> As it entered the tube, the Berkeley air contained CO2 in concentrations ranging from 410 ppm to 517 ppm. When it came out the other side, the scientists could not detect any carbon dioxide at all, Zhou said.
This sounds like it could be the basis for a respirator-like breathing apparatus, not requiring tanks, for entering and staying in enclosed spaces where the concentration of CO2 is high. (Provided there is enough oxygen.)
That feels super dangerous. CO2 is mostly fine to breathe, but it triggers the impulse to breathe. Without it you won't feel that you're running out of oxygen.
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.
What if that's not the case though. Spaces that are high in CO2 are dangerous because the CO2 has displaced the oxygen below a safe percentage. Maybe by scrubbing the CO2 we can increase the oxygen concentration.
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.
With real-time detection (I'd expect that exists, but don't know for sure) you can divert some of the airstream through this scrubber to target a particular concentration of CO2.
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.
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)
You don’t need co2 in the air to tell you to breathe. Your body makes co2, which is what you feel. Once you run out of oxygen to make co2, you are already unconscious.
If you go into an area with no oxygen, you will pass out very quickly with little warning except being dizzy, but you will not fail to feel like you need to breathe.
It might be slightly more safe to enter into a room full of co2 than a room full of nitrogen, because you might be alerted by the high co2 a few seconds before the dizziness takes over, but that doesn’t make rebreathers dangerous because you will forget to breathe. If you run out of oxygen, you’re unconscious in a few seconds anyway, co2 or no co2.
Might be cool to have this in an office or school classes. I realize that proper ventilation is the real fix, but it's not realistic to rebuild all buildings.
Just think about it, you have a decorative box in your office that absorbs CO2, would it slow the inevitable cognitive decline that happens when you close your door in your poorly ventilated room?
I suspect that previously acceptable building designs now cause cognitive decline because of much higher outdoor CO2 levels- it’s a bigger problem than people realize. I live in a mild climate where I can just keep the windows open year round- but when the neighbors have a loud party I close them to focus or sleep and CO2 will quickly climb to over 2000ppm, well over the 1400 or so that causes measurable negative effects. I suspect most people in climates that require heating or cooling are almost permanently experiencing reduced cognition and might not know.
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 open so often. My climate makes that impossible for much of the year; I'm looking in to getting an ERV installed asap.
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 push things over the limit where there are now problems, everything else remaining the same.
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.
> 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.
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.
So it acts like a reusable CO2 trap, then releases said CO2 at the cost of heating it up to 140F. Which then releases it.
It doesn't really talk about how you would sequester the gaseous CO2 other than "put it underground."... But if you put a gas underground it will eventually leak out. Even a liquid is prone to leak out eventually due to plate techtonics, but a liquid doesn't immediately turn into gaseous CO2.
So though a crucial technology, I don't see how effective it would be in a long term solution.
Many common minerals like olivine react with CO2 at high concentrations to form carbonates which are geologically stable. The issue is getting the high carbon concentrations to make this process fast. Concentrating CO2 is the major technical hurdle of carbon sequestration.
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 I'm sure that can be figured out given enough opportunity.
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 10% of efficiency.
If they use a coal plant to power the CO2 -> C + O2 conversion, they will release like 20 times the amount of CO2 absorbed.
If they use a renewable source, it's better to close the absortion plant and also 20 coal plants.
Until we close all the coal plants and we get very cheep carbon-free energy, it's bad for the environment to try a CO2 -> C + O2 conversion.
There are reasons you would want to use fossil fuels and use renewables to reverse the process. Fossil fuels have high energy density, can be transported and stored with minimal losses, and consumed anywhere anytime. There are lots of things that are difficult to directly electrify like say planes. You can't simply stick a bunch of batteries on a plane to replace a jet engine and its fuel tanks. But building an excess of solar panels on the ground to mop up the CO2 equivalent of the jet engine's exhaust is simply a matter of cost. E-fuels are basically just really dense chemical batteries.
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.
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.
Energy can be economically cheap in the current paradigm, while also being insufficiently cheap or insufficient quantities of clean energy to make the above comments suggestion work.
What I'm about to say may sound absurd and an attempt to be funny, but I'm being serious.
The other day I was wondering how people always talk about sending undesirable material (garbage, spent radioactive fuel, etc.) on a one way trip to the sun. Why not send things to the surface of Venus? It has an ultra dense atmosphere that pulverizes anything that reaches the surface. In the case of this material, it's just more C02, which is what the atmosphere of Venus is already primarily composed of. We aren't going to ever explore the surface of Venus, or at least we won't for thousands, if not millions of years, barring we can easily convert co2 into energy, so is this a bad idea?
Let's take the 2020 figures for annual human carbon dioxide emmissions.
35 billion metric tons.
What's your back of the envelope energy figure for extracting that weight of a gas from the atmosphere, pressurising it, and lifting it to orbit and sending it to Venus?
Got a rough notion of the number of trips, fuel and resources that would need every single year?
It seems like it's a MOF amine approach which does have some benefits against the MEA used in submarines, such as lower corrosive properties potentially, lower heating requirements as you don't have to heat an aqueous solution, and it can be easier to discard the remnants once its co2 absorbing properties are diminished.
Wondering how inert and/or toxic this stuff is. Could you mass produce it and just sprinkle it across the arctic? Sequester carbon and have it locked up in the permafrost.
> As it entered the tube, the Berkeley air contained CO2 in concentrations ranging from 410 ppm to 517 ppm. When it came out the other side, the scientists could not detect any carbon dioxide at all, Zhou said.
This sounds like it could be the basis for a respirator-like breathing apparatus, not requiring tanks, for entering and staying in enclosed spaces where the concentration of CO2 is high. (Provided there is enough oxygen.)
That feels super dangerous. CO2 is mostly fine to breathe, but it triggers the impulse to breathe. Without it you won't feel that you're running out of oxygen.
That's CO2 IN the blood that "triggers breathing". Unless you plan to inject the powder, that's not really an issue.
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.
What if that's not the case though. Spaces that are high in CO2 are dangerous because the CO2 has displaced the oxygen below a safe percentage. Maybe by scrubbing the CO2 we can increase the oxygen concentration.
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 assumes you're breathing something besides pure oxygen.
And the "device" is called a 'rebreather.' https://en.m.wikipedia.org/wiki/Rebreather
With real-time detection (I'd expect that exists, but don't know for sure) you can divert some of the airstream through this scrubber to target a particular concentration of CO2.
You don't need any CO2. Oxygen bottle, co2 scrubber, pure oxygen purge prior to diving... and you've got yourself a rebreather.
https://en.m.wikipedia.org/wiki/Rebreather
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.
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)
You don’t need co2 in the air to tell you to breathe. Your body makes co2, which is what you feel. Once you run out of oxygen to make co2, you are already unconscious.
If you go into an area with no oxygen, you will pass out very quickly with little warning except being dizzy, but you will not fail to feel like you need to breathe.
It might be slightly more safe to enter into a room full of co2 than a room full of nitrogen, because you might be alerted by the high co2 a few seconds before the dizziness takes over, but that doesn’t make rebreathers dangerous because you will forget to breathe. If you run out of oxygen, you’re unconscious in a few seconds anyway, co2 or no co2.
Any context in which it is being used as a scrubber would be one where the people designing it would 100% be aware of this.
Might be cool to have this in an office or school classes. I realize that proper ventilation is the real fix, but it's not realistic to rebuild all buildings.
Just think about it, you have a decorative box in your office that absorbs CO2, would it slow the inevitable cognitive decline that happens when you close your door in your poorly ventilated room?
I suspect that previously acceptable building designs now cause cognitive decline because of much higher outdoor CO2 levels- it’s a bigger problem than people realize. I live in a mild climate where I can just keep the windows open year round- but when the neighbors have a loud party I close them to focus or sleep and CO2 will quickly climb to over 2000ppm, well over the 1400 or so that causes measurable negative effects. I suspect most people in climates that require heating or cooling are almost permanently experiencing reduced cognition and might not know.
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 open so often. My climate makes that impossible for much of the year; I'm looking in to getting an ERV installed asap.
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 push things over the limit where there are now problems, everything else remaining the same.
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.
> 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.
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
I think that I shall never see
A half a pound of powder as lovely as a tree. -- Joyce Kilmer
So it acts like a reusable CO2 trap, then releases said CO2 at the cost of heating it up to 140F. Which then releases it.
It doesn't really talk about how you would sequester the gaseous CO2 other than "put it underground."... But if you put a gas underground it will eventually leak out. Even a liquid is prone to leak out eventually due to plate techtonics, but a liquid doesn't immediately turn into gaseous CO2.
So though a crucial technology, I don't see how effective it would be in a long term solution.
Many common minerals like olivine react with CO2 at high concentrations to form carbonates which are geologically stable. The issue is getting the high carbon concentrations to make this process fast. Concentrating CO2 is the major technical hurdle of carbon sequestration.
>how you would sequester the gaseous CO2 other than "put it underground."
I wonder if there is a reason you couldn't just sequester the powder. Probably too expensive? Or not volume efficient?
>to leak out eventually due to plate techtonics
This might seem shortsighted, but I'm OK pushing the problem out by 50 million years or so.
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 :>
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 I'm sure that can be figured out given enough opportunity.
Plants do it, after all. It's not impossible.
> 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 10% of efficiency.
If they use a coal plant to power the CO2 -> C + O2 conversion, they will release like 20 times the amount of CO2 absorbed.
If they use a renewable source, it's better to close the absortion plant and also 20 coal plants.
Until we close all the coal plants and we get very cheep carbon-free energy, it's bad for the environment to try a CO2 -> C + O2 conversion.
There are reasons you would want to use fossil fuels and use renewables to reverse the process. Fossil fuels have high energy density, can be transported and stored with minimal losses, and consumed anywhere anytime. There are lots of things that are difficult to directly electrify like say planes. You can't simply stick a bunch of batteries on a plane to replace a jet engine and its fuel tanks. But building an excess of solar panels on the ground to mop up the CO2 equivalent of the jet engine's exhaust is simply a matter of cost. E-fuels are basically just really dense chemical batteries.
I agree. I'd prefer using something like biodiesel in planes, but I'm not sure if there is a technical limitation.
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.
Plants do it using the energy from the sun.
All of these “can’t we just unburn burnt things” forget that the reason we burnt the carbon in the first place was to get that energy.
Unburning it would need to return that energy and more because of inefficiencies.
If you have energy to spare, you don’t need to burn the carbon in the first place.
With global fossil fuel usage still rising, we clearly don’t have any to spare.
It's not so clear to me -- the MIT Technology Review is already wringing its hands about energy being so cheap it causes problems with economics.
[1] https://www.technologyreview.com/2021/07/14/1028461/solar-va...
Energy can be economically cheap in the current paradigm, while also being insufficiently cheap or insufficient quantities of clean energy to make the above comments suggestion work.
What I'm about to say may sound absurd and an attempt to be funny, but I'm being serious.
The other day I was wondering how people always talk about sending undesirable material (garbage, spent radioactive fuel, etc.) on a one way trip to the sun. Why not send things to the surface of Venus? It has an ultra dense atmosphere that pulverizes anything that reaches the surface. In the case of this material, it's just more C02, which is what the atmosphere of Venus is already primarily composed of. We aren't going to ever explore the surface of Venus, or at least we won't for thousands, if not millions of years, barring we can easily convert co2 into energy, so is this a bad idea?
Let's take the 2020 figures for annual human carbon dioxide emmissions.
35 billion metric tons.
What's your back of the envelope energy figure for extracting that weight of a gas from the atmosphere, pressurising it, and lifting it to orbit and sending it to Venus?
Got a rough notion of the number of trips, fuel and resources that would need every single year?
Sharing this for the community's take on whether it has potential or is just another non-viable option.
It seems like it's a MOF amine approach which does have some benefits against the MEA used in submarines, such as lower corrosive properties potentially, lower heating requirements as you don't have to heat an aqueous solution, and it can be easier to discard the remnants once its co2 absorbing properties are diminished.
Wondering how inert and/or toxic this stuff is. Could you mass produce it and just sprinkle it across the arctic? Sequester carbon and have it locked up in the permafrost.
https://archive.ph/JPmvj