4 ms·

I had the same thought as well. It's an option, but the energy required to cool air to the precipitation point of CO2 (-79C) is pretty large, and the cooling p

I had the same thought as well. It's an option, but the energy required to cool air to the precipitation point of CO2 (-79C) is pretty large, and the cooling process itself will produce greenhouse gas, so you end up with a pretty small return.

avmich 7y ago
How do you calculate how much energy is required? You would use cooled separated products to pre-cool incoming stream of "dirty" air. CO2, having low concentration, won't fall off at -79C (or we'd have that effect in Antarctica today), but if you go to ~-140C, you'll have some results. Why cooling process will produce greenhouse gas? You'd use energy from "green" sources to compensate for required expenses.
- stouset 7y ago
  > You’d use energy from “green” sources… This isn’t something you can just assert as if by magic. By using this kind of technology, you increase the total power requirements of our civilization. That power has to come from somewhere. If you earmark green energy sources for it, something else will need to use a dirty energy source. This remains true as long as green energy production falls short of planetary demand (modulo carbon taxes/credits/caps which change the math here a bit depending on specifics). The leftover slack will be met by burning fossil fuels.
  - avmich 7y ago
    That's why I'm trying to estimate energy requirements of such a process. Somebody experienced with gas liquification could perhaps help. You have to build these cleaning devices, and you'll need to build energy sources for them. We do have both power and increase in power supply with time; the question is specific numbers, which I'm trying to estimate.
    - stouset 7y ago
      But that’s the problem. When you say you could just build new clean energy sources for these things, you’d be better off by only doing that. Every kWh of clean energy produced is far more effective at addressing climate change when it replaces a kWh generated by fossil fuel than it is trying to remove the carbon from that fossil fuel after the fact.
      - avmich 7y ago
        > Every kWh of clean energy produced is far more effective at addressing climate change when it replaces a kWh generated by fossil fuel than it is trying to remove the carbon from that fossil fuel after the fact. True. However, here are two significant, in my opinion, notes. 1) We already have a lot of CO2 in the air. We'd better get it out, and sooner. 2) We're proving every day our limited abilities in organizing focused efforts in fighting climate crisis, particularly by a single specific way. So, if we could reduce organizational problems by choosing a solution which has less of them, we could win in practice. It's rather obvious that it's better not to get CO2 into the air in the first place. Looks like we can't avoid doing that now. So other options become interesting.
- rckoepke 7y ago
  -140C only works for CO2-rich streams (> 10%). As the partial pressure of CO2 decreases, you'll need to get asymptotically closer to the melting point of oxygen/nitrogen. You'll also need to increase the pressure, but again that only gets you reasonable temperature gains if the partial pressure of CO2 is >>0mmHg. Currently it is 0.3mmHg @ 400ppm. In short, this is not a viable method for removing CO2 from the atmosphere. For a fun take on some of this see https://wattsupwiththat.com/2009/06/13/results-lab-experiment-regarding-co2-snow-in-antarctica-at-113f-80-5c-not-possible/ https://wattsupwiththat.com/2009/06/13/results-lab-experimen...
  - avmich 7y ago
    > -140C only works for CO2-rich streams (> 10%). The chart in the article by the link suggests -140C would work for pressure of 0,0004 atm. How did you get that number - >10% ?
jdsully 7y ago
Antartica is -56C right now. Another 23C should be manageable. This doesn’t have to be done in the tropics.
- rckoepke 7y ago
  https://wattsupwiththat.com/2009/06/13/results-lab-experiment-regarding-co2-snow-in-antarctica-at-113f-80-5c-not-possible/ https://wattsupwiththat.com/2009/06/13/results-lab-experimen... I made some slightly more detailed posts elsewhere but this article addresses your point directly. Essentially, this is not a viable method for removing CO2 from the sky, because there's so little CO2 in the sky that it changes all the basic physics assumptions. This is actually relatively basic undergraduate level napkin math from a chemical engineering perspective, but outside of that discipline most people understandably don't have experience with estimating physical states of mixed gases.

avmich 7y ago

How do you calculate how much energy is required? You would use cooled separated products to pre-cool incoming stream of "dirty" air. CO2, having low concentration, won't fall off at -79C (or we'd have that effect in Antarctica today), but if you go to ~-140C, you'll have some results. Why cooling process will produce greenhouse gas? You'd use energy from "green" sources to compensate for required expenses.

stouset 7y ago
> You’d use energy from “green” sources… This isn’t something you can just assert as if by magic. By using this kind of technology, you increase the total power requirements of our civilization. That power has to come from somewhere. If you earmark green energy sources for it, something else will need to use a dirty energy source. This remains true as long as green energy production falls short of planetary demand (modulo carbon taxes/credits/caps which change the math here a bit depending on specifics). The leftover slack will be met by burning fossil fuels.
- avmich 7y ago
  That's why I'm trying to estimate energy requirements of such a process. Somebody experienced with gas liquification could perhaps help. You have to build these cleaning devices, and you'll need to build energy sources for them. We do have both power and increase in power supply with time; the question is specific numbers, which I'm trying to estimate.
  - stouset 7y ago
    But that’s the problem. When you say you could just build new clean energy sources for these things, you’d be better off by only doing that. Every kWh of clean energy produced is far more effective at addressing climate change when it replaces a kWh generated by fossil fuel than it is trying to remove the carbon from that fossil fuel after the fact.
    - avmich 7y ago
      > Every kWh of clean energy produced is far more effective at addressing climate change when it replaces a kWh generated by fossil fuel than it is trying to remove the carbon from that fossil fuel after the fact. True. However, here are two significant, in my opinion, notes. 1) We already have a lot of CO2 in the air. We'd better get it out, and sooner. 2) We're proving every day our limited abilities in organizing focused efforts in fighting climate crisis, particularly by a single specific way. So, if we could reduce organizational problems by choosing a solution which has less of them, we could win in practice. It's rather obvious that it's better not to get CO2 into the air in the first place. Looks like we can't avoid doing that now. So other options become interesting.
rckoepke 7y ago
-140C only works for CO2-rich streams (> 10%). As the partial pressure of CO2 decreases, you'll need to get asymptotically closer to the melting point of oxygen/nitrogen. You'll also need to increase the pressure, but again that only gets you reasonable temperature gains if the partial pressure of CO2 is >>0mmHg. Currently it is 0.3mmHg @ 400ppm. In short, this is not a viable method for removing CO2 from the atmosphere. For a fun take on some of this see https://wattsupwiththat.com/2009/06/13/results-lab-experiment-regarding-co2-snow-in-antarctica-at-113f-80-5c-not-possible/ https://wattsupwiththat.com/2009/06/13/results-lab-experimen...
- avmich 7y ago
  > -140C only works for CO2-rich streams (> 10%). The chart in the article by the link suggests -140C would work for pressure of 0,0004 atm. How did you get that number - >10% ?

jdsully 7y ago

Antartica is -56C right now. Another 23C should be manageable. This doesn’t have to be done in the tropics.

rckoepke 7y ago
https://wattsupwiththat.com/2009/06/13/results-lab-experiment-regarding-co2-snow-in-antarctica-at-113f-80-5c-not-possible/ https://wattsupwiththat.com/2009/06/13/results-lab-experimen... I made some slightly more detailed posts elsewhere but this article addresses your point directly. Essentially, this is not a viable method for removing CO2 from the sky, because there's so little CO2 in the sky that it changes all the basic physics assumptions. This is actually relatively basic undergraduate level napkin math from a chemical engineering perspective, but outside of that discipline most people understandably don't have experience with estimating physical states of mixed gases.