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How (Carbon) Negative Is Direct Air Capture? Life Cycle Assessment of an Industrial Temperature-Vacuum Swing Adsorption Process

revised on 22.01.2021, 12:50 and posted on 25.01.2021, 08:24 by Sarah Deutz, André Bardow
Current climate targets require negative emissions. Direct air capture (DAC) is a promising negative emission technology, but energy and materials demands lead to trade-offs with indirect emissions and other environmental impacts. Here, we show by Life Cycle Assessment (LCA) that the first commercial DAC plants in Hinwil and Hellisheiði can achieve negative emissions already today with carbon capture efficiencies of 85.4 % and 93.1 %. Climate benefits of DAC, however, depend strongly on the energy source. When using low-carbon energy, as in Hellisheiði, adsorbent choice and plant construction become important with up to 45 and 15 gCO2e per kg CO2 captured, respectively. Large-scale deployment of DAC for 1 % of the global annual CO2 emissions would not be limited by material and energy availability. However, current small-scale production of amines for adsorbent production would be needed to be scaled up by an order of magnitude. Other environmental impacts would increase by less than 0.057 %. Energy source and efficiency are essential for DAC to enable both negative emissions and low-carbon fuels.


The authors gratefully acknowledge funding by the German Federal Ministry of Education and Research (BMBF) within the Kopernikus Project P2X: flexible use of renewable resources – exploration, validation and implementation of ‘Power-to-X’ concepts. We thank our partners from Climeworks, who provided data, insight, and expertise in their technology that greatly assisted our research. We thank Leif Kroeger and Kai Leonhard for the valuable discussions on reaction kinetics and thermochemistry, and Dominik Bongartz for conducting the process simulations on heat integration of DAC and synthetic fuel production. We further thank Noah McQueen and Jennifer Wilcox for comments helping us to improve our study, and Verena Beckert, Lukas Dörpinghaus, Niklas Groll, Felicitas Pellengahr, and Nergiz Tigu for their technical support.


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Chair of Technical Thermodynamics, RWTH Aachen, University



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Declaration of Conflict of Interest

No Conflicts of Interest