Introduction
With the increased concern over the depletion of fossil fuels
worldwide, the search for alternative energy/chemical sources has
been becoming urgent more than ever before. Biodiesel produced
from renewable animal or plant oil has been one of two most
commonly explored bio-fuels (the other is bio-ethanol) that could
effectively reduce the global dependence on the fossil fuels and the
greenhouse gas emission.
Biodiesel is mainly produced by the transesterification of animal
fats or vegetable oils (triglyceride) with methanol in presence of an
alkali or acid catalyst [1,2]. During the transesterification process in a
biodiesel plant, crude glycerol is the primary byproduct, accounting
for about 10 wt% of the biodiesel product [3,4].