The invention relates to a fermentation device and a method for the biological degradation of a substrate containing organic material and for the recovery of the biogas that is produced in the degradation process. The fermentation device has an elongated sealed container (1) with a feed opening (26) for the substrate and removal openings (19, 20) for the degraded products. The container is equipped with several reaction volume cells (2), each of which has at least one individually driven mixing unit (3) for mixing the fermentation product. According to the invention, the substrate is not only fed into the container (1) via the front end of the fermentation device but also at other discrete feed points (6, 7, 8, 9) in the overlap or tangential region of adjacent mixing units, distributing said substrate over the length of the container.