Skierpage, left a comment on my Bio Fuel post below, with a link to a Wikipedia article on Bio Diesel. What really interested me was the list of plants used and their yeild per acre. Amazingly algae was the highest yeild and according to the article, can be made at existing water sewage treatment plants.
Of course the biggest problems with Bio Diesel are water and gelling. Water can condense in storage tanks and Bio Diesel gels at a higher temp than petro Diesel. Both can be a problem in colder climates. But blending the two forms of fuel seems to solve that problem.
Read the article when you have a chance, it's amazing what the benefits of Bio Diesel are.