Monoethanolamine as a CO2 Scrubber

On submarines, CO₂ is removed with a chemical scrubber, called monoethanolamine. MEA is supplied in liquid form, although it may be a solid dissolved in water. When cold, MEA takes in CO₂, when heated, MEA gives up the CO₂. On submarines, the CO₂ is pumped overboard. On a lunar base, the CO₂ would be stored under pressure or liquified until either there was enough plant life to recycle it naturally, or enough spare energy available to dissociate the CO₂ into carbon and O₂.

LiOH is suitable for short duration missions, but is a one-time-use item. It turns into lithium carbonate, after which it absorbs no more CO₂, while MEA absorbs and gives up CO₂ in a continuous heating/cooling cycle.

LiOH is currently used on spacecraft because of weight considerations--the weight of the needed LiOH is less than the weight of a regenerative CO₂ scrubber. Also, current MEA-type scrubber designs require gravity to work.

For a short duration confinement with a limited number of people, LiOH is the better solution regarding CO₂. For longer missions, MEA becomes more economical, but after that, immediate chemical processing would be more effective once the necessary equipment is in place in the habitat.