The transesterification reaction to produce biodiesel in the presence
of basic homogeneous catalysts, e.g. KOH, NaOH or methoxides,
has been extensively investigated in the last decade [1–4]. It
is well established that this alkaline catalyzed transesterification
is strongly affected by the presence of free fatty acids [4,5]. The
presence of these acids in concentrations higher than ca. 2% can
hinder the reaction and form surface active molecules with significant
complications in the purification step due to the formation
of stable emulsions [6].