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
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.
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