NOVELTY - Methanization of an organic matter which is at least partly solid involves introduction of the organic matter into a first reaction space; hydrolysis of at least a part of the solid organic matter and acidogenesis of the organic matter within the first reaction space; discharge of the organic matter from the first reaction space via a first extraction unit; introduction of at least a part of the organic matter discharged from the first reaction space into a second reaction space; and acetogenesis and methanogenesis of the organic matter present within the second reaction space.    USE - The process or apparatus is useful for methanization of organic matter which is at least partly solid (claimed).    ADVANTAGE - Two-step process for methanization of organic matter is provided in which the parameters of each of the steps are controlled independently of one another in order to obtain a satisfactory overall reaction yield according to the nature of the organic matter used in the methanization process. The process and apparatus make it possible to have a better yield by optimizing the treatment times.    DETAILED DESCRIPTION - Methanization of an organic matter which is at least partly solid involves introduction of the organic matter into a first reaction space; hydrolysis of at least a part of the solid organic matter and acidogenesis of the organic matter within the first reaction space; discharge of the organic matter from the first reaction space via a first extraction unit; introduction of at least a part of the organic matter discharged from the first reaction space into a second reaction space; acetogenesis and methanogenesis of the organic matter present within the second reaction space; and discharge of a first digestate from the second reaction space via a second extraction unit. The step of discharge of the organic matter from the first reaction space is activated according to a degree of hydrolysis of the solid part of the organic matter introduced within the first reaction space, and in that, after the discharge of organic matter from the first reaction space, no solid part of the organic matter extracted is reintroduced into the first reaction space. An INDEPENDENT CLAIM is included for a methanization apparatus for methanization of organic matter which is at least partly solid, comprising a first reaction space designed for carrying out a hydrolysis and also an acidogenesis of the organic matter and comprising a first inlet for organic matter and also a first outlet for organic matter, a second reaction space designed for carrying out an acetogenesis and also a methanogenesis of organic matter and comprising a second inlet for organic matter and also a first outlet for a digestate, and first controllable extraction unit designed for extracting organic matter from the first space via the first outlet and for transferring this organic matter to the second inlet, where the apparatus also comprises first measuring unit for measuring a degree of hydrolysis of the solid part of the solid organic matter contained in the first space, a first controller having a first measuring inlet connected to the first measuring unit and a first control outlet connected to the first controllable extraction unit, the first controller being configured for controlling an activation of the first controllable extraction unit according to a degree of hydrolysis provided by the first measuring unit, and in that no unit for returning solid organic matter originating from the first reaction space to the first reaction space is present.