Understanding environmental trade-offs and resource demand of direct air capture technologies through comparative life-cycle assessment

Direct air capture (DAC) technologies remove carbon dioxide (CO2) from ambient air through chemical sorbents. Their scale-up is a backstop in many climate policy scenarios, but their environmental implications are debated. Here we present a comparative life-cycle assessment of the current demonstration plants of two main DAC technologies coupled with carbon storage: temperature swing adsorption (TSA) and high-temperature aqueous solution (HT-Aq) DAC. Our results show that TSA DAC outperforms HT-Aq DAC by a factor of 1.3-10 in all environmental impact categories studied. With a low-carbon energy supply, HT-Aq and TSA DAC have a net carbon removal of up to 73% and 86% per ton of CO2 captured and stored. For the same climate change mitigation effect, TSA DAC needs about as much renewable energy and land occupation as a switch from gasoline to electric vehicles, but with approximately five times higher material consumption. Input requirements for chemical absorbents do not limit DAC scale-up. Direct air capture (DAC) technologies to remove CO2 from the atmosphere are widely used in climate policy scenarios, but their real-world impacts are not well understood. A life-cycle assessment by Madhu et al. compares two main DAC approaches and quantifies their environmental impact and resource needs.