And better than the bio-diesel process is the Thermal Depolymerization process. I don't know why this isn't being implemented more than it is:
http://en.wikipedia.org/wiki/Thermal_depolymerization
http://www.thermaldepolymerization.org/
http://www.res-energy.com/index.asp
http://www.usatoday.com/tech/columnist/andrewkantor/2004-01-22-kantor_x.htm