(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?
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
> Briefly: there are plant-based, mineral-based, and chemical options.
Where are cryocooling-based options?
Aren't there plenty of places where energy is so plentiful that you don't need to care that much?
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?
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.
Not exactly.
The idea is that you don't just compress air - and let the heated compressed air cool to the atmosphere in order to then expand it so it would cool some more, and then just release whatever's left back to the atmosphere. No, you use those leftovers to cool the incoming air - so you need to compress air spending less energy - and you also get the expanding air to help you to compress incoming air.
The principal point where you have non-reversibility is that extra cooling - making compressed cold air to do the work - which you need to reach necessary temperature. And you only need that temperature to separate gases; after that you can use the cold products to help with compression.
So - without colorful metaphors - I'd like to figure out how much energy will you need.
I see the approach of SES with flue gases. I'm not sure how it will look like with regular air.