The world's first process for making zero emissions cement

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. Concrete is the second-most-used material on the planet, after water, and is responsible for approximately 7.5% of total anthropogenic CO₂ emissions. A scalable, cost-effective way of reducing concrete emissions while meeting global demand is one of the world’s biggest decarbonisation challenges. The cement recycling method developed by the Cambridge researchers, 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 in Teesside, 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. 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. Over the past decade, scientists have been investigating substitutes for cement, and have found that roughly half of the cement in concrete can be replaced with alternative materials, such as fly ash, but these alternatives need to be chemically activated by the remaining cement in order to harden. The research was supported in part by Innovate UK and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Reference: Cyrille F Dunant, Shiju Joseph, Rohit Prajapati, Julian M Allwood. ‘Electric recycling of Portland cement at scale.’ Nature (2024). DOI: 10.1038/s41586-024-07338-8