Scalable Method Discovered for Recycling Concrete with Near-Zero Emissions

From Construction Waste to New Concrete: Breakthrough Enables Endless Recycling

In a potential game-changer for reducing global emissions, researchers at the University of Cambridge have developed a method to recycle old cement into new, ultra-low emission concrete at an industrial scale. The innovation, which the scientists describe as "an absolute miracle," could play a pivotal role in decarbonizing one of the world's most emission-intensive industries.

Concrete is the second most consumed material on Earth after water and accounts for a staggering 7.5% of total man-made carbon dioxide emissions. With global demand for concrete expected to keep rising to meet infrastructure needs, finding a scalable and cost-effective way to slash emissions from this ubiquitous building material has been one of the world's most vexing decarbonization challenges.

The Cambridge team's breakthrough, published in the journal Nature, involves repurposing electric arc furnaces that are conventionally used for recycling steel. By substituting used cement for the lime flux typically added during steel recycling, the furnaces can simultaneously recycle both steel and cement without additional costs.

"We held workshops with the construction industry on reducing emissions, but one thing they wouldn't consider was a world without cement," said Professor Julian Allwood, who led the research. "We've identified low-hanging fruit for using less cement through careful mixing, but to get to zero emissions, we needed to think outside the box."

During the recycling process, crushed old concrete is fed into the electric arc furnace along with molten steel. The high temperatures reactivate the cement's chemical components, allowing it to be rapidly cooled and reformed into a recycled cement clinker that can be used to produce new concrete.

Recent tests showed this "Cambridge Electric Cement" method can be carried out at industrial scale without compromising concrete performance. If powered by renewable energy, it could eventually produce zero-emission cement at an annual rate of 1 billion tonnes by 2050 – about a quarter of current global production.

"Producing zero emissions cement is an absolute miracle," said Allwood. "But we've also got to reduce the sheer amount of cement and concrete we use, which could be done without sacrificing safety through smarter policies and practices."

While hailing the recycling technology as a breakthrough, the researchers emphasize the need for broader efforts to curb concrete's environmental footprint through more efficient use and alternative construction methods.

"We hope Cambridge Electric Cement will spur governments to recognize that the road to net-zero extends far beyond just the energy sector," Allwood stated. "There are tremendous innovation opportunities across all emissions-intensive industries."