Innovation & Technology

New Partnerships, Processes Aim to Slash Concrete’s Climate Impacts

UNIDO and the GCCA have partnered to decarbonize the cement and concrete industry, with a strong focus on the Global South; while Cambridge researchers have developed a potentially game-changing cement-recycling process.

Published 5 months ago | About a 8 minute read

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UNIDO, GCCA partner to decarbonize concrete industry around the globe

Image credit: Rodolfo Quirós

The UN’s Industrial Development Organisation (UNIDO) has partnered with the Global Cement and Concrete Association (GCCA) to work on decarbonizing the cement and concrete industry, with a strong focus on the Global South.

UNIDO supports its 172 Member States with economic and industrial development, in line with the UN’s Sustainable Development Goals (SDGs). With its long-standing experience in renewable-energy projects and the application of clean-energy technologies in industry, UNIDO successfully collaborates with a wide range of partners globally to support industries on their pathway to net-zero emissions.

The GCCA is the cement and concrete industry’s main membership body — representing 80 percent of cement production outside of China, as well as several leading Chinese manufacturers. It is leading the industry’s decarbonization work, through delivery of the GCCA 2050 Roadmap for Net-Zero Concrete.

Cement and concrete are essential materials — vital for modern infrastructure including homes, hospitals, bridges, tunnels, roads and so much more. But their manufacture and wide use (concrete is the most used material on earth after water) account for around 7 percent of the world’s CO2 emissions.

In early 2022, the GCCA launched its Net-Zero Roadmap Accelerator initiative, to help national cement and concrete industries decarbonize in line with the GCCA’s 2050 Net Zero Global Industry Roadmap. It was start of the national and regional phase of the GCCA’s 2050 Net Zero Global Roadmap, which emphasizes the importance of local action and policymaking to help the cement and concrete industry achieve its decarbonization commitments.

While the GCCA 2050 Roadmap was a global commitment, many of the levers need to be implemented on a country or regional basis. Under the accelerators, the GCCA is working with local industry and policymakers to identify the local levers and challenges and recommending key actions. The first phase of the Accelerator program includes focus across the Global South to help decarbonization progress where building and infrastructure needs have been called the most pressing — national roadmaps and government dialogues are taking place in Egypt, India, Thailand and Colombia.

“Through our Net-Zero Roadmap and the Accelerator program, we are already working with policymakers, governments and industry to overcome procurement and resourcing challenges across the Global South,” said GCCA CEO Thomas Guillot. “Having this groundbreaking agreement with UNIDO is a natural progression, which we hope will fast-track progress in a meaningful way.”

The partnership agreement includes pledges to:

provide recommendations for decision-makers to create the right market environments for the development of low- and near-zero-emissions cement and concrete
develop innovative technological solutions to help meet net-zero commitments
organize joint international industry and government events
jointly author and publish documents, recommendations and research tools
identify promising companies and innovative solutions and showcase these at relevant events and in publications.

“Decarbonizing the cement and concrete sectors worldwide is essential to reducing CO2 emissions and tackling climate change,” said UNIDO Director General Gerd Müller. “The GCCA and its members are leading the way on doing so for this important global industry. Our UNIDO Member States face a number of technical, market-related and policy hurdles that make decarbonization commitments even more challenging. That is why I am very glad to sign this Memorandum of Understanding with the GCCA and start a new phase of closer cooperation that will help our Member States overcome those challenges."

Cambridge cement-recycling method could help solve one of the world’s biggest climate challenges

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Meanwhile, researchers from the University of Cambridge have developed a method to produce very low-emission concrete at scale — an innovation that could be transformative in the transition to net zero.

The method, which the researchers say is “an absolute miracle,” uses the electrically powered arc furnaces used for steel recycling to simultaneously recycle cement — the carbon-hungry component of concrete.

A scalable, cost-effective way of reducing concrete emissions while meeting global demand is one of the world’s biggest decarbonization challenges. A growing number of startups are developing much lower-impact solutions based on alternative materials, some that even absorb carbon; and a 2023 McKinsey report asserts that circular models for production and reuse of concrete and cement could produce €110 billion in net value and avoid or mitigate two billion tons of CO₂ emissions by 2050.

Exploring the circularity angle, the Cambridge researchers found that used cement is an effective substitute for lime flux, which is used in steel recycling to remove impurities and normally ends up as a waste product known as slag. But by replacing lime with used cement, the end product is recycled cement that can be used to make new concrete.

The Cambridge cement-recycling method — supported in part by Innovate UK and the Engineering and Physical Sciences Research Council (part of UK Research and Innovation) and reported in the journal Nature — does not add any significant costs to concrete or steel production and significantly reduces emissions from both concrete and steel, due to the reduced need for lime flux.

Recent tests carried out by the Materials Processing Institute, a partner in the project, showed that recycled cement can be produced at scale in an electric arc furnace (EAF) — the first time this has been achieved. Eventually, this method could produce zero-emission cement, if the EAF was powered by renewable energy.

“We held a series of workshops with members of the construction industry on how we could reduce emissions from the sector,” said Professor Julian Allwood from Cambridge’s Department of Engineering, who led the research. “Lots of great ideas came out of those discussions, but one thing they couldn’t or wouldn’t consider was a world without cement.”

Conventional concrete is made from sand, gravel, water and cement — which serves as a binder. Although it’s a small proportion of concrete, cement is responsible for almost 90 percent of concrete emissions. Cement is made through a process called clinkering, where limestone and other raw materials are crushed and heated to about 1,450°C in large kilns. The process converts the materials into cement, but releases large amounts of CO₂ as limestone decarbonates into lime.

“I had a vague idea from previous work that if it were possible to crush old concrete, taking out the sand and stones, heating the cement would remove the water, and then it would form clinker again,” said first author Dr. Cyrille Dunant, also from the Department of Engineering. “A bath of liquid metal would help this chemical reaction along, and an electric arc furnace — used to recycle steel — felt like a strong possibility. We had to try.”

The clinkering process requires heat and the right combination of oxides, all of which are in used cement, but need to be reactivated. The researchers tested a range of slags, made from demolition waste and added lime, alumina and silica. The slags were processed in the Materials Processing Institute’s EAF with molten steel and rapidly cooled.

“We found the combination of cement clinker and iron oxide is an excellent steelmaking slag because it foams and it flows well,” Dunant said. “And if you get the balance right and cool the slag quickly enough, you end up with reactivated cement without adding any cost to the steelmaking process.”

The cement made through this recycling process contains higher levels of iron oxide than conventional cement, but the researchers say this has little effect on performance.

The Cambridge Electric Cement process is scaling rapidly, and the researchers say they could be producing one billion tonnes per year by 2050 — which represents roughly a quarter of current annual cement production. The researchers have filed a patent on the process to support its commercialization.

“Producing zero-emission cement is an absolute miracle, but we’ve also got to reduce the amount of cement and concrete we use,” Allwood stated. “Concrete is cheap, strong and can be made almost anywhere; but we just use far too much of it. We could dramatically reduce the amount of concrete we use without any reduction in safety, but there needs to be political will to make that happen.

“As well as being a breakthrough for the construction industry, we hope that Cambridge Electric Cement will also be a flag to help the government recognize that the opportunities for innovation on our journey to zero emissions extend far beyond the energy sector.”