Concrete’s carbon problem
The world’s most common building material has a huge carbon footprint. Angeli Mehta talks to the scientists trying to reduce it
Four billion tonnes of cement are made every year. That’s four billion tonnes of the glue that makes concrete such a cheap, versatile and durable material – in demand for homes and roads, dams and bridges across the globe. Unfortunately those immense quantities mean cement accounts for 8% of global carbon dioxide emissions, and there’s no let-up in demand, as the developing world builds homes and cities for its growing population. Not only are large amounts of energy (from fossil fuels) needed to heat the kilns to such high temperatures, but the breakdown of calcium carbonate itself releases carbon dioxide – accounting for more than half of the emissions associated with making cement.
The strategies being worked on are to use less fossil fuel to heat the kilns; less clinker to make cement; less cement in the concrete; and less concrete to build infrastructure overall, including more recycling.