produce it, where ethanol, in comparison, only provides about
25% net energy [5].
Generally, homogeneous base/acid catalysts are used in commercial
biodiesel production via transesterification process. The
traditional homogeneous catalysts (base or acid) show a very good
catalytic activity in biodiesel production [6]. However, the separation
of these catalysts from biodiesel requires washing with water
which in turn results in loss of fatty acid alkyl esters (FAAE), energy
consumption, and generates large amounts of waste water [7,8].
Moreover, these catalysts cause reactor corrosion and are difficult
to recover, thus increases the overall biodiesel production cost.
The problems associated with the conventional homogeneous
catalysts can be resolved by using the heterogeneous catalysts in
the biodiesel production technology [9]. Heterogeneous catalysts
simplify the biodiesel production process; where they can be
reused repeatedly without any major loss in their catalytic activity,
making the process more economical [10,11].
The high cost of biodiesel is the key issue for a large scale
application of biodiesel as compared to that of conventional petroleum
based diesel [12]. The high cost of biodiesel is mainly
concerned with the cost of feedstock oils as both the edible and the
non-edible oils are limited. It has been reported that approximately
70e95% of the total biodiesel production cost is related to the cost