The world’s first biogas-powered passenger train is taking its first passengers between the Swedish cities of Linkoping and Vastervik. And the biogas comes from the entrails of dead cows.
More information and pictures:
Svensk Biogas : Biogas – ren drivkraft
and an article from the BBC website
http://news.bbc.co.uk/1/hi/sci/tech/4373440.stm