In the Cröbern bio-mechanical waste treatment plant, household and industrial waste is accepted, mechanically crushed, split in different sub-streams and then recycled.
The MBA Cröbern is designed for a total waste treatment capacity of 300.000 Mg/a.
As a result of crushing, filtering and multiple-stage separation, the mechanical treatment gives an organic fine fraction and different marketable material streams for energy recovery and material recycling. The separation of high-calorific fractions, wood, ferrous metals and non-ferrous metals enables the recycling of remarkable amounts of accepted waste.
The biological treatment is designed to achieve extensive breakdown of the organic components in the separated fine fraction. This happens through the aerobic treatment in a two-stage rotting process (intensive composting and maturing process). The treatment aims to obtain safe landfill material, which meets the requirements for storage in landfills and long-term storage facilities (DepV).
The organic and fuel-containing waste is delivered to different lines, crushed during several treatment stages, filtered, sifted, divided into different material streams.
The waste from the flat bunker undergoes a preliminary crushing process and then it is subdivided by a rotary drum screen into three fractions (fine fraction < 40 mm, middle fraction 40 – 300 mm and coarse fraction > 300 mm).
During further process stages metals and non-ferrous metals are removed from the fine fraction (< 40 mm): The remaining material stream is conveyed to the biological treatment line.
The middle fraction is led to an air separation system, that removes the light-weight materials with high calorific values (films, paper) by means of an air stream.
The coarse fraction is taken through belt conveyors back into the flat bunker to the acceptance area, then shredded by rotary shears. After that it is supplied to the treatment line again.
Ferrous metals are removed from heavy waste by means of Fe-separators and in the following treatment stages plastic selectors remove synthetic materials. The heavy waste loaded in the consolidated container is left over.
The light waste thus obtained includes mainly plastic, that after removal of the Fe-metals, undergoes a secondary shredding process together with the plastic removed from the heavy waste and the resulting material is input to the loading process.
During the biological treatment of the organic material stream, the fine fractions from the rotary drum screen is basically treated. This process aims to achieve a rapid and thorough bio-degradation process of organic substances under controlled conditions, so that after this stage the decomposed material meets the requirements of the landfill regulation.
After mechanical treatment, the material is fed into the automatic feed rotting tunnel, where intensive digestion takes place.
In the tunnel the material is intensively pressurized with air. Air flows upward through the decomposed material and provides the live microorganisms (bacteria, fungi) with oxygen. The organic carbon content in the waste is converted by microorganisms to source of nourishment and forms CO2 or it is used to enhance its own cell matter.
As the material resulting from such intensive digestion still does not meet the requirements of the landfill regulation, it must undergo stage number 2 of the ongoing the biological treatment, the so-called maturing process. The input of the digested materials into the maturing process occurs automatically.
Within 7 weeks the decomposition of still resisting, organic key constituents takes place. During this period, heap of materials are fed into a mobile converter and sprayed, if necessary.
Exhaust Air Treatment
The halls are completely closed structures that are encapsulated in sub-sections. They are vented and the exhaust air is partly used to aerate the material during intensive digestion. The exhaust air deriving from the rotting tunnel is fed into a thermal exhaust air treatment unit (RTO - Regenerative Thermal Oxidation)
Once the mechanical process air is extracted and cleaned by dust filters, it is supplied to the feeding hall.
After removing ammonia, the contaminated exhaust air deriving from the rotting tunnel is let into a fume scrubber (acid scrubbers - use of sulphuric acid) of the thermal treatment (RTO - Regenerative Thermal Oxidation).
The less contaminated air released from the feeding hall is let into the bio-filter and cleaned.
In the bio-filter air flows downwards through a filter layer, where microorganisms ensure the decomposition of organic air compounds. The exhaust air from both the RTO and the bio-filter system is released into the atmosphere through a shared chimney.
Process Water System
The waste treatment in the Cröbern MBA results in a small quantity of effluents. These effluents can be found in the digestion area as process water and downstream the exhaust air system as well as the cleaning process as condensate.
All these types of effluent are conveyed into the process water reservoir, in order to extensively reuse them.