Submarines don't turn CO2 back into O2. They "scrub" the CO2 out using Soda Lime (or similar). They use electrolysis or oxygen candles to generate new oxygen.
After the soda lime is maxed out, it's tossed. At least so far as I understand you can't meaningfully re-use it for scrubbing, though there are other industrial uses where it can be re-purposed. Also O2 electrolysis takes a fairly substantial amount of electricity, which is OK when you've got a nuclear generator on your hands.
So.... it's a lot cheaper (and more environmentally friendly) to use an ERV system in your HVAC system even at "only" 80% recovery. Let the plants do what they are good at and deal with capturing CO2 and giving us O2.
The problem is we don't generally build insulated enough or tight enough houses to matter. If everything was built to passive house standard, we'd save HUGE amounts of energy globally.
> After the soda lime is maxed out, it's tossed. At least so far as I understand you can't meaningfully re-use it for scrubbing, though there are other industrial uses where it can be re-purposed.
Does it get re-purposed? Is there an issue to "tossing" it out of the sub while submerged?
The soda lime solution is only used for shipboard casualties. The normal service system on a submarine uses a regenerative fluid to scrub the air of CO2.
Interesting. I did more research and there isn't a ton out in the public domain, but it looks to be that the USN and others are using MonoEthanolAmine (MEA) as a regenerative CO2 scrubber. MEA
>Weeks et al. (1960) reported that volunteers who smelled MEA vapor described the odor as ammoniacal, musty, or foreign; some volunteers were unable to characterize the odor.
> Ethanolamine is a colorless, viscous liquid with an odor reminiscent of ammonia.
Ammonia is a lot of what "cat piss" smells of, so that tracks. Thanks! That was really interesting to read about!
If I remember my chemistry correctly Soda lime + CO2 results in Sodium Bicarbonate (baking soda) and Calcium Carbonate. I'm not a submariner, so I have no idea if they have re-purposes use for it onboard. I would assume it is stored, like all trash/waste, onboard until the sub is resupplied.
https://www.analoxgroup.com/blog/how-do-you-breath-onboard-s...
After the soda lime is maxed out, it's tossed. At least so far as I understand you can't meaningfully re-use it for scrubbing, though there are other industrial uses where it can be re-purposed. Also O2 electrolysis takes a fairly substantial amount of electricity, which is OK when you've got a nuclear generator on your hands.
So.... it's a lot cheaper (and more environmentally friendly) to use an ERV system in your HVAC system even at "only" 80% recovery. Let the plants do what they are good at and deal with capturing CO2 and giving us O2.
The problem is we don't generally build insulated enough or tight enough houses to matter. If everything was built to passive house standard, we'd save HUGE amounts of energy globally.