A container for fermenting bio-degradable substances, the container comprising: a base and a wall, wherein an interior of the container is enclosed by the base and the wall; a rotatable agitator that protrudes into the interior and is supported in an upper bearing and a lower bearing in an installed position of the rotatable agitator in the container, wherein the rotatable agitator includes a shaft that is drivable by a drive, wherein at least one stirring paddle is arranged at the shaft and configured to co-rotate with the shaft so that substances arranged in the container are stirrable, wherein the lower bearing is arranged at the at least one base of the container and a bearing device located at a lower end of the shaft is supported in the lower bearing in the installed position of the rotatable agitator.

A biogas plant contains a fermenter vessel, in which an assembly support is mounted, preferably vertically oriented. An assembly, in particular a submersible motor driven stirrer, is retained by a height adjustment device so as to be vertically adjustable on the assembly support. Accordingly, the height adjustment device is formed by a belt drive of which a traction device is guided around at least two deflecting elements spaced apart from one another in the longitudinal direction of the assembly support. At least one of the deflecting elements can be driven in rotation by a driving device and the assembly is coupled to the traction device in such a way that when the deflecting element is rotationally actuated in a first direction the assembly is raised and when the deflecting element is rotationally actuated in a second, opposite direction, the assembly is lowered.