Which is worse to the air the burning of coal or internal combustion engines?

Which is worse to the air the burning of coal or internal combustion engines?
The question cannot be answered unless you define what you mean by "worse". Both pollute.You also have to describe the conditions under which the coal is burnt. Burning high sulfur coal can produce oxides of sulfur that cause acid rain but emissions regulations may require scrubbers on coal-fired power plants that remove the oxides of sulfur.Internal combustion engines in new cars have catalytic converters that remove oxides of sulfur and nitrogen. Diesel engines may not be regulated to have catalytic converters. Lawnmower and motorcycle engines generally don't have catalytic converters either.The cleanest coal and the cleanest internal combustion (gasoline) engine both dump carbon dioxide into the air. For the same weight of fuel burnt, coal produces about twice as much energy (A pound of coal produces 43000 btu and a pound of gasoline produces 18000 btu). 1 pound of coal produces 3.3 pounds of carbon dioxide (CO2) and 1 pound of gasoline produces 2.8 pounds of CO2. This assumes perfect burning. Based on this, alone, coal produces half as much CO2 for the same amount of energy. CO2 is considered a greenhouse gas and is credited with causing global warming.If the internal combustion engine uses hydrogen for fuel, the engine dumps only water and a small quantity of nitrogen oxides into the air... but, in order to make the hydrogen, you would need to use about twice as much electrical energy as ends up stored in the hydrogen - probably from burning, you guessed it, coal.