lowering energy costs. In general, the predominant energy policies have been divided into two categories:
(1) the development of renewable energy resources and (2) the recycling and reuse of waste energy.
There are increasing interest in developing alternative energy resources, which include hydrogen
cells [3], solar energy [4], and wind power [5]. However, these technologies are still at the developing
stage and the cost of applying them is high. Biomass is the only renewable energy resource that can lead
to competitive prices for liquid fuels in transport. Many benefits of using this renewable resources are
increased environmental protection, lower toxic gas emissions, lower level of oil imports (67% of oil is
for transportation fuels), and increased safety of fuel supply [6].
Bio-diesel is the result of a simple trans-esterification reaction using vegetable oil and methanol as
substrates (Fig. 1). The most commonly used catalysts in trans-esterification reactions are NaOH, KOH
and H2SO4. The starting oil and methanol are generally heated and stirred with the catalyst or else, in the
case of the basic catalysts, the base is first dissolved in the methanol prior to addition. Trans-esterification
is not the only route to production of fatty acid methyl esters. An alternative approach is to hydrolyze all
tri-glycerides to free fatty acids, and then directly esterify these fatty acids with methanol. However,
trans-esterification is the process of choice in the majority, if not all, of the commercial biodiesel
production facilities that have come on line. The preparation of biodiesel by trans-esterification was
shown in the Fig.1.