TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The catalysts are acids or salts, solids or liquids such as tin and its salts, zinc and its salts, titanium and its salts and esters or sulphuric acid, para-toluensulphonic acid, methanesulphonic acid or phosphoric acid, (optionally supported on resins and zeolites) and basic catalysts such as sodium hydroxide, potassium hydroxide, sodium methylate, potassium methylate, sodium carbonate, calcium hydrate.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred method: The fatty substances result from the chemical and/or physical deacidification of oils and/or fats, from the cleaving of the soaps present in the glycerines from biodiesel and/or from the distillation of the fatty substances derived from chemical or physical deacidification of oils and/or fats, in any percentage. The direct esterification with glycerol (0.7-20 mole) and the glyceric ester obtained has a neutralisation number 0-30. The reaction is carried out at 50-300degreesC, at a pressure of 0-10 bar with a basic catalyst The catalysts (0.01-5 wt.%) or without a catalyst. The transesterification reaction takes place with alcohols such as methanol, ethanol, propanol and butanol. The ester distillation feeding temperature is 0-200degreesC. EXAMPLE - Acid fatty substance (1000 g) resulting from the refining of rapeseed oil with an acidity 120 mg KOH/g, glycerol (66 g), 2-ethylhexyl titanate (4.26 g) were placed in a stirred reactor and heated. The reaction began at 130degreesC and ended at 230degreesC in 8 hours. The absolute pressure up to the sixth hour was 1 bar, in the last 2 hours the absolute pressure was residual 5-10 mbar, the final acidity of the triglyceride was 0.5 mg KOH/g. The temperature was brought to 30degreesC, the pressure was brought to 1 bar absolute and any mineral and organic acids present were neutralised with Na2CO3 (4634 mg), followed by dehydration of the mass by means of a vacuum; methanol (113 g) and sodium methylate (4.55 g) were introduced into the system. The methyl ester that forms was deprived of glycerine and of the residual methanol. The methyl ester was distilled to obtain biodiesel by means of the process that used a thin layer or molecular evaporator with ester distillation feeding temperatures 0-200degreesC, with absolute distillation pressures 0-4 bar and with distillation temperatures 150-200degreesC.