Breakthrough turns carbon dioxide into rock

The breakthrough has the potential to mitigate the CO2 produced by the cement industry, which, according to climate change researcher the Carbon Disclosure Project (CDP), is one of the primary producers of the greenhouse gas, accounting for five per cent of global emissions.

A study published in Science on 9 June claims to demonstrate for the first time that the gas, which is a by-product when limestone is thermally decomposed during the cement making process, can be stored safely and permanently.

A previous approach to carbon capture has been to seal it in vast underground voids, such as former oil and gas reservoirs, but these are susceptible to leakage. The scientific community has turned its attention to permanent mineralisation instead.

For the latest experiment, researchers at Columbia University, University of Iceland, University of Toulouse and Reykjavik Energy dissolved CO2 in water and carried it 400 to 800 metres down a well. On contact with the surrounding basalt rock it formed carbonate minerals.

It was thought this process would take thousands of years but the authors of the study say it can take as little as two years.

“Our results show that between 95 and 98 per cent of the injected CO2 was mineralised over the period of less than two years,” lead author and associate professor in geo-engineering at the University of Southampton Dr Juerg Matter said. “That is amazingly fast.”

He added: “Basalt is one of the most common rock types on Earth, potentially providing one of the largest CO2 storage capacities.”

Matter now hopes the project, which was funded by the European Commission and the US Department of Energy, will be expanded to store large quantities of the gas.

Paris Agreement

The discovery comes at the same time as cement manufacturers are being urged to take a more proactive approach to cutting their carbon emissions.

The CDP released a report on 9 June that states the 12 largest cement companies risk $USD4.5 billion ($AUD6 billion) in lost earnings if they fail to meet the objectives of the Paris Agreement once it comes into effect in 2020.

The climate deal, signed by 177 countries including Australia in April, sets CO2 reduction targets.

The CDP warns companies that fail to cut emissions could be exposed to “carbon pricing”, where companies are charged for the amount of greenhouse gas they produce.

The organisation’s report, which ranks the 12 companies on their environmental efforts, estimates the worst performers, such as Italy’s Italcementi and Cementir, could have up to 114 per cent of their earnings before interest and tax at risk at even a relatively low carbon price.

“To deliver deep decarbonisation in coming years, cement companies need to seek longer-term solutions such as carbon capture and storage and develop less carbon-intensive cement products,” the report stated.

In related news, a consortium known as Low Emissions Intensity Lime And Cement (LEILAC) has recently been awarded a €12 million ($AUD18 million) grant towards its own carbon reduction efforts.

The group, which comprises global construction companies such as Cemex, Tamac, and Heidelberg as well as Imperial College London and environmental organisations, estimates as much as two-thirds of emissions from the cement sector comes from the decomposition of limestone into lime and CO2.

LEILAC’s method involves capturing the carbon dioxide by separating the furnace exhaust gases from the limestone by heating it indirectly in a special steel vessel.

More reading
Breakthrough in ‘green’ building materials
Research puts a ‘green’ spin on concrete

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