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Searching for ways to make skyscrapers greener. Image by Kyle Field, CleanTechnica.


Greening Cement & Steel, the Building Blocks of Our Civilization

A recent report in Nature not only highlighted the need for greening the building blocks of our civilization, but also made some strong suggestions for how to do so.

“Cement and steel are essential ingredients of buildings, cars, dams, bridges and skyscrapers. But these industries are among the dirtiest on the planet. Production of cement creates 2.3 billion tonnes of carbon dioxide per year, and making iron and steel releases some 2.6 billion tonnes — or 6.5% and 7.0% of global CO2 emissions, respectively.

“That’s in part owing to the large quantities in which these materials are used: concrete is the second-most-consumed product on the planet, after clean water. It’s also thanks to their carbon-intensive methods of production. The chemical reactions involved give off CO2, as does burning fossil fuels to deliver the extreme temperatures required in the manufacturing processes.”

How do we green the production and use of steel and cement? Here are the researchers’ suggestions: Ensure that production plants are fitted with the best technology and are well insulated, and use better boilers and heat exchangers. To do that, changes to building codes and improved education in this sector are needed.

“Today, the most efficient cement plants can squeeze only 0.04% of energy savings per year by upgrading technologies. More needs to be done.

“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.”

By using only green hydrogen for “direct reduced iron steel” production, “we can reduce CO2 emissions to 50 kilograms or less per tonne of steel — a 97% reduction. Firms in Europe, China and Australia are piloting such plants, with several slated to open in 2025 or 2026.”

If we make cement without limestone, we can reduce the carbon footprint of the industry. However there are many challenges to overcome when substituting materials.

Perhaps the most radical suggestion is that of storing CO2 within the concrete itself. “If CO2 comprises just 1.3% of the weight of concrete, the material’s hardness can increase by around 10%. That reduces the amount of cement needed in a structure — along with net emissions — by about 5%.” This is an active area of research with some promising results coming out of Canada’s Carbon Cure concrete.

Steel can also be efficiently recycled. “One-quarter of steel production today is based on recycled scrap. Globally, recycled production is expected to double by 2050, reducing emissions by 20–25% from today (depending on how the electricity is produced).”

We can begin to decarbonize our skyscrapers by improving design and using fewer materials (31%), switching processes (33%), and decarbonizing heating (6.6%). These changes will go a long way towards greening the building blocks of our civilization and therefore giving it a chance of survival.

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David Waterworth is a retired teacher who divides his time between looking after his grandchildren and trying to make sure they have a planet to live on. He is long on Tesla [NASDAQ:TSLA].


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