Producer gas, bitches!
 

http://www.instructables.com/id/Conv..._run_on_trash/

Some people did this during WW1-2 when there was little/no gasoline for civilians. They used wood, but apparently any old thing with do the trick.

Re: Producer gas, bitches!
 

Ive done it. Well kinda. I ran a lawnmower motor from a burn barrel. We hosed in right under the fire that only burns at the top of the barrel where it is exposed to O2 (this is after its been burning for a while). Start the mower on gas and stick in the hose.It will start to choke rich and pinch off the fuel line and it will keep going. ;D I won that drunken bet.