TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The feedstock is mixed with glycerin at elevated temperature in the absence of a catalyst and reduced pressure for time sufficient to convert fatty acid into glyceride.The glyceride is reacted with alcohol in the presence of an alkali catalyst, and high purity glycerin and fatty acid alkyl ester are produced.The feedstock is conditioned to remove solids before converting into glyceride.The fatty acid is converted to glyceride in a glycerolysis reactor and further glycerin is continuously added at a rate more than the stoichiometric amount of glycerin required for glycerolysis. The glycerin is continuously added to the glycerolysis reactor at a rate of 110-400% of the stoichiometric amount of glycerin required for glycerolysis.The alcohol is added at a rate of 200% of the stoichiometric amount of alcohol required for transesterification. The glyceride is reacted with alcohol and fatty acid ester and glycerin are produced.The liquid phase (I) containing fatty acid alkyl ester and liquid phase (II) containing glycerin are separated to produce fatty acid alkyl ester rich stream and glycerin rich stream, and a biodiesel containing separated fatty acid alkyl ester is recovered.The fatty acid alkyl ester rich stream is purified in a distillation or fractionation system.The pH of glycerin rich stream is adjusted to neutral and then purified by distillation or fractionation.The reaction of fatty acid and glycerin is conducted in at least two continuous stirred tank reactors.The two reactors have combined residence time of less than 500 minutes.The glyceride is reacted with alcohol at 150-250 degrees C.The fatty acid is reacted with glycerin at 20-250 degrees C, preferably 55-65 degrees C and absolute pressure of 1-250 bar, preferably 1 bar.The fatty acid ester rich stream and glycerin rich stream are separated based on density difference between liquid phases (I, II).The fatty acid alkyl ester rich stream is separated in a distillation or fractionation column into bottoms fraction, overhead fraction comprising primarily alcohol, and side stream fraction comprising fatty acid alkyl ester product.The bottom fraction comprises impurities, unsaponafiable materials, unreacted monoglyceride, unreacted diglyceride, unreacted triglyceride and fatty acid.The overhead fraction comprises essentially alcohol.The distillation or fractionation column is operated at 180-280 degrees C, preferably 180-230 degrees C and less than 2 pounds/square inch, preferably 0.1-2 pounds/square inch.The pH adjustment is performed using ion exchange media.Preferred Composition: The content of fatty acid in feedstock is 3-97 wt.%.The glyceride is reacted with alcohol and an effluent stream containing fatty acid alkyl ester is produced, fatty acid alkyl ester is purified and biodiesel containing purified fatty acid alkyl ester is recovered.The wet alcohol stream is recovered from the effluent stream.The wet alcohol stream is purified in a distillation or fractionation column to remove excess water.The pH is adjusted by addition of a mineral acid.The fatty acid and glycerin are reacted in the presence of an alkali catalyst and mineral acid reacts with the alkali catalyst to render a precipitate and a precipitate-free permeate.The precipitate is separated from the precipitate-free permeate by filtration.The precipitate is washed with methanol.The precipitate-free permeate is further separated into fatty acid alkyl ester rich stream (II) and glycerin rich stream (II).The pH of the glycerin rich stream (II) is neutralized by the addition of caustic.The fatty alkyl ester rich stream (II) is combined with the separated fatty acid alkyl ester stream (I) to form a combined stream.The combined stream is fractionated.The alcohol and water in the neutralized glycerin rich stream (II) are separated from the glycerin.The separated glycerin is further subjected to distillation or fractionation to remove high boiling impurities.The resulting glycerin stream is decolorized.Preferred Compound: The alcohol is 1-5C alcohol, preferably methanol.The conditioned feedstock is a uniform mixture of liquid lipids at 35-250 degrees C.The fatty acid alkyl ester separated in the distillation or fractionation column met ASTM D 6751.Preferred Catalyst: The alkali catalyst is sodium hydroxide and/or potassium hydroxide.Preferred Apparatus: The distillation or fractionation column contains a packing material.