportion of low carbon cement in targeted products.
While a considerable proportion of cement production is not exposed to cross-border competition, measures may be needed to help ensure the competitiveness of domestic industries and prevent carbon leakage if the strength of policy efforts differs considerably from one region to another.
Examples include time-limited measures to ease transition, such as declining free allocation of permits, or novel measures to apply emissions regulations on the lifecycle emissions of end-products rather than directly on materials production. The latter could potentially be used to apply border carbon adjustments, provided that they are implemented in line with international trade rules.
Governments can extend the reach of their efforts by partaking in multilateral forums to facilitate low-carbon technology transfer and to encourage other countries to also adopt mandatory CO2 emissions policies.
Improving the collection, transparency and accessibility of cement subsector energy performance and CO2 emissions statistics would facilitate research regulatory and monitoring efforts (including, for example, multi-country performance benchmarking assessments).
Consistently-reported data covering a larger share of global production is especially needed, as reporting from some key regions is currently limited. Industry participation and government co‑ordination are both important to improve data collection and reporting.
Technology innovation will be crucial to reduce cement subsector emissions, particularly process emissions for which commercially available mitigation options are relatively limited. CCUS can play a key role, with post-combustion chemical absorption carbon capture currently the most advanced technology. Other capture options under development include oxy-fuel capture, membrane CO2 separation and calcium looping.
Processes are also being developed to utilise captured CO2 for inert carbonate materials in concrete aggregates. Alternative cement constituents, which can be blended into cement to replace a portion of the clinker, require further deployment. R&D is needed on alternative binding materials that rely on raw materials or mixes different from those of OPC clinker, and in many cases result in lower emissions.
Of the various alternative binding materials under development, belite calcium sulphoaluminate (BCSA) shows particular promise in terms of a reasonable balance between remaining technical hurdles and CO2 emissions reduction potential.
- Including a larger proportion of alternative constituents in cement (likely possible in the 15‑35% mass range – and potentially even up to 50%) reduces the quantity of clinker required as well as the process and energy-related CO2 emissions associated with clinker production.
- Using newer alternative cement constituents, such as ground limestone, calcined clay, volcanic ash, rice husk ash, and silica fume, will be increasingly important in the future because fly ash from coal power plants and granulated blast furnace slag from steel production – currently commonly used as alternative cement constituents – will likely become less available.
Technology principles: Clinker is the main active ingredient in cement, and producing it is the most emissions-intensive step of cement production. Alternative constituents are materials that can replace a portion of it while conserving the required performance properties of the cement. The resulting cement is commonly referred to as blended cement.
CO2 capture could produce capture yields of up to 95%, and widespread application would reduce clinker production process emissions, for which reduction options are limited.
- A number of CCS technologies are available for application in the cement sector, with the two most advanced being chemcial absorption post-combustion and oxy-fuel capture.
- In chemical absorption post-combustion capture, CO2 is separated from the clinker kiln exhaust gases using a chemical sorbent at the end of the production process. Due to high sorbent costs, however, additional thermal energy is required to regenerate the saturated sorbent to make it reusable, and electricity is also needed to operate the capture unit.
- In oxy-fuel capture, oxygen is separated from air prior to combustion, so that flue-gases are composed of mainly CO2 and water, making capture easier.
Using belite calcium sulphoaluminate (BCSA) clinker can result in process CO2 emissions 20‑30% lower than those of Ordinary Portland Cement (OPC) clinker.
Technology principles: Clinker is the main active ingredient in cement. During its production, calcination results in process emissions, which account for about two-thirds of cement production emissions. Using alternative binding materials that rely on raw materials or mixes different from OPC clinker can help reduce process emissions.
- Bioenergy International (2019), Vattenfall and Cementa proceed towards climate neutral cement with CemZero, https://bioenergyinternational.com/heat-power/vattenfall-and-cementa-take-the-next-step-towards-a-climate-neutral-cement.
- Bjerge, L-M. and P. Brevik (2014), "CO2 capture in the cement industry, Norcem CO2 capture Project (Norway)", Energy Procedia, No. 63, pp. 6455-6463.
- Carbonfree Chemicals (2017), "Capture harmful pollutants with Skymine", Carbonfree Chemicals, http://www.carbonfreechem.com/technologies/skymine.
- Cementa (2019), "CemZero – for a climate-neutral cement production", https://www.cementa.se/sv/cemzero.
- CLEANKER (2019), "Project contents", http://www.cleanker.eu/the-project/project-contents.
- ECRA (2017), Development of State of the Art-Techniques in Cement Manufacturing: Trying to Look Ahead, European Cement Research Academy, Düsseldorf, Germany.
- IEA GHG TCP (IEA Greenhouse Gas Technology Collaboration Programme) (2014), "Pilot plant trial of oxy-combustion at a cement plant", IEAGHG information paper 2014‑IP7, Cheltenham, UK.
- Gartner, E. and T. Sui (2018), "Alternative cement clinkers", Cement and Concrete Research, No. 114, pp. 27-39.
- LC3 (Limestone Calcined Clay Cement) (n.d.), "New cement blend to cut CO2 emissions by up to 30%", https://www.lc3.ch/new-cement-blend-to-cut-co2-emissions-by-up-to-30/.
- LEILAC (Low Emissions Intensity Lime & Cement project) (2017), LEILAC website, www.project-leilac.eu/.
- Perilli, D. (2015), "The Skyonic SkyMine: The future of cement plant carbon capture?", Global Cement Magazine, No. 5, Epsom, UKpp. 8-12.
- UN Environment (United Nations Environment programme) (2017), "Eco-efficient cements: Potential economically viable solutions for a low-CO2 cement-based materials industry", http://wedocs.unep.org/handle/20.500.11822/25281.
- USGS (United States Geological Survey) (2019), "Cement mineral commodity summary 2019", https://minerals.usgs.gov/minerals/pubs/commodity/cement/mcs-2019-cemen.pdf.
- USGS (2018), Cement Minerals Yearbook 2015, https://minerals.usgs.gov/minerals/pubs/commodity/cement/myb1-2015-cemen.pdf.
Claude Lorea (Global Cement and Concrete Association), Hidemi Nakamura (Taiheiyo Cement Corporation), Hugo Salamanca (IEA), Joe Ritchie (IEA), Marcela Ruiz de Chavez Velez (IEA)