The research is part of the CORAL project, an acronym made up of the German words for CO2 as an airborne resource, is supported with a €755,000 grant from The Federal Ministry of Education and Research.
The CORAL project aims to readdress previously used methods of capturing CO2 from the air, which exclusively rely on electricity for power, a less efficient and less economical method.
“We use a chemical that binds with CO2 and is soluble in water to extract CO2 from the air – that is, to separate it from nitrogen and oxygen. When air is blown through this solution, the CO2 remains suspended and can be released again later,” said Dr. Ulrich Zuberbühler, Deputy Head of the ZSW’s Regenerative Energy Sources and Processes division.
To end this, scientists have developed a process that involves scrubbing with an aqueous solution and subsequent CO2 desorption. The researchers use electrical power to blow through the scrubber.
The waste heat produced by electrolysis and a methanation unit such as a power-to-gas plant then serves to expel the CO2 from the solution. The final step of the process cuts the energy consumption and costs.
It takes four to five kilowatt hours of waste heat and only one to two kilowatt hours of electricity to filter a cubic meter of CO2 out of the air. Without the energy from the waste heat, this would require around three times as much electricity.
The reused waste heat brings the process’s costs down to a level that could compete with these incurred by commercial CO2 suppliers, which extract CO2 mostly from fossil sources.
“CO2 extraction is a very interesting option when using vast amounts of electricity to produce e-fuels – that is, electricity-based regenerative fuels – in places like Chile and Australia that have excellent solar and wind conditions, but lack extensive power grids or sources of concentrated CO2,” said Zuberhühler.
The ZSW is collaborating with the University of Stuttgart’s Institute of Polymer Chemistry (IPOC) and the Heidelberg Institute for Energy and Environmental Research (ifeu) in the CORAL project.
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