TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The liquid (preferably water, methanol or ethanol) is heated by combustion of some of the organic matter in the presence of the oxygen; where supercritical liquid conditions are achieved by pressurization. The pressurization is achieved by locating the liquid in a sub-terrestrial or sub-oceanic vessel or by the use of a pump. The supercritical liquid is water with a pressure of greater than or equal to 220 bar and a temperature of 350-420 degrees C. The organic matter is present in a ground particulate form suitable for mixing into a slurry. The ratio of liquid to solid in the slurry is less than or equal to 12:1 (preferably greater than or equal to 2:1). The chemical decomposition of the organic matter is by depolymerization. Preferred Components: The oxidizing agent is selected from oxygen, hydrogen peroxide or sodium nitrate. Preferred Apparatus: The oxidizing agent introduction device is a metering device arranged for delivering a source of oxygen into or prior to the reactor. The reactor is a sub-terrestrial or sub-oceanic vessel (preferably flexible tube) positioned at a depth where pressurization of liquid to supercritical conditions occurs in use. The reaction zone is located in a lowermost region of the vessel which experiences a maximum pressure. The sub-terrestrial vessel is a vertical drill shaft. The drill shaft is arranged with a pipe that is concentric with the shaft and the tube is arranged with a pipe that is concentric with the tube and which both is arranged for the in use delivery of a flow of organic matter to the reaction zone. An annular concentric space around the pipe and within the drill shaft is arranged for the in use delivery of a flow of product from the reaction zone to an uppermost end of the vessel. The reactor is serpentine tubular or pressurizer column reactor further comprising a depressurizer located after the vessel and arranged for depressurizing the product. EXAMPLE - No suitable example given.