Concrete and steel production are major sources of CO2 emissions, but a new solution from Cambridge could recycle both at the same time. Throwing old concrete into steel-processing furnaces not only purifies iron but produces “reactivated cement” as a byproduct. If done using renewable energy, the process could make for completely carbon-zero cement.

Concrete is the world’s most used building material, and making it is a particularly dirty business – concrete production alone is responsible for about 8% of total global CO2 emissions. Unfortunately it’s not easy to recycle back into a form that can be used to make new concrete structures.

Scientists have of course been investigating ways to make concrete greener. That can include changing the recipe to switch out the most polluting ingredients – specifically limestone – or designing concrete so that it absorbs more CO2 from the air after it’s laid. For the new study, Cambridge researchers investigated how waste concrete […]