Kelkar et al. [22] studied esterification of fatty acids (in range
C8–C10) for biodiesel production using acoustic and hydrody-
namic cavitation. Santos et al. [23] produced biodiesel from
Oreochromis niloticus oil using ultrasound. Deng et al. [24] studied
ultrasonic esterification and transesterification of Jatropha curcas
L. oil for biodiesel production. All these studies have used sulfuric
acid as a catalyst to convert FFA to FAME. A study on the effect of
ultrasonic energy on vegetable oil based biodiesel was carried out
by Lee et al. [25]. Recently, biodiesel produced from non-edible
oils using a sequential combination of microwave and ultrasound
[26]. Likewise, biodiesel was prepared from Nag champu oil with
high acid value using sonoreactors [27]. Waste cooking oil was
used as a low cost raw material for synthesis of biodiesel [28]. In
recent literature, few studies have used chemical reactors to treat
acidic oils such as low grade crude palm oil [29,30]. The
application of ultrasonic energy for the treatment of high FFA
content such as LGPO and for biodiesel production has not been
yet studied. Therefore, the main aim of this study is to use LGPO as
a cheap raw material, in the presence of an acidic catalyst using
ultrasonic energy. Optimization of various parameters was
conducted to find the optimum conditions for the pretreatment
of LGPO using a sonoreactor. These included the effect of different
acids, catalyst dosage, molar ratio, and temperature. Finally,
characterization of the biodiesel