Biodiesel from algae intrigues me because from what research I have seen on it, it seems feasible. I was talking to my sister, a bioengineer, about it because she once worked for a start-up that was trying to cultivate algae for vitamin A. I think she said that the problem was finding a cold water species that was suitable for northern climes. From memory, I saw at least one report that may have found a species in the waters of Washington or Oregon that could be a contender.
Here’s an interesting oddities, stumbled upon:
http://store.homebiodieselkits.com/
http://peswiki.com/index.php/Directory:Biodiesel_from_Algae_Oil