Cement is responsible for 5% of the world's carbon emissions, and the race is on to find an alternative
What do you do with a problem like cement? Around 2bn tonnes are used every year, each tonne a source of 0.4 tonnes of carbon dioxide as it is made. The cement industry is responsible for 5% of the world's carbon emissions – more than the entire aviation industry.
Standard, or Portland, cement is made by heating limestone or clay to around 1,500C. This use of energy and the decomposition of the limestone as it cooks releases copious amounts of CO2. As the carbon reduction targets from global climate agreements begin to bite, sorting out cement will become a priority.
Engineers have been working hard on the problem in recent years, with a range of approaches to cutting the environmental impact of the construction industry: some have tried synthetic polymers that would remove the need for limestone; others have fiddled with how cement is used in buildings. The latest on the block is Liquid Granite, a binding material that, according to its inventor, could almost