NOVELTY - The method comprises: performing a first digestion (13) of mesophilic or thermophilic types on a fraction of an organic waste; performing (16) ventilated thermal hydrolysis of the dehydrated waste with the injection of an oxidant in am amount less than that corresponding to stoichiometry for the oxidation of organic matters at a desired temperature of a heating unit; and performing a second digestion (17) of mesophilic or thermophilic types on the flow of hydrolyzed waste. The amount of injected oxidant is 20-30% of the stoechiometric amount.    USE - The method is useful for treating organic waste such as muds of sewage treatment plants to produce energy and/or sanitized organic matters (claimed).    ADVANTAGE - The method is capable of reliably and energy-efficiently treating the organic waste, and improving the production of the energy and/or the sanitized organic matters without requiring high costs for installation and exploitation.    DETAILED DESCRIPTION - The method comprises: performing a first digestion (13) of mesophilic or thermophilic types on a fraction of an organic waste; dehydrating (15) a totality of digested and undigested waste; performing (16) ventilated thermal hydrolysis of the dehydrated waste with the injection of an oxidant in am amount less than that corresponding to stoichiometry for the oxidation of organic matters at a desired temperature of a heating unit; and performing a second digestion (17) of mesophilic or thermophilic types on the flow of hydrolyzed waste. The amount of injected oxidant is 20-30% of the stoechiometric amount. The heating unit during the thermal hydrolysis consists of a steam injector (16a). The flow of waste is subjected to cooling by heat transfer to re-use the calories leaving the thermal hydrolysis for heating digesters after the thermal hydrolysis and before the second digestion. A portion of hydrolyzed waste is recycled, at an exit of hydrolysis, to the first digestion. The organic waste is heated at a temperature of 160 degrees C and under a pressure of 8 bars for 5 to 90 minutes during the thermal hydrolysis. The injection of oxidant is controlled by a measurement of carbon dioxide in a gas overhead of a hydrolysis reactor, and a staging of the injection is carried out to ensure a homogeneous reaction. A water injection in the flow of waste is carried out in an upstream entry of the second digester to ensure a dilution flow and to control the operation of the second digestion. The method further comprises: regulating vapor injection by checking the temperature in the gas overhead of the hydrolysis reactor; pretreating to remove sand according to the amount of the organic waste to be treated; and injecting acid or base during the thermal hydrolysis so that an acid pH is lower than 2, while the base pH is lower than 12. Duration of the first digestion is 14-15 days as that of the second digestion. The regulation of dilution is carried out according to the content of ammonia and a pH of exit of the second digestion. The flow of organics waste at the exit of the thermal hydrolysis undergoes the heat transfer to provide calories to a water loop. A temperature of the organic waste is controlled at the exit of the thermal hydrolysis and the dilution. The temperature control of the organic waste is provided in the entry of the first digestion by heating the water loop and/or by exchanging with the hydrolyzed waste. A biogas produced by the digestion is used as fuel to produce energy and heat. The heat of the biogas is used through an exchanger in order to provide energy necessary for the thermal hydrolysis and for reheating the digester. An INDEPENDENT CLAIM is included for an installation for treating organic waste.    DESCRIPTION OF DRAWING(S) - The figure shows a block diagram of an installation for treating organic waste (Drawing includes non-English language text).    First digestion step (13)    Dehydration step (15)    Performing ventilated thermal hydrolysis (15)    Second digestion (17)    Steam injector. (16a)