Biodiesel?

 Here's one of the best websites out there for biodiesel processor plans
and instructions:
   http://www.biodieseltutorial.com/appleseedprocessor/
 More details on the processing cycle:
   http://www.brevardbiodiesel.org/EV/ev.html
 Emissions information for biodiesel vs. normal diesel:
   http://www.biodiesel.org/pdf_files/fuelfactsheets/emissions.PDF
 And the advantages and disadvantages of biodiesel:
   http://www.fueleconomy.gov/FEG/biodiesel.shtml
   http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/biodiesel.htm

 Note that the last two sites disagree on the number of vehicles that can
run on pure biodiesel. My understanding is that most engines can run on
pure biodiesel (B100). Many manufacturers don't test their engines with
biodiesel, though, and therefore don't recommend it. You can look at
biodiesel forums and find out whether or not your engine can run on
biodiesel, and the answer is almost always "yes". My VW Jetta can run on
B100 without any problems.