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
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.
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...
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.
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!
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.
The output might be quite low. But I doubt it would be negative.
guess, the same way we got it - bath, electricity, cathode and anode
Ignore those rocks that are already hot, let's keep digging up these black ones and burning them!
Please have a look at Limestone Calcined Clay Cement: https://lc3.ch/
This is only one of the cement alternatives I believe.
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.