NOVELTY - A bioreactor (1), for microbial conversion of solid and/or paste materials (2), having a gas and/or fluid delivery where at least part of the feeds (6) are deployed in a semicircular zone of the reactor trough (4), under the axis of the segment screw conveyor (5), is new.    USE - The bioreactor is for an aerobic degrading of waste materials, with a significant organic matter content.    ADVANTAGE - The system gives an effective feed of gas, and especially air, into the bioreactor with penetration into the waste materials being processed, and with a trouble-free screw conveyor operation.    DETAILED DESCRIPTION - A bioreactor having gas and/or fluid feeds which deliver the gas/fluid under pressure into the material being moved in the reactor trough, and then drawn through the material by a vacuum, is new. The ends of the gas/fluid feeds are at a perforated plate, forming the wall of the reactor trough, or they end in jets to spray the material in the trough. The bioreactor can have at least two reactor troughs, parallel to each other. The segment screw conveyor has conveyor segments with a shaft extending radially from the conveyor axis, with a head section at the free end of each shaft. The free end of each shaft may be curved to the conveyor axis. The head sections are aligned on the pitch direction of the conveyor screw line. The radial outer surfaces of the head sections can be fitted with projecting teeth. The screw conveyor has a programmed drive, to be operated at time intervals in a forward direction and at time intervals in a reverse direction. The time intervals are equal, or the reverse movement time span is shorter than the forward movement time. The screw conveyor is rotated at a slow speed of at most 10 rotations/hour. The material feed into the reactor trough is at the start of the screw conveyor path, and the extraction point is after the end of the trough or close to its free lateral side. The reactor trough, or the whole bioreactor, can be tilted by up to 90 degrees longitudinally from the horizontal function position. At least one heat exchanger and filter cools the exhaust and filters the exhaust gas and heats the gas fed into the bioreactor.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic cross section through a bioreactor.    Bioreactor (1)    Waste materials (2)    Reactor trough (4)    Segment screw conveyor (5)    Gas/fluid feeds (6)    Conveyor axis (7).