Developing processes, methods, and solutions to produce concrete with low or zero CO2 emissions is crucial for achieving carbon neutrality by 2050, particularly in the construction sector and the cement industry.
After water, concrete is the most widely used material on Earth, with approximately 30 billion tonnesproduced annually [source: Towards Sustainable Concrete, Nature Materials].
This demand is increasing: global consumption is expected to rise from the current 14 billion cubic metres of concrete to around 20 billion cubic metres by 2050 [source: Global Cement and Concrete Association].
As the most commonly used construction material worldwide, concrete production accounts for approximately 8.6% of all anthropogenic CO2 emissions [source: Department of Civil and Environmental Engineering, University of California].
Given the urgency of achieving climate neutrality, industry and research are actively working to develop significantly less impactful solutions, especially considering the anticipated growth in the use of concrete and its primary component, cement. Cement demand is projected to increase by 14% between 2020 and 2030 and by a further 22% by 2050 [source: Making Net-Zero Concrete and Cement Possible – Mission Possible Partnership].
TAKEAWAYS
The industry’s focus on sustainable cement and concrete
The cement and concrete industries are targeting full decarbonisation by 2050. According to projections from the MPP Global Project Tracker, cited by the World Economic Forum, «if 45 low-emission cement plants are operational by 2030, the industry will be on track to keep global warming below 1.5°C».
Efforts to progressively and significantly reduce emissions start with products themselves. In 2020, companies within the Global Cement and Concrete Association (GCCA) – representing 80% of the global concrete industry, excluding China – committed to producing zero-emission concrete and achieving carbon neutrality across the sector by 2050. This ambition is outlined in the GCCA’s manifesto, Concrete Future.
To meet these goals, the industry must intensify its investments. McKinsey estimates that annual capital expenditure will need to nearly double, reaching $60 billion from 2021 to 2050 [source: Cementing Your Lead: The Cement Industry in the Net-Zero Transition].
Reducing emissions, however, is no easy task, largely due to the inherent nature of cement production. The process begins with the extraction of limestone, whose primary component is calcium carbonate (CaCO₃).After being mixed with clay, the limestone is heated in a rotary kiln at over 1,400°C to initiate calcination, a process responsible for significant CO₂ emissions.
Approximately 60% of these emissions come from limestone calcination, with the remaining 40% arising from clinker production, the base component used to manufacture Portland cement, the most common type of cement used in concrete production [source: CO₂ Capture in Cement Plants by “Tail-End” Calcium Looping – ScienceDirect].
The role of startups
Numerous solutions are being explored and implemented to create sustainable concrete and low-emission cement. As a recent example, two of the world’s top ten construction companies announced a $75 million investment last September in the startup Sublime Systems. Founded by an MIT professor and postdoc, the company has developed an electrochemical cement production method that, in initial tests, has achieved a 90% reduction in emissions.
Shortly before this, another U.S. startup, Frontera, secured $85 million in funding to scale its technology commercially. Frontera’s approach involves retrofitting existing cement production plants with technology that captures CO₂ emissions from traditional cement production and mineralises them to produce low-carbon, ready-to-use cement.
Similarly, Canadian startup CarbonCure has created a technology that enables concrete producers to inject captured CO₂ directly into fresh concrete during mixing. Once injected, the carbon dioxide reacts with the concrete mix, becoming permanently embedded as a mineral.
Reducing cement emissions: recent research trends
Research has long focused on generating sustainable concrete. A method recently developed by a team from the University of Cambridge employs electric arc furnaces (EAFs), commonly used in steel recycling, to recycle cement as well.
As detailed in their article published in Nature (Electric recycling of Portland cement at scale), the innovation involves replacing lime in the steel recycling process with reclaimed cement paste (RCP). Steel recycling typically occurs in two stages:
- scrap is melted and oxidised to remove impurities
- sulphur is eliminated
In both stages, cement is introduced as a fluxing material to protect steel from air exposure and enhance energy efficiency.
Currently, RCP is not widely available on a commercial scale. However, interest in this material is growing due to its potential use in carbon mineralisation processes.
The University of Cambridge team has founded a startup, Cambridge Electric Cement, to industrialise their method. They demonstrated that EAFs create optimal conditions to reactivate RCP extracted from old concrete waste, without interfering with steel production.
This process effectively recycles both steel and cement, producing circular, low-CO₂ cement while significantly reducing emissions in both industries. Additionally, it minimises the need for virgin lime as a fluxing agent. If powered by renewable energy, this method could achieve zero-emission cement production.
Cambridge Electric Cement recently completed a $2.2 million funding round to scale up its industrial production of circular, low-emission cement.
Possible pathways for low-emission cement and concrete
In Australia, efforts are underway to develop low-carbon concrete using locally sourced calcined clay. The process employs an electric kiln powered by renewable energy. The University of Technology Sydney, in collaboration with the SmartCrete Cooperative Research Centre and industry partners, is working to create, test, and optimise concrete mixes that incorporate calcined clay – one of Australia’s most abundant materials – as an alternative to ordinary Portland cement. This approach aims to reduce emissions while meeting the country’s construction standards.
In Saudi Arabia, a different strategy focuses on producing sustainable concrete without Portland cement. The King Abdullah University of Science and Technology (KAUST) is working with a startup to create a patented concrete capable of absorbing atmospheric CO₂ molecules. Instead of Portland cement, the process uses a binder derived from natural and recycled materials, including seawater. This binder hardens at room temperature, eliminating the energy-intensive clinker generation process.
In the United States, researchers at Princeton University are exploring natural materials to create low-carbon cement. Their work involves nacre-like composites inspired by the structure of mother-of-pearl, the inner layer of mollusc shells. Known for its exceptional fracture toughness, mother-of-pearl served as the model for a cement composite with remarkable structural properties. According to their study, published in Advanced Functional Materials (Tough and Ductile Architected Nacre-Like Cementitious Composites), the composite is 17 times more crack-resistant and 19 times more ductile than standard cement.
Another research stream focuses on using fly ash, a by-product of coal combustion in thermal power plants. Despite the global shift toward renewable energy, more than 2,400 coal-fired power plants remain operational worldwide, generating significant volumes of fly ash, over 1.2 billion tonnes in 2022 alone [source: RMIT University]. When incorporated into concrete production, fly ash reacts to improve the material’s properties and durability.
In Australia, scientists at the Royal Melbourne Institute of Technology (RMIT) are developing sustainable concrete that doubles the fly ash content used in traditional mixes. Their method includes the addition of nano-additives to alter the concrete’s chemistry, enabling the use of higher proportions of fly ash without compromising performance. In fact, the process enhances the material’s density and compactness. This approach is a significant improvement over current concrete mixes, which typically replace no more than 40% of cement with fly ash.
Producing sustainable and circular concrete: italian projects
In Italy, research into low-impact concrete production is advancing with notable projects.
One such initiative is CASA (Circular and Sustainable Concretes Enhanced with Recycled Materials from Local Supply Chains). Coordinated by the University of Parma, this project «aims to develop “green” cementitious materials incorporating waste from various production sectors in the Emilia-Romagna region. These include: Synthetic fibres from sports flooring, Ceramic waste from the ceramics industry, Gasbeton (aerated concrete) from construction, Agricultural by-products such as cattle manure and rice husks, Biochar from energy production».
Launched this year, CASA will run for 28 months, aiming to introduce new products to the market that combine industrial waste reuse with enhanced concrete performance.
Another critical challenge the project addresses is reducing construction and demolition waste, of which concrete is a major component. In Europe, nearly 375 million tonnes of such waste are generated annually, making it the largest single source of waste in the EU [source: European Environment Agency].
To tackle this, Certimac – a research and certification body founded by ENEA and CNR – has launched the Rewinds project (Recycling of Waste into New Demonstrated Sustainable Solutions). Rewinds is dedicated to developing high-performance sustainable materials derived from waste, by-products, and demolition debris, contributing to a more circular and sustainable construction industry.
Glimpses of Futures
Improving the properties of concrete, progressively and significantly reducing emissions, and ensuring its production is as circular as possible are key goals in the effort to decarbonise the world’s most widely used material for construction and infrastructure.
To anticipate possible future scenarios, we will use the STEPS matrix to explore the potential impacts of advancements in this field from social, technological, economic, political, and sustainability perspectives.
S – SOCIAL: the adoption of sustainable concrete can significantly contribute to reducing CO₂ emissions. This positive environmental impact would improve air quality, especially in densely populated urban areas. Efforts are also focused on enhancing the circularity of concrete production. Researchers from October 6 University and Al-Azhar University in Egypt have investigated the use of recycled aggregate and Portland slag cement in concrete production. By combining these materials with ordinary Portland cement, they demonstrated a significant improvement in the mechanical properties of reinforced concrete, along with environmental and structural benefits. Their findings are detailed in the article “Optimizing sustainable concrete mixes with recycled aggregate and Portland slag cement for reducing environmental impact”, published in Discover Materials.
T – TECHNOLOGICAL: developing low-emission concrete requires careful consideration of numerous factors, making the design process highly complex. Artificial intelligence (AI) techniques can play a crucial role in this endeavour. For instance, the study “Optimizing compressive strength in sustainable concrete: a machine learning approach with iron waste integration” demonstrates the potential of machine learning algorithms to predict the compressive strength of concrete. This approach allows for the optimisation of results and the identification of the ideal combination of elements in the mix, significantly enhancing performance and sustainability.
E – ECONOMIC: economically, the availability of sustainable concrete opens up significant international market opportunities. Reducing emissions in the construction sector is vital to achieving the carbon neutrality goals that many countries, including the EU and the USA, have set for 2050. The challenge is considerable, given that the sector accounted for 37% of global CO₂ emissions from operational energy and processes in 2022 [source: Global Status Report for Buildings and Construction – UNEP]. Interest in green concrete is expected to grow significantly in the coming years. The global market value, estimated at $39.17 billion in 2024, is projected to increase to $83.37 billion by 2032 [source: Market Research Future].
P – POLITICAL: the availability of low-impact concrete will enable compliance with increasingly stringent regulations aimed at reducing emissions in the building sector. For instance, the Energy Performance Buildings Directive (EU/2024/1275), updated this year, mandates a 60% reduction in greenhouse gas emissions in the construction sector by 2030 (compared to 2015 levels) and a fully decarbonised, zero-emission building stock by 2050. The ability to develop and mass-produce low- or zero-emission concrete is directly tied to the decarbonisation of the cement industry, a key player in energy-intensive and hard-to-abate sectors. At COP29, the Industrial Transition Accelerator coalition – launched by the UAE, the United Nations Framework Convention on Climate Change, and Bloomberg Philanthropies during the COP28 World Climate Action Summit – published an open letter urging governments to adopt proven policies to stimulate demand for eco-friendly products and maximise industrial decarbonisation potential. The UN estimates that these measures could unlock $1 trillion in investments and pave the way for over 500 green industrial facilities. The letter also highlights that one-third of global emissions stem from heavy industry and transport, with cement plants being a significant contributor.
S – SUSTAINABILITY: the most critical impact of sustainable concrete will be its contribution to environmental sustainability. To mitigate climate change, it is essential to reduce CO₂ and other greenhouse gas emissions. Low-impact raw materials, combined with greener and more circular processes, will facilitate the decarbonisation of the construction supply chain, significantly advancing global sustainability goals.
