FYI, as a chemist I have a unique perspective. Having looked at the list of chemicals used by the natural gas companies. IMO, some are doing chemistry on a global scale. Natural gas is produce by serpentinization where the minerals use CO2, water, and pressure to produce methane and the longer chains are formed from the pressure. Thus they are reseeding the process with more CO2 to overcome the natural flux and likely trying to convert minerals back to the olivine faster than it naturally would.
An example is looking at what they use to “kill bacteria” which they dub ammonium salts. Well, (alkyl dimethyl) benzylammonium chlorides are used for disinfectants in barber shops (barbicide) but in chemistry they’re used as phase transfer catalysts which help speed up chemistry that needs to transfer between aqueous and organic layers. So they are injecting aqueous solutions and organic solutions to speed up the chemistry. Benzylammonium chloride is known for being efficient at transferring [CO2-].
i.e. invest in capture all you want but the storage credits will be raked in by the natural gas companies. Capture for industrial use makes sense but investing in storage should just invest in natural gas because they’r using it to speed up the process but want to keep the intellectual secrets and will never patent or make public their efforts.
this is a tough question. i'm not even sure which chemical and physical processes would be the best to end up with a pure C02 end product....if you could get pure co2 maybe reacting it with fe would work, but your feed should have next to zero O2......your by product would be graphite.