> even if powered 100% by coal plants, these plants have an higher efficiency than cars' internal combustion engines Yes they have incredible thermal efficienc

> even if powered 100% by coal plants, these plants have an higher efficiency than cars' internal combustion engines Yes they have incredible thermal efficiency, but two things come to mind: The grid does not, and coal has particular difficulty in controlling particulate emissions. This is particularly true of brown coal, which has a very high water content. Just to be particularly frustrating, coal is not distilled the way diesel is (which is famous for particulate emissions) so it tends to have other stuff like excessive sulphur. Though in that case, that stuff ends up in the bunker oil that goes in big ships.