Harvesting Carbon (and other elements) from an atmosphere.

[Joshua Jones]

I am working on a bit of tech for a story I am writing, and I am curious what technological challenges may need to be overcome to harvest elements, especially Carbon, directly from an atmosphere (for ease of discussion, we will say Earth's atmosphere) at an industrial scale. Can anyone point me to any good articles or share some of their own research on the matter?

 

[Venusian Broon]

Is the reason for harvesting Carbon from the atmosphere because you want to remove carbon from it, to reduce global warming say, or because you want carbon for another process - like making diamond objects?

Because if it is not for the first reason, then surely there would be much more concentrated forms of carbon in the ground as rock/stone that would be much easier to extract

 

[HareBrain]

This one seems to sum up the challenges with carbon pretty well:

Artificial Photosynthesis - TheGreenAge

 

[Joshua Jones]

Is the reason for harvesting Carbon from the atmosphere because you want to remove carbon from it, to reduce global warming say, or because you want carbon for another process - like making diamond objects?

Because if it is not for the first reason, then surely there would be much more concentrated forms of carbon in the ground as rock/stone that would be much easier to extract

Terraformation in broad terms while still creating a usable product. So, yeah, it could be used for global warming, or over a longer period to help make a planet like Venus more inhabitable.

This one seems to sum up the challenges with carbon pretty well:

Artificial Photosynthesis - TheGreenAge

Thanks for the link! I'll take a look when I get off work tonight.

 

[Venusian Broon]

The 'Terraforming of Venus' page on Wikipedia has quite a few general approaches on what to do with something as extreme as a Venusian atmosphere. (Why they would want to, I don't know, it's a lovely time of year at my ranch near Maxwell Monte; the metallic snow is particularly Christmassy).

Some of the solutions, (nay, all of them!) are pretty long-term, far off future SF

If it is for Earth, I think you'll find that a lot of industrial capture of Carbon, is focused on trying to capture it at the primary sources that produce it before it is released, i.e. at the coal, gas and oil power stations. Here's a page on t'internet I found: How does carbon capture and storage work? | Cosmos

I am no expert but I'd guess that the easiest way to scrub CO2 from the atmosphere that is already floating about, would be maybe engineering very large scale biome changes (i.e. planting loads of fast growing trees. They are pretty good at fixing CO2 into something solid and valuable.)

EDIT: Thinking about it, it is more complex than just planting rows of trees - if temperatures are rising, your trees might be more likely to dry out and burn, so perhaps it's only part of the solution and you'd need to do something to depress temperatures long enough for nature to suck up enough carbon. (Cue space mirrors or megatons of pollution to divert some of the sun's light away from the Earth)

 

[EdLincoln]

Turning C02 into elemental carbon takes a lot of energy, so the main thing you need is an energy source.

If you are doing it with Earth type plants you need liquid water and reasonable temperatures.

If you are fine with keeping it oxidized, some minerals absorb C02. Plants get all the attention because they make oxygen, but by some accounts most of Earth's CO2 got absorbed into the shells of shellfish and became limestone.

 

[Venusian Broon]

If you are fine with keeping it oxidized, some minerals absorb C02. Plants get all the attention because they make oxygen, but by some accounts most of Earth's CO2 got absorbed into the shells of shellfish and became limestone.

Which again where temperature comes into it - the warmer the oceans apparently the less carbon they are able to absorb. I've seen current estimates to be about 40% of the Carbon we emit at the moment.

But also paradoxically, if we 'spike' the ocean with lots of Carbon (before the water warms up, there is a lag) this increase in Carbon acidifies the water more than animals can handle and can limit the amount of CO2 absorbed into animals shells. Which would possibly mean a lot of this spare carbon being ejected back into the atmosphere as the waters warm.

It's complex.

 

[RJM Corbet]

It sounds really difficult. Rather surprisingly.
Researchers discover a way to tease oxygen molecules from carbon dioxide

Not, for instance, like simply separating hydrogen and oxygen from H2O by the hydrolysis of water. This may be because liquid CO2 would be extremely difficult to obtain, for purpose of hydrolysis?

@Venusian Broon seems to have the best solution: grow trees etc, and extract the carbon from them.

Always something new to learn here on Chrons.

But of course if it's global warming you're after, you'd just leave the CO2 up there in the atmosphere. I believe the atmosphere of Mars is mostly CO2 but Mars stays quite cold, because the atmosphere isn't very dense -- or something like that?

 

[Joshua Jones]

It sounds really difficult. Rather surprisingly.
Researchers discover a way to tease oxygen molecules from carbon dioxide

Not, for instance, like simply separating hydrogen and oxygen from H2O by the hydrolysis of water. This may be because liquid CO2 would be extremely difficult to obtain, for purpose of hydrolysis?

@Venusian Broon seems to have the best solution: grow trees etc, and extract the carbon from them.

Always something new to learn here on Chrons.

But of course if it's global warming you're after, you'd just leave the CO2 up there in the atmosphere. I believe the atmosphere of Mars is mostly CO2 but Mars stays quite cold, because the atmosphere isn't very dense -- or something like that?

I think we have a pretty good handle as a society on how to increase global temperatures and CO2 density... it is bringing it down which seems rather tricky.

Correct me if I am wrong, but if you are going for a biological means, isn't photosynthetic algae much more efficient than trees? If not, please correct me, because all my spaceships have a marshy smell because of this, and there is quite a cast of characters who would prefer birch over marsh any day of the week...

 

[Venusian Broon]

But of course if it's global warming you're after, you'd just leave the CO2 up there in the atmosphere. I believe the atmosphere of Mars is mostly CO2 but Mars stays quite cold, because the atmosphere isn't very dense -- or something like that?

Mars' atmosphere is very nebulous for a number of reasons - the planet is quite small, so it's gravity let's it's atmosphere roam very far from the surface, in fact many small molecules could easily gain terminal velocity and escape the Martian atmosphere completely...but as there is no global magnetic field, the Solar wind easily strips away atmosphere from the planet. It's been downhill there for a long time there

But if you were doing it artificially you'd want something dense and greenhouse effective on Mars, purely because it is much further from the sun and the planet needs all the help it can get to hold onto the heat that actually gets to it.

Problem with lots of CO2 as a greenhouse shield , which might be plausible, is that at a certain percentage of the atmosphere it becomes toxic to humans - about 5-6% of total volume at Earth pressures, apparently.

 

[RJM Corbet]

I think we have a pretty good handle as a society on how to increase global temperatures and CO2 density... it is bringing it down which seems rather tricky.

Correct me if I am wrong, but if you are going for a biological means, isn't photosynthetic algae much more efficient than trees? If not, please correct me, because all my spaceships have a marshy smell because of this, and there is quote a cast of characters who would prefer birch over marsh any day of the week...

Algae may work. Perhaps well. But are you thinking about reducing atmospheric carbon (which is effectively captured as CO2) because of the global warming of Earth, or in harvesting atomic carbon from atmosphere is general?

 

[Venusian Broon]

Correct me if I am wrong, but if you are going for a biological means, isn't photosynthetic algae much more efficient than trees? If not, please correct me, because all my spaceships have a marshy smell because of this, and there is quote a cast of characters who would prefer birch over marsh any day of the week...

I think if you were filtering a CO2 heavy source - like a power station (or a volcano?) - then you'd want some complex system of algae/plankton that bubbles the CO2 through it. I suppose you could flood an ocean with them, on a grand scale...but then you'd destroy the eco-system that was originally there.

Trees and plants are, I feel, a bit more 'fire and forget' and perhaps a bit less destructive (stationary and local!), and they're 'programmed' to just get on with it and adapt to the biome they find themselves in. Greenify the Sahara anyone?

 

[RJM Corbet]

...Trees and plants are, I feel, a bit more 'fire and forget' and perhaps a bit less destructive (stationary and local!), and they're 'programmed' to just get on with it and adapt to the biome they find themselves in. Greenify the Sahara anyone?

Well, that's it. Let's do it with our own deserts before trying to terraform distant worlds. But this is a speculative sc-fi site, obviously, lol

 

[Venusian Broon]

Talking about proper Sci-fi, there was that Arthur C. Clarke short story about the mad Russian scientist that breed a plant that could survive on the Moon. At least I think it was a plant. (I mean do you really need an atmosphere )

 

[Joshua Jones]

Algae may work. Perhaps well. But are you thinking about reducing atmospheric carbon (which is effectively captured as CO2) because of the global warming of Earth, or in harvesting atomic carbon from atmosphere is general?

The original idea was to harvest the carbon for the sake of simultaneously terraforming a CO2 rich atmosphere and gaining industrial benefit from doing so in the form of carbon based materials. My initial thoughts included nanotube based armors and building materials, but plastics, synthetic fossil fuels... just about anything could be a final outcome.

The advantage of a mechanical means rather than a biological means is that it could more easily be adapted to other elements/molecules for different atmospheres, then a different "production module" attached to make whatever is intended.

I think if you were filtering a CO2 heavy source - like a power station (or a volcano?) - then you'd want some complex system of algae/plankton that bubbles the CO2 through it. I suppose you could flood an ocean with them, on a grand scale...but then you'd destroy the eco-system that was originally there.

Trees and plants are, I feel, a bit more 'fire and forget' and perhaps a bit less destructive (stationary and local!), and they're 'programmed' to just get on with it and adapt to the biome they find themselves in. Greenify the Sahara anyone?

Indeed they are, and quite a bit more pleasant to look at and smell, too... but, when you have a warship with a bunch of people inconveniently respirating everywhere, having a box buried in the wall that the atmosphere circulates through (especially if there is a separation mechanism for O2 and CO2) is a much more efficient use of space than an atrium...

But, I digress, in my own post, no less!

 

[Joshua Jones]

Side note; why the devil is autocorrect correcting words which are already correct, into incorrect words and words which make no sense in context? Why, oh why, dost thou hate me, oh autocorrect!?

 

[RJM Corbet]

The original idea was to harvest the carbon for the sake of simultaneously terraforming a CO2 rich atmosphere and gaining industrial benefit from doing so in the form of carbon based materials. My initial thoughts included nanotube based armors and building materials, but plastics, synthetic fossil fuels... just about anything could be a final outcome.

The advantage of a mechanical means rather than a biological means is that it could more easily be adapted to other elements/molecules for different atmospheres, then a different "production module" attached to make whatever is intended...

Well, I'm going with electrolysis of liquid CO2. But first you've got the difficulty of getting the pressure and temperature right to maintain CO2 in a difficult liquid transient state between solid and sublimated gas, and then pass an electric current through it; and if you use one carbon electrode (whether anode or cathode I'm not sure) and the other of a different material, platinum perhaps, then that carbon electrode should capture carbon, while oxygen gas should bubble from the other?

Will that work?

EDIT: Electrolysis. Not hydrolysis ... duh. Sorry

 

[Venusian Broon]

Indeed they are, and quite a bit more pleasant to look at and smell, too... but, when you have a warship with a bunch of people inconveniently respirating everywhere, having a box buried in the wall that the atmosphere circulates through (especially if there is a separation mechanism for O2 and CO2) is a much more efficient use of space than an atrium...

But, I digress, in my own post, no less!

Right, so rather than change the planet to make it more human friendly, why not change the humans to make them more planet-friendly. Add a surface layer of some super-photosynthetic mechanism on their skin so that CO2 is turned into delicious O2...saves on canteen rations also.

(okay, I think there will be lots of problems with this idea...but, hey, it's SF)

 

[Joshua Jones]

Right, so rather than change the planet to make it more human friendly, why not change the humans to make them more planet-friendly. Add a surface layer of some super-photosynthetic mechanism on their skin so that CO2 is turned into delicious O2...saves on canteen rations also.

(okay, I think there will be lots of problems with this idea...but, hey, it's SF)

You know, that could hypothetically be a survival backpack... filters out the atmosphere, produces sugars for emergency nutrition...

 

[RJM Corbet]

Pure indudtrial oxygen is fractionated from air by freezing and pressurizing air to separate out the predominant nitrogen, and more closely to separate it from the CO2 and argon mix inert gasses. These gasses are sold separately in cylinders. At -78 deg C at sea level, the CO2 easilly solidifies out of the air as 'dry ice'

Medical oxygen concentrators pull air through zeolite cat litter like material, which at room temp and pressure absorbs the nitrogen and results in oxygen pure enough for medical use mixed with a small amount of CO2 and argon, etc.

*post edited