A plant for biological degradation of organic material through fermentation for production of biogas comprises a closed contained (1) for the fermentation, one or more openings (7) for removal of biogas produced in the container in the upper part of the container, members (29) configured to be driven to stir the organic material inside the container as well as members (17, 18, 21, 22) configured to be controllable to generate heat for heating the organic material in the container. At least three zones in a row between a first and a second end of the container are ar-ranged to be consecutively passed by biological material fed through the container, and each zone has at least one stirring member controllable separately from the stirring members be-longing to the other zones.
