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
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.
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.
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.
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.
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).
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.
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.
I am not against doing research in this area, please do, it is interesting and likely has many applications but global CO2 removal isn't one of them. Nothing proposed, including this, is within any orders of magnitude of a viable solution. The only solution we have is put less in the air in the first place. This tech looks interesting for transporting CO2 but that doesn't mean it sequesters it and even if sequestration was solved the scales here are massive. If we don't have the political will to reduce the amount going into the air then what makes anyone think we would have the political will to build out some system to capture and sequester? We need to focus more on not putting CO2 into the air and less on trying to take it out.
> If we don't have the political will to reduce the amount going into the air then what makes anyone think we would have the political will to build out some system to capture and sequester?
Because political will requires coordination, building systems and turning them on doesn't have to!
> We need to focus more on not putting CO2 into the air and less on trying to take it out.
What part of the "we" in this coordination problem doesn't require political will?
The implicit model in "just emit less" is that human coordination problems are easier than engineering problems. That's historically backwards. We're extremely good at building things. We're terrible at getting everyone to sacrifice simultaneously for diffuse future benefits. Please generalize this!
The is one trick that doesn't require political will. If you can make the microeconomics work it can be made to scale it self.
E.G. Make CO2 extraction so cheap it's worth everyone doing it and say, make a market to sell the CO2 to farmers. Then make burying inedible bits of plants so cheap it's done on a large scale.
Then you just wait. Microeconomics takes over.
They did this with plastic clean up. By building a machine that makes plastic into fuel & construction pellets. Then stuck such a machine on a plastic poluted island and waited.
For this trick. All you require from your políticans is that they don't lie or bomb the place.
I think you have a point. It could be difficult to justify the cost of carbon capture based on sequestration alone. One of the reasons I think this might still work is that captured carbon can be used to create platform chemicals (various hydrocarbons) using the fischer tropsch process. Electrofuels are using direct air capture to generate fossil replacements.
Only requirement is energy and there too it isn't all that expensive to pull air in from the atmosphere or to seperate CO2 from adsorbent via low grade heat (70-100c)
So far into the future this method could allow us to continue produce critical hydrocarbon materials (used everywhere from plastics to pharamaceuticals) without having to depend upon concentrated and contested oil supplies.
More than energy efficiency its volumetric efficiency that's the issue. At the moment (to the best of my knowledge) kg of capturing materials capture tens of grams of CO2. Pulling it from air is not that energy intensive but finding materials that can actually filter out CO2 from that air is difficult. If breakthroughs are made in this area it will have industrial applications. Then it won't be just sequestering.
Of course the easier solution is to plant more trees and grasses but they grow very slowly and require valuable land. Still this approach is feasible in some uncultivable lands. Crops like cottongrass[1] can grow even in tundra climate and can be valuable source of both technically imp carbon via cellulose and a means to capture CO2. We don't have to make a choice. We can do both simultaneously.
I wonder what the economics could look like for using this with remote solar for production instead of considering it for global removal/sequestration. If you build a solar farm in a desert and use this to pull raw materials from the air to create something actually worth money, what levels of efficiency do you need to make that profitable? How close is something like that in reality?
Giant miscanthus can grow on land that's not viable for farming food (other than grazing grasses), has a lot of properties that ready it for becoming charcoal (high tonnage per acre, self drying, minimal inputs needed). Without a price for carbon, it's hard to make it work, though.
This is called Carbon Capture and Storage and so far it has never been worth it energetically. And the only companies doing it are oil companies in a process known as enhanced recovery which pushes more co2 out than is pushed in. The OP was right. Better to leave it in the ground
I've wondered if capturing carbon emissions from industrial-scale compost facilities would be a net positive. It would have the added benefit of the carbon initially being captured by natural organic processes (i.e. growing food), so it avoids the problem of the energy requirements from trying to just pull carbon from the ambient atmosphere. I don't know if this is feasible but I haven't seen any research on it.
There are applications where weight still makes battery storage impossible. By capturing carbon, we may give ourselves the ability to harvest fuel from the air instead of the ground. Given the sometimes negative cost of electricity, this could make it more cost effective to do so. If we replace fossil fuel drilling with sequestration then we are at net zero.
This may be part of the solution … or maybe we find a way to make a utopia where we can all agree to just stop polluting. Historically, the utopia has no precedent that I am aware of.
> The only solution we have is put less in the air in the first place
That’s not a solution either, because the developing world is not going to stop increasing their CO2 output until they fully industrialize. They’re just not. Feel free to seek reductions where you can, but don’t think of it as a solution because it’s not.
The technical problems with CO2 capture are far more solvable than the sociological problems with net zero emissions.
Actually, solar and other renewables are making it easy to skip legacy hydrocarbon based infrastructure and the 'developing world' (not the west) is snapping it up [1]. Additionally, the big problem countries aren't really the developing world. China is rapidly hitting its targets and other than a brief moment where they threw up a lot of coal fired generation to meet immediate demand it looks like they will very rapidly decarbonize in the coming years and start having so much excess renewable energy that they will pay people to use it for manufacturing [2][3].
I think they are, but more by accident. They’re going to industrialize with renewables, batteries, EVs and electric everything. It’s inevitable due to economics
Removing CO2 from the air is a pipe dream for several obvious reasons.
Firstly, it will always be more difficult and energy-intensive to extract CO2 than to just stop putting it into the atmosphere in the first place. Yet the world is nowhere near agreeing any meaningful framework on reducing emissions, and the party in power in the largest democracy in the world is in denial that a problem even exists.
But mainly, if there was an effective means of CO2 removal, who will be in charge of the dials, and who will set the targets?
Atmospheric CO2 is now 50% higher than when I was born. Will we go back to the levels as at the 60s, or perhaps the beginning of the industrial revolution? Obviously that is unfavorable to the frozen regions that are now thawing - like Russia (and Greenland), who benefit from climate change.
Unfortunately, Technological solutions are more politically feasible than attempting to reduce via restrictions and regulations that require intense global coordination that does not exist.
You are 100% right that we _should_ be focusing on reducing emissions, but the reason we would prefer to capture-and-sequester is... money. We make money by emitting C02, and it looks like we will also pay to have it captured again. Is this madness? Also yes.
There are 4 different categories of fixing the global CO2 challenge:
a. Remove CO2 from atmosphere
b. Prevent adding new CO2 from reaching atmosphere
This could also be a good use case for #b where CO2 is captured before being released to the atmosphere. For example factories and vehicles could be mandated to use this.
Maybe we need to genetically engineer special of trees that are active only during the day and sleep at night. Photosynthesis at daytime and Dormancy at nighttime for maximum CO2 conversion.
"The Wizard and the Prophet" by Charles C Mann sets up an interesting duality that I think more people should be aware of.
Mann describes "Prophets" as people who see a problem and then try to prod people to change their behaviour in order to avoid it. e.g. Thomas Malthus observed that exponential population growth had humanity on track to experience severe famine, conflict, etc. that would violently and savagely bring our numbers back within the carrying capacity of the Earth. Multiple people have made predictions about when humanity would reach the brink at numerous points in the years since Malthus, but were always wrong about when the Malthusian trap would finally spring...
...because of "Wizards". Wizards are people who set about solving problems with tech. Advances like the use of fertilizer, first bat guano and then the Haber-Bosch process, followed by scientific crop breeding have effectively raised the carrying capacity of the Earth so much that, despite our exponentially ballooning numbers, there are far more calories per person available now than in Malthus' day.
Prophets are valuable for their ability to observe and raise awareness about problems. The Earth does have an ultimate carrying capacity too, which we should keep in mind even if we don't know what it is. However, the track record undeniably favours the Wizards. They get things done. Prophets hate this, because it makes it look like they were wrong. They weren't wrong. They were just too focused on an approach to the problem that rarely works.
The modern environmentalist movement is dominated by prophets. So much so, that wizards are often portrayed as the enemy. History has shown that this is wrong-headed. We should value prophets for what they do, but ignore them when they tell us not to fund the wizards.
This. The fossil fuel industry continues to overflow the tub with CO2, but instead of turning off the tap, we keep trying to invent a better sponge.
We need carbon taxes, tariffs on high-emitting countries and products, and support for adopting clean energy, clean transportation, and clean everything else. Lobbying and misinformation has made these actual solutions politically impossible to implement though, so we continue to waste resources on sponges.
I'm going to have to disagree in a (hopefully) nuanced way. First, I just ran an end-to-end continent scale simulation of CO2 sequestration for the US, as is. To put it bluntly: there's no way outside of magical pocket sized fusion that will make this work. If you add full ground transportation abatement; full power abatement; and, then, use dedicated thermal sources, then the final cost is ~1 trillion a year. And, that's after all the positive upsides to the economy. There's a bunch of "almost unlimited upside" to be had from not having to move Miami, Houston, etc., but it's too complicated to model. However, just the healthcare implication upsides are roughly parity, disaster included.
But! Notice that abatement doesn't get us to 0. It merely slows the process. The remainder absolutely needs ACC. The output stream needs to be dirt cheap, the thermals need to be 100°C and not 900°C. Those sorts of things would bring ACC down to "hundreds of billions" rather than a trillion.
There's no general will, it's not specifically political will. Emitting less CO2 means doing less things or doing them for much more money due to high taxes to discourage it (and also disproportionately affect poor people). Other than some luddites I've never met anyone that genuinely was willing to sacrifice eating a nice steak or going on vacation unless they are millionaires, and that's only because those people know they can do it as much as they want. You have a huge mass of people getting lifted from poverty that will tell you to fuck off if you tell them that now they are finally out of eating rice and starving they can't have a steak, because of CO2.
All the things silicon valley "caviar communists" say you need to stop doing are basically the dreams of a whole mass of people coming out of poverty. Nice food, traveling, having a car, having A/C, etc.
So we can either find alternatives, or slowly figure out more geoengineering projects like mass absorbing CO2 and the like.
At current rates of emissions, we’re only about 20 years away from people needing to install CO2 scrubbers in their homes.
Soda lime, or calcium hydroxide, is the current state of the art. We use that in an anesthesia and in saltwater aquariums and in scuba rebreathers. An idealized system can capture 500 mg per gram, but in practice you only capture around 250mg/g. This outperforms the method in the article but it’s one-shot. There are interesting proposals to use this for direct capture at industrial facilities and to turn the waste material into bricks for building.
The key advantage of this new material appears to be that it can be heated and reused. That would be very valuable in an interior direct air capture use case. Think about filtering the CO2 from an office or a home to get us back to pre-industrial levels indoors.
I think it’s little appreciated that high CO2 levels cause cognitive impairment, and with the same amount of (often very poor) air exchange, higher outdoor concentrations can push indoor spaces to levels that cause impaired cognition and poor sleep. I’ve already been seeing this in my home, and will often open windows even when cold just to keep co2 levels reasonable. One solution that can help is an external air heat exchanger, which can exchange air with the outdoors without compromising your homes heating and cooling like an open window will do.
Noticeable cognitive impairment starts in the 700-1000ppm range, whereas it is very common for homes to reach 2000-3000ppm, especially when in a closed bedroom.
> Noticeable cognitive impairment starts in the 700-1000ppm range
The US navy failed to detect such effects in submarine crew, even at much higher levels like 10,000 ppm.
Another reason to be skeptical is that exhaled breath is 4% CO2 (40,000 ppm!). Therefore a few thousand extra ppm in the inhaled air should not make much of a difference to the homeostasis mechanisms in our bodies.
>One solution that can help is an external air heat exchanger
I have one of those, it blows fresh air in through the bedroom and sucks it back out through the kitchen (loft house, this route prevents food smells from wafting into the bedroom). Aside from just feeling fresh all year, this system also prevents mosquitoes from entering in summer while still allowing air circulation, it automatically bypasses the exchanger at night to provide cool air and it has some pollen filters installed which helps with hay fever.
So great economic return and a bunch of upsides, but it does require space for the exchanger and the ducts throughout the house.
I have been monitoring for high CO2 for a few months now. I easily find myself in the 1000 - 1400 range for some time before I finally let some air in in winter.
I have not noticed significant cognitive impairment (not saying it did not happen)
My quality of sleep/life have greatly increased since installing an Energy Recovery Vent (ERV) — it exchanges outside/inside air through a membrane, which is about 60-80% efficient for both humidity and temperature re-capture (depending on fan speed).
I use a Panasonic model — readily available from Big Box Retail (~$700 + $100 in vent/conduit) — which can do 20 - 60 cfm (in my 900 sqft home this can easiliy exchange the entire volume several times per day).
> The ease of releasing CO2 is the key advantage of the new compound.
I have no idea why the journalist that wrote this article choose to highlight the carbon density of the sub-header. It's almost completely irrelevant for carbon capture plants.
Another clear benefit is that it's a liquid.
Today people mostly use the substances that you called non-reversible in research plants (AFAIK, all plants are research right now). They are perfectly reversible, but that uses a lot of energy.
> perfectly reversible, but that uses a lot of energy
Looks like a perfect match to a solar plant, which provides basically free energy periodically. All you need is a large enough cistern to hold the liquid during night time.
160F, non toxic, this already sounds like something that could feasibly be used in the home. I would already be interested in installing one. And would absolutely love to see what it would do to school performance.
According to https://www.co2meter.com/blogs/news/carbon-dioxide-indoor-le..., at 1000 ppm people start getting drowsy. Let's assume that a decent indoor environment has 300 ppm more CO2 This means that our threshold for when people start getting drowsy even in decent indoor environments is when atmospheric CO2 reaches 700 ppm. For reference, it is currently around 420 ppm, and pre-industrial levels were 280 ppm.
The 300 ppm offset compared to the outside air is naturally just an arbitrary number, everything up to 1000 ppm (meaning everything up to 580 ppm more than atmospheric levels) is considered "acceptable". That means any increase in CO2 concentration will take an indoor environment which used to be considered "acceptable" and make it cross the threshold into "unacceptable". An indoor environment which would've been at 900 ppm around the industrial revolution (280 ppm) would've crossed the threshold when we surpassed 380 ppm (which was in 1965 according to https://www.statista.com/statistics/1091926/atmospheric-conc...).
let's compare the past 20 years. In 2004, the concentration was ~377 ppm. That's 47 ppm lower than what was in 2024. An indoor environment which was "borderline but acceptable" at 955 ppm CO2 in 2004 would've crossed the arbitrary 1000 ppm threshold by now, and therefore would benefit from a CO2 scrubber. The next 20 years will likely have a higher increase than the past 20 years, so there will be a larger range of currently acceptable indoor environments which will cross the 1000 ppm threshold by 2045.
TL;DR: It's complicated, 20 years is arbitrary, but as CO2 concentrations increase, indoor quality gets worse so indoor environments which were already bad will become worse. 45 years is a more realistic estimate for when your typical good indoor environment will become unacceptable, but it's a gradient.
You can store CO2 and sell it to construction companies (to cure ferrock), to energy storage companies (who like to put the CO2 in huge bubbles nowadays, go figure), or to agricultural corporations (who enrich greenhouses air in CO2 to accelerate growth).
"outperform" by only one metric too often fails usefulness. It's a one shot unless you heat the calcium carbonate to 900C, the compound in the article only requires 70C, and has quite a bit of ability to re-process CO2 absorption multiple times. Although solar ovens could reach over 900C, probably too dangerous for residential use.
Please stop trying to hurt every single human being with these derailments. There is no plausible mechanism by which carbondioxide levels would halve. That means you're just trying to derail the discussion by appealing to people's instincts about how fragile atmospheric composition is. Stop.
Direct air capture imo can’t escape the scaling problem - when the feedstock has CO2 at ~400 ppm the economics simply won’t work out despite various oil companies backing one off systems around the globe.
Capturing CO2 at the source (power plant, etc) would be simpler to reach economic viability but without incentives it’s dead on arrival. I believe the IRA infra bill had put a price ~$50/ton of CO2 captured.
But we still need to remove all the excess co2 that we released into the atmosphere since the start of the industrial revolution if we want to reduce the temperature back to what it was before we started disrupting the natural state of the plane.
We and previous generations took out a loan and the payment is coming due.
Because of the framing about degrees in celcius change people are thinking in small numbers, like "oh, it's just 1.5'C over normal. oops, we missed that, well maybe we'll get it at 2.0'C. They don't realize that if we want normal we ahve to reduce the temperaure and to do that we need to take that c02 blanket off that we've been tightly wrapping around our collective bodies for decades.
And that endeavor is nearly unfathomable. Think of all the energy used by humanity since the industrial revolution and the energy we're going to be producing in the time period that we attempt to sequester the previously poduced C02. All of that needs to be accounted for.
And then there's the surplus energy roiling around in the system now, and the collapse of food webs.
I don't see how we get our way out of this in the next 50 years.
With ice caps melted off, just removing all the excess CO2 isn't even enough since with that reflective surface gone, more energy from sunlight stays in the atmosphere than previously when more of it was reflected back into space instead of nowadays being absorbed by the ocean.
That’s true. It’s more of a policy issue that’s like carbon credits… nice on paper but a big nothing burger. Look at F1 and Porsche talking about sustainable synthetic fuels.
When you compare round trip efficiencies and economics it makes sense to just not burn the hydrocarbons to begin with.
If stored near a populated area, hundreds of thousands could be kill, including all animals and insects, in a matter of minutes if the "vault" has a catastrophic failure. I would rather live near a nuclear waste site than a CO2 Site.
Well as far as storing it goes, if you can capture it, turn it into a solid and stick it in the ground.
Imagine you were growing a huge biomass that you harvest, dry out, and then store. We know how the bacteria and processes that stripped co2 from the atmosphere in the past, we just need to do that in a big way. Good thing we have places on earth that are huge and flat and growing algae won't be a problem.
And then we complement that with green energy and an attempt at net zero.
Capturing CO2 at the source will always be worse than removing the source. At the same time, capturing CO2 from the air will stay necessary until we do it.
DAC is unsustainable, and shouldn't be a primary offset mechanism. What would be more sustainable is less net emissions and using something else like oceanic biomass CCS by taking advantage of blooming kelp and/or phytoplankton and then processing it for sequestration using floating, automated harvesting rigs.
A better title would be "More efficient method to capture CO2 from the atmosphere." The method is not objectively efficient, but may be more efficient than other methods (solvents/sorbents) used for DAC.
I gave my engineering students a CO2 removal design problem once, and at the end, asked why the theoretical efficiency had increased in the time since the textbook was written. The answer was that the concentration of CO2 in the atmosphere was higher.
Economics rules everything. How much does this cost vs simply planting trees, when the value of harvesting the trees is included? Since tree farms are generally profitable, and wood is expensive, it seems this method is likely to be economically less efficient.
The problem is you cannot plant enough trees around the globe to offset our CO2 emissions.
Also, a forest only absorbs CO2 while alive. Once it dies, it emits CO2 too.
You would need to permanently store the wood somewhere (submerging in water, etc).
Planting trees solves both the carbon capture and the emissions issue from different angles. Some examples are:
- With more wood available it’s more economical to use it as a building/manufacturing material over other emissive sources (concrete, steel, plastic)
- We can replant the same area multiple times
- Even if we plant crops for biofuels, it’s closer to carbon neutral than burning fossil anyway
Every move we can make towards planting (and managing) more of the surface of the Earth is an improvement, without waiting for miraculous new technology.
If these forests are planted by humans, why do we think the dead trees would just be left to rot like you suggest vs being harvested for wood? The logic does not compute other than trying to make a ridiculous point.
One little appreciated fact is that trees also respirate CO2 when they are cracking their stored sugars produced via photosynthesis. So they don’t sequester all of the CO2 that they consume.
Physics rules everything, once you start trying to run at scale.
The density of carbon per unit volume in solid materials of interest doesn't vary that much, whether you sink it in trees or in exotic materials like diamonds. That means you can calculate the volume of material required so sink a desired amount of atmospheric carbon.
If you want to have a measurable impact on the atmosphere, say dialing it back to 1980 CO2 levels, you're talking not about making a pile of stuff but about making a mountain range that's a mile high and hundreds of miles long.
Now figure out how many trucks you're going to need to move that much material from where your sequestering machine is to where your pile of stuff is.
Or if you want to dump that material in the ocean (which someone else will certainly object to), extend your calculation to figure out how many container trucks worth of material you need to dump into the ocean every hour to accomplish your atmospheric cleanup in whatever amount of time you choose (a decade? If it takes a century, that's not fast enough).
And finally think about surface to volume ratios. You're trying to sink it into a volume, but you can only get the gas into the volume through its surface, so the speed of your process is limited by surface area.
If you want to do it with trees,
my personal spitball estimates are that you probably need to plant somewhere between the entire state of Connecticut and the entire state of Colorado to have the kind of impact one would want (there's more subtlety to tree calculations than one generally likes to admit, so feel free to come in with way higher numbers than I did).
Which brings us back to economics. If you have a well-managed forest of that size and scale, someone is eventually going to come along, maybe in 100 years, maybe in 500 years, and say "hey if we cut this down, we could burn the wood to heat our homes" and all that carbon goes back into the atmosphere, so you actually need to sink it into something that is energetically unfavorable for recovery, which means you also need to expand a huge amount of energy to sink the carbon into that energetically unfavorable state.
If we took all the CO2 out of the atmosphere and converted the C into graphite and spread that uniformly over the top 10 subtropical deserts it would be around 2 cm deep.
This suggests a long term approach of building solar powered carbon capture plants in subtropical deserts, they capture it and convert to graphite, which is then spread out under the solar panels.
I once did the math on this, using the specs for currently available solar powered carbon capture, and it came out to something like if we used 100 years worth of the current production annual production of solar panels for this we could carbon capture at a rate that could drop the atmosphere from current levels of CO2 to pre-industrial levels in a few years even if we do not reduce emission rates.
So...not practical now, but might be feasible as a very long term project that over many decades builds out enough capacity to get things under control as long as we can keep everything from going to hell over that time.
> you're talking not about making a pile of stuff but about making a mountain range that's a mile high and hundreds of miles long.
Just to put it into numbers, wikipedia has the total amount of CO2 on the global warming page, if we assume it's in a 2 kg/l substance it totals to around 180 km^3.
1. Even if we do magic and emit nothing, we still need to remove CO2 from the atmosphere or it will cook us over time, just longer.
2. We would need an enormous area for forests (which i great), which would mean a lot of intervention, like resettling people, demolishing and constructing new buildings, a lot of machinery time to move people to and from the new forests, a lot of planting and forest maintenance involved. And add he work to cut and bury resulting wood. If you would sum all the incidental emissions from this process it would rapidly become much less efficient (if at all).
Without either CO2 capture or a sun shade of some sort, the CO2 levels and temperature will only ever increase, just like now.
I agree. Plants are not very efficient (1% or 2%) but they include packaging the CO2 in a stable form. You can store the grain or wood for long periods of times.
In this case, it looks like they get CO2 as a gas. It's cheaper because you don't have to use energy to undo the burning, but it's difficult to store for a long time.
(I'm not sure if someone tried to make a fake underground bog in abandoned mine. Just fill with wood and water to keep the oxygen low and make the wood decompose slowly.)
Take a look at "wood vault".
'Wood vaulting': A simple climate solution you’ve probably never heard of | Grist https://share.google/lS8xnMGEd1pMzlNg2
Economically not attractive but apparently very efficient in locking up CO2.
Planting trees is not effective since it takes decades to capture the carbon, but the next years are crucial for determining long term climate developments.
There is no carbon capture technology on earth that can be rolled out at a scale over the next few years that can compete with planting trees. Especially not one that has just been invented in one university. Ash grows 90cm per year, that's all carbon. Scale that to millions and billions.
The thing people don't think about with regards to CO2 capture is that you have to get the atmosphere in order to capture CO2 from it. You essentially have to suck the entire atmosphere into these carbon capture facilities.
Using something like this to capture carbon from an exhaust pipe might be viable, but scrubbing CO2 out of the atmosphere is not even remotely viable. There's just too much air out there.
You can actually capture CO2 from sea water thereby reducing ocean acidification and improving its capability to continue as our planets biggest CO2 sink.
The best carbon capture device is the ocean, and for the last 10 years or so huge amounts of free-floating sargassum seaweed have grown in warm ocean waters around the world. Nobody is certain why the sargassum has appeared in such volume lately, but it's plausible to speculate that increased CO2 in ocean water plays a role. As far as I can see the only remotely efficient way to sequester carbon at scale is to leverage the ocean by gathering the seaweed and dumping it on marginal or desert land, both to trap the carbon and fertilize the soil, thus promoting additional carbon-binding plant growth.
> Nobody is certain why the sargassum has appeared in such volume lately
For the record 2025 volumes specifically, the ABC article notes that sudden phosphorus flushes as a result of multi-year drought-hit watersheds finally being flushed out likely contributed. Ocean ecology at scale is usually highly correlated with nutrient density.
As a layman on this topic, but assuming the gathering requires fossil fuel and probably lots of it given the scale, is it feasible to do the gathering in a net negative carbon way?
I feel like anything I hear about that teases net negative sequestration at scale eventually falls apart or is found to be akin to a perpetual energy machine that eventually is debunked.
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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.
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.
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
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.
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.
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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.
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.
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Because political will requires coordination, building systems and turning them on doesn't have to!
> We need to focus more on not putting CO2 into the air and less on trying to take it out.
What part of the "we" in this coordination problem doesn't require political will?
E.G. Make CO2 extraction so cheap it's worth everyone doing it and say, make a market to sell the CO2 to farmers. Then make burying inedible bits of plants so cheap it's done on a large scale.
Then you just wait. Microeconomics takes over.
They did this with plastic clean up. By building a machine that makes plastic into fuel & construction pellets. Then stuck such a machine on a plastic poluted island and waited.
For this trick. All you require from your políticans is that they don't lie or bomb the place.
Only requirement is energy and there too it isn't all that expensive to pull air in from the atmosphere or to seperate CO2 from adsorbent via low grade heat (70-100c)
So far into the future this method could allow us to continue produce critical hydrocarbon materials (used everywhere from plastics to pharamaceuticals) without having to depend upon concentrated and contested oil supplies.
More than energy efficiency its volumetric efficiency that's the issue. At the moment (to the best of my knowledge) kg of capturing materials capture tens of grams of CO2. Pulling it from air is not that energy intensive but finding materials that can actually filter out CO2 from that air is difficult. If breakthroughs are made in this area it will have industrial applications. Then it won't be just sequestering.
Of course the easier solution is to plant more trees and grasses but they grow very slowly and require valuable land. Still this approach is feasible in some uncultivable lands. Crops like cottongrass[1] can grow even in tundra climate and can be valuable source of both technically imp carbon via cellulose and a means to capture CO2. We don't have to make a choice. We can do both simultaneously.
[1] https://www.fs.usda.gov/database/feis/plants/graminoid/eriva...
I. e. Collection is half the problem.
Collecting it in a way it's cheap to get it back again is potentially just less than minus half the problem.
This may be part of the solution … or maybe we find a way to make a utopia where we can all agree to just stop polluting. Historically, the utopia has no precedent that I am aware of.
That’s not a solution either, because the developing world is not going to stop increasing their CO2 output until they fully industrialize. They’re just not. Feel free to seek reductions where you can, but don’t think of it as a solution because it’s not.
The technical problems with CO2 capture are far more solvable than the sociological problems with net zero emissions.
[1] https://www.nytimes.com/2025/12/30/climate/solar-south-afric...
[2] https://energy.economictimes.indiatimes.com/news/renewable/g...
[3]https://www.pv-magazine.com/2025/06/23/china-hits-1-tw-solar...
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Firstly, it will always be more difficult and energy-intensive to extract CO2 than to just stop putting it into the atmosphere in the first place. Yet the world is nowhere near agreeing any meaningful framework on reducing emissions, and the party in power in the largest democracy in the world is in denial that a problem even exists.
But mainly, if there was an effective means of CO2 removal, who will be in charge of the dials, and who will set the targets?
Atmospheric CO2 is now 50% higher than when I was born. Will we go back to the levels as at the 60s, or perhaps the beginning of the industrial revolution? Obviously that is unfavorable to the frozen regions that are now thawing - like Russia (and Greenland), who benefit from climate change.
For me at least both your arguments are not obvious.
There are a lot of things that are harder to put in the atmosphere than to remove them. Stones for example.
The second one is less of an argument, but rather a question. Why not the UN, the US, China, or Europe?
Someone will make a trillion dollars out of this.
This could also be a good use case for #b where CO2 is captured before being released to the atmosphere. For example factories and vehicles could be mandated to use this.
Mann describes "Prophets" as people who see a problem and then try to prod people to change their behaviour in order to avoid it. e.g. Thomas Malthus observed that exponential population growth had humanity on track to experience severe famine, conflict, etc. that would violently and savagely bring our numbers back within the carrying capacity of the Earth. Multiple people have made predictions about when humanity would reach the brink at numerous points in the years since Malthus, but were always wrong about when the Malthusian trap would finally spring...
...because of "Wizards". Wizards are people who set about solving problems with tech. Advances like the use of fertilizer, first bat guano and then the Haber-Bosch process, followed by scientific crop breeding have effectively raised the carrying capacity of the Earth so much that, despite our exponentially ballooning numbers, there are far more calories per person available now than in Malthus' day.
Prophets are valuable for their ability to observe and raise awareness about problems. The Earth does have an ultimate carrying capacity too, which we should keep in mind even if we don't know what it is. However, the track record undeniably favours the Wizards. They get things done. Prophets hate this, because it makes it look like they were wrong. They weren't wrong. They were just too focused on an approach to the problem that rarely works.
The modern environmentalist movement is dominated by prophets. So much so, that wizards are often portrayed as the enemy. History has shown that this is wrong-headed. We should value prophets for what they do, but ignore them when they tell us not to fund the wizards.
We need carbon taxes, tariffs on high-emitting countries and products, and support for adopting clean energy, clean transportation, and clean everything else. Lobbying and misinformation has made these actual solutions politically impossible to implement though, so we continue to waste resources on sponges.
But! Notice that abatement doesn't get us to 0. It merely slows the process. The remainder absolutely needs ACC. The output stream needs to be dirt cheap, the thermals need to be 100°C and not 900°C. Those sorts of things would bring ACC down to "hundreds of billions" rather than a trillion.
“Why not both?”
All the things silicon valley "caviar communists" say you need to stop doing are basically the dreams of a whole mass of people coming out of poverty. Nice food, traveling, having a car, having A/C, etc.
So we can either find alternatives, or slowly figure out more geoengineering projects like mass absorbing CO2 and the like.
I am definitely part of this group you describe.
Soda lime, or calcium hydroxide, is the current state of the art. We use that in an anesthesia and in saltwater aquariums and in scuba rebreathers. An idealized system can capture 500 mg per gram, but in practice you only capture around 250mg/g. This outperforms the method in the article but it’s one-shot. There are interesting proposals to use this for direct capture at industrial facilities and to turn the waste material into bricks for building.
The key advantage of this new material appears to be that it can be heated and reused. That would be very valuable in an interior direct air capture use case. Think about filtering the CO2 from an office or a home to get us back to pre-industrial levels indoors.
Noticeable cognitive impairment starts in the 700-1000ppm range, whereas it is very common for homes to reach 2000-3000ppm, especially when in a closed bedroom.
The US navy failed to detect such effects in submarine crew, even at much higher levels like 10,000 ppm.
Another reason to be skeptical is that exhaled breath is 4% CO2 (40,000 ppm!). Therefore a few thousand extra ppm in the inhaled air should not make much of a difference to the homeostasis mechanisms in our bodies.
I have one of those, it blows fresh air in through the bedroom and sucks it back out through the kitchen (loft house, this route prevents food smells from wafting into the bedroom). Aside from just feeling fresh all year, this system also prevents mosquitoes from entering in summer while still allowing air circulation, it automatically bypasses the exchanger at night to provide cool air and it has some pollen filters installed which helps with hay fever.
So great economic return and a bunch of upsides, but it does require space for the exchanger and the ducts throughout the house.
I have not noticed significant cognitive impairment (not saying it did not happen)
[•] <https://en.wikipedia.org/wiki/Heat_recovery_ventilation#Ener...>
I use a Panasonic model — readily available from Big Box Retail (~$700 + $100 in vent/conduit) — which can do 20 - 60 cfm (in my 900 sqft home this can easiliy exchange the entire volume several times per day).
I am somewhat skeptical of this:
https://www.astralcodexten.com/p/eight-hundred-slightly-pois...
Have you been telling representatives? Here's a letter I wrote to mine:
https://pdfhost.io/v/bRJEGptatL_climate-change
Sounds seriously unlikely. How would this work in practice, at the level of bodily functions?
I have no idea why the journalist that wrote this article choose to highlight the carbon density of the sub-header. It's almost completely irrelevant for carbon capture plants.
Another clear benefit is that it's a liquid.
Today people mostly use the substances that you called non-reversible in research plants (AFAIK, all plants are research right now). They are perfectly reversible, but that uses a lot of energy.
Looks like a perfect match to a solar plant, which provides basically free energy periodically. All you need is a large enough cistern to hold the liquid during night time.
The hard part is capture and disposal.
Extending the current exponential for 20 years, we get into the 500ppm region.
I don't think that's enough to need scrubbers.
From https://www.climate.gov/news-features/understanding-climate/..., the pessimistic projections suggest that we may reach our 700 ppm threshold by roughly 2070; 45 years from now. (The graphs are hard to read precisely)
The 300 ppm offset compared to the outside air is naturally just an arbitrary number, everything up to 1000 ppm (meaning everything up to 580 ppm more than atmospheric levels) is considered "acceptable". That means any increase in CO2 concentration will take an indoor environment which used to be considered "acceptable" and make it cross the threshold into "unacceptable". An indoor environment which would've been at 900 ppm around the industrial revolution (280 ppm) would've crossed the threshold when we surpassed 380 ppm (which was in 1965 according to https://www.statista.com/statistics/1091926/atmospheric-conc...).
let's compare the past 20 years. In 2004, the concentration was ~377 ppm. That's 47 ppm lower than what was in 2024. An indoor environment which was "borderline but acceptable" at 955 ppm CO2 in 2004 would've crossed the arbitrary 1000 ppm threshold by now, and therefore would benefit from a CO2 scrubber. The next 20 years will likely have a higher increase than the past 20 years, so there will be a larger range of currently acceptable indoor environments which will cross the 1000 ppm threshold by 2045.
TL;DR: It's complicated, 20 years is arbitrary, but as CO2 concentrations increase, indoor quality gets worse so indoor environments which were already bad will become worse. 45 years is a more realistic estimate for when your typical good indoor environment will become unacceptable, but it's a gradient.
Buildings with higher people/sqft could already take advantage of indoor co2 scrubbers today.
Just extrapolate.
Imagine capturing CO2 to turn it into cement, used for constructions.
Pardon my ignorance, though.
Dead Comment
https://www.researchgate.net/post/Minimum_necessary_concentr...
Cost will be the biggest question. A reusable scrubber need to be cheap enough that the reduce efficiency is worth it.
Capturing CO2 at the source (power plant, etc) would be simpler to reach economic viability but without incentives it’s dead on arrival. I believe the IRA infra bill had put a price ~$50/ton of CO2 captured.
We and previous generations took out a loan and the payment is coming due.
Because of the framing about degrees in celcius change people are thinking in small numbers, like "oh, it's just 1.5'C over normal. oops, we missed that, well maybe we'll get it at 2.0'C. They don't realize that if we want normal we ahve to reduce the temperaure and to do that we need to take that c02 blanket off that we've been tightly wrapping around our collective bodies for decades.
And that endeavor is nearly unfathomable. Think of all the energy used by humanity since the industrial revolution and the energy we're going to be producing in the time period that we attempt to sequester the previously poduced C02. All of that needs to be accounted for.
And then there's the surplus energy roiling around in the system now, and the collapse of food webs.
I don't see how we get our way out of this in the next 50 years.
For the atmospheric one, grow trees and algae
When you compare round trip efficiencies and economics it makes sense to just not burn the hydrocarbons to begin with.
Another concern, who will pay for maintenance ? See this for why you cannot let CO2 escape from underground storage:
https://en.wikipedia.org/wiki/Lake_Nyos_disaster
If stored near a populated area, hundreds of thousands could be kill, including all animals and insects, in a matter of minutes if the "vault" has a catastrophic failure. I would rather live near a nuclear waste site than a CO2 Site.
Imagine you were growing a huge biomass that you harvest, dry out, and then store. We know how the bacteria and processes that stripped co2 from the atmosphere in the past, we just need to do that in a big way. Good thing we have places on earth that are huge and flat and growing algae won't be a problem.
And then we complement that with green energy and an attempt at net zero.
If it's between immediate death and a slow one of cancer, I'm not sure your choice is the obvious one.
Recent article: https://www.theguardian.com/environment/2025/nov/28/africa-f...
- With more wood available it’s more economical to use it as a building/manufacturing material over other emissive sources (concrete, steel, plastic)
- We can replant the same area multiple times
- Even if we plant crops for biofuels, it’s closer to carbon neutral than burning fossil anyway
Every move we can make towards planting (and managing) more of the surface of the Earth is an improvement, without waiting for miraculous new technology.
But left out to rot and yeah, the fungus and bacteria will ultimately consume the wood and release CO2 as a byproduct.
Physics rules everything, once you start trying to run at scale.
The density of carbon per unit volume in solid materials of interest doesn't vary that much, whether you sink it in trees or in exotic materials like diamonds. That means you can calculate the volume of material required so sink a desired amount of atmospheric carbon.
If you want to have a measurable impact on the atmosphere, say dialing it back to 1980 CO2 levels, you're talking not about making a pile of stuff but about making a mountain range that's a mile high and hundreds of miles long.
Now figure out how many trucks you're going to need to move that much material from where your sequestering machine is to where your pile of stuff is.
Or if you want to dump that material in the ocean (which someone else will certainly object to), extend your calculation to figure out how many container trucks worth of material you need to dump into the ocean every hour to accomplish your atmospheric cleanup in whatever amount of time you choose (a decade? If it takes a century, that's not fast enough).
And finally think about surface to volume ratios. You're trying to sink it into a volume, but you can only get the gas into the volume through its surface, so the speed of your process is limited by surface area.
If you want to do it with trees, my personal spitball estimates are that you probably need to plant somewhere between the entire state of Connecticut and the entire state of Colorado to have the kind of impact one would want (there's more subtlety to tree calculations than one generally likes to admit, so feel free to come in with way higher numbers than I did).
Which brings us back to economics. If you have a well-managed forest of that size and scale, someone is eventually going to come along, maybe in 100 years, maybe in 500 years, and say "hey if we cut this down, we could burn the wood to heat our homes" and all that carbon goes back into the atmosphere, so you actually need to sink it into something that is energetically unfavorable for recovery, which means you also need to expand a huge amount of energy to sink the carbon into that energetically unfavorable state.
This suggests a long term approach of building solar powered carbon capture plants in subtropical deserts, they capture it and convert to graphite, which is then spread out under the solar panels.
I once did the math on this, using the specs for currently available solar powered carbon capture, and it came out to something like if we used 100 years worth of the current production annual production of solar panels for this we could carbon capture at a rate that could drop the atmosphere from current levels of CO2 to pre-industrial levels in a few years even if we do not reduce emission rates.
So...not practical now, but might be feasible as a very long term project that over many decades builds out enough capacity to get things under control as long as we can keep everything from going to hell over that time.
Just to put it into numbers, wikipedia has the total amount of CO2 on the global warming page, if we assume it's in a 2 kg/l substance it totals to around 180 km^3.
1. Even if we do magic and emit nothing, we still need to remove CO2 from the atmosphere or it will cook us over time, just longer.
2. We would need an enormous area for forests (which i great), which would mean a lot of intervention, like resettling people, demolishing and constructing new buildings, a lot of machinery time to move people to and from the new forests, a lot of planting and forest maintenance involved. And add he work to cut and bury resulting wood. If you would sum all the incidental emissions from this process it would rapidly become much less efficient (if at all).
Without either CO2 capture or a sun shade of some sort, the CO2 levels and temperature will only ever increase, just like now.
The largest sous-vide cooking pot ever...
In this case, it looks like they get CO2 as a gas. It's cheaper because you don't have to use energy to undo the burning, but it's difficult to store for a long time.
(I'm not sure if someone tried to make a fake underground bog in abandoned mine. Just fill with wood and water to keep the oxygen low and make the wood decompose slowly.)
Not really, forest fires happen and then a few hundred of years of sequestered CO2 gets released back in an instant.
Organic material with oxygen gas floating around is not stable.
Sequestering carbon into the ocean might be a better strategy. Not flammable and not subject to stupid capitalism effects around land prices.
Dead Comment
Using something like this to capture carbon from an exhaust pipe might be viable, but scrubbing CO2 out of the atmosphere is not even remotely viable. There's just too much air out there.
How long and how many terawatts of power do you think it'll take to suck a significant fraction of the earth's seawater through a capture facility?
The problem is the same, the relative concentration of oxygen in air is less than 0.05% (~450pars per million). In water much less.
Even if you could make it a thousand times more efficient it would be a stretch.
For those curious about numbers for 2025, a couple links: https://optics.marine.usf.edu/projects/SaWS/pdf/Sargassum_ou... https://abcnews.go.com/International/scientists-concerned-re...
> Nobody is certain why the sargassum has appeared in such volume lately
For the record 2025 volumes specifically, the ABC article notes that sudden phosphorus flushes as a result of multi-year drought-hit watersheds finally being flushed out likely contributed. Ocean ecology at scale is usually highly correlated with nutrient density.
I feel like anything I hear about that teases net negative sequestration at scale eventually falls apart or is found to be akin to a perpetual energy machine that eventually is debunked.
https://oceanvisions.org/ocean-alkalinity-enhancement/
But in general carbon absorption by oceans leads to acidification and habitat destruction.
Why would it gather more CO2 over there than it does where it already is?