NOVELTY - Producing biodiesel involves adding to feed-stream having glyceride of fatty acid and free fatty acids (at least 1 wt.%), water immiscible alcohol to form mixture; forming ester of free fatty acid and alcohol by heating in presence of acidic catalyst and stripping water and some alcohol; adding glycerol to form second mixture; forming glycerides of free fatty acids by heating it and stripping alcohol; adding 1-4C alcohol to form third mixture; and forming ester of fatty acid and alcohol and glycerol byproduct, by heating in presence of catalyst having sodium/potassium alkoxide of alcohol.    USE - For production of biodiesel (claimed) fuels.    ADVANTAGE - The method provides efficient production of biodiesel fuels using waste oil feeds containing high concentrations of free fatty acids. The method is efficient, low-investment process for converting high fatty acid content feeds to biodiesel fuel. The method allows feed of relatively high free fatty acid content to be used in production of biodiesel at mild conditions using simple equipment in relatively short batch or residence time with excellent yields and improved properties. The method provides an efficient process for conversion of high fatty acid content feed to biodiesel fuel. The method provides relatively rapid esterification of free fatty acids to glycerides; a simple, clean separation of water of reaction; effective catalyst concentration with negligible contribution to cost or acidity; a built in opportunity to improve cetane rating; and a process which uses simple and commonly available equipment.    DETAILED DESCRIPTION - Producing biodiesel involves providing feed stream comprising glycerides of at least one fatty acid and free fatty acids (at least 1 wt.%); adding water immiscible alcohol to the feed stream to form a first reaction mixture, where alcohol is added in a molar excess relative the amount of free fatty acids in the feed stream; forming an ester of free fatty acids and alcohol by heating the first reaction mixture in the presence of an acidic catalyst and stripping water and some of water immiscible alcohol from the first reaction mixture; adding glycerol to the ester thus produced to form a second reaction mixture; forming glycerides of the free fatty acids by heating the second reaction mixture and stripping the water immiscible alcohol from second reaction mixture; adding at least one 1-4C alcohol to the glycerides thus produced to form a third reaction mixture; and forming ester of the fatty acids and at least one 1-4C alcohol and a glycerol byproduct, by heating the third reaction mixture in the presence of a catalyst comprising a sodium or potassium alkoxide of the at least one 1-4C alcohol.