Could cement and steel team up to cut emissions?

The production of cement and steel creates roughly 13% of the world's anthropogenic carbon dioxide emissions. Combining the recycling of the two ubiquitous building materials could cut those emissions, researchers say ( Nature 2024, DOI: 10.1038/s41586-024-07338-8 ). They show that adding waste cement into the electric arc furnaces (EAFs) used to recycle steel produces a material that can be recycled into new cement. Cement holds together the gravel and sand in concrete . Producing both cement and steel involves high temperatures—typically generated by burning fossil fuels—and chemical reactions that release CO 2 . Cement is made by mixing calcium carbonate with clays and heating in a kiln to form calcium silicates, called clinker, a precursor of cement. The process converts calcium carbonate to calcium oxide—or lime—releasing CO 2 . Producing steel, meanwhile, involves smelting iron oxide ore and carbon in a blast furnace. Decarbonizing cement and steel is a formidable