Concrete is strong and durable \u2013 which is why it\u2019s the basis for so much of our infrastructure. It\u2019s also terrible for the planet, due to one key ingredient: cement, which is responsible for almost 90% of concrete emissions. Researchers have now found a way to recover old cement while also reducing the environmental impact of recycling steel. Madeleine Finlay speaks to Julian Allwood, professor of engineering and the environment at the University Of Cambridge, to find out how the process works, and what it could mean for the emissions generated by the construction industry. Help support our independent journalism at theguardian.com/sciencepod