Producer gas has been with us for a long time. Many large European cities
were lighted at night in the early 19th century by producer gas made from
coal. The first IC engines in the early 19th century were powered by coal
gas. Residues from coal gas helped start the huge German chemical industry.
In the late 70s Mother Earth News built a producer gas powered pickup. I
have pictures of an producer gas powered International Harvester F12 built
in Germany at the end of WWII. Sometime in the thirties Henry Ford had
several test cars set up for producer gas.
The process uses energy to drive off the hydrogen which is the fuel. As for
energy usage it is not very efficient. There is at least one Yahoo group on
wood gas.