Carbon capture and sequestration (storage) has been part of the discussion concerning how to deal with greenhouse gases primarily from burning coal, for decades.

“CCS” has been talked about, researched, pilot projects initiated, but the process never has been determined to be the answer to what happens to the emissions when coal is burned.

More recently, researchers have been getting creative, turning carbon dioxide into everything from carbon monoxide, to oxalic acid for processing rare earth elements.

Returning to the source

Finally, it appears a worldwide research team led by researchers at RMIT University in Melbourne, Australia, have determined the best way to deal with CO2, is to turn it into its source.

The researchers are using liquid metals as a catalyst to convert CO2 back into solid coal, which can actually be returned to the ground from whence it came.

Current technologies for carbon capture and storage focus on compressing CO2 into a liquid form, transporting it to a suitable site and injecting it underground.

But implementation has been hampered by engineering challenges, issues around economic viability and environmental concerns about possible leaks from the storage sites. The entire process also can be very expensive.

Billions of tonnes released annually

Reducing CO2 to value-added chemicals that can be either used as fuels themselves or as feedstock for chemical industries using renewable energy sources, has been identified as an ideal outcome for a carbon neutral future,” according to the RMIT researchers, in a study recently published in the journal Nature Communications, reviewed by Kallanish Energy.

“However, the extraordinary scale of carbon emissions, with an estimated 40 Gt CO2 (giga-tonnes CO2) (40 billion metric tonnes) being currently emitted annually and a total emitted CO2 mass in the order of 1000s Gt CO2, casts doubt on the possibility of finding suitable value-added products that can fully mitigate current and past greenhouse gas emissions.”

RMIT researcher Torben Daeneke said converting CO2 into a solid could be a more sustainable approach.

‘Rewinding the emissions clock’

“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, told a RMIT news service reporter.

“To date, CO2 has only been converted into a solid at extremely high temperatures, making it industrially unviable,” Daeneke added. “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.”

Daeneke called the research “a crucial first step to delivering solid storage of carbon.”

“We have been working on this particular topic since about 18 month,” Daeneke told Kallanish Energy. About 18 months ago, I conducted a major review of the field of liquid metal research and that’s when we put one and one together and came up with the idea.” 

How the conversion works

Lead author, Dr Dorna Esrafilzadeh, a Vice-Chancellor’s Research Fellow in RMIT’s School of Engineering, developed the electrochemical technique to capture and convert atmospheric CO2 to storable solid 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.

“Initially, we were trying to convert CO2 into synthetic fuels … ,” Daeneke told Kallanish Energy. “However, when we conducted the first experiments we found that instead of making gasses or liquids we were producing black particulates that turned out to essentially resemble coal.” 

Solid carbon flakes

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.

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.”

The collaboration involved researchers from the U.S. (North Carolina State University), Germany (University of Munster), China (Nanjing University of Aeronautics and Astronautics), and Australia (University of New South Wales, University of Wollongong, Monash University, and Queensland University of Technology).

Room temperature CO2 reduction to solid carbon species on liquid metals featuring atomically thin ceria interfaces

Source: RMIT University

Daeneke told Kallanish Energy the researchers are mostly facing engineering challenges that they believe can be overcome. “We will, however, have to upscale by several orders of magnitude,” he said. “This will take a number of years. The final costs of the process will ultimately determine whether the process can be run profitably.” 

The RMIT researcher added he and his compatriots have been talking to a number of commercial entities from diverse industries, and “continue to consider several options.”

This post appeared first on Kallanish Energy News.