This is wildly optimistic, but personally, I'm looking forward to CO2 captured from the atmosphere, reformed into hydrocarbons on-site, and used as feedstock in the global plastics and fertilizer trades.
Yes, balancing that equation is going to require energy input. Yes, probably gonna require some pretty smart chemists. But impossible? Well, I don't see why not.
Edit: There's probably not that much utility in this. See comments below.
Poster probably refers to Ammonia from Haber-Bosch process which generally used methane for H2 source (although I guess if we get to the point where we have the technical capability to take CO2 to energy feedstocks we probably have the capability to generate real green H2)
Yes but OP’s whole spiel is about us having enough excess energy to do things like turn CO2 into feedstocks and currently we can’t do that (well at least in no way is it economically viable to do that), and the proportion of green H2 is tiny in comparison to that made with fossil fuels, so it clearly isn’t economically effective to do that yet either
Carbon itself is a soil amendment. (think compost). Organic farms use tonnes of the stuff every year as a top dressing. If you have pure carbon you could mix it up with NPK and micronutrients and have a compost alternative for large scale industrial farming.
The only synthetic fertilizers that include hydrocarbons in their production chain are ammonia based, but all CO2 (or as much as is practicable) is removed from the end product. It's really only used on the way to producing hydrogen.
Furthermore the ammonia production processes use natural gas (not crude oil!) only as a source of hydrogen. They could split water instead, it’s just that the natural gas is cheaper.
Yes, balancing that equation is going to require energy input. Yes, probably gonna require some pretty smart chemists. But impossible? Well, I don't see why not.
Edit: There's probably not that much utility in this. See comments below.