Abstract
Direct air capture is gaining significant interest due to its potential to achieve carbon-negative emissions. With the aim to reduce the energy consumption and in line with the electrification of chemical processes, the absorption direct air capture system is integrated into a bipolar membrane electrodialysis cell stack for solvent regeneration and carbon dioxide release. The scheme solution is characterized by carbon dioxide bubbles inside the cell reducing efficiency so that other regeneration schemes have been proposed in the literature. A direct comparison of those is missing in the existing state of the art: the present work wants to fill this gap. In addition to the above process, the reaction of the rich solution with a weak organic acid and the use of both nanofiltration and reverse osmosis membranes are considered in other process schemes. The three case studies are modelled in Aspen Plus software with the aim to compare the energy consumption and total cost while the environmental impact is evaluated with the life cycle assessment methodology. Results show that the best capture process from economic and environmental point of views is that using only a bipolar membrane electrodialysis for solvent regeneration and carbon dioxide release despite a higher energy consumption for the cell stack. Here total capture cost and environmental impact are respectively 480 $/tonCO2 and -0.9593 kgCO2eq/kgCO2 while the energy requirement in the BPMED stack is 408 kJ/molCO2.