4 ms·

(I wrote the post) This is good feedback that this is buried in the appendix -- I pulled that section up and made it inline with the flow of the post. Does tha

by orbuch 7y ago

(I wrote the post) This is good feedback that this is buried in the appendix -- I pulled that section up and made it inline with the flow of the post. Does that help?

avmich 7y ago
Section "How to take CO2 out of the sky" > Briefly: there are plant-based, mineral-based, and chemical options. Where are cryocooling-based options?
- orbuch 7y ago
  I'm not sure what this is? You might be thinking of solar radiation management or other "geoengineering" techniques to try to make the earth shiner and reflect more sunlight, making us cooler at a constant CO2 concentration. Theres a ton of interesting topics within that to write about, I mention it briefly as "things I didn't include"
  - foxhill 7y ago
    having not read the article (yet), i the OP is referring to “cooling down air until it liquifies then using fractional distillation to pull out the CO2”?
    - avmich 7y ago
      You don't want to do unnecessary transformations, to preserve as much energy as possible (so the turbine, which is needed for cooling, should work on small pressure difference). So, no air liquification - just let CO2 separate and send cleaned air back to the heat exchanger.
      - peteretep 7y ago
        > to preserve as much energy as possible Aren't there plenty of places where energy is so plentiful that you don't need to care that much?
        adrianN 7y ago
        Not really?
  - avmich 7y ago
    No, the idea is something similar to this - https://sesinnovation.com/ https://sesinnovation.com/ . You carefully compress incoming air. Separate water vapors (and liquids, and hopefully not solids) from it. Cool this air in thermal exchanger - at this point CO2 falls off. Then you pass that air through turbo detander, which returns you some energy, and get a pre-liquified air, which pass to the thermal exchanger. Clean air of normal temperature is released to atmosphere. You have to compress the air - but you also cool air, so compression is easier, and you also get some energy from the turbine where you decrease the pressure. Subject to optimizations. How much energy will you need?
    - orbuch 7y ago
      Ah, thanks! I haven't seen this before. Will look into it.
    - rckoepke 7y ago
      > How much energy will you need? A lot. Air compression is not cheap, energetically. Chilling is also energetically expensive. You'll need to do both. This would be pretty much the "brute force" method, like O(n!) in software engineering. The concept would be to bring half the planet's atmosphere down to near its liquid temperature. Currently in most US homes, Air Conditioning (air cooling) contributes the majority of each home's energy use. This would be much greater than that, it requires chilling air to -140 °C to get CO2 to "drop out". In contrast, seeding the ocean with iron would be fairly close to O(1). However, potential side effects of this process concern some scientists greatly. Googling 'Russ George' may provide more insight. Side note: The press material for sesinnovation also says the outlet stream is nearly 100% nitrogen...that means they're using a stream which already has oxygen removed from it (likely because the air was just used for combusting fuels). Air is roughly 21% oxygen so you can't take air, only remove CO2, and get 100% nitrogen out. Generally these "Carbon Capture" technologies only work on feed streams with high CO2. So hey're placed at industrial outlets, where fuel/coal is being burned. These streams can be > 10% CO2. Often they don't work as well, or at all, on diffuse streams like 0.04% atmospheric CO2. The technical reasons why this is the case deal with "partial pressures" as well as general entropy.
      - 7y ago
matco11 7y ago
Yes, it does. GREAT work. Two (small) comments: - Perhaps the review of the re-forestation option could mention that this has a number of positive side effects (outside of carbon capture), for example on rainfall and wildlife. - as there is a time constraint on co2 capture (e.g. 2050), and as the various co2 capture solutions are not all at the same stage of maturity, it could be useful to have a table/chart that summarizes which co2 capture options are deployable now vs. at some stage in the future

by orbuch 7y ago

(I wrote the post) This is good feedback that this is buried in the appendix -- I pulled that section up and made it inline with the flow of the post. Does that help?

avmich 7y ago

Section "How to take CO2 out of the sky" > Briefly: there are plant-based, mineral-based, and chemical options. Where are cryocooling-based options?

orbuch 7y ago
I'm not sure what this is? You might be thinking of solar radiation management or other "geoengineering" techniques to try to make the earth shiner and reflect more sunlight, making us cooler at a constant CO2 concentration. Theres a ton of interesting topics within that to write about, I mention it briefly as "things I didn't include"
- foxhill 7y ago
  having not read the article (yet), i the OP is referring to “cooling down air until it liquifies then using fractional distillation to pull out the CO2”?
  - avmich 7y ago
    You don't want to do unnecessary transformations, to preserve as much energy as possible (so the turbine, which is needed for cooling, should work on small pressure difference). So, no air liquification - just let CO2 separate and send cleaned air back to the heat exchanger.
    - peteretep 7y ago
      > to preserve as much energy as possible Aren't there plenty of places where energy is so plentiful that you don't need to care that much?
      - adrianN 7y ago
        Not really?
- avmich 7y ago
  No, the idea is something similar to this - https://sesinnovation.com/ https://sesinnovation.com/ . You carefully compress incoming air. Separate water vapors (and liquids, and hopefully not solids) from it. Cool this air in thermal exchanger - at this point CO2 falls off. Then you pass that air through turbo detander, which returns you some energy, and get a pre-liquified air, which pass to the thermal exchanger. Clean air of normal temperature is released to atmosphere. You have to compress the air - but you also cool air, so compression is easier, and you also get some energy from the turbine where you decrease the pressure. Subject to optimizations. How much energy will you need?
  - orbuch 7y ago
    Ah, thanks! I haven't seen this before. Will look into it.
  - rckoepke 7y ago
    > How much energy will you need? A lot. Air compression is not cheap, energetically. Chilling is also energetically expensive. You'll need to do both. This would be pretty much the "brute force" method, like O(n!) in software engineering. The concept would be to bring half the planet's atmosphere down to near its liquid temperature. Currently in most US homes, Air Conditioning (air cooling) contributes the majority of each home's energy use. This would be much greater than that, it requires chilling air to -140 °C to get CO2 to "drop out". In contrast, seeding the ocean with iron would be fairly close to O(1). However, potential side effects of this process concern some scientists greatly. Googling 'Russ George' may provide more insight. Side note: The press material for sesinnovation also says the outlet stream is nearly 100% nitrogen...that means they're using a stream which already has oxygen removed from it (likely because the air was just used for combusting fuels). Air is roughly 21% oxygen so you can't take air, only remove CO2, and get 100% nitrogen out. Generally these "Carbon Capture" technologies only work on feed streams with high CO2. So hey're placed at industrial outlets, where fuel/coal is being burned. These streams can be > 10% CO2. Often they don't work as well, or at all, on diffuse streams like 0.04% atmospheric CO2. The technical reasons why this is the case deal with "partial pressures" as well as general entropy.
    - 7y ago

matco11 7y ago

Yes, it does. GREAT work. Two (small) comments: - Perhaps the review of the re-forestation option could mention that this has a number of positive side effects (outside of carbon capture), for example on rainfall and wildlife. - as there is a time constraint on co2 capture (e.g. 2050), and as the various co2 capture solutions are not all at the same stage of maturity, it could be useful to have a table/chart that summarizes which co2 capture options are deployable now vs. at some stage in the future