Greening cement and steel, the cornerstones of our civilization

A recent report in Nature not only emphasized the need to green the building blocks of our civilization, but also made strong suggestions on 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. Cement production creates 2.3 billion tonnes of carbon dioxide annually, and iron and steel manufacturing releases some 2.6 billion tonnes, or 6.5% and 7.0% of global emissions of CO2, respectively.

“This is partly explained by the large quantities in which these materials are used: concrete is the second most consumed product on the planet, after clean water. This is also thanks to their carbon-intensive production methods. The chemical reactions involved release CO2, as does the burning of fossil fuels to provide the extreme temperatures required in manufacturing processes.

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

“Today, the most efficient cement plants can achieve only 0.04% energy savings per year by improving technologies. We need to do more.

“The world produces 530 kilograms of cement and 240 kilograms of steel per person per year. According to the International Energy Agency, small but significant changes to building codes and training for architects, engineers and contractors could reduce demand for cement by up to 26% and steel by 24%. Many building codes rely on over-engineering for safety reasons.

By using only green hydrogen for the production of “direct reduction iron steel”, “we can reduce CO2 emissions to 50 kilograms or less per ton of steel, a reduction of 97%. Companies in Europe, China and Australia are piloting such factories, with several expected to open in 2025 or 2026.”

If we make lime-free cement, we can reduce the industry’s carbon footprint. However, there are many challenges to overcome when substituting materials.

Perhaps the most radical suggestion is to store the CO2 in the concrete itself. “If the CO2 is only 1.3% of the weight of the concrete, the hardness of the material can increase by about 10%. This reduces the amount of cement needed in a structure – as well as net emissions – by around 5%.” This is an active area of ​​research with promising results from Carbon treatment concrete.

Steel can also be effectively recycled. “A quarter of steel production today relies on recycled scrap. Globally, recycled production is expected to double by 2050, reducing emissions by 20-25% compared to today (depending on how the electricity is generated).”

We can start decarbonizing our skyscrapers by improving the design and using fewer materials (31%), changing the process (33%) and decarbonizing the heating (6.6%). These changes will go a long way towards greening the building blocks of our civilization and thus giving it a chance of survival.


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