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Half a pound of this powder can remove as much CO2 from the air as a tree

latimes.com

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Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#41

Post by telgareith »

kazinator wrote: post #37
hansvm wrote: post #27

Earlier quoted context omitted.

Right, and you want that. Scrubbing the CO2 without adding oxygen leaves you in a state where the air is useless and your body can't tell.

If we mix, say, 25% CO2 and 75% regular air, we will get something which still has oxygen, but at too low a concentration to support breathing: the oxygen will have dropped from 21% to around 16%. That's still a lot of oxygen, but not at a breathable concentration. If all the CO2 is removed, then the breathable air is recovered.

Simple rebreathers use pure oxygen, and even when they don't- as long as co2 is steadily scrubbed out, its little more than a regular scuba regulator.

Oxygen has to go above a certain partial pressure (happens at a couple meters down, I don't know the numbers of the top of my head) before it's toxic. And, carrying a tank that's got more than oxygen in it defeats the original military development and use model of rebreathers: no bubbles, and long submersion times.

The real problem for users is a lot of carbon dioxide scrubbing compounds will kill you if they get wet.

Engineering wise, I seem to recall pressure balancing (countering the water's pressure), and forcing your exhalation air through the scrubber being the complexity.

Theres a ton of complexity with rebreathers. And, thats before accounting for the fact they're mostly used in combat and cave diving. (Last I checked. Tbf, I got scared and changed career paths away from the sea after Rouge Waves became irrefutable fact)

Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#42

Post by Woodi »

entropicdrifter wrote: post #21
BizarroLand wrote: post #12

Earlier quoted context omitted.

Since the powder is reusable, it likely wouldn't make sense to sequester it with the CO2 either materially or financially.

This. The powder is more efficiently used as a way to move the CO2 around than as a means to keep it sequestered.

Still, tree produce oxygen from that CO_2. And do not need energy from grid for that :)

Threating CO_2 like radioactive waste, putting it underground etc - that what I call not self-sustained :>

Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#43

Post by kadoban »

_yb2s wrote: post #28
kadoban wrote: post #16

Earlier quoted context omitted.

This is definitely a real problem, but it's not caused by higher outdoor CO2 levels. The levels outside are typically in the 400-500ppm range. When you're enclosed with not enough ventilation, the issue is you (and other breathing organisms) and the lack of ventilation, not the outdoor level. The outdoor level has absolutely risen, it's just not the important factor here. You're very lucky that you can keep windows o…

I disagree- many people, especially in Europe are still using buildings designed in pre-industrial times, when CO2 levels were as low as half what they are in urban areas now. Those buildings now will have much higher CO2 levels indoors than when first built, with the same amount of air exchange. One could estimate exactly how much higher with some differential equations, but certainly in some cases it is possible to…

> One could estimate exactly how much higher with some differential equations, but certainly in some cases it is possible to push things over the limit where there are now problems, everything else remaining the same.

It's obviously in the direction of higher indoor CO2 levels, but the effect just isn't that big if you're talking about your indoor levels being 2000ppm. It's not the cause of that.

I'll see if I can math up some numbers later to quantify.

> Moreover, those buildings likely now have much less air exchange than when designed now that they use AC instead of open windows, forced air heat instead of unsealed fireplaces (which turn over a lot of air), and possibly have been updated to more airtight doors and windows.

Yes, these are the causes. Well insulated homes are legitimately great, but now we're finding out that ventilation is also quite important and wasn't well enough planned for in many cases.

It's also that CO2 wasn't easy to measure decades ago. I'm sure many homes had high levels even with no door seals and leaky windows, just nobody had a great way to know or care. I'm sure ways existed, to be clear, but it wasn't like today where you can grab a monitor on amazon on a whim.

Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#44

Post by _yb2s »

kadoban wrote: post #43
_yb2s wrote: post #28

Earlier quoted context omitted.

I disagree- many people, especially in Europe are still using buildings designed in pre-industrial times, when CO2 levels were as low as half what they are in urban areas now. Those buildings now will have much higher CO2 levels indoors than when first built, with the same amount of air exchange. One could estimate exactly how much higher with some differential equations, but certainly in some cases it is possible to…

> One could estimate exactly how much higher with some differential equations, but certainly in some cases it is possible to push things over the limit where there are now problems, everything else remaining the same. It's obviously in the direction of higher indoor CO2 levels, but the effect just isn't that big if you're talking about your indoor levels being 2000ppm. It's not the cause of that. I'll see if I can ma…

You are correct after all. I setup some equations and solved for the interior steady state CO2 levels as a rough approximation the steady state interior CO2 levels are proportional to CO2_outside + generation rate / ventilation rate.

Therefore, steady state interior levels will only rise by approximately the same amount as the outside levels, which does seem insignificant.

Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#45

Post by jjk166 »

hansvm wrote: post #27
jjk166 wrote: post #22

Earlier quoted context omitted.

You produce the CO2 that causes the impulse to breathe. That's what you are exhaling.

Right, and you want that. Scrubbing the CO2 without adding oxygen leaves you in a state where the air is useless and your body can't tell.

Scrubbing the CO2 from the air has no effect on it. The CO2 that tells you to breathe is not in the air. You exhale the CO2 because you specifically do not want it, you need to get rid of it. Hence the scrubbing.

If there is not enough oxygen in the air to breathe, having more CO2 in the air will not save you.

Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#46

Post by BizarroLand »

gus_massa wrote: post #17
BizarroLand wrote: post #10

Earlier quoted context omitted.

If you can extract ~100% pure CO2 from the powder, then it might be feasible to develop a process that can convert very dense CO2 into Carbon and Oxygen. Carbon is about 3/8ths of the total weight of a CO2 molecule and is solid and relatively inert at room temperature and pressure. Of course, if there were a convenient way to simply strip carbon off of a CO2 molecule to begin with that would be the ideal system, but…

> Plants do it, after all. It's not impossible. The problem is that to reverse CO2 -> C + O2 you need the same amount of energy that you get burning coal C + O2 -> CO2. But burning coal, like half of the energy is lost as unuseful heat. The reaction of plants is different, but plants only has a 2% of efficiency. The chemical reaction of plants is more complicated, so let's be optimistic and assume this reaction has a…

Seems like the chemical process has been a solved equation for a while. Rather than directly splitting the molecule, they use high pressure and heat to incorporate a hydrogen atom into it, converting it into Methane which can then be broken down with high heat to carbon and hydrogen.

From the page https://chemistry.stackexchange.com/questions/915/how-can-ca...

----------

React carbon-dioxide with hydrogen in the Sabatier (https://en.wikipedia.org/wiki/Sabatier_reaction) process to get methane. 400 °C, high pressure and Nickel catalyst needed. The process is slightly exothermic so it can keep going on its own:

CO2+4H2→CH4+2H2O

This process have been proposed to generate fuel on Mars, and used on the ISS to process exhaled carbon-dioxide.

Split the resulting water (use electrolysis or some other thermochemical cycle) take the oxygen, bring the hydrogen back to Step 1:

2H2O→2H2+O2

Electricity for this may come off solar panels.

Methane decomposes at high temperatures. The process goes to completion around 1200°C. Collect the condensed carbon, bring the hydrogen back to step 1.

CH4→C+2H2

This process is proposed as an emissions free alternative to produce hydrogen from natural gas. Heat may come from concentrated solar light.

------------

The missing ingredients are excess CO2 from the atmosphere and a machine system to do the full process with, and of course the math about economies of scale regarding how fast a machine that uses this method combined with the powder in the article can actually strip carbon from CO2 in the atmosphere.

It likely would neither be cheap nor fast, but since it uses nickle as a catalyst at least it is not fancy rarefied expensive hard to find materials, just more an issue of getting all of the parts together and making the whole machine run as efficiently and effectively as possible.

Also, if the methane is generated from CO2, then burning it is nearly carbon neutral, so in places where fossil fuels are the ideal energy source it would allow us to use Green energy to make transportable low-carbon fossil fuels for them to use.

Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#47

Post by kadoban »

_yb2s wrote: post #44
kadoban wrote: post #43

Earlier quoted context omitted.

> One could estimate exactly how much higher with some differential equations, but certainly in some cases it is possible to push things over the limit where there are now problems, everything else remaining the same. It's obviously in the direction of higher indoor CO2 levels, but the effect just isn't that big if you're talking about your indoor levels being 2000ppm. It's not the cause of that. I'll see if I can ma…

You are correct after all. I setup some equations and solved for the interior steady state CO2 levels as a rough approximation the steady state interior CO2 levels are proportional to CO2_outside + generation rate / ventilation rate. Therefore, steady state interior levels will only rise by approximately the same amount as the outside levels, which does seem insignificant.

Thanks for doing that, I got lost in the math and couldn't figure it out in the time I had, too rusty xD

Re: Half a pound of this powder can remove as much CO2 from the air as a tree

#48

Post by hansvm »

K0balt wrote: post #38
hansvm wrote: post #23

Earlier quoted context omitted.

What I mean is that scrubbing the CO2 leaves you in a scenario where the air is just as dangerous as before (no oxygen) but you don't have any reflexes or senses letting you know of the danger.

It’s the co2 in your blood that you make in your body( not that you breathe in) that makes you want to breathe. You can breathe pure oxygen and you will still feel the need to breathe, because your body uses the oxygen to make co2 which then needs to be expelled.

That only applies (gives you a trigger that you should breathe when the environment is dangerous) if you never exhale though. Is that really an argument for the technique being safe?
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