This thing isn't a *source*
This thing isn't a *source* of electricity at all. That comment by the article's author is the dumbest thing I've ever heard.
If you look past that to perhaps what the author *meant*, I agree that the original source of the energy is likely coal or some other other fossil fuel and this makes these semis - like most electric vehicles - not entirely clean. That said I think it's easier to scrub the emissions of one coal plant than it is to scrub the emissions of 1,000,000 ICE vehicles, so likely electric vehicles are still an environmental improvement.