TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The alkali catalyst is sodium hydroxide, potassium hydroxide, sodium methoxide or potassium methoxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The glycerides are produced by converting fatty acids in a feedstock. The glycerides are prepared by mixing the feedstock and glycerin at an elevated temperature in the absence of a catalyst. The step (a) comprises reacting the glycerides with the at least one alcohol in the presence of an alkali catalyst to produce a fatty acid alkyl ester stream containing glycerin and fatty acid alkyl esters. The feedstock is conditioned to remove solids prior to converting the feedstock to glycerides. The product of step (a) is separated gravimetrically into a fatty acid ester rich stream and a glycerin rich stream and further introducing to the glycerin rich stream an organic acid and producing a purified glycerin rich stream from it. The process is continuous. The glycerides of step (a1) are: obtained by reacting a feedstock containing free fatty acids with glycerin; and reacted with the at least one alcohol in the presence of an alkali catalyst. Preferred Components: The organic acid is a weak organic acid comprising acetic acid (preferred), formic acid and propionic acid. The alcohol is a 1-5C alcohol, which is methanol. The fatty acids are provided by fatty acid alkyl esters. EXAMPLE - Rendered yellow grease with a free fatty acid concentration (20 wt.%) was fed to continuous stirred tank glycerolysis reactors at 100 pounds per minute (lbs/minutes). The grease was filtered and titrated intermittently as it was fed to the glycerolysis reactor. Glycerin was added at a rate of 13 lbs/minutes. The temperature of the grease and glycerin mixture was raised to 210 degrees C as it was fed into the first of the glycerolysis continuous stirred tank reactors. In the reactor, the pressure was reduced to 2 psia and the temperature was maintained at 210 degrees C. The vessel was fitted with a high intensity agitator to keep the immiscible liquids in contact. Water vapor produced by the reaction was removed through vents in the reactor headspace. The residence time in each of the glycerolysis reactors was 2.5 hours. The fatty acid concentration leaving the second reactor was maintained at 0.5 wt.%. The product from the glycerolysis reactors was cooled to 50 degrees C and fed continuously to the transesterification reactors in which a solution of potassium hydroxide in methanol was added. The potassium hydroxide was added at a rate of 1.1 lbs/minutes and mixed with 22 lbs/minutes of methanol. The transesterified product was then fed to a phase separation tank. The bottom, or heavy phase was added to an acidification reactor, where the potassium hydroxide catalyst was added in the transesterification step was reacted with 1.96 lbs/minutes phosphoric acid. The soaps converted to free fatty acids and the potassium hydroxide was neutralized. The monobasic potassium phosphate precipitate was filtered out and the filtrate was fed to a second phase separation tank. The top, or light, phase was mixed with the light phase from the first phase separation tank and fed to the fatty acid methyl ester fractionation column. The pH of the heavy phase was adjusted back to 7.5 with potassium hydroxide and fed to the glycerin fractionation column and worked up to give biodiesel.