(DE4102210-A)      Process for controlling the air flow amt. of aeration air during the compositing of organic waster and/or clarifier sludge is claimed. The material to be composted flows through a closed reaction container from an inlet opening to an opening in counterflow to the aeration air. The O2 content of the air leaving the reaction container is monitored continuously and the air flow amt. starting from a min. value is raised to a max. value until the measured O2 content of the outlet air has dropped to a min. value increased and then reduced again. The min. value of the air flow amt. is chosen such that the O2 content of the exit air has begun to fall w.r.t. the O2 content of the inlet air, and the air flow amt. between the minimum value and the maximum value is controlled as a monotonously reducing function of the measured O2 content.    USE/ADVANTAGE -   The process allows close control of the amt. of air flow to that which corresponds most closely to the value required at all stages of the process to give optimum composting of organic waste and/or clarifier sludge    (US5234596-A)      To control the throughput rate of aeration air when composting organic waste and/or sewage sludge migrating through a closed vessel from inlet to outlet with the air flowing counter-curent, the oxygen content of the air evacuated from the vessel is continuously monitored, and starting from a min. value the air rate is increased to a max. until the oxygen content has dropped to a min. and is decreased again when the oxygen content increases.    The min. air throughput value is set at that at which the oxygen content just begins to drop compared to that of the air supplied, and throughput rate is controlled between the min. and max. values as a monotonically descending function of the measured oxygen content.    ADVANTAGE -   Keeps the throughput rate at that required for optimum composting.    (EP496271-B1)      Process for controlling the aeration air flow rate in the composting of organic wastes and/or sewage sludges which pass through a closed reaction vessel from an intake orifice to a discharge orifice and in the course of this the aeration air fed to the reaction vessel flows through them in countercurrent, a measured value being continuously formed corresponding to the O2 content of the exhaust air removed from the reaction vessel and the aeration air flow rate, starting from a minimum value, being increased up to a maximum value until the measured O2 content of the exhaust air has decreased to its minimum value and being decreased again in the event of an increase of the O2 content of the exhaust air, characterised in that the minimum value of the flow rate selected is that value at which the O2 content of the removed exhaust air just begins to decrease in comparison with the O2 content of the aeration air fed, and in that the flow rate is controlled between the minimum value and the maximum value as a monotonically decreasing function of the measured O2 content.