[gpm]

98% curiosity, 2% lack of faith in our long term ability to keep CO2 levels down to healthy levels (1000ppm is enough that we can detect minor negative effects... I have to wonder if really minor ones exist even at 400 ppm).

Wikipedia was similarly not useful for me. Scuba divers and the like apparently use a one-time-use non-regenerative mineral that absorbs CO2. The space station has something that regenerates but I haven't been able to figure out what.

[swiley]

I know older spacecraft didn’t have a regenerative material, this is the first I’ve heard about the space station.

You’d have to reduce the CO2 pretty far (I’m betting reducing to CO like in TFA isn’t what you’re looking for.) I think a lot of people underestimate how much energy this takes.

[gpm]

Re ISS, I've been clicking around on this a bit more, and

> While cabin air processing, one carbon dioxide removal bed is in the process of regeneration. Regeneration is accomplished using pressure/thermal swing methodology. First, the two-stage pump removes the free air from the adsorbent bed and returns it to the cabin, reducing oxygen ullage. Then Kapton heaters integrated within the adsorbent bed raise the zeolite temperature, and space vacuum creates a low, partial pressure driving the carbon dioxide gas overboard. Daylight and continuous day power cycle is overlapped with the operating cycle. In the daylight power cycle, the carbon dioxide adsorbent bed heaters are only allowed to be powered on during the day portion of the cycle

> [...]

> The CDRA continuously removes 6 person-equivalents of CO, when operating with both C02 removal beds (dual beds) functioning.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/200502...

Converting CO2 into CO would be rather counterproductive (absent a reliable and efficient mechanism to remove CO), I suspect an efficient setup will involve "mechanical" filtration not chemical reactions.

[gpm]

Ah, and this paper contains an incredible amount of details, and zeolite 13x and 5a is really cheap on Alibaba, I'm going to have to try this

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/199700...

[marcosdumay]

Just be careful during the regeneration. CO2 is toxic at high concentrations.

[namibj]

If you figure out some concrete setup, let me know. I am fairly certain that there are measurable cognitive effects at "just" 500 ppm, and good luck staying below that when you can't just sit at an open window outside of a city.

1000 ppm is btw. enough to feel uncomfortable. Cognitive impairment will be much more subtle.

[lugorrr]

I am fairly certain that there are measurable cognitive effects at "just" 500 ppm

Well, that would be problematic sooner or later [1].

[1] https://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/co2_data_m...

[gpm]

Indoors that's problematic today, outdoors we have "awhile" if you make 500 your cutoff, we're only growing at ~2.4 ppm per and the yearly peak is at roughly 420 right now, we can probably count on 20 years before we hit 500 outdoors.

https://www.co2.earth/co2-acceleration

[mulcyber]

Casual technical diver here. It's lime (maybe something else sometime, not 100%).

The process of making lime from limestone actually produces CO2, so it's use in CO2 scrubbers are more or less carbone neutral.