CO2 already has value, if it's concentrated enough (stack emissions, unfortunately, aren't). There are CO2 mines in multiple western US states where the CO2 is

CO2 already has value, if it's concentrated enough (stack emissions, unfortunately, aren't). There are CO2 mines in multiple western US states where the CO2 is dug up, sent through pipelines, and reinjected into oil wells. "Enhanced oil recovery", they call it, and it's big business. So big, in fact, that the supply from the McElmo dome in the SW corner of Colorado, pipelined across the entirety of New Mexico, into Texas, is oversubscribed and you can't buy any. CO2 needs hydrogen, pure and simple, to become almost any other substance of value (I suppose lithium extraction could use the gas instead of trona, but not a big market there considering the supply). Any plastic, polymer, or vegetation needs hydrogen to exist. So the CO2 problem is the hydrogen problem, but on steroids. You can't get reduced atmospheric CO2 with hydrogen if making that same hydrogen molecule created 2 or 3 CO2 molecules. This leaves you with plant-based approaches (photosynthesis is ridiculously inefficient, which itself is probably a good thing considering how much we like some of the greenhouse effect), or "clean" hydrogen.