TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The porous structure is reticulated foam. The porous structure is selected from mesh materials, foam, or foam like structures consisting of aggregations of hollow fibers, fibers, sponges, granules or spheres. The co-solvent is carbon dioxide, nitrous oxide, sulfur dioxide or sulfur hexafluoride. The transition metal or transition metal oxide or silicate, or an oxide or silicate of zirconium, titanium, manganese, or nickel. The catalyst is transition metal, transition metal oxide or silicate, or oxide or silicate of aluminum, silicon, magnesium, or calcium. The transition metal oxide is selected from nickel oxide, titanium oxide, zirconium oxide, or manganese oxide. The porous structure comprises the catalyst. The catalyst enters in the vessel through the input.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Vessel: The vessel additionally comprises a regulated heating system for maintaining the temperature greater than 200 degrees C, where the temperature is maintained near or above the supercritical temperature of the reactant mixture; system of pumps, tubing and pressure regulators (204) for maintaining the pressure greater than 5 mPa, where the regulator is a pressure regulating valve; and system for flow control of the substances entering and exiting the vessel. A co-solvent enters the vessel through the input, either alone or in combination with the lipid substance and alcohol. The pressure is maintained near or above a supercritical pressure of the co-solvent; or near or above a supercritical pressure of the alcohol. The vessel additionally comprises a catalyst. The body is cylindrical in shape; and is 10-2000 cm (preferably 30-200 cm inches) in length, and has an inner diameter of 1-200 (preferably 8-20) cm.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The co-solvent is ether, and ester, dialkyl carbonate, 1-12C alkane, or halogenated compound. The lipid-containing substance is a fatty acid or its ester (preferably waste oil, vegetable oil, animal oil, or animal fat). EXAMPLE - A reaction vessel consisted of 316 Stainless steel cylinder, 30 cm in length, with an inside diameter of 1.9 cm. Virgin canola oil (as lipid feedstock (free fatty acid content of 0.13%, as oleic acid, determined by NaOH titration)) and anhydrous ethanol (as the alcohol reactant) were pumped via separate channels of an Eldex high pressure HPLC pump through sections of 3 mm stainless steel tubing through a condensing fluid heat exchanger, then brought into contact through a piping'tee'before entering the cylindrical reactor. The reactor was tested in an'empty'configuration, without a porous structure, as well as in a configuration where a porous aluminum oxide foam (40 pore per cm) was fitted to the inside of the reactor vessel, completely filling the vessel. The reactants were preheated to approximately 260 degrees C and were held at this temperature in the reaction vessel as well, for the duration of the reaction. The ratio of alcohol to oil was set by a flow rate of approximately 40 to 1 as the molar ratio. A pressure of 21 mPa was maintained in the reactor by a back pressure relief valve. Upon exiting the valve, the reaction mixture was cooled by transit through a coil of 3 mm stainless steel tubing immersed in a water bath, then collected. The alcohol was removed by rotary evaporator (20 mm Hg, 90 degrees C water bath) and 0.1 ml sample of the residue was silated and analyzed by chromatograph system for determination of fatty acid ethyl ester content. The ethyl ester output relative rate and relative ester output per minute from reactor tube with alumina foam/without foam was found to be 20.15/10.43 and 3.30/1.41 respectively. Thus the result demonstrates the effectiveness of the addition of the aluminum oxide foam to the reaction vessel in that the relative rate of ester formation was well over twice as fast with incorporation of the porous structure compared to the reactor without the porous alumina foam.