Process and plant for treating organic residues, in particular for waste disposal and waste water purification, producing biogas

The invention relates to a process for treating organic residues, producing biogas, the residue-containing substrate being subjected to a fermentation process, which is characterised in that the substrate is divided into a relatively liquid and a relatively sedimentary phase in a first anaerobic fermentation process, and in that the relatively liquid phase is subjected to a second fermentation process, while the relatively sedimentary phase is subjected longer to the first fermentation process. A plant for treating organic residues having a stirred-chamber reactor which is provided with a stirred chamber in which a stirrer element is arranged and which is equipped with a substrate feed, a substrate discharge and a biogas outlet, is characterised in that a second reactor flow-connected to the substrate discharge is connected downstream of the stirred-chamber reactor, which second reactor likewise has a biogas outlet, and in that the substrate discharge is arranged on the side of the stirred chamber, arranged above the sediment bed established on separation of the substrate situated in the stirred chamber into a relatively liquid and relatively sedimentary phase.