...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.
Use the Force, Luke.