The source of Biodiesel usually depends on the crops amenable
to the regional climate. In the United States, soybean oil is the
most commonly Biodiesel feedstock, whereas the rapeseed
(canola) oil and palm oil are the most common source for
Biodiesel, in Europe, and in tropical countries respectively [68]. A
suitable source to produce Biodiesel should not competent with
other applications that rise prices, for example pharmaceutical
raw materials. But the demand for pharmaceutical raw material is
lower than for fuel sources. As much as possible the Biodiesel
source should fulfill two requirements: low production costs and
large production scale. Refined oils have high production costs,
but low production scale; on the other side, non-edible seeds,
algae and sewerage have low production costs and are more
available than refined or recycled oils.