I know what you are thinking right now, you're thinking, "coal-powered cars? You already talked about steam cars though!" But I am not talking about a coal steamers (especially since steam cars mostly ran on kerosene or gasoline), but rather cars that ran on coal gas.
As with most things, necessity is the mother of all invention, and this situation is no different. During WWII, gasoline was in short supply because the war effort was consuming all of the world's gasoline production, leaving little for consumers. Tinkerers and inventors the world over began thinking of replacements for gasoline (and for rubber, cotton, and a host of other rationed goods). One solution for the gasoline crisis was to find other sources of combustible gases to force into the cylinders of existing vehicles. In France, the solution came in the form of coal gas.
The basic principle of the engine was based on the fact that the combustion of coal produces a similarly combustible gas, coal gas. As such, a conversion kit was devised that would mount two coal gas generators on the fenders. The generators would burn coal, then suck the gas straight into the engine and running the engine off of the coal gas.
Few surviving conversion kits exists, but one such kit turned up on a 1938 Citroen Traction Avant at the 2006 Amelia Island Concours. Photos sourced from Stanley Motor Carriage and Ultimatecarpage.com