Direct conversion of CO2 to solid carbon by Gallium-based liquid metals
pubs.rsc.org
pubs.rsc.org
Gallium is cheap (~$300/kg), abundant (by product of Aluminum mining).
This process runs at 200C and 1 Bar (=0.98 ATM).
Temperature can be concentrated via greenhouses/mirrors to 200C with 0 carbon by-products, 0 advances in battery tech, 0 advances in solar tech.
We could start pulling more CO2 out of the atmosphere than we put in, and at that point we'd be pretty confident things won't get worse for the climate.
I'm sure there's a negative view of this and something too easy that I'm missing. But right now I'm very excited.
Not sure that would be terribly efficient to pull CO2 out of the atmosphere to pump through this setup.
Would be fine for many other reasons though. I wonder how it behaves with "non clean" CO2 sources. Like say at the output of a coal fired PowerStation.
Let's not be misleadingly precise. It runs at 1 atmosphere.
The world generates ~40 billion tons of CO2 a year, meanwhile the total mass of everything transported in the entire world is only around ~12b tons.
It's certainly going to be cheaper, in most cases, to avoid emissions in the first place. But there will also be cases, like long-haul jets, where it may be cheaper to remove the CO2 later. Plus the CO2 is already above a safe level, so we'll have to draw it down somehow anyway.
Not sure if that answered your question or if you meant something else.
I mean think about it, we can't be emitting more waste than we are transporting, because that waste comes from fuel, and the fuel itself is part of what we're transporting.
Maybe something like building solar arrays in semi-arid regions and mixing up the resulting solid carbon into the local soil for some ecological engineering or filling up old mining pits.
I think that was the idea. He's viewing it as a mass transfer problem. You "harvest" CO2 with trees, then put it back in the ground.
I think the hard part is not hurting ecosystems in the process, but at this point honestly this might still be the best solution we have available.
Which government? Is that some hypothesised World Government?
The UK Government runs a lot of the forestry in this country. It is run as a commercial timber operation. The Brazilian and Indonesian governments appear to be committed to commercial exploitation of enormous amounts of old-growth rainforest timber. The Polish and Hungarian governments are also committed to logging old-growth.
There's no time left for this kind of dreaming.
I meant the US government. But you can insert lots of other governments in there, including the UK like you mentioned.
> There's no time left for this kind of dreaming.
Nobody's dreaming. I'm just talking about the feasibility, not claiming anything about the likelihood.
Do you have links to more reading on that? This is the first time I've heard of this particular reason why it might not work.
Conclusion: all that old wood is either buried, or it's busy turning into CO2.
So I'm not impressed by claims of "carbon offsetting". On the contrary, I take such claims as evidence that the organisation in question is part of the problem.
Incidentally, how are you supposed to recycle chipboard? Like, for example a chipboard kitchen counter? For several decades, I had in my home a pair of oak side tables, that were made by my grandfather from the remains of a large oak dining table. You can't do that nowadays with chipboard.
But regardless, I also don't get where you see a discussion of "carbon offsetting". This isn't about "offsetting" emissions or impressing you, this is about repaying "debt" that's already incurred. Pulling down old carbon is something we have to do regardless of what we do with our current emissions, even if we drive them to 0, because the current carbon in the atmosphere is already too much. Whether we do it with trees or machines or something else, it needs to happen.
This would use that energy directly. To sequester carbon.
> why burn carbon
I didn’t say anything about burning carbon.
If you didn't say anything about burning carbon, you weren't paying attention.
Here is a system for collecting CO2 from ambient air and discharging a stream of pure CO2:
https://news.mit.edu/2019/mit-engineers-develop-new-way-remo...
> If you didn't say anything about burning carbon, you weren't paying attention.
Wrong.
We have to start from where we are: we can't just warp into a future where Dyson Spheres are realistic. We have less than thirty years. I suspect it's actually already too late. Using solar to reduce Gallium, so we can use the Gallium to reduce CO2, while we continue burning hydrocarbons because the solar is all being used to reduce Gallium (or solve hashes), doesn't look to me like the way forward.
It provides more than enough energy for these things in some places at certain times, we can build the CO2 extractors in these locations
One thing I learned is that these experiments are generally done with a pure CO2 stream. The reactions taking place often compete with other molecules (especially O2), making this approach best for capturing carbon from tailpipes and smokestacks. There's still a lot of work to be done to get this sort of thing to work reliably for direct air capture (which IMO will be needed to actually draw down carbon from the atmosphere).
Anyway, this research is being commercialized via a company called LMPlus (https://lmplus.com.au). While I appreciate that the technology is being brought to market, it probably means that future breakthroughs will occur in private labs, protected by patents and trade secret laws.
We have a an urgent need to conduct more of this kind of research out in the open and to make breakthrough carbon capture technology available to everyone, for free. If you're interested in helping out on this front, please consider joining me in the OpenAir Collective discord (https://openaircollective.cc/).
According to this comment three months ago [1] "they used 6%-20% CO2 mixtures with balance nitrogen and some water to try and approximate different exhausts including flue gas".
GP proposed to filter out O2 by burning carbon. This will create a CO2-rich gas, perhaps at about 30% (depends of the density of CO2 compared to O2).
GP didn't mean that we deplete oxygen in the athmosphere, but that this is an intermediate step inside the CO2 scrubbing apparatus. Perhaps that's why you got downvotes.
The burnt carbon will be gained back by the Gallium process, however this might not work out anyway because the process needs to be very efficient in filtering out CO2, as someone else already pointed out.
In my opinion the idea of burning hydrogen seems a lot better: https://news.ycombinator.com/item?id=29994000
I do wonder if it would be much cheaper to capture CO2 by investing technology and capital into 'building' forests. What if we can irrigate Sahara and cultivate some fast-growing plants like bamboos there? Maybe that has ecological consequences but it doesn't seem to be much different than the agricultural land expansion that has happened in rainforests in the first place.
However, we do know of how the deposits of fossil fuels formed in the first place, and most places newer than the carboniferous, formed at the bottom of deep lakes and especially oceans. They form from the anoxic compaction of marine snow. Either during massive algae booms, or more slowly from slightly larger corpses. This process is slow for several reasons, but a significant, in particular for the latter category, one is the lack of surfaces for attachment on the open ocean. The creation of large floating artificial coral reefs could provide this, and with it a highly productive rich ecosystem. We could further fertilize these, with iron in particular being rare, but also regular fertilizer.
I don't imagine this would be particularly efficient, however.
This does well to incentivize the inventors; perhaps they could be purchased rather than nationalizing the successful innovation models.
That's probably why these kinds of things will likely only be super effective if taking the immediate exhaust of carbon fuel burning.
So...
1. Legally require all fossil fuel plants capture the carbon from their exhaust, which will have the knock on effect of increasing the economic cost of burning fuel, which means economic forces will naturally start to more strongly prefer carbon free sources, because they're cheaper.
2. Keep pushing for the migration to full BEVs and possibly have a similar requirement of carbon capture devices added to industrial vehicles that can't reasonably be EVs. I could see things like mining and construction vehicles go out with a tank full of fuel and return with a tank full of captured carbon to leave at a dump.
I for one find the future where we're not actively managing the Earth's climate in some way to be the more pessimistic outcome. It indicates that civilization has failed to continue advancing, probably isn't spacefaring, and that the light of consciousness will eventually twinkle out once the Earth becomes uninhabitable in about 500 million years.
We'll see.
That's the problem. Maybe it's better, maybe it's worse, and there is only one way to find out. But if it's worse, finding out is very bad. And there is no way to know ahead of time.
The "everything is so uncertain, we must do nothing" line has worn out its welcome. It was dishonest 30 years ago, and is reprehensible today.
In forums like this, where everyone has a well paying job and fuck you money, it is important to preserve the planet, just not enough that more than 1% here would approve a build permit for a windfarm next door to their house. Arguably we mostly care about preserving the nice nature we now enjoy for free, and this is as good as it gets. The vast majority of people who specifically feel climate change is important still dont think the near guarantee of climate change is more important than the negligible risks of nuclear power.
Basically, politicians are representing the true interests of the population, which to be fair is their job. We just arent who we want to pretend we are.
This shows that the vast majority of people in these countries, while publicly concerned, and privately mildly alarmed about climate change, prioritize other things and that their politicians are responding to their constituent priorities. Why would this be different in the US? everything from median education to city planning, predicts that US population cares much less about environmental impact. Poor people living on welfare in some Nordic country sometimes care about climate change, but mostly dont, certainly much less so than average citizens. The number of poor in the US who prioritize climate change over saving 5 bucks on gas so their kid can eat that night is zero.
When people aren't lying to themselves, its easy to see that preventing climate change is a policy favored by, and forced upon the public, by elites. Speaking as one, if of the lowest possible level, obviously we should do it. I'm certainly willing to sacrifice the poor both abroad and at home, but I think tigers are cool, that nature is nice to look at, and I would like to keep it that way. On the rare occasion I happen to meet some of my old friends turned politicians, I naturally point this out. And they listen, far more than they should, given neither my phd nor my career is in an applicable field. The few times I meet 0.001%ers, they have been more concerned than I. They haven't needed to status signal for decades, certainly not in private to someone like me, and they all had significant interests in industry which would be negatively affected.
This changes the story of who is preventing such policy and of if its democratic. There isn't a conspiracy by the elite to prevent climate change from being solved, if anything its the opposite, and the problem is that common people aren't stupid enough to let us get away with it.
The argument loses all interest, but the questions remain why the argument is being made, and who wants it made.
You might want to read up on the effects of higher CO2 levels on human cognition. It's not pretty. And it completely blows your comment out of the water.
We already know that the CO2 levels that are forecast this century are going to be catastrophic. This isn't a "we'll see" situation anymore. We have seen. The only question is whether we will do something about it before it is far, far too late.
You need to worry about the next 50 years before you start worrying about 500 million years.
The natural way to of carbon sequestion on a planetary scale is - life ( plants / organisms / microbes etc). The catch is that if we fuck it up, and you know we will, we will pay a hefty price (like we do now with red tides, dead zones, bleeching). The added bonus is that we just do not sequester carbon, but we supercharge all the plantatary processes.
For that matter, if it did work, would the satellites not reflect IR back to Earth? They might even hurt more than they help because they would be blocking sunlight on one side of the Earth only but would be blocking IR escaping on both sides.
Is the "opposition" mainly that the process as stated isn't reversible? Is there a way to improve the original idea to make it reversible in a short order?
The opposition comes from political signaling and tribalism.
Read more:
How many efforts at international cooperation have survived for centuries?
A lot of the comments upthread seem to be assuming that we live under some kind of World Government.
To return we probably need to capture well below the "safe" boundary of 350 ppm of CO2, to engage all the feedback loops that will refreeze the arctic etc.
But also, why bother? Biggest problems from climate change are due to the fast change, which causes destruction of ecosystems (including human habitat). Even if we refreeze, we won't revert these losses.
you mean, like, throwing a spanner into a machinery we hardly understand and see whether "it sticks"? Give me a hundred planets and start the trials!
https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_chapte...
Even at the low partial pressure of atmospheric CO2 and at ambient temperature, carbonation of metal oxide bearing minerals occurs spontaneously, though on geological time scales (Robie et al., 1978; Lasaga and Berner, 1998). Limitations arise from the formation of silica or carbonate layers on the mineral surface during carbonation that tend to hinder further reaction and to limit conversion (Butt et al., 1996) and from the rate of CO2 uptake from the gas phase in the case of aqueous reactions. The challenge for mineral carbonation is to find ways to accelerate carbonation and to exploit the heat of reaction within the environmental constraints, for example with minimal energy and material losses.
guess, the same way we got it - bath, electricity, cathode and anode
Burning fossil fuels for energy: hydrocarbon + O2 -> atmospheric CO2 + other stuff
Sequestration: atmospheric CO2 -> not-amospheric-CO2 e.g. solid C + other stuff
Notice that those are not exact reverses of each other, so there is no requirement that the energy released in one be the same quantity as the energy absorbed in the other.
Hydrocarbon fuels have very high Gibbs free energy. Solid carbon does not. We're only trying to get the CO2 out of the atmosphere, not return it to the form of the original fuel that was burned. Therefore, sequestration can potentially require less energy than was originally released from burning the hydrocarbons.
Solid carbon is basically coal. It has more usable energy per mass than any hydrocarbon, and just a little bit less per carbon.
And we can get this energy from sunlight.
But nobody is planning on deploying something like it currently anyway.
To make it concrete, let's look at methane, the hydrocarbon with most hydrogen.
One kg of methane contains 0.75 kg of C and 0.25 kg of H. When it burns it realeases 55.6 MJ (per wikipedia [1]). Carbon's energy density is 32.7 MJ/kg, so the 750 g release 24.6 MJ. More importantly, you could in principle split the CO2 for the cost of 24.6 MJ and be left with a net of 31 MJ. Q.E.D.
Well, except in real life nothing is done with 100% efficiency. You can't just use all the 55.6 MJ released by burning CH4, you first convert it to electricity, and the best you get is 63%, so you make 35 MJ of electricity. If you get 70% efficiency in splitting CO2, you get exactly the 24.6 MJ you need. But you don't get that efficiency. But let's just say you get even more than that, let's say you get a whooping 85%. That means you need 30 MJ for the splitting, and you are left with a net of 5 MJ of electricity. Which is another way of saying you increased the cost of electricity you generate by a factor of 6 (=30/5), this ignoring altogether the capital cost associated with the splitting of CO2.
But all is not lost.
If we get back to 1kg CH4 = 0.75 kg C + 0.25 kg H2, burning the CH4 we get 55.6 MJ, burning the C and H2 separately, we get 24.6 MJ + 35.5 MJ = 60.1 MJ, which is 4.5 MJ more. That's a different way of saying you need 4.5 MJ to split CH4 into C and H2. That reaction is called methane pyrolysis [2]. Let's say you manage to deliver this with only 30% efficiency, i.e. for 15 MJ. You are left with 35.5-15=20.5 MJ net energy. If you convert this to electricity you get about 13 MJ, which is not that great. But hydrogen is valuable in itself. If we move towards the hydrogen economy, this method of generating hydrogen may be the winner.
[1] https://en.wikipedia.org/wiki/Energy_density
[2] https://en.wikipedia.org/wiki/Pyrolysis#Methane_pyrolysis_fo...
Take take the gallium example, for atmospheric levels of CO2, is 400:1. Add the thermodynamic minimum to reverse GalliumOxide to Gallium and O2, and its 800:1, at an absolute minimum. This crushes the difference to methane.
More importantly its a pointless argument, we have practically endless nuclear fuel available, enough to supply the world with power entirely for millions of years. So it does not matter if its inefficient, its climate neutral anyways as long as we stop being idiots and use what we have better. That said there are way simpler more cost effective methods than using a rare earth metal.
Please have a look at Limestone Calcined Clay Cement: https://lc3.ch/
This is only one of the cement alternatives I believe.
But there are plenty of point emitters of CO2, so if we imagine a grid that's actually renewable sure. Capture though? It could always be paired with another capture method to concentrate it first, it's usually cheap to concentrate things a little and expensive to concentrate them a lot.
We can decide only to emit CO2 at the times when we don't have clean energy ready to use and decide to recapture CO2 when we do have clean energy to use.
And there could be inherent value there, especially as a carbon capture tax credit. Instead of proof of work or proof of state, it's proof of capture. You'd have to put together some kind of distributed capture hardware, but... That's maybe possible with current tech?
If this token gets you $100 worth of carbon emissions, it's hard to justify a price higher than $100. If the token gets you absolutely nothing, then the value is absolutely arbitrary - enabling spectacular rise
But recapturing CO2 from air isn't pointless - because we can use surplus renewable energy to do so (and then burn C later as fuel). Basically it would use air as infinite capacity (but low-efficiency) rechargeable battery. I've seen estimates of about 13% efficiency over the whole cycle (capturing + burning).
[1] https://caseyhandmer.wordpress.com/2021/11/01/scaling-carbon...
This could be done at scale in central Antarctica using enormous refrigerating complexes[1], but it would be the most ambitious engineering project ever undertaken by humanity.
Generally this is not seriously discussed by experts as a solution to global warming not because it is not feasible, but because it would diminish the sense of urgency and discourage the much more prudent and affordable approach of simply reducing emissions.
[1] https://journals.ametsoc.org/view/journals/apme/52/2/jamc-d-...
Let us say it is not being discussed because it is not feasible. Unless of course we build massive nuclear power plants in Antarctica with all what that entails. We are not any time soon in a position where we can produce any nontrivial amount of solar or wind energy in the hostile environment of that continent, plus it's dark night down there for half a year each year. Meaning the only remaining option would be to ship coal or oil down there to burn it so we can cool air to –140°C, obviously a non-starter if there ever was one.
> and discourage the much more prudent and affordable approach of simply reducing emissions.
This. The entire plan is madness: you'd burn two tons of oil and coal to get rid of part of what burning one ton of oil and coal leave behind in the atmosphere. It is not clear to me at this point if it is at all feasible to use fossil fuel to get more CO2 out of the atmosphere than burning it puts into the atmosphere in the first place. Because in this household we obey the laws of thermodynamic. And if it's possible at all it's not easy to see why continuing to burn oil and coal and capturing the CO2 at other sites should be better than not burning part of those fuels and capturing the CO2 right at their point of emission should be the better option. It is a hare-brained plan.
Maybe it really is because it's not feasible, I concede that's not something I can really know. But nuclear power plants are not necessary. As the paper sets out, there is abundant wind energy in Antarctica. Setting up a medium-size (1200 MW) wind farm on the Antarctic coast is actually not a crazy proposal, since the construction can be undertaken by ship alone.
Moreover it's very clear that the energy required to freeze one ton of CO2 is substantially less than the useful energy obtained by its combustion (this is intuitive from the magnitude difference between heat of combustion and enthalpy of sublimation: combusting one mol of pure coal to CO2 liberates 393 kJ, freezing one mol of CO2 out of the air consumes 26 kJ). In no way does that violate thermodynamics; the CO2 still exists, it just isn't doing any harm.
This project would not just ameliorate global warming, it could allow useful exploitation of all the remaining global fossil fuels.
If air capture costs more, then simple economics will keep us more focused on reducing emissions. If it somehow costs less, then doing the air capture is a win.
Most likely, air capture will cost more in some cases (power plant emissions), and less in other cases (long-haul jets). Ideally we'd set a price on carbon, award credits for verifiable air capture/sequestration, and let the market sort all this out.
A slower variant is to build artificial floating reefs, increasing the amount of marine snow. That improves the ecosystem, but requires significant investment.
is where you lost me. Hell coal is projected to get burned by the megaton for another half century or so because China and India have those resources and that demand. Mankind does not currently have surplus renewable energy.
Maybe if you were allocating resources across the world's economies, it would be better to invest in solar panels in Shanghai than capture carbon in Billings, but that's not the actual situation.
On the contrary - we have a lot of surplus renewable energy, and it's a problem [1].
Energy isn't fungible. 1 MWh in Texas at 12:00 on 4th July is not the same as 1MWh in London at 23:30 on 25th December.
Energy consumption vary a lot through the day and year. Energy production of solar and wind vary a lot as well, and these variances aren't correlated with each other.
Most big scale energy grids are created with the assumption that every millisecond energy produced == energy consumed. When this isn't true - frequency in the grid rises or drops. If it drops too much you just have blackouts, if it rises too much - devices blow up AND you have blackouts until you replace the blown up devices.
Even if a grid as a whole has energy deficit - it's often true that one part of the network is producing too much but the power lines between them might not be "thick" enough to transfer all that energy to the part of the grid that has deficit at the moment.
If we moved completely away from fossil fuels towards renewables - to serve energy needs of customers we would need a lot of overcapacity (because you can't count on sun and wind producing at 100% power all the time). Usually the overcapacity for wind is 2x and for solar is 10x compared to traditional sources. Better batteries might change that, but it still won't be 1x. So when there's a very good weather grids with a lot of renewables will by definition produce too much energy.
There's a lot of factors, and in practice even in countries with less than 50% renewable power installed - often they have too much renewable energy. This will only get worse as we replace more energy production with renewables.
Big batteries like the one in Australia are very profitable and solve short-term (sub-hour) balancing, but aren't big enough to shift the solar production peak in the noon to the consumption peak late evening.
So indeed we have a lot of surplus renewable power already that gets wasted every day and causes problems, and it will only get worse.
[1] https://www.sierraclub.org/sierra/what-do-we-do-too-much-ren...
The output might be quite low. But I doubt it would be negative.
However, in some cases it's quite difficult to stop burning C. Long-haul jets are one example. So for those, it makes sense to make carbon-neutral liquid fuels, even though there's an energy penalty. Pull CO2 from the atmosphere, use renewables or nuclear as an energy source to turn it into fuel. CO2 emissions from steel plants might be another good application.
Ideally we might be better off using clean energy sources to displace fossil plants, but that doesn't happen as fast as we'd like for all sorts of political and economic reasons. So we might as well get started now on other reductions, because it'll still help some, and we can get it scaled up by the time we've decarbonized the energy grid and want to decarbonize everything else.
Ignore those rocks that are already hot, let's keep digging up these black ones and burning them!
But if you could eliminate fossil fuel burning and use processes like this to reduce the amount of CO2 already emitted (a big "if" because you have to concentrate it somehow) it could be useful.
It could be useful if we 'just' greatly reduce fossil fuel burning for electricity, even if we don't eliminate it and even if we still use fossil fuels for other things.
How much of the atmospheric CO2 can you actually capture with stations at ground level? I assume this isn't critical since I haven't seen anyone propose a Tower of Babel of carbon capture machines, but I'm not sure why it isn't.
Of course it's going to be more efficient with more air flow, I don't know how turbulent the wind really is, how I could picture it in terms of something I understand like a bottle water, but I assume pretty turbulent?
If you weigh it against the scale of death and destruction from climate change impact yet to come, that could change very quickly.
Please correct me if I get the numbers wrong but if that is the price, that means the price of 1 ton Gallium is $300,000 per ton
From [another comment](https://news.ycombinator.com/item?id=29990056) I got that the ratio of CO2 to Ga would be 1 to 2. So in order to reduce 1 ton of CO2 you'll need to spend $600,000. That seems insane. Especially when the damage done per ton of CO2 is usually valued at ~$200.
I’m dubious but open to try anything halfway plausible at this point.
We extract it from aluminum (and zinc) refinery waste because it is relatively convenient in an industrial process sense, but the amount that can be produced this way is inconsequential. The gallium in all the known aluminum ore reserves is measured in kilotons. For this application, we would need something closer to gigatons. We could produce the necessary quantities if that was the sole objective, but the cost per gram would be closer to gold which is not great when you need gigatons.
Hiw do you separate it from carbon or from indium?
electricity? Cathode and Anode?
https://en.wikipedia.org/wiki/Gallium(III)_oxide
So we'd turn the gallium oxide back into gallium the same way we did in the first place, when we made the gallium. I'm guessing we can also come up with chemical reactions for the other two.
However, you're right that gallium production is quite low. It's a byproduct of zinc production from bauxite, and we get only a few hundred tons per year. Wikipedia doesn't say what the potential might be if we gallium were the main product.
https://en.wikipedia.org/wiki/Gallium#Production_and_availab...
Is gallium oxide dissolved in EGaIn?
If you need to remove tens of gigatons of carbon per year, you are going to need similar scales of gallium to have enough reactant operating concurrently.
ca 720t in 2019
Since fossil fuels are being burned as fast as ever and we can't even slow that down (Biden selling new coal leases in the US, etc.), running it at full speed backwards seems like a pipe dream. If we're going to be that utopian, we might as well think bigger and get started on a Dyson sphere.
That's ... not a lot.
Could still work of course if it used solar heat or surplus industrial heat. If it was low maintenance you could deploy in places like the Sahara. Lots of free heat there.
Edit: gas on the other hand could in theory be burned without CO2. A lot of the net energy there is the hydrogens combining with oxygen to form H2O. You could use fuel cells for maximum conversion efficiency and then recover the carbon.
Don't get me wrong, if this works we HAVE to do this. I'm just not very optimistic that it could save us at this point. We'd still be fucked, just a little less so.
The the paper uses a simple input of CO2 and nitrogen. Though O2 could be added as well, as the gallium will simply react with it too. After all, More energy is released by gallium reacting with O2, than by carbon reacting by O2, or it would not happen in the first place. In the atmosphere, CO2:O2 is say 400:1 meaning you need 400 times more gallium.
The next step would be to separate the gallium from the gallium oxide, which is energy intensive, though this can be climate neural using nuclear. To do so would require hundreds of times the global energy production from coal, oil, and gas. And if you have built these, why not just use them instead, global warming would already be effectively stopped.
It also cannot be used in car catalyzes, providing an anoxic reaction chamber which can collect and separate the outputs simply isn't feasible at small scale. The carbon would be in a fine powder, likely to spontaneously react with O2 if exposed to air, either slowly, or if given a spark, very rapidly indeed. The gallium also should not be released into the environment. Not only would large scale use of this tech make it very expensive, gallium is also mildly toxic. However, because it is rare in our environment, there are few if any studies on the impact of long term low dose gallium poisoning. As a result, its a comparable to lead, a few decades ago. Not saying its as deadly, just saying its a metal we are rarely if ever exposed to, known to be mildly poisonous in the short term. And this is before you add the problems of contaminants in fuel, and partial combustion. For similar reasons it also cannot be used in aviation.
On a whim I clicked on the comments though expecting the first comment to be, "This will never work, because..." So I was happy to see that the top comment was actually positive! Then I saw your response.
One of the things which I've seen but feel is rarely talked about is that the planet is sequestering a large amount of CO2 and this increases positively proportionally to CO2 concentration. Over longer periods of time, the CO2 levels drop, and sudden shocks such as volcanos and cataclysmic massive forest fires, are parried by the increase, quickly returning to previous levels. This proves that sequestration does work which is nice. There are many problems with this. At historic CO2 levels on human timelines the natural sequestration is effectively in balance with CO2 production. So its not enough to sequester the additional modern human production, and the prop increase is less than 1, so it wont be. Two, at least some of the systems which are sequestering are doing so as a side effect of severe to catastrophic ecological damage. For rare events this isn't a problem, but our current production is not one year in a century.
It does mean that if we stop using fossile, CO2 levels will revert on their own. Though it will take a long time.
The gotcha is right there in the Abstract: "solid carbon and gallium oxide are the final reaction products of this process."
This is the thermodynamic equivalent of rearranging the deckchairs on the Titanic. It achieves literally nothing except for shifting the oxygens around. They're still around, still bonded, but even harder. That's what this process doing -- reducing the carbon using a liquid metal. Reducing the gallium oxide back to the metal takes even more energy than was released by burning the C to CO2 in the first place! If you have an energy source that exceeds the world total carbon usage... then you don't need to burn carbon any more![1]
At best, this could be used to convert some magical future energy source like unlimited fusion power into pure carbon, eliminating the need for coal mining. But that's it.
This -- and any approach like this -- can never be practically used to counter the effects of CO2.
The finance equivalent would be: "We found this new way of producing $100 that only requires $110 in expenses!"
Actually not $110 at all. A sibling comment mentioned that "Gallium is cheap (~$300/kg)".
For comparison, coal is on the order of $150/ton. Not kilograms. Tons. Literally 2,000x cheaper than Gallium per unit weight!
So this paper proposes reducing $100 of carbon by using $200,000 of gallium.
Sure, you have gallium oxide left behind that can be recycled for a bit less than $300/kg, but certainly not for $150/ton!
[1] The few direct uses such as using coke to produce iron from its ore can be replaced by hydrogen gas. Similarly, groups are working on processes for iron similar to the one used for aluminium that requires only electricity as the input.
Too much co2 in the atmosphere is assumed to be a bad thing.
Someone says they can sequester co2 from the atmosphere at a certain energy cost.
Is your point that this energy cost is unrealizable?
This is literally[1] burning $300,000 to save $100. No matter how well you optimise that $300K, it will never ever EVER be less than $100. It can't possibly be, that would break the laws of physics and you'd have essentially a perpetual motion (free energy) machine.
If you have 'x' units of carbon (coal), which you burn to make 'e(x)' units of energy and some CO2, turning the resulting CO2 back into 'x' units of carbon will always take more than 'e(x)' units of energy. There is no magical future science that can enable this. It's a fundamental law of thermodynamics!
If it were possible, then you could turn 'x' units of carbon back into 'x' units of carbon PLUS have some free energy left over by running the above in a loop. That's absurd. That's literally a perpetual motion machine. You could start with one ton of carbon and never need more to make infinite energy.
There is an endless series of "science" papers like this published every year, because it gets funding and attention from people that just don't understand that "there ain't no such thing as a free lunch". They're a total waste of time, and have the same logic as trying to power your ceiling lights by using solar cells as your wallpaper and then connecting the lights to the wallpaper. Isn't that brilliant!? The photons from the ceiling lights will produce electricity in the solar cells, which in turn will power your lights! Never pay electricity bills ever again!
NOTE: There are ways of capturing (not "un-burning"!) carbon dioxide and trapping it for less energy that was released by burning the carbon that went into it. That's fundamentally different, and potentially economically viable.
[1] Literally! Not figuratively! This process literally burns expensive gallium metal to produce cheap carbon and burnt gallium (gallium oxide).
If it requires that, then its even more pointless apart from the learnings of course, because such scenarios are super super rare in the real world of industry.
and in a marketing/politics point of view there is a LOT of bullshit going around about "Carbon Capture and Storage". This POC is likely to revamp that bullshit all over again.. its worth pointing out that this POC did not even slightly come close to the idea of "pulling carbon from the atmosphere".
The cost of doing it is so far down the list of reasons to not get overly excited about it.
The question is then, can we spin up sufficient capacity, and can we find a scalable, sufficiently efficient way of capturing said carbon, thus the research into this area.
Nobody is talking perpetual motion here.
If you just want to remove CO2 from the air, there are much better ways than “un-burning” it.
2: Solar is unreliable, requiring tiding over on nights/cloudy days/etc. In theory, this would allow for excess energy -> fuel, or other things, since coke is also useful for a number of other industrial processes.
3: Does this scale? I have no idea. It's not quite burning gallium though, since from what I'm seeing, gallium can then be regenerated to elemental gallium (at the cost of more energy). This is more an engineering, rather than a research question though.
4: This is just one of many projects (with some nice characteristics), if something else better turns up, then so be it.
This isn't a problem of scale, and the problem is that optimistic people just don't get this.
There is no way to make this work, ever. It's like the old joke: "Sure, we're selling every unit at a loss, but we'll make up for it with volume!"
You can't take a "business plan" that inherently loses money and try to scale it up to... what? Even greater losses?
(In this case, this is both a thermodynamic and a financial loss. You're burning both energy and cash!)
My life is bigger then lunch though. Lunch enables me to do other things that do make money - so I take a loss on lunch with a view towards the other stuff.
It’s impossible, of the perpetual machine variety.
This is precisely analogous to this gallium example! You can’t unburn something without losing more energy in the process than the burning produced. It’s always over 100% overhead.
ALWAYS!! The details and the path taken through the world of chemistry or electrochemistry are totally irrelevant and can never alter this.
Thanks to this technology with proper economic incentives we might use surplus electricity in peak renewables production hours to make carbon to burn later, or to bury underground.
Similarly, in this paper, electrochemical activity is converting CO2 and Ga into C and gallium oxide. The C and the Ga swap. The reaction is spontaneous. No need to add any energy for this reaction to occur; it proceeds because the products are more stable than the reactants.
Where is extra energy required in the process? Energy is required to melt the Ga to about 200C. Energy is also required to reverse the oxidation, i.e. to replenish the Ga. A supplement to the article explains that this was done by electrolysis: gallium oxide was converted into Ga and oxygen [0]. I guess, that they figure to use solar energy to generate the needed electricity.
I'm with you as regards the unfeasibility cost-wise. What they are obviously doing is exploring uses of low melting-point metals [1], hoping to strike it lucky with one of their projects. And, yes, these guys have obviously got their publicity department working overtime in order to generate more grants.
In a recent video, the co-lead scientist, Associate Professor Torben Daeneke [1], explains his various projects.
-- 13 min: The melting point temperatures of the metal/alloys they are working with.
-- 61 min: Their latest work , CO2 to coal.
And here's a video showing the bubbling of CO2 through Ga-In (gallium-indium) alloy to form carbon [2].
[0] https://www.rsc.org/suppdata/d1/ee/d1ee03283f/d1ee03283f1.pd...
[1] https://www.youtube.com/watch?v=fvsON7af2J0 Jan 2022
[2] https://www.linkedin.com/feed/update/urn%3Ali%3Aactivity%3A6...
All of these reactions just go “downhill”, and no amount of hand waving will make the uphill journey go away if you want to run any part of this in a loop — e.g.: to treat the gallium as a non consumable catalyst.
There is no infinite free supply of gallium, and there are no ski lifts in the electrochemical world.
Going uphill is the hard part. Any idiot can go downhill.
1. Emit carbon when there is no wind or sun and capture it with gallium.
2. Reduce the resulting gallium oxide when clean energy is available.
That makes this essentially a gallium/CO2 battery.
Also, it’s not true that cycles like this necessarily require more energy than is generated from the CO2 source. I can’t speak to this one in particular, but there are carbon capture techniques that use less energy than is generated by the combustion source. That’s because the carbon ends up in an energy state that’s lower than it’s energy state in the fuel source (e.g. solid carbon is higher energy than CO2 gas but lower energy than hydrocarbons) and because carbon isn’t the only molecule oxidizing in the combustion reaction, hydrogen is too.
Renewable energy is not available. It's needed now, in much greater quantities than are available, to supplant hydrocarbons and coal.
Real trouble is that as long as this excess energy is useless there's no economic incentives to build more renewables.
You would though? Carbon is dense and easy to store and transport in bulk, in your car/plane/etc. Whereas solar/nuclear/etc. aren't.
Anyway, good to see it works in two different labs.
EDIT: The Advanced Materials paper's process seems to produce carbon oxides, whereas the OP paper produces solid carbon. I suppose this is an important difference, the latter being more useful.
Turing CO2 back into C and O2 will require adding at least as much energy as was released in its formation.
Where is this energy coming from?
1. The hydrogen in the fuel remains oxidized.
2. Captured carbon (compressed CO2 gas, solid carbon) is still at a lower energy state than the source fuel (octane, etc.)
3CO2 + 4Ga => 3C + 2Ga2O3
How much spare gallium is there in the world? Is it anywhere near enough to put a dent in the ~1,000 tonnes per second that humans are emitting?
So, process can be created wherein
3CO2 + 4Ga => 3C + 2Ga2O3 => 4Ga + ... => 3CO2 + 4Ga ....
You should be able to do it with heat, electrolysis hydrogen + heat to reduce it, or electrolysis itself. Theoretically you can do these all with electricity.
It makes way more sense than when I see carbonates brought up as a way to sequester things at least, since the thing being cycled has no carbon in it at least.
In other words, this doesn't sound to me like a solution to our clean energy problems, so much as a cool thing we might be able to do on a mass scale after our clean energy problems have already been solved.
What happens to the Gallium Oxide? Edit: Follow up - Is pure CO2 required as input or can the input be air?
You could get that reducing gas from hydrolysis, and solar, but it's not energy cheap (~50% efficiency).
But regardless it is certainly possible to regenerate it using only electricity possibly with intermediate but renewable substances (water, sodium chloride, etc)
How about converting CO2 to value-added hydrocarbons? This article seems to say it's possible. Imagine that, using hydrocarbons as a storage battery for electricity used to power the reaction:
"Heterogeneous catalytic CO2 conversion to value-added hydrocarbons" https://pubs.rsc.org/en/content/articlelanding/2010/EE/c0015...
I also didn't realize Gallium is one of those weird metals with a really low melting point but quite high boiling point.
Melting point 302.9146 K (29.7646 °C, 85.5763 °F)
Boiling point 2673 K (2400 °C, 4352 °F)
(It’s doesn’t melt it exactly, it destroys the structure because Gallium atoms are very small and insert themselves through).
Which nearly all involve converting carbon to atmospheric CO2.
Granted, we need to be carbon negative but it could still be used for some of portion of existing supply that is carbon positive.
Even it will capture CO2 (with a high energy cost, assuming it's nuclear energy), CO2 is diluted in the atmosphere.
They would like to plug this to coal and gas plants, but that will not be enough.
Humanity is too dependent on technology and carbon energy, today it's unthinkable, taboo and controversial to tell everyone to reduce their standard of living, to live a sober life, to work less, to eat less meat, because it's just too complicated to separate ecology from social inequality.
Instead, you have big oil trying to save itself by any means they can find, including trying things that don't make sense with physics.
You can however, use it as a form of storage if you get sufficiently good efficiency.
Gallium suboxide then decomposes into it's components at temperatures above 500 C.
Feasibility of this is an exercise to the reader (I have no clue).
Presumably one could chain that system to this system to produce solid carbon from atmospheric CO2.
Put it out in the middle of nowhere, where energy storage/transportation would be uneconomical, like a desert, and power it with the sun, and maybe you’d have a decent carbon sink where otherwise there’d be nothing.
There is no danger of overloading the depths with CO2 or acidity. The sheer volume of deep ocean water to disperse the surface CO2 into is overwhelmingly greater than what could be pumped from the surface in even the largest conceivable process.
Gallium can serve as no part of a practical solution.
https://news.ycombinator.com/item?id=29912896
Except at certain well-known places, very little mixing happens naturally.
Of course we need thousands or tens of thousands of them, not just one, but there has to be a first one.
Do you have any source or actual maths on that claim? As in the aspect that pumping CO2 into seawater would not significantly increase ocean acidification?
I thought ocean acidification is basically one of those extinction level events. It affects the building of shells in crustaceans and the ability for fish to hunt (see shark electroceptors) it basically is a catalyst to disrupt the food chain all the way up to us, no?
It's about numbers. The carbonic acid produced by excess atmospheric CO2 dissolving into the water is concentrated in the few feet right at the top of the water column. If we took the top 50 ft of the the ocean and distributed it between, say, 3000 and 4000 ft deep, the excess acidity per unit volume there would be 1/20th what we have at the surface. Furthermore, the number of animals there dependent on forming shells is many fewer than 1/20 the number near the surface.
Keep at it long enough, without actually reducing the atmospheric excess, and you end up with the whole ocean too acidic, not just the top. But very soon, on a geologic timescale, we will perforce radically reduce the atmospheric CO2 overburden, or civilization will collapse and do that for us.
If you asked residents below 3000 ft if the extra dissolved oxygen coming down is worth the extra acidity, I am certain they would not say "no". (Full disclosure, they wouldn't say anything, but hey.)