World’s first process for making zero-emissions cement

The cement recycling method could help solve one of the world's biggest climate challenges.

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Concrete, the second-most-used material on the planet after water, accounts for approximately 7.5% of total anthropogenic CO₂ emissions. Despite current decarbonization efforts, such as substituting Portland clinker with supplementary materials and exploring alternative binders, concrete production still poses a significant environmental challenge.

To address this issue, researchers from the University of Cambridge have developed a groundbreaking method to produce very low-emission concrete at scale. This innovative approach recycles hydrated Portland cement – the carbon-intensive component of concrete – using electrically-powered arc furnaces originally used for steel recycling. This could be a transformative solution in the global effort to achieve net zero emissions.

The innovative research by Cambridge has discovered that used cement can effectively replace lime flux in steel recycling, eliminating the production of waste slag. This breakthrough process results in recycled cement that can be used to create new concrete.

The method developed by the researchers doesn’t increase the production costs of concrete or steel and notably reduces emissions from both industries due to decreased reliance on lime flux.

Tests conducted by the Materials Processing Institute have demonstrated the feasibility of producing recycled cement at scale in an electric arc furnace (EAF) for the first time. This method holds the potential to generate zero-emission cement if powered by renewable energy sources.

Reclaimed cement paste is combined with fresh material to create a flux that shields molten steel in an EAF from the atmosphere. This innovative process leads to the formation of a slag layer that, when cooled down, can be ground up and turned into cement clinker. This cement clinker is then used to produce fresh cement.

This patented process by Cambridge, known as ‘Cambridge Electric Cement’, has the potential to revolutionize cement production. By utilizing low-carbon power sources such as hydro and nuclear for the EAF, this cement could significantly reduce emissions and contribute to a sustainable, zero-landfill future.

With further development and the use of low-carbon power sources, this approach could lead to the creation of cement with minimal emissions and zero waste. This has the potential to revolutionize cement production, reduce the need for limestone mining, and eliminate the use of questionable additives like heavy metal-laden fly ash as filler for concrete.

Journal reference:

  1. 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

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