The increasing industrialization and motorization of the world led to a steep rise in the demand of petroleum products. Petroleum based fuels are stored fuels in the earth and are irreplaceable. Apart from the problem of fast vanishing reserve and irreplaceable nature of petroleum fuels, another important aspect of their use is the extent and the nature of environmental pollution caused by their combustion in the vehicular engines. Petroleum fueled vehicles discharge significant amount of pollutants like CO, HC, NOx, soot, lead compounds and aldehydes. In view of these problems, attempts must be made to develop the technology of alternative clean burning synthetic fuels.Biodiesel is a renewable fuel comprised of mono-alkyl esters of long chain fatty acids manufactured from vegetable oils, animal fats & recycled cooking oils. It is one of the several alternative fuels that can play important role in development of energy policy. Biodiesel contains no petrochemical products. Pure Biodiesel is bio degradable, non toxic & essentially free from sulphur and aromatic compounds. Thus it is a clean burning fuel, therefore helpful in reducing emission levels and ultimately preventing global warming Biodiesel can be blended easily with petroleum diesel in various proportions to create a Biodiesel blends. B-20 (20 % Biodiesel & 80% diesel fuel) is widely used blend because it balances the property difference with conventional diesel, performance, emission benefits and cost. B-20 can be used in automotive engines with no major modifications. The present paper will outline the manufacturing main aspects of methyl esters (Biodiesel) and the various blends of itwith fossil diesel as a fuel for automotive engine.

Key words: Biodiesel, emissions, global warming and blends.