Burning coal is generally known for being really bad for air quality. The ash is somewhat radioactive, and if there's any sulphur in the coal it'll cause acid r

Burning coal is generally known for being really bad for air quality. The ash is somewhat radioactive, and if there's any sulphur in the coal it'll cause acid rain. The exhaust from burning the coal nowadays ends up going through treatment to clean it up (remove sulphur and particulates), which is an added expense. In comparison, natural gas tends to be rather pure, so when burned it produces just carbon dioxide and water.