Towards a ‘greener’ cement - are there low carbon alternatives?
Cement is the source of an estimated 8 percent of the world's carbon dioxide (CO2) emissions. If the cement industry were a country, it would be the third largest emitter in the world - behind China and the US. It contributes more CO2 than aviation fuel (2.5 percent) and is not far behind the global agriculture business (12 percent) [1]. The terms “cement” and “concrete” are often used interchangeably. However, concrete is actually the final product made from cement. The primary component of cement is limestone. To produce cement, limestone and other clay-like materials are heated in a kiln at 1400°C and then ground to form a lumpy, solid substance called clinker; clinker is then combined with gypsum to form cement [2].
Concrete is the most widely used man-made material in existence. It is second only to water as the most-consumed resource on the planet [2]. But, while cement - the key ingredient in concrete - has shaped much of our built environment, it also has a massive carbon footprint [5] Significant changes in how cement and concrete are produced and used are urgently needed to achieve deep cuts in emissions [1]. Alternatives need to be found, either to cement itself or to utilise more sustainable and less environmentally damaging binders [3].
Dr Ruben Paul Borg from the Built Environment at the University of Malta, has been working to find such alternatives using cement bound materials that can lead towards more sustainable, durable buildings, with a lower carbon footprint. Quarry limestone and excavation waste have been cited as alternatives to cement and aggregate to produce strong and durable cement bound materials. In addition, construction and demolition waste, which accounts for the largest portion of waste generated in Malta, has been used to produce concrete with improved lifecycle performance, effectively resulting in reductions in raw material being extracted and in waste produced [3].
Alternatives from prickly pear extract to alternative high-performance fibre-reinforced concrete structures and the exploitation of materials such as waste limestone are being explored in research development, but to date there has been no dependable alternative developed [4]. As the crisis deepens as to the disposal of construction waste in Malta, surely one of the best solutions is to re-use construction waste as we enter the age of the circular economy.
“There will need to be a step-change in the pace at which lower carbon cements are developed and deployed.”
There needs to be a step-change in the pace at which lower carbon cements are developed and deployed. Advances in digital technology should play a key role in building the market for novel cement and concrete products by addressing misinformation, enhancing collaboration and disseminating best practices along the value chain. Disruptive trends in the broader construction sector could unlock new opportunities to reduce emissions more quickly with significant value creation opportunities for companies that align their strategies with decarbonisation, and growing regulatory and political risks for those that are unable to do so [1].