Turning back time on CO2

Caption: Making this out thin air isn’t easy, but Australian scientists have done it.

Carbon capture and storage is something of a holy grail of modern engineering. If feasible, it would offer the potential to scrub human-produced carbon dioxide from the atmosphere. The problem has been, though, that it has so far proved to be somewhat less than feasible. Not only has the capture involved complex processes, but safely storing the captured liquid carbon dioxide (usually underground) presents a whole other level of difficulty and risk.

Experimental research from Australia?s RMIT University has resulted in a promising new technique. Carbon dioxide is extracted at room temperature, and converted into solid, stable carbon. It?s not quite re-creating coal from carbon-dioxide, but it?s close. Quote:

Published in the journal Nature Communications, the research offers an alternative pathway for safely and permanently removing the greenhouse gas from our atmosphere?RMIT researcher Dr Torben Daeneke said converting CO2 into a solid could be a more sustainable approach.

?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,? Daeneke, an Australian Research Council DECRA Fellow, said.

?To date, CO2 has only been converted into a solid at extremely high temperatures, making it industrially unviable. End of quote.

Liquid metals are elements of alloys with such low melting points that they are liquid at room temperatures. Mercury is the most well-known. The RMIT process uses gallium and cerium. Quote:

?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.

?While more research needs to be done, it?s a crucial first step to delivering solid storage of carbon.?

?To convert CO2, the researchers designed a liquid metal catalyst with specific surface properties that made it extremely efficient at conducting electricity while chemically activating the surface.

The carbon dioxide is dissolved in a beaker filled with an electrolyte liquid and a small amount of the liquid metal, which is then charged with an electrical current.

The CO2 slowly converts into solid flakes of carbon, which are naturally detached from the liquid metal surface, allowing the continuous production of carbonaceous solid. End of quote.

While this is only a baby step, the crucial point is that they have shown that it can be done. Cerium, despite its ?rare earth? status, is a common element ? more common than lead ? while gallium is produced most often as a by-product of aluminium production from bauxite. Both metals are non-toxic. Scaling the process up to the scale that it can be usefully applied to carbon capture is the obvious engineering challenge, as is supplying the necessary energy. So, it?s hardly time to start singing the hallelujahs about slaying the sky dragon, just yet. Quote:

[Lead author, Dr Dorna] Esrafilzadeh said the carbon produced could also be used as an electrode.

?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.?

?The process also produces synthetic fuel as a by-product, which could also have industrial applications.? End of quote.


The full paper detailing their experiment is available from Nature.