Decarbonisation Technology May 2026 Issue

CO 2 capture screening device for sorbent optimisation Automated screening can accelerate the development of direct air capture sorbents by utilising a sample exchanger

Andreas Sundermann, Charlotte Langheck, and Robert Baumgarten hte GmbH

T he increasing concentration of atmospheric carbon dioxide (CO 2 ) is the primary cause of global climate change ( Filonchyk et al., 2024 ). Since the start of the industrial era, human activities have released more than 1,100 gigatons of CO 2 into the Earth’s atmosphere, and current emissions exceed 40 Gt annually ( Etheridge et al., 1996 ). Natural sinks – forests, soils, and oceans – absorb only around 26 Gt of CO 2 per year, and this buffering comes at the cost of ocean acidification ( Friedlingstein et al., 2022; Janowiak et al., 2017 ). Thus, mitigating climate change requires not only capturing new CO 2 at the point of emission but also removing CO 2 from historical emissions already accumulated in the atmosphere (Sekera et al., 2023). This emphasises the urgent need for effective and scalable CO 2 removal (CDR) technologies. At the same time, CDR offers the chance to reclaim CO 2 as a valuable building block for the chemical industry ( Huo et al., 2023; Wittich et al., 2020 ). Direct air capture Among the portfolio of CDR strategies, direct air capture (DAC) has emerged as a promising technology capable of removing historical and diffuse CO 2 emissions directly from the ambient air ( Beuttler et al., 2019 ). Unlike point- source capture, which targets emissions from industrial flue gas streams, DAC addresses the much lower atmospheric concentration of CO 2 (approximately 400 ppm), posing distinct chemical and engineering challenges. Currently, two principal technological pathways dominate the DAC landscape: solid sorbent- based systems (S-DAC) and liquid solvent-

based systems (L-DAC) ( Sodiq et al., 2023 ). S-DAC technologies, for instance, employ solid amine-functionalised adsorbents that bind with CO 2 at ambient temperatures and release it upon heating, typically at low to medium temperatures (60-120°C) ( Xu et al., 2024 ). L-DAC systems, conversely, utilise aqueous alkaline solutions, such as potassium hydroxide, to capture CO 2 as carbonate, which is regenerated through a high- temperature (>900°C) calcination ( Keith et al., 2018 ). While both approaches have been demonstrated at pilot and even commercial scales, significant advancements are required to reduce the substantial energy penalty and associated costs to facilitate gigaton-scale deployment ( Bouaboula et al., 2024 ). Moreover, the net effectiveness of DAC plants is often questionable, especially after accounting for the CO 2 emissions associated with their construction and operation ( Terlouw et al., 2021 ). One way to improve overall effectiveness is to enhance the performance and sustainability of CO 2 capture materials, which can be achieved through intensive material screening. Ideal sorbents should exhibit rapid CO 2 diffusion and adsorption kinetics at the ambient atmospheric partial pressure. CO 2 binding should be stable at the adsorption temperature and still allow for sufficiently low desorption temperatures ( Priyadarshini et al., 2023 ). This way, excessive thermal or pressure requirements and, therefore, energy demand can be avoided in the overall process. Research indicates that amine-modified, porous adsorbents are promising candidates due to their high CO 2 uptake capacities, low