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Researchers said Wednesday they were a step closer to solving one of the toughest problems in tackling climate change — how to keep producing cement despite a huge carbon footprint.
In a world first, engineers from the UK’s University of Cambridge have shown that cement can be recycled without as much environmental cost as making it from scratch.
Cement binds concrete together, but the off-white powder is carbon-intensive to produce, with the sector producing 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 has struggled to produce it in a less climate-damaging way.
The Cambridge team believe they have a solution, pioneering a method that modifies an existing steelmaking process to produce recycled cement without the associated CO2 pollution.
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This discovery, published in the journal Nature, could cause “an absolutely massive change” by providing low-cost, low-emission cement at scale, said Julian Allwood, who co-authored the research.
“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 the U.N. climate change panel’s reports.
To produce cement, the main component of concrete, limestone must be fired in kilns at very high temperatures usually achieved by burning fossil fuels such as coal.
In addition, limestone produces significant additional CO2 when heated.
“Bright Hope”
The cement industry alone accounts for nearly eight percent of human-caused CO2 emissions — more than any country except China and the United States.
About 14 billion cubic meters of concrete are poured each year, according to industry figures, and even more will be needed as economies and cities grow in the future.
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The International Energy Agency says that if emissions from the cement industry continue to rise, a promise 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 scale, rely on unproven technologies, or fall short of zero emissions.
The Cambridge researchers approached the problem by looking at an industry that was already well established — steel recycling, which uses electric furnaces to produce the alloy.
They replaced a key ingredient in that process with old cement sourced from demolished buildings, Allwood said.
Instead of producing waste, the end result was recycled cement ready for use in concrete, bypassing the high-emission process of overheating limestone in kilns.
That method — which is patent pending — was “a very low-disruption innovation” that required little change or additional cost on the part of businesses, Allwood said.
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If powered by renewable energy, he said, these kilns could hopefully produce zero-emissions concrete at scale.
“Since electricity has no emissions, then our process will have no emissions,” Allwood said.
Countries could not hope to achieve zero CO2 emissions by 2050 – the key promise of the Paris climate agreement – using concrete as it exists today, he added.
“That’s the big bright hope, I think,” Allwood said.
Source: AFP