Sno matter how many solar and wind power plants are built and means of transport emit less and less carbon dioxide: It is not enough to keep global warming below the magic threshold of 1.5 degrees Celsius, says the Intergovernmental Panel on Climate Change (IPCC). That is why he is calling for billions of tons of greenhouse gas to be removed from the atmosphere. This is associated with high costs and high energy consumption, at least with the techniques used up to now.
Cora – the name stands for CO2 raw material from air – should now remedy the situation. Researchers from three scientific institutes and industry are developing a process with which CO2 can be removed from the air at low cost. The separated climate gas is then to be used as a chemical raw material to replace fossil raw materials, or stored in gaseous or solid form underground.
The decisive material component was developed by the German Institutes for Textile and Fiber Research (DITF) in Denkendorf near Stuttgart: a fleece made of the natural substance cellulose, which offers little resistance to the air flowing through, so that little pumping energy is required, and yet the CO2 contained in the air flow largely captured. Amines serve as CO2 scavengers, these are organic compounds with which the fleece is impregnated.
The second innovation reduces energy consumption even more significantly compared to established processes. The fleece is designed as a slowly moving endless loop, similar to a conveyor belt. Part of it is exposed and air flows through it. It then slides into a heat chamber where the bound CO2 is released and can be captured. The amines adhere so firmly to the cellulose that as soon as the fleece leaves the heating chamber and air flows through it again, they capture greenhouse gas again. Among other things, the system could be integrated into the air conditioning circuit of buildings. Then additional pump energy would not be necessary.
Amines also played a crucial role in test systems for flue gas scrubbing. The exhaust gases from the coal-fired power plants were fed into an amine bath, where they were freed of CO2. If the organic compound was saturated, the liquid had to be heated to separate the greenhouse gas. This caused the energy balance to falter alarmingly. The result: This technique is only pursued with slowed down foam.
The consortium of DITF, the Center for Solar Energy and Hydrogen Research Baden-Württemberg in Stuttgart, the Institute for Energy and Environmental Research Heidelberg and Mercedes-Benz Sindelfingen believes that Cora is also energetically cheaper than the discontinuous process of the Swiss pioneer Climeworks, which captures carbon dioxide with a special sponge. If this is saturated, it must be replaced by a fresh one and regenerated in a heating chamber.
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