Carbon Dioxide Emissions From Cement Have Doubled—We Should Be Ashamed

We have "flight shaming" and it's time for some "building shaming."

Cement plant

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While nations worldwide have been making pledges to reduce carbon dioxide emissions and have made some progress in decarbonizing energy and transportation, one source of emissions just keeps growing: cement. Seth Borenstein of AP reports that emissions from cement production have doubled in the last 20 years and are now fully 7% of global emissions.

Despite "road maps" from the American and global cement and concrete industries, it is not getting any less carbon-intensive. "Cement has actually been going in the opposite direction. The carbon intensity of cement — how much pollution is emitted per ton — has increased 9.3% from 2015 to 2020, primarily because of China, according to the International Energy Agency," wrote Borenstein.

Borenstein quoted Steven J. Davis of the University of California, Irvine's Department of Earth System Science, writing: "And while people talk about curtailing flying, global aviation emissions are less than half of that coming from concrete, according to Global Carbon Project. There's "flight shaming" among scientists and activists, but no building shaming, Davis said."

One might argue there is some building shaming happening these days, though it is much bigger a deal in the United Kingdom, where it has gotten to the point where architects have to justify every proposed demolition, as we saw recently with Marks and Spencer on Oxford Street in London. It's beginning to happen in North America, and there will be a lot more of it as the understanding of embodied carbon becomes more widespread.

We certainly need more of it; Davis contributed to a paper that helps explain why. The report—"Going Net Zero for cement and steel"; (PDF here)—is full of suggestions for reducing the impact of building materials, starting with simply using less of the stuff through material efficiency.

"Smaller quantities of steel and cement can be used for the same job. Today, the world produces 530 kilograms of cement and 240 kilograms of steel per person per year. Small but significant changes to building codes and education for architects, engineers and contractors could reduce demand for cement by up to 26% and for steel by 24%, according to the International Energy Agency. Many building codes rely on over-engineering for safety's sake. That margin could be limited by using modern materials and computer modeling to whittle down designs to use only the necessary amount of resources."

They go on to suggest cement can be reinvented by reformulating cement, using greener fuels in cement kilns, and capturing the carbon emissions from calcination. 

What they never suggest is simply not building a skyscraper in the first place—this is why it's time for some serious building shaming. 

There are all these papers and discussions about material efficiency, but almost no discussion of simplicity: Why build complex towers that require more materials and fancy systems? We know embodied and operating carbon increases with height, and we have studies that show how "building height influences energy consumption directly through mechanisms such as changes in external temperature and wind speed with altitude, access to daylight and solar gains, as well as the need for lifts (elevators)."

Nor is there any discussion of sufficiency: How much do we really need? Do we actually need this building at all? Or as the World Building Council noted in its document Bringing Embodied Carbon Upfront, the need to "question the need to use materials at all, considering alternative strategies for delivering the desired function, such as increasing utilisation of existing assets through renovation or reuse."

This is why we need building shaming. Just as flight shaming leads us to question the way we travel, building shaming helps us question the way we build. 

Aviation is responsible for perhaps 4% of carbon emissions; according to AP, concrete is perhaps 7%. Architecture 2030 says building construction and operations are about 39% of emissions and transportation emissions are about 23%, but as I have noted, "We have to stop talking about transportation emissions as something detached from building emissions. What we design and build determines how we get around (and vice versa) and you cannot separate the two. They are all Built Environment Emissions, and we have to deal with them together." I calculated that Built Environment Emissions could total as much as 75% of all emissions.

Davis is on to something here. We need some serious building, planning, and engineering shaming. All of us in the built environment business should be ashamed. Nothing else seems to have worked.

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  1. Lee, D.S., et al. "The Contribution of Global Aviation to Anthropogenic Climate Forcing For 2000 to 2018." Atmospheric Environment, vol. 244, 2021, p. 117834., doi:10.1016/j.atmosenv.2020.117834