TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst comprises a metal oxide (preferably a metal oxide of an alkaline earth metal; especially magnesium oxide (MgO)), or a metal carbonate (preferably a metal carbonate of an alkaline earth metal; especially especially calcium carbonate (CaCO3)).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The residence time of the mixture in the tubular reactor is (1-100, preferably 1-45, especially 5-15) minutes. The contact time of the mixture with the catalyst is (1 to lower than 40, preferably 1 to lower than 20, particularly 2-8) minutes. The pressure is (5-400, preferably 5-150, especially lower than 80.9, particularly 40-80) bar. The ratio of alcohol to fat or oil is lower than 30 mole/mole. Preferred Components: The alcohol is methanol.    TECHNOLOGY FOCUS - POLYMERS - Preferred Catalyst: The catalyst is immobilized in a fixed bed, as pellets, as a coating or in a porous structure. EXAMPLE - A test transesterification for production of fatty acid alkylester biodiesel was carried out as follows. The biodiesel was produced in a tubular reactor. The reactor contained the heterogeneous catalyst immobilized on a fixed bed. Rapeseed oil and preheated methanol were compressed up to 150 bar and pumped in a tubular reactor. A correct mixing of both reactants was assured in the setup. The mixed streams were then heated up to 300degreesC in a furnace or oil bath and brought in contact with the immobilized heterogeneous catalyst. The residence time was 10 minutes. The pressure was 150 bar. After contact, the resulting stream was cooled, depressurized and collected. A comparative transesterification was carried out similarly, except that the reactor did not contain the fixed bed of the catalyst. The total volume of the tubular reactor was 20 ml. The methanol and oil were added at a rate ensuring a residence time of 10 minutes. The pressure was 150 bar. The results for the test/comparative process were as follows: % conversion = 96/29; and methanol excess (g/g) = 0.6/0.46.