Scientists at Cambridge University have pioneered a groundbreaking method to recycle cement from demolished concrete buildings, significantly advancing the production of zero-carbon cement. This innovative technique hinges on the reactivation of old cement through high temperatures, utilizing heat from electric arc furnaces commonly employed in steel recycling. This not only recycles cement but also curtails the carbon footprint associated with traditional cement production methods.
Cement is ubiquitous in modern construction and is the most utilized material globally after water. However, its production is one of the major contributors to greenhouse gas emissions, accounting for approximately 7.5% of human-made CO2 emissions. This is primarily due to the energy-intensive process of heating limestone to about 1600 Celsius in kilns powered by fossil fuels, which emits a significant amount of CO2. By adopting electric-powered furnaces and sourcing energy from renewable resources like wind and solar, the Cambridge team’s process completely eliminates the release of greenhouse gases, making a substantial leap towards zero-carbon cement.
The chemistry involved in reactivating cement is already well-established and has been previously executed at scale within cement kilns. The Cambridge team’s breakthrough lies in their method of leveraging the residual heat from steel recycling processes. Typically, steel recycling involves adding chemicals to molten metal to prevent oxidation, resulting in a byproduct called slag, which remarkably shares a similar composition with used cement. This discovery has enabled the effective reuse of slag in the production of high-grade Portland cement, dubbed “electric cement” by the researchers.
This new method of producing zero-carbon cement was demonstrated at a small-scale electric arc furnace at the Materials Processing Institute in Middlesbrough, with the BBC documenting the production of the first batch of this innovative cement. The lead scientist, Cyrille Dunant, emphasized the dual benefits of this method: producing zero-carbon cement and reducing the pollution associated with steel recycling. This is because the electric arc furnace operates on electricity that can be sourced from renewable energy, thus decarbonizing the entire cement-making process.
Mark Miodownik, Professor of Materials and Society at University College London, hailed the Cambridge team’s approach as “genius.” He highlighted the potential for this method to disrupt the cement industry, which is currently dominated by unsustainable practices. If scalable and profitable, this technique could significantly reduce global emissions. Looking forward, a Spanish company, Celsa, plans to replicate this process in a full-scale electric arc furnace in Cardiff, potentially scaling the production to meet a quarter of the UK’s cement demand.
The implications of this technology are far-reaching. As the use of electric arc furnaces is anticipated to rise, the potential for producing more zero-carbon cement increases, which could drastically reduce the cement industry’s impact on climate change globally. This innovative recycling process not only addresses the emissions from cement production but also enhances the sustainability of steel manufacturing, showcasing a remarkable example of industrial symbiosis.