Abstract: The present invention relates to an integrated method and system to produce biodiesel from a plurality of assorted feed stocks. The feedstocks are pretreated with degumming, physical refining and glycerolysis. The degumming removes impurities, except free fatty acid (FFA), from the recovered vegetable oil and the animal fats. The physical refining removes the free fatty acid (FFA) by heating the recovered vegetable oil and the animal fats and pulling vacuum to allow separation of boiling points between the oil of the feedstocks and the free fatty acids (FFA). The glycerolysis converts the free fatty acid (FFA) from the physical refining into a single methyl ester (SME). The single methyl ester (SME) is combined with the refined natural oil and unrefined natural oil to form a combined oil feedstock. The combined oil feedstock is subject to transesterification by reacting the combined feedstock oil with a catalyst and a solvent to produce biodiesel and glycerin.