Substitutes for clinker. Carbon capture, use and storage. Process electrification. New construction codes. All are vitally important for taking urgent action to cut the footprint of the most widely used manmade resource on Earth.
By Nancy Gillis & Annika Ramsköld
February 16, 2023
Concrete being poured at a construction site. Image via Shutterstock/Bannafarsai
[This article is part of a series by members of the First Movers Coalition. You can read more stories about the initiative here.]
Concrete is the most-consumed human-made resource on Earth, and the 14 billion cubic meters produced every year are projected to climb to 20 billion cubic meters by 2050, as human societies urbanize and demand for infrastructure grows. From bridges and hospitals to apartment blocks, offices and schools, concrete structures connect communities and shelter us as we work, study and sleep.
In the hands of skilful architects, concrete can create works of awe-inspiring beauty, such as Le Corbusier’s Chapelle Notre Dame du Haut, Mexico City’s Los Manantiales restaurant or Indonesia’s Merah Putih Bridge. For climate campaigners, however, concrete is one of the ugliest materials on the planet, because its manufacture is responsible for 7 percent of global carbon dioxide emissions.
So we urgently need to find ways to decarbonize the creation of cement — concrete’s key ingredient — if we are to limit global warming to 1.5 degrees Celsius. This article explores how investment in transformative, zero-carbon technologies can be ramped up, through global initiatives such as the World Economic Forum’s First Movers Coalition (FMC), which aims to harness the purchasing power of companies to decarbonize the “hardest-to-abate” industrial sectors responsible for a third of the world’s emissions.
Concrete’s popularity comes from its versatility. It can be poured and shaped into myriad forms, it’s highly durable when reinforced with steel, and it’s relatively cheap. The secret to its versatility lies in the binding capacity of the clinker that goes into cement. Clinker is made by roasting limestone to over 2,552 degrees Fahrenheit in kilns usually fueled by coal, natural gas or waste products from industrial fossil fuel use. The problem is, this process emits huge amounts of CO2, about 622 kilograms for every metric ton of cement produced.
Two routes to low-emissions cement show particular promise, each roughly halving clinker’s carbon footprint. One is to decarbonize the production of clinker, the other is to avoid using it altogether. Both processes will be needed, but right now, the technologies are at different stages of viability and each has its own obstacles to overcome. Let’s take a closer look.
Decarbonizing clinker requires roasting the limestone using alternative heat source such as electricity as a heat source instead of fossil fuels. New technology for this process includes plasma torches powered by renewable energy.
Another way to decarbonize clinker is to capture the CO2 emitted by its production, use it and/or store it safely in an inert form forever. This process — known as carbon capture, use and storage — is nascent, expensive and can be energy-intensive. That’s especially true if the flue gases captured during clinker production contains low concentrations of CO2 (15-20 percent) and to enrich that CO2, a lot of energy is required.
Innovations such as electrifying the clinker production or replacing air with oxygen in the combustion process can lead to a greater concentration of CO2 in flue gases. This cuts cost and makes the CO2 emissions more suitable for direct use in industrial processes, such as production of sustainable aviation fuel.
Avoiding clinker is another way for the sector to make progress on decarbonization, and it’s both a viable and effective short-term option. Clinker substitutes already exist including, conveniently, waste products from industrial fossil fuel use. Fly ash, a by-product of burning coal, is one such option. Another comes from the nasty molten muck left behind from iron-making, which dries into balls of waste known as ground and granulated blast furnace slag (GGBS). Using either option solves two problems — avoiding emissions from making clinker and consuming waste that is otherwise an environmental hazard.
The irony is that, as coal power fades and steel production turns greener, supplies of fly ash and GGBS will start to dry up. But there are other low-emissions alternatives to clinker.
For instance, calcined clay, a derivative of a naturally occurring material found across the world, especially in the Global South. Its location is significant, because cement and concrete manufacture is a very local process. The stuff is so heavy and expensive to move that most of it is sold within 150 miles of its production site. So having an abundant, alternative feedstock such as calcined clay could be a game changer, especially if you can source it in the geographies where concrete consumption is predicted to peak. Some estimates suggest that if this material became the dominant way to make cement, it could reduce the sector’s emissions by 30-40 percent.
Making cement using these clinker substitutes — known in the trade as supplementary cementitious materials (SCMs) — typically doesn’t cost much more than producing Ordinary Portland Cement (OPC). So why isn’t it happening at any scale? That word “Portland” is part of the problem. It’s the gold standard for cement, creating it requires clinker and it’s baked in to virtually every building code on the planet.
The engineers that write these codes, along with construction companies and their real estate clients, are typically risk-averse. And for good reason: No one wants buildings collapsing on their occupants. One concern is that SCMs might not perform as well as clinker. Another is that pouring and curing these new types of concrete onsite would take more skill and training. The status quo is hard to shift, but it’s completely incompatible with any net-zero pathway. Building techniques and codes need to evolve, which will require action by both policymakers and the private sector to address regulations and industry norms.
We noted earlier that the cement and concrete sector is very localized, because of the cost of moving around such a heavy, low-margin commodity. The sector is very different from, say, aluminium, where the handful of refineries and smelters needed to supply global demand can be decarbonized or shifted to areas with a wealth of renewable energy. To clean up cement, you need to meet the problem where you find it — at the local level, in the thousands of locations across the world where clinker is produced and used.
This is challenging for global businesses such as Vattenfall, a state-owned Swedish energy company and founding member of the FMC, which — given its science-based target to go net zero by 2040 — needs to source near-zero emissions concrete in all the local geographies where it operates. Vattenfall has taken a full value-chain approach towards decarbonizing cement production. This means having conversations with cement manufacturers, cement suppliers and the construction industry about the quickest pathways to scale-up transformative technologies.
Transparency and collaboration are vital to decarbonize emissions across the value chain. For Vattenfall, the goal is not incremental change that might halve the industry’s carbon footprint, it is transformative change to decarbonize cement production completely. A transparent, value-chain approach like this has several major advantages.
First, it helps partners to understand each other’s requirements and identify areas where they can work together and leverage each other’s assets and capabilities to find solutions and drive change.
Second, if all value-chain partners can align around the same goal of zero-emissions cement, that can send a powerful demand signal to cement producers and their investors that it’s worth manufacturing a product which, currently, can cost about twice as much as regular OPC.
Third, if all partners can align their demand for clean cement, this can help spread the risk of the green premium, so that no single actor bears an unreasonable proportion of the cost. To make such an approach work, it takes initiatives such as the FMC to bring the key value-chain players together — within all their various geographies — in an environment of coopetition that encourages openness and collaboration to find solutions that work for everyone.
Given the urgency to start decarbonizing heavy emitting sectors this decade, collaboration needs to be swiftly followed up with commitment. On the dancefloor of supply and demand, someone needs to make the first move, which is where the FMC comes in. For this sector, coalition members — whether construction and engineering firms or developers and architects — must commit to purchase or specify near-zero emissions cement for at least 10 percent of their annual volumes by 2030.
As part of its 10 percent commitment, Vattenfall is in the process of exploring potentially transformative, zero-emissions cement technologies being developed by both incumbent and startup producers. Vattenfall’s view is that, although the costs and risks of acting early are high, the risks of doing nothing are higher. Because once demand takes off, you want to be at the front of the queue in case supply needs time to catch up.
Take low-carbon steel, for example, another value chain in which Vattenfall is playing a lead role through its investment in hydrogen breakthrough ironmaking technology (HYBRIT). Swedish suppliers of fossil-free steel have seen a spectacular growth in demand for their product in recent years, despite a price premium of 20-25 percent, and similar demand is anticipated for near-zero cement.
Vattenfall predicts that the near-term trajectory of renewable energy supply will see a quadrupling of capacity from today to 2030, and the need to build infrastructure such as concrete foundations for wind farms will ensure ongoing demand for fossil-free cement. Furthermore, the right to build major new installations of renewables is granted through competitive public auctions, in which the sustainability of construction methods will become an increasingly decisive parameter.
But as we’ve seen, companies are only half the solution. Governments urgently need to join in. They have key roles to play in terms of revising building codes and setting clear requirements on the share of near-zero materials in public tenders and auctioning. Governments may offer greater incentives to unlock new technologies on a broad scale. Take CCUS. It can cost as much as $170 to remove and store one metric ton of CO2 from cement production, an enormous amount compared to the average price of $50-60 per metric ton for cement production in Europe. The Norwegian government is leading in this area. It has co-invested with Heidelberg Materials to construct the world’s first industrial-scale carbon capture facility at a cement plant, due to become fully operational in late 2024. Governments should also streamline the permit process for building CCUS plants, to accelerate the commercial viability of this technology.
Another role for governments to play given that state-funded infrastructure accounts for an estimated 40-60 percent of all global concrete sales is tied to their purchasing habits: We need more governments to send demand signals through public procurement targets for near-zero cement.
The World Economic Forum — in association with the Global Cement and Concrete Association and the Mission Possible Partnership’s Concrete Action for Climate initiative — has issued a call to action for policymakers to decarbonize the cement sector and is also working with the Clean Energy Ministerial’s Industrial Deep Decarbonisation Initiative (IDDI) to encourage governments to make the first public procurement commitments.
There are promising signs: France recently framed a policy to reduce emissions from cement production by 35 percent by 2030, while Japan has also released its own roadmap (Japanese). Canada has committed to co-lead the Breakthrough Agenda on Cement and Concrete. And China, which produces more than half the world’s cement, is planning to expand its emissions trading scheme to include the cement sector from 2023 or 2024 onwards. Meanwhile, President Joe Biden’s Inflation Reduction Act of August is a potential game changer for CCUS technology, offering a tax credit of up to $85 per metric ton of carbon dioxide captured and sequestered.
Cement is a building material of exceptional versatility, practicality and even beauty. But rather like the lead character in Oscar Wilde’s famous novel “The Picture of Dorian Gray,” despite its attractions, cement hides a dirty secret. If we are to create a more sustainable future that enables both developed and emerging markets to build the infrastructure they need to survive and thrive in the face of ever-greater climate impacts, we have no choice but to work together to decarbonize cement and concrete as an urgent priority.
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