NOVELTY - Composting material is supplied with conditioned air in storage locations or containers (5). Temperature, moisture, partial pressure and air quantity are controlled from measurement in the air outlet- (14) and supply- (13) locations. The thermal flux is determined at inlets and outlets of the storage locations or containers (5). Airflow extraction is controlled accordingly. Compost is moistened and the humidity of air from each location is determined. The air leaving, is controlled in terms of nominal moisture and temperature, to suit requirements of the filter or purification plant which follows.    USE - A composting system.    ADVANTAGE - The plant is controlled continuously, for optimum processing conditions. It is compact and environmentally friendly. All relevant parameters are measured and are under computer control. Plant operation provides a flow of outlet air at the correct condition for post-filtration and purification, before release from the plant.    DETAILED DESCRIPTION - Preferred features: The conditioning plant (10) air humidifier operates independently of the irrigation plant (16) which directly moistens the compost itself. Irrigation plant water control valves are connected to the control system (15). Compost storage containers (5) are moved for loading and unloading. They are placed in a climatically-controlled building, air conditions being controlled as described. The computer individually controls air supplied to, and processing in, each container (5). Moistening systems for the compost can be switched individually. Flow direction in the closed composting containers is reversible. The extraction unit has central blower (4), if appropriate a Roots blower. This is connected to extraction lines from the composting containers or locations. In the extraction manifold (2) heat exchangers (9, 11) remove process heat, preferably supplying it to a heat pump. A fresh air connection is made into the process air outlet line. The conditioning plant has a fresh air scrubber. Its thermodynamic state is controlled by a heater, especially formed by the condenser of a heat pump in the extraction manifold. The heat pump can be reversed to cool process air at the inlet and heat extracted air. The outlet air scrubber is centralized, especially cooling outlet air with fresh air, and is located in the suction line or after the extractor.    DESCRIPTION OF DRAWING(S) - A schematic diagram of the plant, partially in plan view, is provided.    extraction manifold (2)    central blower (4)    containers (5)    heat exchangers (9, 11)    conditioning plant (10)    air supply measurement point (13)    air outlet measurement point (14)    computerized control system (15)    irrigation plant (16)