Concrete is one of civilisation’s game-changing building materials. It was material that helped to build the cities of ancient Rome and Constantinople. It also built modern megacities like London and New York. Concrete is one of the defining materials of the human race. Should it be any surprise then that we use concrete more than any other material, other than water?
However, this civilisation shaping material has some major issues. This can primarily be seen with its catastrophic impact on the natural world, and the huge contribution concrete has toward climate change.
Manufacturing cement is the most carbon-intensive process in the production if concrete. Making 10-15% of the material, cement requires limestone to be heated to over 1000C, often using fossil fuels. This part of the process accounts for nearly 40% of concretes CO2 output.
The original BBC article stated “a British academic and head of Ecole Polytechnique Fédérale de Lausanne, Karen Scrivener, says we could replace cement with heated clay and unburnt limestone. She states that this means 40% less CO2 from the concrete making process.”
Part of the issue with this process is that it is not as cheap as regular concrete, and requires consumers to demand, and pay for, more sustainable concrete. Are people willing to pay higher prices? Especially during the post-COVID effects when so many have struggled for so long, can we expect a change in buying?
A third approach to reducing the carbon created from concrete is to use a wide 60-meter steel tube that can be added to existing cement plants. You feed materials from the top, and they float down the tube which is being heated for outside. The CO2 which escapes is captured at the top of the tube, and the calcium oxide floats to the bottom to be used.
At the Hanover plant in Germany, with 20% going through this new process, over 100,000 tonnes of CO2 every year is being saved. The saved carbon is compressed and transported to Norway to be stored under the North Sea under an empty oil reservoir.
Since 1990, cement makers have reduced their carbon output by near 20%. But there is still a long way to go. Part of the issue is that 90% of future cement production will happen outside of wealthy OECD nations. Will developing states, with complex and numerous priorities, be able to adapt and implement this more expensive method in the name of reducing climate impact?
China made more concrete between 2011 and 2013 than the US did in the whole 20th Century.
What is the way forward to cleaning up this hugely polluting sector? Should we start to look beyond concrete and return to more natural and local building materials? How can we keep up with the incessant demands of growth from the global economy?
There are a lot of challenges when tackling climate change. The construction industry has an important role to play.