Concrete has long been one of the most notorious sources of carbon emissions. But a new development could change all that and cut pollution down to virtually nothing.

A major problem with concrete is that it contains cement, which is made by heating limestone. The burning of fossil fuels in the process is highly polluting, while more carbon is extracted by the limestone heating itself.

Put together, this accounts for 7.5 per cent of carbon emissions. If concrete was a country, it would have the third largest footprint in the world after the US and China.

That means concrete plants have been in the unfortunate position of being a major polluter, while at the same time being a crucial contributor to the construction of the built environment we see all around us in towns and cities. 

However, the good news is that these emissions could be slashed by ensuring that used concrete ends up on a conveyor belt to an arc recycling furnace that runs on green energy.

Researchers at Cambridge University have found that this is because used cement can work just as well as the lime flux in the steel recycling process. But instead of creating the by-product known as slag, the result is recycled and reusable cement that can be used to make new concrete, saving large quantities of emissions.

That means steel and concrete plants can combine their operations to recycle both steel and cement. If the furnaces are run on green energy too, this can cut the carbon footprint to almost nothing. As such it offers a massively significant solution to one of the world’s biggest decarbonisation challenges.

Moreover, in research carried out in partnership with the Materials Processing Institute, it was shown that this process can be carried out at scale and that it adds no extra costs to production. The research has been published in the journal Nature.

Plants that implement this system could find their services are in big demand, so they may need more conveyor belt maintenance to keep the material flowing.

Concerns about the issue of embodied carbon in concrete buildings have been concerning the construction sector and architects for years. Suggested solutions have included a greater focus on re-using and modifying existing buildings rather than demolishing them and then starting again with fresh construction and new concrete.

Other innovations have focused on finding ways of producing new concrete in a way that produces lower emissions.

However, the new process combined with steel recycling offers a solution that may prove ideal when other possibilities have been exhausted, such as when a building has become derelict or is no longer structurally safe, or where there is no practical use in retaining it. In such instances, the material can now be more effectively recycled.

With the global building floor area projected to double by 2026, this innovation may be crucial, both here in the UK and around the world. It will enable cities to go on being developed without the very stuff buildings are made from being part of the environmental problem.