Comment by PeterHolzwarth
1 month ago
Well, instead of repeating myself manually, I'll paste in a comment of mine here from a past discussion on carbon capture:
It's easy to forget why there is a bit of a challenge to getting C02 out of the air: there's so little of it, comparatively.
In order, air is, broadly, made up of the following:
Nitrogen: %78.084
Oxygen: %20.946
Argon: %00.934
CO2: %00.042
The stuff is essentially beyond a rounding error - it really gives one an appreciation of the "either don't release it, or capture it at the point of release" sentiment, and for the difficulties in making carbon capture outside of these scenarios be even slightly cost-effective.
Also more fundamentally it's always going to be more efficient to not produce CO2 than to unproduce it.
Ok maybe in a small number of circumstances there's no other option (e.g. planes), but mostly you're far better off spending your energy making solar, wind, batteries, heat pumps, insulation etc.
In today's world there is a roadmap for a < 20 year transition for the entire world if planned and executed collectively.
However Chinese domination, global geopolitics being changed and fossil fuel industries and countries still being extremely large and powerful make even choosing the obviously cheapest (and incidentally clean) option difficult in many parts of the world.
Nonetheless, it seems much more optimistic today in 2025 than say 2015 speaking purely based on where technology stands
> However Chinese domination .. make even choosing the obviously cheapest (and incidentally clean) option difficult in many parts of the world.
In what way? China has basically dwarfed solar installations of any other country combined for the last two years, and produces so many panels and so cheap that EU and US competitors are being driven out of business.
China might be the reason we CAN make the transition actually.
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It's hard to put my finger on why, but that's a really weird way to frame the situation.
For one thing, most of us don't control any CO₂ production we can turn off.
Also, even if/when we finally produced our last CO₂ molecule, the excess CO₂ will last for many centuries, and we really should get it back to lower levels.
With good capture tech, you can keep keep doing some important CO₂ producing activities.
Sure, it seems very unfeasible with current technology, but that is bound to improve as you work on it.
> Sure, it seems very unfeasible with current technology, but that is bound to improve as you work on it.
That not a good logical argument as there's no guarantee that every technology can be improved enough to be better than the alternatives. e.g. Steam engine tech is bound to improve as you work on it, but it's not going to be as efficient/useful as an internal combustion engine.
History is littered with examples of tech that has been surpassed by better ideas, so the lesson to learn is to optimise the best current solution. In this instance, the best (most efficient, practical) solution is to stop emitting so much CO2 rather than a long bet that capture tech will ever be feasible - with atmospheric concentrations being so low, the scale required makes it a non-starter.
> most of us don't control any CO₂ production we can turn off.
Uhm what? Driving? Flying? Heating?
> Sure, it seems very unfeasible with current technology, but that is bound to improve as you work on it.
Improve, yes. Break the laws of thermodynamics? No.
You can improve a perpetual motion machine but it's never going to be useful.
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Indeed. I've always had trouble picturing how to efficiently "unmix the cake" too. CO2 is rare and throughout the whole atmospheric column. What kind of concentration gradient can you get going to meaningfully pull it out from everywhere in human timescales? (Sorry if this nerd-snipes someone stronger with calculus than me.)
Plants capture CO2 from photo synthesis at huge scale. That seems like a great way to capture it at a higher concentration. We’d need to handle the organic matter before natural decomposition, but quite doable.
It’s even less energy efficient gathering up plant matter at this scale and permanently sequestering it, than getting it from the atmosphere. At least with the current technology required to harvest, move and process it. It’s why biomass is still a relatively niche ‘carbon offset’ technique.
It is also highly space inefficient and time consuming to grow and store (sequester).
Even if we converted all US cropland (and the US is one of the largest and most fertile countries for growing crops!) to growing trees, for example, we’d need multiple years of growth for every year of fossil carbon we currently release. And we’d all starve.
There is also generally less carbon by weight than you might imagine - even hardwood is typically more water than carbon when harvested, which is a big part of the problem.
To make it time efficient and also stable to store (not just rot and release the carbon immediately as methane or the like), it needs to be converted to a more stable form like charcoal or coke. Which further decreases efficiency and adds costs.
Near as we can tell, it is much better to just not release it (electric cars + solar?), or geo sequester it (olivine minerals seem promising!) or capture and sequester it directly (inefficient, but hey, there are techniques that should scale like pumping back into the original fossil aquifers!).
The biggest issue is economic (and hence political) - fossil fuels are energetically the equivalent of free money. It’s pretty hard to convince people to stop getting free money and pay money instead!
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Diffusion and convection would do all the work. You dont need to worry. You can see the stuff mix around https://www.youtube.com/watch?v=-aSBfn6_pUY
I get what you're saying, but couldn't this be used in a place with high concentrations of CO2, like factory chimneys?
That would be “capture it at the point of release”
Yes, but these scrubbers need vast amounts of energy. Most of which emit carbon. We simply need to curb emissions. With the possible exception of basaltic rock weathering, DAC is not practical. Large DAC projects fail to reach forecasts, even when these forecasts for plants costing tens of millions of dollars only aim to extract global emissions of two or three seconds.
That same money could replace a lot more emissions with other sources of energy. How much solar and batteries does it buy? It’s always struck me as a moonshot project for people who don’t understand thermodynamics.
You could probably unstir the cream from the coffee with an elaborate chemical processing system costing more than what thousands of coffee makers and dairy cows cost.
The only CO2 removal project I’ve seen that seems like it might be viable is ocean fertilization. That’s not a thermodynamic free lunch. You’re letting solar powered microorganisms do it. But it needs to be studied and monitored to make sure it doesn’t ruin ocean ecosystems and that enough of the carbon actually does get sequestered to make it actually worthwhile.
Plants seem to manage it okay.
They don't, and they can't cheat physical realities either.
Plants only filter out very small amounts of CO2 from the air over relatively long timeframes. That's why crop-based biofuels require such enormous amounts of space.
'Very small'?? Depends on your perspective.
"The amount of CO2 removed from the atmosphere via photosynthesis from land plants is known as Terrestrial Gross Primary Production, or GPP. It represents the largest carbon exchange between land and atmosphere on the planet. GPP is typically cited in petagrams of carbon per year. One petagram equals 1 billion metric tons, which is roughly the amount of CO2 emitted each year from 238 million gas-powered passenger vehicles."
The article: https://www.technologynetworks.com/applied-sciences/news/pla...
The paper: doi: 10.1038/s41586-024-08050-3
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They're pretty amazing for the amount of capital cost. $50 in seed and an acre of land can sequester several to over a dozen tons of carbon per year. It might not be space efficient but it requires basically zero infrastructure.
Which is something that when I try to explain to some 'environmentalists' do not get the point.
The other benefits of a biodiverse green belt are great, but if tomorrow I have a concrete system that captures CO2 at 10x the level of trees over lifetime in a similar density, guess what I would like my futuristic city to look like.
So then, is it really the CO2 that produces the cognitive impairment, or is the CO2 here just the proxy value that we are measuring, and the real reason for the cognitive impairment is low oxygen?
If the amount of CO2 is basically a rounding error, so too would be the reduction in oxygen.
Nitrogen also causes cognitive impairment. It is essentially a very weak anesthetic. If you can replace all of the nitrogen in your breathing gas with helium then you'll probably gain the equivalent of a couple IQ points (although obviously that isn't generally practical).
Nitrogen narcosis is especially relevant to divers. Recreational SCUBA diving is usually limited to around 30m depth and some divers will start noticing effects (basically like getting drunk) near that depth when using air in the tanks. This is why different mixtures (e.g. trimix) are used at increased depths, though there are other important effects of breathing air at pressure such as oxygen toxicity.
It’s also the metabolic changes in pH. CO2 is a proxy for ph as carbon dioxide acidifies the blood as it dissolves.
You could climb a mountain to test your hypothesis, keeping an eye on partial pressure of O2
We have a natural experiment. People in Denver aren't especially stupid.
What if one started emitting Nitrogen, Oxygen and Argon in the right proportions instead to get the mix right again?
I like the unconventional approach. A few minutes with GPT raises two issues:
1. We've raised CO2 from 280ppm to 420ppm, about a 50% increase. To dilute it back down would require 50% more total atmosphere. This would also raise the surface air pressure 1.5x.
2. How much heat is trapped is related to the absolute amount of CO2 in the atmosphere, not the fraction. So the diluted atmosphere would retain just as much heat.
Would it increase the steady state surface air pressure by 50%, or would more molecules offgas into outer space to compensate?
If the latter, it might actually work. Assuming they offgas at-proportion. Which they probably wouldn’t…
Interesting thought but you would need a lot of these gasses on the one hand and on the other hand it doesn’t help in working against the greenhouse effect. The greenhouse effect depends on the absolute amount of CO2 in the atmosphere, not the percentage. How much infrared light is absorbed by CO2 primarily depends on the amount of CO2 in the atmosphere.
My naive guess is that since CO2 takes up so few percentage, you would need an unfathomable amount of N, O, and Ar to get the mix right..?
We will unquestionably reach more than twice the CO2 concentration of pre-industrial levels (which was around 280 ppm; we're at 424 ppm now, it'll increase to beyond 560 ppm in most not-super-optimistic projections).
Do you really think it's both feasible and a good idea to release so much O2 and N2 to double the mass of the atmosphere? Or even just increase it by some appreciable fraction?
For the record, the atmosphere is around 5 150 000 000 000 000 metric tons. 5 quintillion kilograms. You're talking about producing metric exatons of gas.
Wikipedia says that there's 300 000 to a million gigatons of nitrogen in the earth's crust; that's 300 teratons to a petaton (https://en.wikipedia.org/wiki/Nitrogen#Occurrence). If you extracted LITERALLY ALL THE NITROGEN IN THE CRUST, converted it to nitrogen gas and released it into the atmosphere, and we use the extremely optimistic 1 petaton estimate, you'd have increased the mass of the atmosphere by roughly 1/5000. That means you'd have decreased the CO2 concentration in the atmosphere ... by roughly 1/5000. From 424 ppm to 423.92 ppm.
Think about the magnitude you’re talking about here. Every internal combustion engine on earth is emitting CO2. Every volcano, forest fire, coal power plant, etc. The atmosphere is massive. We’ve been, basically, doing our best to pump it full of CO2 for the last 150 years, and this is what we’ve got. Ignoring the chemical challenges with your idea here, the scale is impossibly gargantuan.
These gases are refined from air to begin with.
Do they need to be?
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Would that actually reduce the greenhouse effect? Intuitively, it seems analogous to putting on a less dense, but thicker blanket.
Lying with statistics while denying science and climate change. Small things sometimes make a big difference. Get the fuck out of here with this Dunning-Kruger effect bullshit.
And yet trees do this trivially?