...Because you can't handle the truth, that's why! (Jack Nicolson mode off)
(Seriously) Biodiesel is an ester, which means it has a lipid (oily) part and an alcohol part. The algae or jatropha supply the lipid, the alcohol is still required.
Ask anyone who has made their own biodiesel - although they use old french-fry oil, they are also mixing it with methanol (if you want to do the reaction at room temp, the ethanol reaction requires heat) and lye.
This is dejavu all over again - Donovan had a song about this in 1973 called "the Intergalactic Laxative". Have a listen to it on YouTube: http://www.youtube.com/watch?v=0u846w66zTQ
The way to make a small fortune in the commodities market is to start with a large fortune.