This yield is similar to those obtained
by other authors who transform FFAs into biodiesel using
other catalysts. For example, Hayyan et al. (21) reduced the FFA
content of sludge palm oil by sulphuric acid catalysed
esterification. This FFA content was reduced from 23.2% to less
than 2% (conversion of around 91.4%) using 0.75 wt% sulphuric
acid, an 8:1 molar ratio of methanol to oil (2.7:1 expressed as
methanol/FFA, as opposed to 1.5:1 in the present work), 60C
(25C in this work) and 60 min for a similar conversion to that
attained in this work.