Dynamic composting process in rotating drums
Organic waste can also be treated efficient by aerobic composting in rotating drums. The technical construction is shown in illustration 2.
 Illustration 1: 3-D-modell of a drum composting plant with two units; Calvia, Mallorca
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Here the first intensive composting process takes place in a closed, forced aerated and temperature controlled steel drum with a specially developed protection layer against corrosion inside. The process is a dynamic system with the possibility to move the drum controlled with a speed of up to 1 rotation per minute.
Thereby compared to static systems a very efficient aeration of the organic waste and an evently distributed heat is ensured in the organic waste. The temperature is measured directly in the organic waste not in the air and is continuously controlled by the air flow. As the drum is a closed system operated with underpressure the odour loaded air leaving the drum will be sucked off with a ventilator and will be treated in a biofilter. |
Illustration 2: Technical construction of rotating drum with main elements
The drum is operated as a batch system and thereby the retention time and the temperature can be controlled and monitored continuously. The loading with organic waste by a hydraulically operated flap can be done with front end loader or automatically. The organic waste is composted usually 5 – 7 days in the drum. After 5 days the sanitation requirements of the BGK for epidemic-hygienic effectiveness are fulfilled. After the composting process is finished in the drums the fresh compost is automatically unloaded at another place by a hydraulically operated flap. Thereby it is ensured that the unclean area and the clean area are strictly separated. Impurities are removed after the intensive composting by mechanical separation with magnetic separator, screening and wind blower. For final compost maturation a simple windrow composting process follows the intensive composting phase in the drum. The capacity of the plants can easily be extended by adding further drum units. The drum system is a possibility to realize economic projects also for smaller amounts of organic waste.
Illustration 3 and 4: Drum composting plant for biowaste in Calvia, Mallorca; Capacity 5.000 t/y
The capacities of the composting plant can be extended stepwise by installing additional drums. The drum technology with a following windrow composting is a economical interesting solution also for smaller capacities.
In Germany seven drum composting plants are in operation. On Mallorca two plants have been realized from Ros Roca, one in Calvia and in Palma de Mallorca.
