Abstract
This paper reviews recent developments on the production and characterization of biodiesel as well as the experimental work carried out by many researchers in this field. Biodiesel is a renewable substitute fuel for petroleum diesel fuel made from vegetable or animal fats by a monoalcholic transesterification process. Biodiesel is produced by the transesterification reaction of triglycerides of vegetable oils with methanol with the help of basic, acidic and enzymatic catalysts. Methanol is the commonly used alcohol in this process, due in part to its low cost. Methyl esters of vegetable oils have several outstanding advantages among other new-renewable and clean engine fuel alternatives. Transesterification of vegetable oils in supercritical methanol are carried out without using any catalyst. In the supercritical methanol transesterification method, yield of conversion rises 95% in 10 min. Viscosity of vegetable oils (27.2-53.6 mm
2
/s) is reduced in vegetable oil methyl esters (3.59-4.63 mm
2
/s). The most important variables affecting the methyl ester yield during the transesterification reaction are molar ratio of alcohol to vegetable oil and reaction temperature. Biodiesel has become more attractive recently because of its environmental benefits. Biodiesel is also better than diesel fuel in terms of sulfur content, ash point, aromatic content and biodegradability.