Instructables has an incredible  do-it-yourself project that shows the step by step instructions to modify a car to run on garbage. Using a process called gasification, which uses heat to transform solid biomass into a natural gas like fuel, this homemade engine runs on nearly anything. Wood, food scraps, leaves – pretty much any kind of solid, dry organic matter you can get your hands on will make this car go.  Equally surprising is the fact that gasification has been in use for quite a long time.
Instructables explains:
Did you know that over one million vehicles in Europe ran onboard gasifiers [...]