ZSW develops new process to capture CO2

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.