Emissions in reverse – carbon dioxide returning to coal

Australian researchers have succeeded in turning the greenhouse gas carbon dioxide back into solid matter at room temperature. So it could be stored more safely than in liquid form.

Industrial towers with smoke on the horizon

As long as carbon dioxide emissions are unavoidable, capture could help reduce climate change

Photo: Hackman / Panthermedia.net

It is a big challenge to limit climate change and it will probably not be enough to reduce harmful emissions. That is why the Intergovernmental Panel on Climate Change, in a special report, has already called for carbon dioxide (CO2) to be withdrawn and safely stored in the atmosphere at the same time. Researchers at the Royal Melbourne Institute of Technology (RMIT) in Melbourne have now succeeded in producing solid matter from the greenhouse gas using energy-efficient methods. This promises safe storage.

Liquid metal electrocatalysts produce flaked carbon

Technically, removing carbon dioxide from the air is no longer a problem – the Drax Power Station in North Yorkshire, UK just started a few weeks ago in the industrial style. The splitting directly at the power plant should lead to the fact that the atmosphere is not burdened by the greenhouse gas. However, the supposed solution directly creates new problems. Because the gas is compressed and is therefore present in liquid form. This raises the question of storage. Some experts fear that underground storage could be too unsafe in the long term because the study of risks is ambiguous. In addition, the energy required for the separation, transport and storage (compression) of the liquid carbon would be high.

Scientists at the University of Southampton are taking a different approach. They are trying to accelerate processes that bind carbon dioxide to carbonate rocks. But your method still takes several months or even years. The RMIT researchers have developed a faster solution. They convert the carbon dioxide back into solid carbon, basically into artificial coal. They do this by using special liquid metal catalysts. The special feature of the process: The processes take place at room temperature.

Energy-efficient process without external heat supply

Practically, the scientists dissolve the CO2 in an electrolyte liquid containing the liquid metal. When energized, the carbon dioxide gradually transforms into solid carbon flocks that naturally dissolve away from the liquid metal surface, allowing the process to continue continuously. According to the researchers, only low voltages are required for this, and catalysis does not have to be accelerated by heat input – similar results have so far only been achieved at elevated temperatures, which is not sufficiently energy-efficient.

The resulting Of course, solid could be stored much lighter than CO2 in liquid form. Torben Daeneke of the RMIT imagines to keep it underground. “While we can not literally turn back time, it’s a bit like rewinding the emission clock by turning carbon dioxide back into coal and putting it back in the ground,” he says. He is convinced that the conversion of CO2 into a solid could be a very sustainable process.

The by-product is supercapacitors

. The process has some useful side effects. Because the carbon that is created, can store electrical charge. So it becomes a supercapacitor and could potentially serve as a battery component in electric cars. Whether the material would actually be suitable for such applications, but is not yet clear. “The process also produces as a by-product synthetic fuel, which could possibly also be used in industry,” says first author Dorna Esrafilzadeh. For the scientists, it is clear that further research would be useful, among other things to further increase the activity of the catalyst.

More about carbon dioxide emissions:

  • Selective separation of low-concentration CO2
  • Reducing carbon dioxide with algae and carbon fibers
  • Cement absorbs CO2