Roberta Alfani, Ecocem, reports on the state of low-carbon cement technologies in the wider industry.
The built environment is responsible for nearly 50% of annual CO2 emissions. Embodied carbon (the carbon produced during the construction of structures) represents about half of these emissions, and concrete is a major contributor. Methods of reducing its impact need to be urgently explored.
Concrete is the second-most consumed product on earth after water. It is ubiquitous to the point of anonymity, yet is the foundation of modern development, putting roofs over the heads of billions, fortifying defences against natural disasters and providing a structure for healthcare, education, transport, energy, and industry.
However, cement, the key component of concrete, is exceptionally polluting; its manufacture accounts for 8% of global CO2 emissions, more than shipping, aviation, and long-distance trucking combined. To put that into perspective, if the cement industry were a country, it would be the third biggest source of CO2 emissions – the same as India, and behind China and the United States.
Specifically, the problem is clinker, the key reactive component within cement. Even though it makes up only ~10% of concrete by mass, it is responsible for 90% of its carbon footprint.
On a global basis, for every tonne of clinker produced, around a tonne of CO2 is emitted. Two-thirds of the CO2 emitted in the manufacture of clinker is generated during the unavoidable chemical reaction when the limestone is baked to produce clinker. The remaining one-third comes from the energy required to heat the kiln and other energy intensive processes. Therefore, even if clinker was produced using entirely green energy, the carbon footprint of clinker would only reduce by one third.
To meet urgent decarbonisation targets the industry needs to focus on clinker and finding ways to reduce its carbon intensive impact through: drastically reducing the amount of clinker used in cement, producing clinker more efficiently from an energy standpoint, and in the future, capturing the remaining CO2 emissions through Carbon Capture Utilisation and Storage (CCUS).
Source: World Cement, Published by David Bizley, Editor
Post time: Jul-28-2022