MSA is a method of adsorbing CO₂ under normal dry conditions and desorbing CO₂ under wet conditions using an ion exchange resin. There is no need for heating for desorption, and it may reduce DAC costs. It is under development mainly in the United States and China, but there is no demonstration facility yet.
　The assumed adsorption facility is a spiral-wound-type membrane module of one meter in diameter and two meters in length, in which a membrane containing an ion exchange resin is wound in an Archimedean spiral form. Assuming that the size of the spacer is 5 mm, the length of the membrane is 119 m, and the adsorption capacity of the membrane is 21.8 g-CO₂/m² , the DAC cost is 39 yen/kg-CO₂, which is comparable with that of the KOH-CaCO₃ based alkali absorption method in the CO₂ collection cost. In the future, it will be necessary to develop and demonstrate it as a national project, such as by developing an inexpensive and high-performance ion exchange resin membrane and confirming that the water required for desorption can be obtained by spraying water.