As early as the 1860s gasification was used to power internal combustion engines. Gasification has been an important and common technology which was widely used to generate Town gas from coal mainly for lighting purposes during the 19th and early 20th century.
During World War II gasoline was rationed and in short supply in both Great Britain and in the United States and large numbers of such generators were constructed or even improvised to convert wood and coal into fuel for vehicles. Commercial generators were in production before and after the war for use in special circumstances or in distressed economies. The German Army operated combat vehicles on wood gasification.
Gasification is a fairly simple process; you heat the wood or coal in a airtight container to a high enough temperature that it releases flammable gases. These gases provide the fuel for the engine. The TV show the Colony had a generator running on wood gas in one of its episodes.
In 1989 FEMA published a manual entitled “Construction of a Simplified Wood Gas Generator for Fueling Internal Combustion Engines in a Petroleum Emergency”. This is a good publication and is still available on the internet. It can be downloaded at http://bit.ly/oB13Ek
This is a manual that you may want to download and keep in your library.