Researchers Can Now Cheaply Turn Atmospheric CO2 Back Into Coal

Researchers at the Royal Melbourne Institute of Technology have worked out a cheap and efficient way to convert atmospheric carbon dioxide into solid particles of carbon. This new carbon-capture technology could be key to reducing the amount of this dangerous greenhouse gas in our atmosphere.

Most approaches to remove CO₂ focus on compressing the gas into a liquid and then injecting it underground. Doing this has significant challenges and there is the possibility that it might eventually leak out from storage sites.

The new approach, reported in Nature Communications, could be more sustainable and prevent unwanted leaks. It is designed in a way that means it could be applied on a large scale and the researchers have been able to resolve previous issues encountered when attempting to turn carbon dioxide into coal.

“While we can’t literally turn back time, turning carbon dioxide back into coal and burying it back in the ground is a bit like rewinding the emissions clock,” co-author Dr Torben Daeneke said in a statement. “To date, CO₂ has only been converted into a solid at extremely high temperatures, making it industrially unviable. By using liquid metals as a catalyst, we’ve shown it’s possible to turn the gas back into carbon at room temperature, in a process that’s efficient and scalable.”

The team used a liquid alloy made of gallium, indium, tin, and cerium. The liquid metal was stored in a glass tube with a wire running through it. Some water was added to the air in the glass tube. The pure CO₂ was sent into the glass tube as electricity was sent down the wire. The team witnessed the formation of carbon flakes on the surface of the alloy. These could be removed to allow for the continuous capture of carbon.

The only by-products of the process are carbon flakes and pure oxygen. The carbon could just be buried back in the ground or used to produce carbon fiber materials, for example.

“A side benefit of the process is that the carbon can hold electrical charge, becoming a supercapacitor, so it could potentially be used as a component in future vehicles,” lead author Dr Dorna Esrafilzadeh explained.

The research is the first realistic step towards solid storage of atmospheric carbon. And it is sorely needed. Since the Industrial Revolution, we have injected over 1,300 billion tons of CO₂ into the atmosphere, about a third of which has been released since the year 2000.