[jbattle]

Assuming abundant power and effective carbon recapture / recycling, how much carbon do you need per person? If it was on the order of 50 lbs of carbon per person, and that could be infinitely recycled, that doesn't seem wildly onerous. It looks like the average person exhales about 2 pounds of carbon per day, so that's a very rough baseline in terms of carbon needs.

Is there a technology available now or soon that can scrub carbon out of the ambient air and capture that in an easy to reuse medium?

[px43]

~~Yeah, I think carbon recycling can be pretty good. They've been doing it on submarines for a while.~~

(edit: nevermind, I was confused about the submarine thing, the user "idlewords" below has a lot of good commentary about this)

At any given moment, any human is about 18% carbon. Carbon is also pretty important in *carbo*hydrates. Any plants that we would grow would need a ton of carbon. It can be done, but any moon colony will basically always be dependent on getting extra carbon from Earth, so it can never be "self sufficient" in the way that Mars can eventually be.

It is kind of funny that on Earth, we're obsessed with capturing and burying as much carbon as possible, when it's going to be an incredibly valuable resource on the moon, assuming that a bunch of people are gong to want to live there.

[shagie]

Submarines restock food, some air supplies, and... deal with waste.

Food https://youtu.be/bPJUVKizh90

Air https://youtu.be/g3Ud6mHdhlQ (MEA and LIOH for CO2, electrolysis and "candles" for oxygen)

Toilet https://youtu.be/SYFuA3xnkUE?t=985

Nothing is "recycled" as such - and certainly not any of the carbon (you're not eating the carbon captured from MEA or LIOH... or your waste).

[wonderwonder]

Seems like carbon capture and export to the moon is a business that is just short of a billionaire to implement it.

[idlewords]

Submarines don't recycle carbon; they capture CO2 and vent it.

[rtkwe]

Mostly because they don't need to retain it though, a sub doesn't need to reprocess the CO2 into C and O2 but the process can be done. The process is largely the same instead of ejecting it as a waste product continue to break it down into useful products like injecting it into a Sabatier process.

[idlewords]

The Sabatier reactor on the space station broke after processing about a thousand liters of water because deodorant and astronaut urine poisoned the catalyst beds.

Everything is easy to do in theory. Recycling carbon in practice is very, very hard if you don't have plants to help you.

[shagie]

Hypothetically... after you have separated the carbon from the oxygen (discounting the human waste which has a significantly more amount of carbon)... what would you do with it as part of a recycling process in a submarine?

[rtkwe]

In current tech not much comes to mine. Maybe it could be reprocessed into dry graphite lubricant but there's not much need for raw carbon or principally carbon materials in a submarine. That's another reason it just gets tossed there's just not a real use for it. On a hypothetical extraplanetary colony though it's a pretty important material just to keep people alive.

[idlewords]

You can store it as methane and cook with it in the galley.

[rtkwe]

You don't want to be simply reintroducing it into the atmosphere again that would just increase the amount you need to scrub out of the air because now your cycle just reintroduces all the CO2 you remove back into the air along with the stuff the sailors are breathing out. Submarines as far as I can see have basically always used electric cook tops for that reason, at least since they were designed to stay submerged most of the time. UBoats probably didn't because electric power was so limited they probably just didn't cook hot food while submerged.

[shagie]

That's not exactly a closed loop recycling system.

Additionally, flame is very restricted on a sub. You wouldn't be using any sort of methane to cook.

https://qr.ae/prgBKF

https://qr.ae/prgBsh

https://www.answers.com/Q/What_fuel_does_a_submarine_use_for...

[TaylorAlexander]

I’m pretty sure NASA has been reusing carbon on human spacecraft since at least the Apollo program.

[idlewords]

That is not the case; carbon (as CO2) was captured by disposable LiOH cartridges through the end of the Shuttle program. On the ISS, it's captured on zeolite beds and vented into space. Except for a few small-scale plant experiments, no space program has demonstrated carbon capture and re-use.

[TaylorAlexander]

Ah I see, thank you! I figured someone would know better than me on this.