‘Cement recycling method could help solve one of the world’s biggest climate challenges’
(Photo: University of Cambridge/YouTube)
May 22, 2024 – Researchers from the University of Cambridge have developed a method to produce concrete with very low emissions on a large scale.
Concrete is the second-most-used material on the planet, after water, and is responsible for approximately 7.5% of total CO₂ emissions. A scalable, cost-effective way of reducing concrete emissions while meeting global demand is one of the world’s biggest decarbonisation challenges.
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 % 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. This process converts the materials into cement, but releases large amounts of CO₂ as limestone decarbonates into lime.
The Cambridge Electric Cement process begins with concrete waste from demolition of old buildings. This is crushed, to separate the stones and sand that form concrete from the mixture of cement powder and water that bind them together. The old cement powder is then used instead of lime-flux in steel recycling.
The cement recycling method developed by the Cambridge researchers 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.
According toe the researchers their process will be able to produce one billion tons annually by 2050, approximately a quarter of the current annual cement production.
This work was published on May 22 in Nature under the title ‘Electric recycling of Portland cement at scale’.
