Researchers working to make carbon capture more useful and efficient have come across what could be a major step in the right direction.
With a near-global focus from governments to reduce the amount of carbon emissions in the world, researchers are working to find new methods of carbon capture that not only significantly reduce emissions, but turn them into a viable energy source of their own.
To that end, researchers at the US Department of Energy’s Idaho National Laboratory (INL) have found a way to turn carbon emissions into syngas, a mixture of hydrogen and carbon monoxide that can be used to make fuels and chemicals.
Using traditional carbon-capture methods, attempts to reuse the carbon involve a reduction step that requires high temperatures and pressures. (At lower temperatures, CO2 doesn’t stay dissolved in water long enough to be useful.)
Detailing its findings in the journal Green Chemistry, the INL team found a way to use specialised liquid materials to make the CO2 more soluble. This allows the carbon-capture medium to be directly introduced into a cell for electrochemical conversion to syngas.
The liquid materials in this case are switchable polarity solvents (SPS), making it possible to control what molecules dissolve in a solvent.
So, to create syngas, hydrogen ions are obtained through oxidation and then react with bicarbonate, allowing the release of CO2 for electrochemical reduction and formation of the gas.
Upon the release of CO2, the SPS switches polarity back to a water-insoluble form, allowing for the recovery and reutilisation of the carbon-capture media.
Writing in its paper, the research team said: “For the first time, it was demonstrated that syngas can be directly produced from captured CO2, eliminating the requirement of downstream separations.”
Unlike other processes that require high temperatures and high pressures, the SPS-based process showed best results at 25C and 40psi.
“It integrates two areas that have been on parallel tracks: carbon capture and sequestration (CCS), and CO2 utilisation,” said the team’s principal investigator, Luis Diaz Aldana.
“The problem with CCS has been its economic feasibility. If you can get some extra value out of the CO2 you are capturing, it’s a different story.”