How to decarbonize concrete and build a better future

[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.

Cutting clinker’s carbon footprint

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.

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.

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.

Cleaner codes

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.

Solution lies in collaboration and 'co-opetition' across the value chain

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.

Building techniques and codes need to evolve, which will require action by both policymakers and the private sector to address regulations and industry norms.

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.

Private and public sectors need to hit the dance floor hand in hand

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 com

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