Total global CO2 emissions from the sector today are in excess of 2.5Gt. They are primarily direct CO2 emissions which in turn are primarily from the heated limestone itself (approx. 60%) and combustion of the fuels used in the cement kiln and other plant processes (approx. 40%). Electricity used by the sector contributes further CO2 emissions as shown. There are multiple levers that will be implemented to reduce CO2 emissions at different stages of the whole life of cement and concrete. Our roadmap process has evaluated the role that each of these levers will play to reach net zero. The global average is presented in the graph below. Across the world each lever will be implemented in accordance with local factors.
01 / Emissions from pure waste biomass and from the biogenic carbon content of mixed fuels is considered as climate neutral in accordance with the Greenhouse Gas Protocol
This includes CO2 reductions through use of decarbonated raw materials, energy efficiency measures, use of sustainable waste materials (“alternative fuels”) to replace fossil fuels and innovations such as use of hydrogen and kiln electrification.
Use of decarbonated raw materials to replace some of the limestone in the kiln reduces the total emissions from decarbonation of the limestone. By definition the decarbonated materials, such as the fine material from recycled concrete, do not emit CO2 when heated because they have already had the CO2 removed. Globally this is forecast to provide a 2% reduction in total emissions from the sector.
Thermal energy efficiency measures are already widely implemented across the globe through deployment of existing state-of-the-art technologies in new cement plants and retrofitting existing facilities. Further improvements will be made. With many newer energy efficient cement plants in emerging economies, this is an area where these regions have already made good progress.
It is to be noted that with an increase in use of alternative fuels, there can be a slight decrease in the thermal energy efficiency. Higher substitution rates of alternative fuels in combination with different parameters, for example burnability, higher moisture content, design and size of the plant, can typically result in a slight increase in thermal energy demand. This effect was taken into account in the forecasting.
Alternative fuels are derived from non-primary materials i.e. waste or by-products and can be biomass, fossil or mixed (fossil and biomass) alternative fuels.01 There are current examples of cement kilns operating with 100% alternative fuels which demonstrates the potential of this lever.
The industry is a well-established consumer of non-recyclable waste-derived alternative fuels from a range of sources, for example, municipal, agricultural, chemical and food production. The extremely high temperatures and residence times reached in cement kilns ensure these are managed in a safe and environmentally sound way. Supply chain logistics and infrastructure, permitting and waste policy to reduce/eliminate waste to land fill are required to support the industry in increasing their use of alternative fuels.
On average globally, alternative fuel use is forecast to increase from the current 6% to 22% and 43% by 2030 and 2050 respectively. Innovations such as use of hydrogen and kiln electrification are forecast to play a small role from 2040.
Utilisation of waste fuels in cement plants results – according to the Greenhouse Gas Protocol – in CO2 and even GHG emission reductions at landfills and incineration plants.
01 / Binder means all material in concrete such as cement, fly ash, ggbs, limestone fines etc. that is permitted as cementing material in the local jurisdiction
02 / Clinker is produced in a cement kiln and is ground to manufacture ordinary Portland cement. Clinker can be ground with other materials to produce cements with lower CO2 emissions
At the cement plant or the concrete plant, fly ash, ggbs, ground limestone and other materials can be added to deliver concretes with reduced CO2 emissions but still the required performance. In some applications the concrete performance is enhanced. This lever is also referred to as clinker02 substitution. In this roadmap it is described by clinker binder ratio.
Availability of suitable materials around the world varies now, and will into the future, because for example fly ash comes from coal fired power stations and ggbs from the steel industry’s blast furnaces and these industries are also transitioning.
In coming decades there will be increased use of ground limestone and the introduction of calcined clays to both compensate for reduced supply of fly ash and ggbs, and further reduce the clinker binder ratio. Calcined clays rely on clay deposits that are geographically spread and sufficiently abundant to meet projected demand.
Whilst availability of materials can be a limitation on clinker binder ratio, client acceptance is a current barrier in fully exploiting this lever in some developed and emerging economies.
On average globally, the clinker binder factor is currently 0.63. It is projected to reduce to 0.58 and 0.52 by 2030 and 2050 respectively. Regional and even country variations are inevitable due to differing material availability and market requirements.
Alternatives to Portland clinker cements have been the subject of much research but their impact is not forecast to be significant primarily because of fundamental lack of availability of raw materials at the scale required. Furthermore, they also come with CO2 emissions (about half of common cements).
On average globally it is forecast that alternatives to Portland clinker cements will be 1% and 5% of cement in 2030 and 2050 respectively and in 2050 contribute a 0.5% reduction in overall CO2 emissions.
In terms of concrete production, industrialisation is the key specific lever. Moving from small project site batching of concrete using bagged cement to industrialised processes offers significant CO2 emissions savings because of the adherence to mix specifications and quality control. In some emerging economies such as India, the vast majority of concrete production is currently on project sites. A transition to industrialised production has been seen in other countries.
More broadly utilisation of admixtures, improved processing of aggregates are good opportunities for CO2 emissions savings in concrete production. These savings have already been implemented by parts of the industry, but broader and deeper application will deliver further savings.
On average globally, optimisation of concrete production in terms of binder utilisation can lead to binder demand reductions of 5% and 14% in 2030 and 2050 respectively.
Is a new lever, and its contribution is forecast to only become significant beyond 2030 when commercial viability and necessary infrastructure have been established. Once captured the CO2 will be utilised within the cement and concrete industry, by other industries or stored.
Utilisation of captured CO2 within the cement and concrete industry includes injection into wet concrete, curing of hardened concrete and in the manufacturing of aggregates from waste products. Further development and expansion of all three of these uses of captured CO2 is underway.
See page 34 for a focus on carbon capture and utilisation/storage.
It is forecast by 2050 that 1370Mt CO2 will be captured and utilised/stored.
Across the globe over coming decades will result in emissions from generation of electricity used in cement and concrete production to be reduced to zero.
Demand for electricity from the sector will increase to 2030 in line with increased total production and to 2050 primarily due to electricity demand of carbon capture. This increase in demand is countered by decarbonisation of the electricity. International Energy Agency (IEA) global data has been used for 2020 and 2030 for forecasting the impact of grid decarbonisation over the next 10 years.
Reductions in CO2 emissions to 2030 are 54% compared with 2020, with 100% reduction to 2050.
01 / “CO2 uptake in cement containing products” www.ivl.se/co2-uptake-concrete
Is a natural process of CO2 uptake by concrete. It has been well understood by engineers and has been incorporated into engineering standards for decades. Only recently has it been considered in carbon accounting, most recently the IPCC 6th Assessment Report published in August 2021.
In this roadmap, tier 1 of the IVL methodology01 has been used. This permits a 20% value for recarbonation to be adopted, with this being applied to the theoretical maximum carbonation possible for a tonne of clinker (525kgCO2/tonne) i.e. 105kgCO2/tonne clinker. This is a lower bound conservative value within the IVL methodology.
From 2020 to 2050, the clinker binder ratio decreases (see savings in cement and binders). The reduced clinker per m3 of concrete, and total clinker volume globally results in a slight decrease in recarbonation over the coming decades.
This forecast is intentionally conservative because it is the first global roadmap to include recarbonation and work is still progressing on more detailed evaluation of recarbonation and efforts to enhance recarbonation through active exposure of crushed concrete to CO2 at end of life.
Global recarbonation is forecast as 319, 318 and 242 Mt CO2 in 2020, 2030 and 2050 respectively.
Can be achieved by applying many specific levers. These levers are able to be applied with current standards and regulations.
The primary means of unlocking design levers is ensuring that reduction of CO2 emissions becomes a design parameter in addition to the current parameters of quality, cost, speed and specific project client requirements.
Designers of buildings, with support of clients, can achieve CO2 emission reductions through their choice of concrete floor slab geometry and system, choice of concrete column spacing and optimisation of concrete strength/element size/reinforcement percentage. This can be achieved whilst still obtaining all the performance benefits of concrete construction. Infrastructure projects offer analogous opportunities.
Across all projects globally, the CO2 emissions reductions achievable through design and construction levers is forecast as 7% and 22% in 2030 and 2050 respectively.