Ecological cement and steel, the building blocks of our civilization

A recent report in Nature not only stressed the need to make the building blocks of our civilization greener, but made some strong suggestions on how to do so.

“Cement and steel are essential components of buildings, cars, dams, bridges and skyscrapers. But these industries are among the dirtiest in the world. Cement production generates 2.3 billion tons of carbon dioxide per year, and iron and steel production releases about 2.6 billion tons – or 6.5% and 7.0% of global CO2 emissions.

“That’s partly because of the large amounts these materials are used in: concrete is the second most consumed product in the world after clean water. This is also due to their carbon-intensive production methods. The chemical reactions involved release CO2, as does the burning of fossil fuels to reach the extreme temperatures required in the manufacturing processes.”

How do we make the production and use of steel and cement more environmentally friendly? Here are the researchers’ suggestions: Ensure production facilities are equipped with the best technology, are well insulated, and use better boilers and heat exchangers. This will require changes in building codes and improved education in the sector.

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

“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 in building codes and training for architects, engineers and contractors could reduce demand by up to 26% for cement and 24% for steel. Many building codes rely on over-engineering for safety reasons.”

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

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

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

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

We can start decarbonizing our skyscrapers by improving design and using fewer materials (31%), switching operations (33%) and decarbonizing heating (6.6%). These changes will go a long way in making the building blocks of our civilization greener, giving it a chance to survive.


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Jane Marczewski

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