TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The step of continuously drying comprises: water adsorption on a solid dessicant within the esterification reaction vessel; pumping the reaction mixture through a packed column packed with a solid dessicant and returning the mixture to the vessel; refluxing the mixture so that wet methanol is condensed and drained through the packed column and/or passing the refluxing wet methanol vapors through a rectifying column to separate water from methanol, where the wet methanol vapors are condensed and held in a side-armed holding vessel and the condensate gradually fed via a valve to a rectifying column for drying and the dried methanol is continuously returned to the vessel. The drying step comprises purging with an inert gas to further augment drying of the methanol and to renew at least one of the catalysts. The drying step dries the methanol external to the vessel. The process further comprises: removing the reaction mixture from the vessel and transesterifying the reaction mixture; and pumping the resulting oils from the vessel after reaching the predetermined value through a filter into a final transesterification vessel for final conversion into bio-fuel. The filter retains the heterogeneous catalyst for re-use in a next process cycle with new feedstock. Preferred Components: The predetermined value of FFA is 0.5%. The feedstock comprises at least one of a vegetable oil and an animal fat. The homogenous catalyst is sulfuric acid and the heterogeneous catalyst is a solid sulfonated catalyst, which is Nafion (RTM: Copolymer of sulfonated tetrafluoroethylene). EXAMPLE - A 250 ml three necked, round-bottomed, standard taper flask was fitted with a reflux condenser (terminating in a drying tube to exclude moist air), a thermometer dipping into the flask contents and stirring gland/stirring shaft assembly with paddle. Into the third neck of the flask, a stabilized poultry fat (100 g with free fatty acid (FFA) content of 50%), a solution of sulfuric acid (1.3 g) dissolved in methanol (74 ml) and Drierite (RTM: Anhydrous calcium sulfate) (50 g) were introduced and neck stoppered. The flask was heated with water bath for 1 hour at 60 degrees C, with stirring, a sample of the oil was removed and found to be 0.42% FFA.