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Comment by derefr | Hacker News Reader

Is there any practical way to have less indoor CO2 than outdoor CO2, without needing to buy expensive single-use scrubber chemicals? Maybe presuming you live somewhere with cheap electricity and/or a cheap fresh water supply?

Basically I’m asking whether there’s a Maxwell’s Daemon-like device for separating the CO2 from the air, and venting the CO2 back outside, while bringing in the rest of the air. Like a CO2 scrubber, but without any need for CO2 sequestration, since you exist inside an open system instead of in a space station/bunker/submarine.

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I don't think this exists on a small scale yet.

On industrial scales, CO2 is commonly removed with reusable scrubber chemicals, referred to as a group as amines. The amine acts as a CO2 solvent, removing the CO2 from the bulk gas. The 'rich' amine is then cycled to a separate location in the process where it is heated up, causing the CO2 to bubble out of solution, regenerating the amine for reuse, etc.

I don't see any reason in principal why this can't be miniaturized, but it would be a challenging engineering problem.

https://en.wikipedia.org/wiki/Amine_gas_treating

Regenerative CO2 scrubbers exist: https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber#Regene...

Sounds like aquariums sometimes use CO2 scrubbers, so regenerative CO2 scrubbers might be commercially available for that market: https://www.youtube.com/watch?v=5_GM5ZBzvdk

> Regenerative CO2 scrubbers exist

AFAIK those still need consumables. NASA says there are ways to reduce the amount of consumables, but not eliminate them [1]:

In the current [...] configuration, carbon dioxide is removed from the cabin and discharged overboard. The gases lost during venting must be replaced, and thus represent a consumable. By comparison, a closed-loop CDRA system could selectively remove carbon dioxide from the cabin air supply, and the concentrated CO, would be routed to a carbon dioxide reduction system, where the oxygen would be recovered, thereby reducing the consumables.

[1] https://ntrs.nasa.gov/citations/20050210002

I think that quote is considering the oxygen in the CO2 to be a consumable, not the scrubber material itself. That's relevant on a spacecraft. But here on earth we've got plenty. :)

There are these things called plants that do that kind of stuff, so maybe if you have enough of them inside your house, they eat the CO2 away... :)

I don’t think there’s any practical level of plant-having that would result in there being less CO2 in the house than in the atmosphere.

IIRC, there’s some point in running an indoor grow-ops where you start needing to worry about spraying CO2-enriched air on the plants; but that’s just to accelerate growth, like a fertilizer. Or, sometimes, it’s because OPSEC requires you to not vent your smelly waste air — and because no human or animal lives in the grow-op house to convert O2 to CO2, the air becomes gradually CO2-poor. But that wouldn’t happen if even one human lived there; humans convert metabolize a lot faster than plants do.

came here for this.

Another solution would just be to pump in cleaner air. You could imagine a truck that drops off a few tanks of CO2-free air.

Perhaps we can install oxygen lines next to our natural gas lines.

I get your sarcasm but it'd probably mostly nitrogen.

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