In principle it ' s easy to believe that a machine that scrubbed pollutants could be more efficient at removing them than its power source was at creating them . There ' s no inherent thermodynamical or other tricksy physical reason that couldn ' t work . Even a coalpowered carbon scrubber could easily work in principle , though the breakeven time might be fairly long . The reason there isn ' t one of these on every corner is that China like everywhere else is already using most of the energy it can conveniently produce . Devoting 70 % of its coalpowered electricity to running these scrubbers or whatever you ' d need to get clean air would mean a 70 % shortfall in the electricity it was using to keep the lights on . tldr you ' re right to think this isn ' t a solution , but at this scale it ' s not doing more harm than good either .