Abstract: A system for pyrolysing/drying biological sludge by indirectly heating the same by means of hot fumes, characterized by the fact that it incorporates a rotary furnace secured angularly to a cover skirt and defining, with the same, a cavity in which to circulate the aforementioned heating fumes; the aforementioned skirt being supported in rotary manner on powered rollers and connection to the utility pipes and to the sludge loading/unloading means fixed to the floor being made by means of devices consisting of a first frame turning together with the furnace and the respective skirt and supporting, in idle manner by means of rolling bodies, and a second frame connected to the aforementioned pipes.