Efficient Removal of Carbon Dioxide From the Atmosphere


RWTH researchers publish on negative emissions and other environmental impacts through direct air capture.


As part of their research activities in the Kopernikus project Power-to-X, Sarah Deutz from the RWTH Chair of Technical Thermodynamics and Professor André Bardow, formerly RWTH Aachen University and and now at ETH Zurich, have shown that the commercial direct air capture plants in Hinwil, Switzerland, and Hellisheiði, Iceland, are already achieving negative emissions today. The facilities attain carbon capture efficiencies of 85.4 and 93.1 percent, respectively.

The scientists have now published their findings in the scientific journal Nature Energy, in an article titledLife-cycle assessment of an industrial direct air capture process based on temperature-vacuum swing adsorption.”

Climate Benefits Depend on the Energy Source Used

According to their research, the climate benefits of direct air capture strongly depend on the energy source used. Adsorbent choice and plant construction, by contrast, only induce up to 45 and 15 g carbon dioxide per kilogram CO2 captured, respectively. Only when using low-carbon energy, such as the geothermal energy generated in Hellisheiði, is this share of emissions significant.

Large-scale deployment of DAC with the aim of removing one percent of the global annual CO2 emissions, the researchers predict, would not be limited by material and energy availability and present a possible step towards meeting current climate targets.

Other environmental impacts would increase by less than 0.3 percent. The captured carbon dioxide could be stored to generate negative emissions or serve as an alternative carbon feedstock for synthetic fuels or other value-added like chemicals and building materials. The environmental friendliness of these applications strongly depends on the energy source used and on energy efficiency.