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.
Probably thinking that if it appears China is getting global dominance in energy production/energy storage/car manufacturing, the West would block imports out of political and economic expediency. Like the current US administration is doing.
The chemical sector is the only reason why emissions haven't meaningfully declined yet, and I suspect it is in part due to conversion of supply chain for electrification.
The point is that they're paying a one-off cost (thus producing a peak) and they're already reaping rewards. Once they fully transition power generation to renewables and electrify transportation, what's left can be better regulated and CO2 recapture more easily scaled thanks to also R&D advances on CO2 recapture (e.g. capturing CO2 emissions from a chemical plant's exhaust). Then, even if you need more energy for CO2 recapture, you can keep scaling renewables further.
If everyone sets goals and starts work to reduce emissions in 2015 you dont get credit for failing to meet all your goals while secretly doing the opposite and trying to create as much growth as possible by scaling coal production. Like how would it be if my country was like ok we will reduce emissions in 2045 and then doubled our emissions in the next 5 years. Thats what China is doing.
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.
>With good capture tech, you can keep keep doing some important
CO₂ producing activities.
We're not asking people to stop breathing while there's no good DAC on the horizon, but I wonder what were the other important CO₂ producing activities you intend to do less of.
The following isn't breaking the law of thermodynamics; just wilfully ignoring it..
Gemini:
>To offset a single typical gasoline car's emissions (around 4.6 metric tons CO2/year), you'd need a substantial fraction of a large DAC plant, as current large plants aim for 1 million tons/year, meaning many tiny DACs or a small portion of one large one; as of late 2025, the largest operating DAC (Mammoth) captures 36k tons, requiring about 80 such facilities to match one average ICE car's annual output, highlighting the massive scale-up needed, with projects like Texas's Stratos targeting 500k tons/year (equivalent to ~108 cars).
There are 3 or 4 laws of thermodynamics, and I can't figure out which one you might possibly be referring to.
I agree that current carbon capture tech is very inadequate, because very little effort has been put into it. How many orders of magnitude better it can get, we don't know until we try, but I don't see any fundamental reason it can't get good enough.
Once you have a solar powered capture machine park pumping CO₂ underground, it can keep working indefinitely at little cost.
> I wonder what were the other important CO₂ producing activities you intend to do less of.
All of them. This is well under way. I don't know how many decades it will take. But that's a separate problem.
The crucial thing to understand is that even if/when all CO₂ production has ended, the produced CO₂ won't disappear by itself for thousands of years!!
So you really need to actively remove it to get back to natural levels. Which is why I think carbon capture tech must be developed.
If you think about it, 2nd law* is the most relevant one because, after all, CO2, being so stable, is one of homo sapiens "favourite" waste materials (partition function yada-yada)
How did plants evolve to use it as nutrients. Solar power. since humans don't need to make fuel from air these days, maybe all of that solar power should go into compute?
.. I'm not saying any laws are broken, just that there are much better (=more efficient, more promising) ways to reduce global warming, like
> Should every car owner personally optimize the CO₂ emissions of their car?
Yes!! Obviously! Buy an electric/hybrid car or at least one with good fuel efficiency. Drive it in an efficient style. Try to avoid unnecessary journeys.
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!
Extraction of the resource is not free. But with advances in solar panels and battery technology, the economic arguments for much fossil fuel use is fast disappearing. We were never going to make difficult decisions for the sakes of our grandchildren - we're much too selfish for that - but as renewables put more money in our pockets, we might just make the right decisions. Even if it is for the wrong reasons.
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.
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.
"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."
Man-made carbon emissions amount to over 40 billion metric tons annually, according to a quick Google search. Worldwide terrestrial plant carbon exchange amounts to less than 2.5% of the CO2 humans release, if plants take in 1 billion tons per year.
From the perspective of averting climate change it is indeed very small.
A team of scientists led by Cornell University, with support from the Department of Energy’s Oak Ridge National Laboratory, used new models and measurements to assess GPP from the land at 157 petagrams of carbon per year, up from an estimate of 120 petagrams established 40 years ago and currently used in most estimates of Earth’s carbon cycle.
Whether 157 billion tons or 120 billion tons, these numbers are large compared to anthropogenic releases. Of course most of this carbon is quickly cycled back out from land plants due to animals/bacteria/fungi consuming the biomass produced by land plants.
You still need to turn incredible amounts of biomass into charcoal or other stable forms of carbon to make a dent in atmospheric co2. It would take decades of hard work on gigantic scales to unburn and bury the fossil fuels we used.
That's the pay-off of our 150-year rush to monetize as much of the Earth's natural resources as possible -- while making stringent efforts to keep quiet knowledge - or suppress any efforts - to utilize the benefits of free solar energy.
Having polluted and despoiled much of the biosphere, of course we'll be donating our supposed wisdom and that hard work to the future generations that will enjoy the fruits of our labors and entreasurement.
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?
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.
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.
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.
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.
Where else are they going to come from? They’re all basic elements, either you separate them from air, or you have to go through an energy intensive process to liberate them from various chemicals they’ve been compounded into.
But guess what, all of those chemicals are extremely valuable, such as nitrates for fertiliser, water, and Argon does really react with anything (it’s a noble gas), which is why we use it as a shield gas in processes like welding.
So producing enough of those gases to somehow offset CO2 production would first require ludicrously large amounts of energy, and if we had access to that amount of clean energy we wouldn’t even be having this discussion. Plus it requires breaking down really valuable chemicals that we spend quite a lot of energy trying to produce or preserve anyway.
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.
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.