15:47 JST, May 30, 2024
PARIS (AFP-Jiji) – Researchers said on May 22 they were one step closer to solving one of the toughest problems in tackling climate change: how to keep making cement despite its huge carbon footprint.
In a world first, engineers from Britain’s University of Cambridge have shown that cement can be recycled without the same high costs to the environment as making cement from scratch.
Cement binds concrete together, but the whitish powder is highly carbon-intensive to produce, with the sector generating more than three times the emissions of global air travel.
Demand for concrete – already the most widely used building material on earth – is soaring, but the notoriously polluting industry is struggling to produce it in a less climate-damaging way.
The Cambridge team believes it has a solution and is pioneering a method that adapts an existing steelmaking process to produce recycled cement without the associated CO2 pollution.
This discovery, published in the journal Nature, could bring about “an absolutely massive change” by providing cheap and low-emission cement on a large scale, says Julian Allwood, co-author of the study.
“It’s an extremely exciting project… I think it’s going to have a huge impact,” said Allwood, an expert on industrial emissions and a key contributor to reports from the UN scientific panel on climate change.
To produce cement, the basic ingredient of concrete, limestone must be fired in kilns at very high temperatures, usually achieved through the combustion of fossil fuels such as coal.
In addition, limestone produces significantly additional CO2 when heated.
‘Light hope’
The cement industry alone is responsible for almost 8% of man-made CO2 emissions – more than any country except China and the United States.
According to industry figures, around 14 billion cubic meters of concrete are poured every year, and more will be needed as economies and cities grow in the future.
The International Energy Agency says if emissions from the cement industry continue to rise, a pledge of carbon neutrality by 2050 will almost certainly remain out of reach.
Many efforts to produce low-carbon or so-called “green cement” are too expensive or difficult to deploy at scale, rely on unproven technologies, or do not come close to zero emissions.
The Cambridge researchers approached the problem by looking at an industry that was already well established: steel recycling, which uses electrically powered furnaces to produce the alloy.
They replaced a key ingredient in that process with old cement sourced from demolished buildings, Allwood said.
Instead of waste being produced, the end result was recycled cement ready for use in concrete, bypassing the emissions-heavy process of superheating limestone in kilns.
This patent-pending method was “a very low disruption innovation” that required little change or additional cost on the part of the business community, Allwood said.
If these kilns are powered by renewable energy, he said, they could produce emission-free concrete on a large scale.
“If the electricity no longer has any emissions, our process would also have no emissions,” Allwood said.
Countries cannot hope to cut carbon emissions to zero by 2050 – the key promise of the Paris climate agreement – using concrete as it exists today, he added.
“This is the big, bright hope, I think,” Allwood said.
