was transesterified with methanol using alkaline catalysts such as
KOH and NaOH and different molar ratios of methanol to oil
(4.5:1, 6:1, and 9:1) [6]. The optimum conditions developed for
production of good quality biodiesel from used sunflower oil
were:molar ratio ofmethanol to oil 6:1,with1%ofKOH, at 25 °C
and reaction time of 30 min. Transesterification of processed
waste cooking oil (citric acid was added to waste cooking oil to
remove solids) and unprocessedwaste cooking oil was carried out
with methanol using KOH (1.75 wt.%) and 1:6 molar ratio of oil
to alcohol at room temperature [7]. Excess catalyst was used to
neutralize free fatty acids (FFA) present in waste cooking oil. The
ester yield was 51 wt.% with processed waste oil and 58 wt.%
with unprocessed waste cooking oil. A process was developed by
Canakci [8] where the high free fatty acid (FFA) feedstock was
initially treated using acidic catalyst to reduce the FFAlevel below
1%. The pre-treated feedstock with FFA less than 1% was then
transesterified with methanol using alkaline catalyst. It was
observed that two-step acid catalyzed esterification followed by
alkaline catalyzed reaction improved the ester yield [8].