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I've been wondering about various carbon sequestration methods myself and am glad to see these topics on HN since it is an opportunity to harvest relevant knowl

I've been wondering about various carbon sequestration methods myself and am glad to see these topics on HN since it is an opportunity to harvest relevant knowledge from the community. Apologies for tangential topic, but give me a sec and it'll try to tie it back to some other discussions happening here - has anyone here heard of "Cryo Carbon Capture"? https://sesinnovation.com/faq.html https://sesinnovation.com/faq.html This seems to involve feeding the exhaust of a power plant into a process which cools the exhaust to the point where CO2 dry ice (and other pollutants) desublimates out of the exhaust and is then extracted for various industrial/commercial applications. I am curious about this model if it feasible then couldn't this also be used on the exhaust stream of a heater for pyrolysis of fast growing trees, grasses, etc. creating biofuel and biochar? You can use biofuels to heat the pyrolysis and biochar to sequester carbon in the soil, while also improving it to grow more biomass for sequestration. The cryo-capture handles your CO2 waste streams and further captures carbon in a cold sink (also useful for refrigeration and can maybe act as a "battery" when combined with a Stirling engine?) which also produces CO2 which can be used to enrich biomass grown in greenhouses and has plenty of other commercial uses. If you add solar and other sustainable power inputs to the cryo-capture process then what you have is basically a farm which creates useful carbon-based products from the atmosphere using plants and basic chemistry... and here is where I hope someone with more knowledge will point out why this isn't already a thing, likely due to some serious inefficiency I'm overlooking.

Skunkleton 7y ago
> This seems to involve feeding the exhaust of a power plant into a process which cools the exhaust to the point where CO2 dry ice (and other pollutants) desublimates out of the exhaust and is then extracted for various industrial/commercial applications. Based on what you said, the dry ice would sublimate and just re-release the carbon into the atmosphere. Or did you have a different place for this carbon to go? If so, how are you planning to keep the dry ice cool, and how are you planning on producing it in the first place?
- gooseus 7y ago
  The dry ice itself would be stored in well-insulated containers, and cold generated from these containers would be useful for refrigeration with the CO2 that does sublimate out as the containers heat up being feed-stock to enrich greenhouses, with the rest would being recycled into the pyrolysis exhaust, and thus back into the dry ice production. One of the things I'm curious about is the efficiency of the dry ice production at various CO2 levels and the physical quantities of material that would be expected from such these kinds of processes. The general idea is that you would be creating a system for accumulating/concentrating carbon as CO2 solid/gas, as well as in biomass, and at the same time creating two large energy differentials that could also be put to work. The major input to this system (assuming the numbers can work) would be photosynthetics and photovoltaics.
  - Skunkleton 7y ago
    AFAIU most of our industrial CO2 (for dry ice, soft drinks, etc) comes from refining natural gas exhaust. From there, if you want to make a dry ice block, you have to take it through a very energy cooling process (similar to how air conditioning works) to create a liquid, and then through a second compression and cooling process to turn it into a solid. It is likely that the process of turning a given volume of CO2 into a solid would produce more emissions than it sequestered. You cannot assume that green energy will be used for this sequestration because if green energy were available at this scale, you wouldn't have the CO2 on your hands in the first place. On the demand side we already collect as much CO2 as we need from e.g. natural gas power plants. We don't have a use for any more. It will just sublimate and be re-released into the atmosphere, or into some containing vessel.

Skunkleton 7y ago

> This seems to involve feeding the exhaust of a power plant into a process which cools the exhaust to the point where CO2 dry ice (and other pollutants) desublimates out of the exhaust and is then extracted for various industrial/commercial applications. Based on what you said, the dry ice would sublimate and just re-release the carbon into the atmosphere. Or did you have a different place for this carbon to go? If so, how are you planning to keep the dry ice cool, and how are you planning on producing it in the first place?

gooseus 7y ago
The dry ice itself would be stored in well-insulated containers, and cold generated from these containers would be useful for refrigeration with the CO2 that does sublimate out as the containers heat up being feed-stock to enrich greenhouses, with the rest would being recycled into the pyrolysis exhaust, and thus back into the dry ice production. One of the things I'm curious about is the efficiency of the dry ice production at various CO2 levels and the physical quantities of material that would be expected from such these kinds of processes. The general idea is that you would be creating a system for accumulating/concentrating carbon as CO2 solid/gas, as well as in biomass, and at the same time creating two large energy differentials that could also be put to work. The major input to this system (assuming the numbers can work) would be photosynthetics and photovoltaics.
- Skunkleton 7y ago
  AFAIU most of our industrial CO2 (for dry ice, soft drinks, etc) comes from refining natural gas exhaust. From there, if you want to make a dry ice block, you have to take it through a very energy cooling process (similar to how air conditioning works) to create a liquid, and then through a second compression and cooling process to turn it into a solid. It is likely that the process of turning a given volume of CO2 into a solid would produce more emissions than it sequestered. You cannot assume that green energy will be used for this sequestration because if green energy were available at this scale, you wouldn't have the CO2 on your hands in the first place. On the demand side we already collect as much CO2 as we need from e.g. natural gas power plants. We don't have a use for any more. It will just sublimate and be re-released into the atmosphere, or into some containing vessel.