When we get the political consensus to put a price on atmospheric carbon, it will give a subsidy to anyone who can make a solid material out of carbon. What will be the most economical way to get those subsidies? I don't think it will be making carbon nanotubes. That requires an extremely pure source of carbon. I think the biggest application will be construction materials:
Mine CaO, use atmospheric CO2 to convert it to CaCO3 this use that as feeder stock for making limestone-like and marble-like construction materials. These could be premium materials -- I could easily see Salesforce paying a premium to cover the floors of Salesforce tower in 'reclaimed atmospheric marble' to advertise their green creds -- or a down market material -- just mix it in to drywall to get the CO2 credits. Either way, this process would be much less fussy about the purity of the CO2 source.
Mine CaO, use atmospheric CO2 to convert it to CaCO3 this use that as feeder stock for making limestone-like and marble-like construction materials. These could be premium materials -- I could easily see Salesforce paying a premium to cover the floors of Salesforce tower in 'reclaimed atmospheric marble' to advertise their green creds -- or a down market material -- just mix it in to drywall to get the CO2 credits. Either way, this process would be much less fussy about the purity of the CO2 source.