Recycled construction waste could cut cement and steel’s carbon footprint
Cement can be regenerated during steel recycling in an electric arc furnace
‘Zero-carbon’ cement made by feeding concrete construction waste into existing steel recycling processes could potentially slash carbon emissions for both cement and steel industries. The approach is the ‘first cement recycling method proposed to date’, according to the team, and could offer a solution to one of the world’s most pressing decarbonisation challenges.
Estimates suggest around 7.5% of current anthropogenic carbon dioxide emissions derive from cement production. Meanwhile, steel production is thought to contribute to at least 6%. Driving these emissions is dependence on lime to make these materials.
Portland cement requires clinker, which is made by heating limestone and minerals in a kiln. This releases carbon dioxide from limestone (calcium carbonate) when it is converted to lime (calcium oxide). Clinker is then combined with silica-rich clays in a furnace to make cement. Meanwhile, steel production requires lime as a flux material to mop-up impurities from the molten metal during the manufacturing process.