TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst includes a calcium-containing catalyst. The calcium-containing catalyst includes 10-80 wt% of calcium. The catalyst includes a porous silica-metal oxide composite catalyst. The amount of the catalyst is 1-10 wt%, with respect to the weight of the feedstock.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The biodiesel production system further comprises a mixer (104) coupled to the reactor and configured to combine the catalyst and the (1-5C)alcohol to produce a catalyst mixture and to convey the catalyst mixture to the reactor. The first alcohol stripper is coupled to the mixer, such that the first unreacted portion of the (1-5C)alcohol is recycled back to the reactor. The second alcohol stripper is coupled to the mixer, such that the second unreacted portion of the (1-5C)alcohol is recycled back to the reactor. The biodiesel production system further comprises a glycerolysis unit coupled to the first alcohol stripper and configured to react the glycerol with a free fatty acid to produce an additional, glyceride-containing feedstock. The biodiesel purification unit is configured to separate soap from the second phase, and further comprises an acidulation unit coupled to the biodiesel purification unit and the glycerolysis unit and configured to react the soap with an acid to produce the free fatty acid.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: In the process: preparing the catalyst mixture includes contacting the catalyst with the (1-5C) alcohol for a duration sufficient to activate the catalyst, where contacting the catalyst with the (1-5C)alcohol is carried out for a duration of 1 minute to 1 hour and at 25-80 degrees C; combining the catalyst mixture with the feedstock is carried out such that an amount of the catalyst is 0.5-30 wt%, with respect to a weight of the feedstock; reacting the reaction mixture is carried out using multiple reactors in a multi-stage configuration; reacting the reaction mixture is carried out at 40-100 degrees C and at a pressure of 0.5-2 atmosphere; and separating the fatty acid (1-5C)alkyl ester includes separating a fatty acid salt from the reaction mixture. The process further comprises: recycling the catalyst and the unreacted portion of the (1-5C)alcohol for a subsequent reaction; reacting the glycerol with a free fatty acid to produce an additional, glyceride-containing feedstock; and reacting the fatty acid salt with an acid to produce a free fatty acid. Preferred Components: The (1-5C)alcohol includes methanol. EXAMPLE - No suitable example given.