2.6. Current techniques available for converting non-edible oil to
biodiesel
The technology for converting edible oil to biodiesel has been
well established, however, the main concern for converting nonedible oil into biodiesel is always associated with the high free
fatty acid (FFA) content. For the production of biodiesel from
jatropha, P. pinnata and rubber seed oil, high FFA content in the oil
has caused conventional transesterification reaction especially the
alkaline-catalyzed process not feasible. The FFA will react with
alkaline catalyst to produce soap that inhibits the separation of
ester and glycerin. A two-step transesterification process is
reported by several researchers as the best method to produce
biodiesel from non-edible oil. At the initial step, the FFA content of
oil is reduced by acid-catalyzed esterification process; meanwhile,
at the second step, an alkaline-catalyzed process is used to
convert oil and methanol to methyl esters and glycerol. This twostep process was found to be very effective with the yield of
biodiesel in the overall process reaching up to above 90% [8–10].
However, the disadvantage of this process is the requirement of
two steps, leading to higher production cost as compared to
conventional process.