![](https://ichef.bbci.co.uk/news/480/cpsprodpb/f555/live/fe3a7d40-1760-11ef-baa7-25d483663b8e.jpg.webp)
Justin Rowlett,BBC Climate Editor , @BBCJustinR
![Getty Images Pollution from cement factories along the Yangtze River in China.](https://ichef.bbci.co.uk/news/480/cpsprodpb/ad90/live/b658ab70-181c-11ef-91fc-5d1a434f5e40.jpg.webp)
Scientists say they have found a way to recycle cement from demolished concrete buildings.
Cement is the most common building material in the modern world, but it is also a large contributor to global warming gas emissions.
This is because chemical reactions occur when fossil fuels are burned to heat limestone to high temperatures.
Recycling cement can significantly reduce carbon emissions. Researchers say switching to electric furnaces and using renewable energy such as wind and solar rather than fossil fuels could result in zero greenhouse gas emissions.
And that's going to be a big thing. Cement forms the foundation of the modern economy, both literally and figuratively.
It serves to bind the sand and aggregate in concrete together, and concrete is the most widely used material on Earth after water.
It is also a major cause of climate change. If cement were a country, it would be the third largest source of emissions, after China and the United States, accounting for 7.5% of human-made CO2.
The problem is the inherent contaminant chemistry of the material.
It is made by heating limestone to 1600 degrees Celsius in huge kilns using fossil fuels.
These emissions are just the beginning. Heat is used to remove carbon dioxide from the limestone, leaving behind a cement residue.
It is estimated that these two pollutants combined produce approximately 1 ton of carbon dioxide per ton of cement.
A team of scientists at the University of Cambridge has found a neat way to avoid these emissions.
This takes advantage of the fact that spent cement can be reactivated by re-exposing it to high temperatures.
The chemistry is well established and carried out on a large scale in cement kilns.
The breakthrough is proving that this is possible by piggybacking on the heat generated by another heavy industry: steel recycling.
When recycling steel, chemicals floating on the surface of the molten metal are added to prevent the molten metal from reacting with air and creating impurities. This is called slag.
The Cambridge team found that the composition of the cement used was almost identical to the slag used in electric arc furnaces.
![As material is added to the molten steel, a flame is generated at the top of the arc furnace.](https://ichef.bbci.co.uk/news/480/cpsprodpb/20fb/live/06bd7920-175e-11ef-b5cc-cb8b8c4cef5a.jpg.webp)
They have been testing the process in a small-scale electric arc furnace at the Materials Processing Laboratory in Middlesbrough.
The BBC was present when the first premium cement, or “Portland” cement, was produced.
They called it ‘electric cement’ and described the event as a world first.
Lead scientist Cyrille Dunant told the BBC the technology could enable zero-carbon cement production.
“We showed that the high temperatures in the furnace reactivate old cement, and because electric arc furnaces use electricity, they can be powered by renewable electricity, decarbonizing the entire cement manufacturing process,” he said.
He also said that making the chemicals currently used as slag also has a high carbon cost, making steel recycling less polluting.
![Image of scientist Dr Cyrille Dunant standing in front of an electric arc furnace at the Middlesborough Materials Processing Laboratory. The furnace is red hot.](https://ichef.bbci.co.uk/news/480/cpsprodpb/83b5/live/b0528490-175d-11ef-8a11-6d604e5f7bb3.jpg.webp)
Mark Miodownik, professor of materials and society at University College London, described the Cambridge team's way of combining cement and steel recycling as “genius” and believes it could lead to huge cost savings if it could operate profitably at scale. emission.
“Can we compete with the existing, highly unsustainable infrastructure that continues to pour cement into our lives?” he asks.
“Cement is already a multi-billion dollar industry. “What we are talking about here is David and Goliath.”
There are hopes that electric cement will become cheaper to manufacture because it uses waste heat from the steel recycling process.
Spanish company Celsa will attempt to replicate the process in a full-scale electric furnace in Cardiff this week.
The Cambridge team estimates that, given current rates of steel recycling, low-carbon cement could produce around a quarter of UK demand.
However, the use of electric furnaces is expected to increase in the future, potentially producing more “electric cement”.
And, of course, this process could be replicated globally, potentially dramatically reducing emissions from cement.