Hans is not crazy. GM, Ford and Mercedes manufactured wood gas mobiles during WWII. They operate by passing oxygen and water vapor over coals. The carbon dioxide is reduced to carbon monoxide and water vapor is reduced to hydrogen - then both gases can be burned in a standard internal combustion engine. The gas mix is about 40% combustible.
These type of engines were largely referred to as Imbert Gasifiers (named after the inventor Jacques Imbert).
Jay Warmke
Instructor - Renewable Energy (Central Ohio Technical College)