Hundreds of feet above the British capital’s Canary Wharf financial district, an office tower under construction grows taller as it draws materials from a source just blocks away. Concrete being poured on to the floor of the 52nd story is made partly with concrete recycled from a building being taken down nearby—part of an initiative to decarbonize office spaces through so-called circular construction practices that aim to maximize the reuse of materials. By putting reduced carbon as a requirement from its suppliers, Canary Wharf helped to transform the supply chain as a whole, largely by giving clarity that this was now a key requirement going forward as a developer.
To produce recycled concrete, waste from demolished buildings is broken down and turned into a powder, after which the aggregates and cements are separated. The cements are processed back into a paste, which makes up about 15% of the final product, while the aggregates are used to make the rest of the concrete, replacing the need for new materials like sand.
Buildings account for 39% of global energy-related carbon emissions, with 11% of that coming from materials and construction, reports The Wall Street Journal (March 27, 2024) . Cement and concrete alone account for 9% of total carbon emissions, so as companies look to lower emissions, the embedded carbon from their offices is a growing concern.
With an increasing world population and urbanization, construction activity will continue to increase. It is estimated that the equivalent of the size of New York City would have to be built every 40 days to meet demand.
Moving to more circular construction methods has shown to be an effective way of cutting emissions. Reusing concrete and cement could help abate 600 million metric tons of carbon-dioxide emissions by 2050. Using recycled concrete reduces carbon-dioxide emissions by about 40% compared with ordinary production.
Construction and real-estate companies are increasingly requesting higher levels of transparency and data. They are asking for Environmental Product Declarations which reveal both the positive and negative impacts of each building material’s life cycle, all the way back to the mine. These give specifiers, designers and tenants a transparent view into a building’s full carbon footprint.
Classroom discussion questions:
- In what other ways are buildings “going green?” (Hint: see the Orlando Magic case study in Supp. 5 of your Heizer/Render/Munson text)
- How can a building being renovated increase its energy efficiency?