Tree powered truck

Here is a story from Planet Mechanics on Green Planet about converting a small pickup to run on gas made from wood.

http://www.youtube.com/watch?v=jwR18kILPWQ

They have a non-profit to plant lots of trees in London before the 2012 Olympics, but the van that they use was burning gasoline, so they decided to see if they could do it more cleanly. They bought an old small pickup and created a wood chip to gas converter that they put in the bed. It produced 95% less hydrocarbon emissions and was carbon neutral. While not practical,
they showed that it could be done.