9 ms·

A physicist runs the math on direct air capture and warns it's a distraction

35 points by miguelazo 2y ago

dave4420 2y ago
I agree we shouldn’t do direct air capture instead of reducing CO2 emissions in the first place, but 420ppm is already too high, we need to remove CO2 from the air somehow.
- codr7 2y ago
  Says who? https://www.youtube.com/watch?v=lX1z_6pvM-Q https://www.youtube.com/watch?v=lX1z_6pvM-Q
  - tln 2y ago
    Almost all scientists? Basically, except the ones with an agenda? Check out where that talk was given. Climate change is inconvenient for them because it's mostly an externality that can't reasonably be solved without government, taxes, or changes to capitalist and individual behaviors. "The Steamboat Institute promotes America's first principles and inspires active involvement in the defense of liberty. We stand for the following five founding principles: 1) Limited government 2) Limited taxes and fiscal responsibility 3) Free market capitalism 4) Strong national defense 5) Individual rights and responsibilities "
    - throwaway-blaze 2y ago
      The only thing that will truly solve climate change is technological innovation. The best system ever invented for that is free market capitalism. People on the left seem to think _all_ people on the right "don't believe in climate change". The truth is that many people don't believe the government can solve the problem... Unless you can convince all of Africa and India to not want electricity, air conditioning, refrigeration, and roads, we better come up with a technological innovation in power generation or some other area that massively impacts the amount of emissions they will begin generating this century.
      - silverquiet 2y ago
        > we better come up with a technological innovation in power generation What if we can’t?
        DennisP 2y ago
        We already are. Wind and solar are already quite cheap, and getting cheaper. I used to worry about grid-scale battery storage but sodium and iron-air batteries pretty much have that solved for reasonable cost too.
      - tln 2y ago
        I don't think technological innovation and free markets are sufficient. Necessary, vital, yes.
      - drekk 2y ago
        Africa (a whole continent) and India consume a lot less per capita & could benefit from the intellectual property we don't share with them. It's in all of our interests to help them electrify differently than previous nation states. We already have the solutions. We instead subsidize meat, dairy, and fossil fuels. We're lucky "developing countries" don't consume at the rate Americans do or we'd already need 5 planets to satisfy the demand. I'm sorry thermodynamics and physics are inconvenient, but that doesn't change the fact that it doesn't make a whole lot of sense to accelerate 2 tons of metal to move one or two people.
      - dehugger 2y ago
        I would argue that the "best" (meaning most rapid pace of development) system for innovation is a total war economy. Perhaps WW3 should be fought against the atmosphere?
    - codr7 2y ago
      So you're saying that scientists with the "correct" opinion don't have an agenda? Why? The problem with blind faith and political correctness is that questioning established truths is how you actually do science.
      - defrost 2y ago
        > questioning established truths is how you actually do science. and that questioning has been done in decades past and answered, also in decades past. Your linked video is of a 74 year biologist with a PhD in measuring stream containmination who raises the claims that increased carbon dioxide in Earth's atmosphere is beneficial, that there is no proof that anthropogenic carbon dioxide emissions are responsible for global warming, and that even if true, increased temperature would be beneficial to life on Earth. These points have been addressed multiple times since they were first raised decades ago and by many better qualified people whose responses and models you can find should you care to look. The Earth Sciences have people that look at small things at local scale (Dr. Moore, last active in science some 40+ years past) and others that look at planet scale effects (not Dr. Moore). The blind faith people have in stale claims from tangential retired scientists that make a living shilling for nuclear, logging, GMO industries and other clients of the Heartland Institute that pay to have noise and FUD thrown into the air in any debate regarding consequences of industry is staggering. You are correct to call out blind faith.
- DennisP 2y ago
  Exactly. Another issue is that some emission sources are very hard to eliminate. All the non-disastrous IPCC scenarios include substantial negative emissions after 2050, and that won't happen unless we start developing and scaling it now.
ceruleanseas 2y ago
When I was in college, a physics professor said investment in solar is a waste of time and that we should invest in nuclear instead. A part of his calculation was the efficiency of solar cells at the time, but he didn’t take into account the radical increases in efficiency that investment was able to bring, making our investments in solar worth it today. I think this may be similar, in that maybe the current solutions are not going to solve the problem, but by investing in these, in the long run, they may prove to be necessary as we get better at it.
- OliverM 2y ago
  No, not in this case. The article already assumes the existence of a near perfectly-efficient process. It's just looking at the minimum energy needed to remove the carbon dioxide from the atmosphere, according to long-established physical laws, no matter what mechanism is used. We could definitely work harder at supporting the existing natural mechanisms for removing CO2 from the atmosphere, but it's far, far easier to reduce the amount we're emitting.
  - aeternum 2y ago
    Are we all just ignoring that plants pull CO2 out of the air and produce usable energy in the process? So clearly it is possible to do more efficiently.
    - LinAGKar 2y ago
      Plants aren't that efficient, there's just a lot of them. You could cover the requisite 764 GW with about 3000 km^2 of solar cells (assuming 250 W/m^2). That's a bit over the land area of Luxembourg. Minuscule compared to the amount of area on Earth taken up by plants, and sunlight that falls on those plants.
- downWidOutaFite 2y ago
  The calculations here are based on the laws of thermodynamics that cannot be broken. This represents the ideal efficiency that is way better than we could achieve in real life.
danans 2y ago
Enhanced rock weathering for CO2 removal potentially avoids the high energy requirement problem of DAC, since it relies directly on natural environmental processes to work. But it has it's own issues and question marks.
gmuslera 2y ago
Were they talking there about the Marxwell's demon? Anyway, CO2 capture, by itself, is not the whole solution, but it should be part of it. There is an unbalance between the energy that comes in and the one that goes out. so things heats up (among other negative consequences, like i.e. ocean acidification). You won't solve the whole problem without addressing that eventually, so some way of carbon capture, going through the use of energy or something else, should be in the map. And the complementary part of that is stop adding new (or, in other way to see it, very old, but that was stored away) carbon to the system. Even with the very worrying signs of the global climate going haywire with the corresponding loses of lives and money we keep adding each year even more fossil carbon than the previous one, no matter how much token energy generation is announced to be done by other means. It may be expensive, or require technologies that we don't have yet, or compromises on what to lose, or whatever, but it is a problem that if left by its own means will eventually make the planet unlivable for us in a way or another. And that will turn all the saved money into something meaningless.
jandrewrogers 2y ago
The article makes a valid point that the amount of energy required for direct air capture (DAC) is extremely prohibitive and far beyond current capacity, but assume for the sake of argument that this is a problem that could be solved. This still leaves the problem that the industrial plant and chemical feedstock required to physically do the DAC at the scale of billions of tons per year is several orders of magnitude beyond what is possible with current supply chains and natural resources. You would have to strip mine the planet just to have the raw materials to build the necessary DAC infrastructure, and we need those resources for other critical things as well. Some proposed DAC chemistries have upstream mineral dependencies that, if done at the scale required just to offset a year's emissions, would consume all known global reserves immediately. This is not solved by recycling because of compounding loss rates; recycling is not 100% efficient, and the amount of energy required to improve recycling efficiency is essentially exponential for rapidly diminishing returns, and we already have an energy problem with DAC. DAC at any scale that is not an exercise in futility will be an exercise in environmental and economic destruction at unprecedented scale. The solution would almost certainly be worse than the problem. There really isn't a path forward that doesn't involve dramatically reducing emissions and letting nature remove the excess carbon.
- DennisP 2y ago
  This could use some citations. In particular, I'm interested in these new methods, which are very energy efficient: https://engineering.princeton.edu/news/2024/03/14/engineers-use-moisture-pull-carbon-dioxide-out-air https://engineering.princeton.edu/news/2024/03/14/engineers-... https://news.mit.edu/2019/mit-engineers-develop-new-way-remove-carbon-dioxide-air-1025 https://news.mit.edu/2019/mit-engineers-develop-new-way-remo... The second article says "the team has proven the system can withstand at least 7,000 charging-discharging cycles, with a 30 percent loss in efficiency over that time. The researchers estimate that they can readily improve that to 20,000 to 50,000 cycles." That's without consumables, just a stack of electrodes coated with an organic compound and carbon nanotubes.
  - jandrewrogers 2y ago
    Your examples are illustrative of the point. These are the equivalent of "in mice" articles in medicine. Showing DAC in a lab is the easy part. Just to offset current emissions, we need to pull 40 billion tons of CO2 out of the air each year. This must work within the constraints of supply chains, upstream chemical feedstock, and available planetary mineral reserves. People are not comprehending the scale: this would be the largest industrial chemistry process in history by orders of magnitude, larger than all other industrial chemistry combined. Scaling either of the above DAC processes to 40 billion tons per year is infeasible. You don't just have to scale the process, you also have to scale the upstream processes and resource extraction activities that enable the process to be built. At 40 billion tons, any chemical engineer can quickly pencil out that these processes have upstream dependencies that have no ability to be scaled sufficient to support the target production process, not even close. In computer terms, it is like trying to train the latest LLMs on a computer from the 1990s. I see a lot of DAC proposals that, at scale, imply a supply chain that instantly consumes the global reserves of critical agricultural minerals like potassium or phosphorus, or which would literally produce e.g. concentrated acid waste at the scale of billions of tons, with no plan for how to keep people from starving or disposing of the chemical waste. Consequently, these processes are not real solutions.
downWidOutaFite 2y ago
Capturing only makes sense at the emission sources where the co2 concentration is high, like at power plants or tailpipes. But that would mean the costs would be borne by the emitters but they'd rather externalize those costs to all of us.
kjkjadksj 2y ago
Cheap direct air capture: grow biomass, sink to bottom of ocean.
- tmnvix 2y ago
  Biomass decomposing in an anaerobic environment creates some very very nasty gases. There are multiple previous extinction events attributed to this. Times when the oceans basically turned to swamps.
  - kjkjadksj 2y ago
    Extinctions attributed to co2 decreasing relative to oxygen, sort of what is required here to a certain scale at least
DennisP 2y ago
The numbers he posts are not all that bad really. It's 181kWh per metric ton CO2. At an electricity cost of 5 cents/kWh that's nine bucks per ton. That's quite a bit cheaper than the actual cost projected by real projects, so I'm not sure what he's debunking. In terms of energy, some emerging tech is pretty close to ideal. Princeton has a project they claim can do 0.7 gigajoule/ton, or 195kWh [1]. And MIT is claiming one gigajoule/ton, or 278kWh [2]. If we transition to a wind/solar/battery grid, the cheapest option in the US at least is to have about four days of battery and 2X overproduction [3]. So that's a lot of extra energy basically available for free. Even today, with relatively small usage of renewables, utilities sometimes let electricity costs go negative [4]. If capital costs aren't too high, then DAC can run whenever there's excess energy available. Of course, capital cost will be a big portion of the expense, though it'll decrease as we scale. Climeworks and Carbon Engineering have estimated $100/ton in total cost, which equates to a dollar per gallon of gasoline. Many places already have gas taxes higher than that. And the MIT and Princeton methods should be cheaper at scale than current methods would be. Actually eliminating all our annual emissions by just doing this would of course be madness. But if we tried, and charged emitters for doing that, then most emitters would find it cheaper to stop emitting instead. Then we'd naturally end up only using DAC for emission sources that are very hard to eliminate. After we hit net zero, we'd be smart to take CO2 down to a safe level. Call it 100ppm of reduction. Hopefully we can do some of that with reforestation and so on, but let's say DAC is our only option. One ppm is 7.8 gigatons CO2, so we're talking 780 gigatons to draw down. At 200kWh/ton that's 156 TWh, not far off from the world's entire energy usage for a year, matching the article's estimate. But if we're at 2X overproduction on energy, then we'll have that much energy available. Only the capital cost of the equipment would really be important, and by the time we scale it that far, that should be fairly low too. The methods I linked use cheap, readily available materials. So it looks pretty feasible to me. We can call this a "distraction" and put up with the terrible consequences of whatever high CO2 level we reach by the time we're at net zero, or we add DAC to a wind/solar/battery world and get down to a nice cool 350ppm. Since it takes time to scale, and climate feedbacks give us a time limit, we need to develop and start scaling DAC now. [1] https://engineering.princeton.edu/news/2024/03/14/engineers-use-moisture-pull-carbon-dioxide-out-air https://engineering.princeton.edu/news/2024/03/14/engineers-... [2] https://news.mit.edu/2019/mit-engineers-develop-new-way-remove-carbon-dioxide-air-1025 https://news.mit.edu/2019/mit-engineers-develop-new-way-remo... [3] https://caseyhandmer.wordpress.com/2023/07/12/grid-storage-batteries-will-win/ https://caseyhandmer.wordpress.com/2023/07/12/grid-storage-b... [4] https://archive.is/WfUIJ https://archive.is/WfUIJ
hinkley 2y ago
Matt Ferrell I think talked a while back about an air battery that captured carbon dioxide while charging and release it while discharging. If the losses aren’t too bad, this could be a cogeneration solution where the batteries are used for load leveling. In essence you are using mostly surplus energy for the task anyway. The carbon footprint of “green” energy is often not that good if you consider the entire cradle to grave lifecycle. Carbon capture would make things less murky.
tmnvix 2y ago
I know this is a somewhat flippant comment but... Trees.
- dotps1 2y ago
  I was going to dismiss your comment thinking that it wouldn't be possible to capture the amount of carbon we are emitting with trees alone .. but after running the numbers, trees seem like a pretty decent solution.
  - timschmidt 2y ago
    I'm picturing a large solar farm powering pumping stations to irrigate a large desert like the Sahara, central Australia, Saudi Arabia, the Gobi, or the American Southwest. Maybe all of them. If we do nothing, Antarctica has 5.5 million square miles of land which might be available for plant growth soon.
- DennisP 2y ago
  DAC uses a thousand times less land area.

35 points by miguelazo 2y ago

I agree we shouldn’t do direct air capture instead of reducing CO2 emissions in the first place, but 420ppm is already too high, we need to remove CO2 from the air somehow.

codr7 2y ago
Says who? https://www.youtube.com/watch?v=lX1z_6pvM-Q https://www.youtube.com/watch?v=lX1z_6pvM-Q
- tln 2y ago
  Almost all scientists? Basically, except the ones with an agenda? Check out where that talk was given. Climate change is inconvenient for them because it's mostly an externality that can't reasonably be solved without government, taxes, or changes to capitalist and individual behaviors. "The Steamboat Institute promotes America's first principles and inspires active involvement in the defense of liberty. We stand for the following five founding principles: 1) Limited government 2) Limited taxes and fiscal responsibility 3) Free market capitalism 4) Strong national defense 5) Individual rights and responsibilities "
  - throwaway-blaze 2y ago
    The only thing that will truly solve climate change is technological innovation. The best system ever invented for that is free market capitalism. People on the left seem to think _all_ people on the right "don't believe in climate change". The truth is that many people don't believe the government can solve the problem... Unless you can convince all of Africa and India to not want electricity, air conditioning, refrigeration, and roads, we better come up with a technological innovation in power generation or some other area that massively impacts the amount of emissions they will begin generating this century.
    - silverquiet 2y ago
      > we better come up with a technological innovation in power generation What if we can’t?
      - DennisP 2y ago
        We already are. Wind and solar are already quite cheap, and getting cheaper. I used to worry about grid-scale battery storage but sodium and iron-air batteries pretty much have that solved for reasonable cost too.
    - tln 2y ago
      I don't think technological innovation and free markets are sufficient. Necessary, vital, yes.
    - drekk 2y ago
      Africa (a whole continent) and India consume a lot less per capita & could benefit from the intellectual property we don't share with them. It's in all of our interests to help them electrify differently than previous nation states. We already have the solutions. We instead subsidize meat, dairy, and fossil fuels. We're lucky "developing countries" don't consume at the rate Americans do or we'd already need 5 planets to satisfy the demand. I'm sorry thermodynamics and physics are inconvenient, but that doesn't change the fact that it doesn't make a whole lot of sense to accelerate 2 tons of metal to move one or two people.
    - dehugger 2y ago
      I would argue that the "best" (meaning most rapid pace of development) system for innovation is a total war economy. Perhaps WW3 should be fought against the atmosphere?
  - codr7 2y ago
    So you're saying that scientists with the "correct" opinion don't have an agenda? Why? The problem with blind faith and political correctness is that questioning established truths is how you actually do science.
    - defrost 2y ago
      > questioning established truths is how you actually do science. and that questioning has been done in decades past and answered, also in decades past. Your linked video is of a 74 year biologist with a PhD in measuring stream containmination who raises the claims that increased carbon dioxide in Earth's atmosphere is beneficial, that there is no proof that anthropogenic carbon dioxide emissions are responsible for global warming, and that even if true, increased temperature would be beneficial to life on Earth. These points have been addressed multiple times since they were first raised decades ago and by many better qualified people whose responses and models you can find should you care to look. The Earth Sciences have people that look at small things at local scale (Dr. Moore, last active in science some 40+ years past) and others that look at planet scale effects (not Dr. Moore). The blind faith people have in stale claims from tangential retired scientists that make a living shilling for nuclear, logging, GMO industries and other clients of the Heartland Institute that pay to have noise and FUD thrown into the air in any debate regarding consequences of industry is staggering. You are correct to call out blind faith.
DennisP 2y ago
Exactly. Another issue is that some emission sources are very hard to eliminate. All the non-disastrous IPCC scenarios include substantial negative emissions after 2050, and that won't happen unless we start developing and scaling it now.

ceruleanseas 2y ago

When I was in college, a physics professor said investment in solar is a waste of time and that we should invest in nuclear instead. A part of his calculation was the efficiency of solar cells at the time, but he didn’t take into account the radical increases in efficiency that investment was able to bring, making our investments in solar worth it today. I think this may be similar, in that maybe the current solutions are not going to solve the problem, but by investing in these, in the long run, they may prove to be necessary as we get better at it.

OliverM 2y ago
No, not in this case. The article already assumes the existence of a near perfectly-efficient process. It's just looking at the minimum energy needed to remove the carbon dioxide from the atmosphere, according to long-established physical laws, no matter what mechanism is used. We could definitely work harder at supporting the existing natural mechanisms for removing CO2 from the atmosphere, but it's far, far easier to reduce the amount we're emitting.
- aeternum 2y ago
  Are we all just ignoring that plants pull CO2 out of the air and produce usable energy in the process? So clearly it is possible to do more efficiently.
  - LinAGKar 2y ago
    Plants aren't that efficient, there's just a lot of them. You could cover the requisite 764 GW with about 3000 km^2 of solar cells (assuming 250 W/m^2). That's a bit over the land area of Luxembourg. Minuscule compared to the amount of area on Earth taken up by plants, and sunlight that falls on those plants.
downWidOutaFite 2y ago
The calculations here are based on the laws of thermodynamics that cannot be broken. This represents the ideal efficiency that is way better than we could achieve in real life.

danans 2y ago

Enhanced rock weathering for CO2 removal potentially avoids the high energy requirement problem of DAC, since it relies directly on natural environmental processes to work. But it has it's own issues and question marks.

gmuslera 2y ago

Were they talking there about the Marxwell's demon? Anyway, CO2 capture, by itself, is not the whole solution, but it should be part of it. There is an unbalance between the energy that comes in and the one that goes out. so things heats up (among other negative consequences, like i.e. ocean acidification). You won't solve the whole problem without addressing that eventually, so some way of carbon capture, going through the use of energy or something else, should be in the map. And the complementary part of that is stop adding new (or, in other way to see it, very old, but that was stored away) carbon to the system. Even with the very worrying signs of the global climate going haywire with the corresponding loses of lives and money we keep adding each year even more fossil carbon than the previous one, no matter how much token energy generation is announced to be done by other means. It may be expensive, or require technologies that we don't have yet, or compromises on what to lose, or whatever, but it is a problem that if left by its own means will eventually make the planet unlivable for us in a way or another. And that will turn all the saved money into something meaningless.

jandrewrogers 2y ago

The article makes a valid point that the amount of energy required for direct air capture (DAC) is extremely prohibitive and far beyond current capacity, but assume for the sake of argument that this is a problem that could be solved. This still leaves the problem that the industrial plant and chemical feedstock required to physically do the DAC at the scale of billions of tons per year is several orders of magnitude beyond what is possible with current supply chains and natural resources. You would have to strip mine the planet just to have the raw materials to build the necessary DAC infrastructure, and we need those resources for other critical things as well. Some proposed DAC chemistries have upstream mineral dependencies that, if done at the scale required just to offset a year's emissions, would consume all known global reserves immediately. This is not solved by recycling because of compounding loss rates; recycling is not 100% efficient, and the amount of energy required to improve recycling efficiency is essentially exponential for rapidly diminishing returns, and we already have an energy problem with DAC. DAC at any scale that is not an exercise in futility will be an exercise in environmental and economic destruction at unprecedented scale. The solution would almost certainly be worse than the problem. There really isn't a path forward that doesn't involve dramatically reducing emissions and letting nature remove the excess carbon.

DennisP 2y ago
This could use some citations. In particular, I'm interested in these new methods, which are very energy efficient: https://engineering.princeton.edu/news/2024/03/14/engineers-use-moisture-pull-carbon-dioxide-out-air https://engineering.princeton.edu/news/2024/03/14/engineers-... https://news.mit.edu/2019/mit-engineers-develop-new-way-remove-carbon-dioxide-air-1025 https://news.mit.edu/2019/mit-engineers-develop-new-way-remo... The second article says "the team has proven the system can withstand at least 7,000 charging-discharging cycles, with a 30 percent loss in efficiency over that time. The researchers estimate that they can readily improve that to 20,000 to 50,000 cycles." That's without consumables, just a stack of electrodes coated with an organic compound and carbon nanotubes.
- jandrewrogers 2y ago
  Your examples are illustrative of the point. These are the equivalent of "in mice" articles in medicine. Showing DAC in a lab is the easy part. Just to offset current emissions, we need to pull 40 billion tons of CO2 out of the air each year. This must work within the constraints of supply chains, upstream chemical feedstock, and available planetary mineral reserves. People are not comprehending the scale: this would be the largest industrial chemistry process in history by orders of magnitude, larger than all other industrial chemistry combined. Scaling either of the above DAC processes to 40 billion tons per year is infeasible. You don't just have to scale the process, you also have to scale the upstream processes and resource extraction activities that enable the process to be built. At 40 billion tons, any chemical engineer can quickly pencil out that these processes have upstream dependencies that have no ability to be scaled sufficient to support the target production process, not even close. In computer terms, it is like trying to train the latest LLMs on a computer from the 1990s. I see a lot of DAC proposals that, at scale, imply a supply chain that instantly consumes the global reserves of critical agricultural minerals like potassium or phosphorus, or which would literally produce e.g. concentrated acid waste at the scale of billions of tons, with no plan for how to keep people from starving or disposing of the chemical waste. Consequently, these processes are not real solutions.

downWidOutaFite 2y ago

Capturing only makes sense at the emission sources where the co2 concentration is high, like at power plants or tailpipes. But that would mean the costs would be borne by the emitters but they'd rather externalize those costs to all of us.

kjkjadksj 2y ago

Cheap direct air capture: grow biomass, sink to bottom of ocean.

tmnvix 2y ago
Biomass decomposing in an anaerobic environment creates some very very nasty gases. There are multiple previous extinction events attributed to this. Times when the oceans basically turned to swamps.
- kjkjadksj 2y ago
  Extinctions attributed to co2 decreasing relative to oxygen, sort of what is required here to a certain scale at least

DennisP 2y ago

The numbers he posts are not all that bad really. It's 181kWh per metric ton CO2. At an electricity cost of 5 cents/kWh that's nine bucks per ton. That's quite a bit cheaper than the actual cost projected by real projects, so I'm not sure what he's debunking. In terms of energy, some emerging tech is pretty close to ideal. Princeton has a project they claim can do 0.7 gigajoule/ton, or 195kWh [1]. And MIT is claiming one gigajoule/ton, or 278kWh [2]. If we transition to a wind/solar/battery grid, the cheapest option in the US at least is to have about four days of battery and 2X overproduction [3]. So that's a lot of extra energy basically available for free. Even today, with relatively small usage of renewables, utilities sometimes let electricity costs go negative [4]. If capital costs aren't too high, then DAC can run whenever there's excess energy available. Of course, capital cost will be a big portion of the expense, though it'll decrease as we scale. Climeworks and Carbon Engineering have estimated $100/ton in total cost, which equates to a dollar per gallon of gasoline. Many places already have gas taxes higher than that. And the MIT and Princeton methods should be cheaper at scale than current methods would be. Actually eliminating all our annual emissions by just doing this would of course be madness. But if we tried, and charged emitters for doing that, then most emitters would find it cheaper to stop emitting instead. Then we'd naturally end up only using DAC for emission sources that are very hard to eliminate. After we hit net zero, we'd be smart to take CO2 down to a safe level. Call it 100ppm of reduction. Hopefully we can do some of that with reforestation and so on, but let's say DAC is our only option. One ppm is 7.8 gigatons CO2, so we're talking 780 gigatons to draw down. At 200kWh/ton that's 156 TWh, not far off from the world's entire energy usage for a year, matching the article's estimate. But if we're at 2X overproduction on energy, then we'll have that much energy available. Only the capital cost of the equipment would really be important, and by the time we scale it that far, that should be fairly low too. The methods I linked use cheap, readily available materials. So it looks pretty feasible to me. We can call this a "distraction" and put up with the terrible consequences of whatever high CO2 level we reach by the time we're at net zero, or we add DAC to a wind/solar/battery world and get down to a nice cool 350ppm. Since it takes time to scale, and climate feedbacks give us a time limit, we need to develop and start scaling DAC now. [1] https://engineering.princeton.edu/news/2024/03/14/engineers-use-moisture-pull-carbon-dioxide-out-air https://engineering.princeton.edu/news/2024/03/14/engineers-... [2] https://news.mit.edu/2019/mit-engineers-develop-new-way-remove-carbon-dioxide-air-1025 https://news.mit.edu/2019/mit-engineers-develop-new-way-remo... [3] https://caseyhandmer.wordpress.com/2023/07/12/grid-storage-batteries-will-win/ https://caseyhandmer.wordpress.com/2023/07/12/grid-storage-b... [4] https://archive.is/WfUIJ https://archive.is/WfUIJ

hinkley 2y ago

Matt Ferrell I think talked a while back about an air battery that captured carbon dioxide while charging and release it while discharging. If the losses aren’t too bad, this could be a cogeneration solution where the batteries are used for load leveling. In essence you are using mostly surplus energy for the task anyway. The carbon footprint of “green” energy is often not that good if you consider the entire cradle to grave lifecycle. Carbon capture would make things less murky.

tmnvix 2y ago

I know this is a somewhat flippant comment but... Trees.

dotps1 2y ago
I was going to dismiss your comment thinking that it wouldn't be possible to capture the amount of carbon we are emitting with trees alone .. but after running the numbers, trees seem like a pretty decent solution.
- timschmidt 2y ago
  I'm picturing a large solar farm powering pumping stations to irrigate a large desert like the Sahara, central Australia, Saudi Arabia, the Gobi, or the American Southwest. Maybe all of them. If we do nothing, Antarctica has 5.5 million square miles of land which might be available for plant growth soon.
DennisP 2y ago
DAC uses a thousand times less land area.