Around 2.5 billion more people will be living in cities in the next 30 years. 1The construction needs to support this influx of people are sizeable. In fact, the Global Construction 2030 study estimates that construction output will grow by 85 per cent to 2030.2 Cement – the main ingredient in concrete – will underpin this expansion.
Cement represents 7 per cent of annual global greenhouse gases (GHG),3 and is the second highest industrial contributor to GHGs after steel production. Material Economics demonstrate that cement is typically the single largest material source in an average building and can account for almost half of its material composition. Two thirds of global cement production is used for buildings, with the remainder typically used for roads, bridges and other infrastructure needs.4
Cement production is technically difficult to decarbonise, which is why efforts in the building sector have so far concentrated on implementing energy efficiency standards. Now, an increased focus from countries, regions and cities on implementing net zero emission targets means that wider approaches to decarbonisation are being explored. A comprehensive decarbonisation strategy inevitably has to address buildings and infrastructure, and by extension, cement.
Work from the Energy Transition Commission, 'Mission Possible: Reaching net zero carbon emissions in cement' provides a roadmap for the cement sector taking into consideration both supply and demand side opportunities. The majority of CO2 emitted in production comes from chemical processes and high intensity heat for kilns. Over 50 per cent of emissions come from the conversion of limestone (the main feedstock) into calcium oxide ('clinker'). This is difficult to abate because of limited viable alternatives. Coal, used in 66 per cent of current production, is the second largest source of emissions. Two hundred kilograms of coal is required to produce one tonne of cement.5
The ETC lays out possible solutions that reduce emissions from cement production. These are at various stages of maturity and include carbon capture, switching from coal to low carbon fuels like gas or biomass, and new concrete chemistries that require less cement and energy efficiency. Other solutions in development include hydrogen, electricity as the main heat source and alternative cement chemistries.
As well as production emissions, work is underway to identify CO2 reduction opportunities on the demand side. The ETC report identifies that a circular economy approach could reduce emissions by up to 45 per cent. The opportunities include digital technologies that enable better use, reuse and recycling of cement during the construction and deconstruction phase. In addition, substituting concrete with other building materials such as cross-laminated timber could help.
Cost is the key barrier to widespread sector decarbonisation so far, as the cost to decarbonise cement could increase the price of concrete by 30 per cent in the most extreme estimates. 6Support for policy and investment that promote innovation in green cement will enable the industry's decarbonisation.
1United Nations Department of Economic and Social Affairs (2018), World Urbanization Prospects
2Global Construction Perspectives and Oxford Economics: Global Construction 2030:
3ETC (2019) Mission Possible: Cement
4Material Economics (2018), The circular economy, a powerful force for climate mitigation
5World Coal Association
6ETC (2019) Mission Possible: Cement