From the atmosphere, sure. But, if they can succeed in building a viable conversion system, then hot exhaust from factories or other sources can be used instead

From the atmosphere, sure. But, if they can succeed in building a viable conversion system, then hot exhaust from factories or other sources can be used instead of air. It could be a closed source system too, for example, in industrial applications that need a lot of heat. An almost closed cycle system may be viable. I have no information about the speed of the reaction, but I guess systems can be scaled. Also, a good amount of heat is produced in the sabatier reaction process itself, which can be used for other systems. Conversion of atmospheric CO2 to usable fuel can become a cheap battery for solar plants. Edit: Such a system already exists, even if as an idea. https://www.carboncommentary.com/blog/2017/7/24/exytron-the-worlds-first-power-to-gas-system-with-integrated-co2-collection-and-reuse https://www.carboncommentary.com/blog/2017/7/24/exytron-the-...