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.
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.
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...
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:
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.
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.
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?
And the superbase is 1,5,7-triazabicyclo [4.3.0] non-6-ene
It is an anime based technology. Other amines in water-based solutions also get regenerated at about <200C. It is great to find new molecules to do this work but as I usual, these marketing articles sensationalize the actual work.
There’s the katabatic winds off of the glaciers in Greenland and Antarctica, which could help things go through.
But I soon realised that CO₂ is so potent, that it’s so such a small proportion of the air that not much would be taken out.
There’s some renewable storage systems that liquify air, that could remove CO₂ but they don’t mention it;,but air liquification doesn’t seem to be growing fast as an option.
The other one from mere A-level chemistry is buffer solutions and using chemical reactions in the Oceans, apart from iron seeding for life, but a chemical that precipitate an insoluble carbonate. Not ideal raining down precipitates, or using the Ocean as a test tube.
A given locale has some metric, based on local generation sources, for grams of CO2 emitted per kWh or whatever. How much CO2 is released to capture 1 gram of CO2? If it is close to a gram or more, this is not worth considering. Maybe one day zero-carbon energy sources become so inexpensive we could contemplate wide-scale CO2 capture, but we aren't anywhere close yet.
Anyway - CO2 in the atmosphere is here to stay. Much more "realistic" approach is to decarbonize the ocean and let the ocean absorb the atmospheric CO2.
the time requirement alone makes it tricky to be used directly at the source of carbon emissions. this might be efficient but unsure about effective.
Electro Carbon https://www.electrocarbon.ca/en
https://sustainablebiz.ca/clear-the-runway-electro-carbon-be...
Their process for generating potassium formate is greener than standard methods. It does require electricity as an input but that can come from renewable, green sources.
Potassium formate is used in de-icing products, fertilizer, heat transfer fluids, drilling fluid, etc... so a useful, monetizeable output comes out of the process.
Disclosure - Know the founders personally. Wanted to shoutout their work. No financial ties to the company.Chemistry is not at all my expertise & I don't have details on their process beyond what's on the website.
IDK, build houses out of limestone like we have been doing for ages.
/s
One of the subplots from the excellent Delta-V series by Daniel Suarez.
Just plant a tree, harvest it to make lumber.
The article's method might be useful in a submarine or spacecraft.
It seems like we have not yet done the full circle, but we are close.
One application I think is neat is that it’s a pretty robust refrigerant in a heat pump application.
The one exception is making synthetic fuels, but in the vast majority of applications it’ll be cheaper to use electricity from clean sources (renewables/fission/fusion/unicorn farts) directly rather than pay all of the efficiency losses of electricity -> thermal -> chemical -> thermal -> (end use).
Ballpark, running a car on synfuels takes 10x the energy of running it on batteries charged directly from renewable sources.
On a much smaller scale I've been hoping for a small solar powered CO2 compressor to exist so I could use it for mosquito traps. The state of the art for those right now is burning propane for the CO2 combined with a scent emitter for the human smell to attract female mosquitos.
Synthetic materials is another. For example carbon electrodes for batteries.
CO2 is fairly inert. This makes it useful. Welding steel is a typical example of something you can use CO2 to shield. There are many other examples in the chemicals industries of things like that where you want to do something at a "higher than natural on earth" temperature to make a reaction happen or happen faster but you don't want that reaction to happen with oxygen all around.
And on the other end of the temperature spectrum....dry ice.
To remove 10ppm of atmospheric CO2 from the atmosphere (which would do nothing to sustainably lower CO2 in the atmosphere) would require processing 10ppm of the entire atmosphere. That is one in 100.000 parts of the atmosphere. The entire atmosphere is around 5x10^18 kg, so we need to process 5x10^13 kg of air. Which is 50 million million (no typo) kilos of air.
The industrial task of doing this unfathomably large and by itself would have no long term Impact.
Human fabricated carbon capture from ambient air is a complete fools errand only promoted by the scientific illiterate or those who benefit from scientific illiteracy. You can essentially just look at the first graph on wikipedia and see that it is never going to work: https://en.wikipedia.org/wiki/Carbon_dioxide_in_the_atmosphe...
