39    AERATION OPTIMIZATION AND
EMISSION CONTROL OF
BIOLOGICAL-MECHANICAL WASTE TREATMENT
Joris Wotte, Professor and Director
Joachim Brummack, Silke Paar, Bernhard Gemende, Lecturers
Dresden University of Technology
Process and Environmental Engineering Institute
D-01062 Dresden, Germany
INTRODUCTION
After a period of testing, biological-mechanical waste treatment (BMWT) prior to disposal has
become an alternative to simple disposal or incineration. Especially in East Germany, where the
incineration capacity is insufficient, BMWT is used to counter the known problems of disposing
untreated waste; such as uncontrolled degradation, settling, leaching, and gas emissions. BMWT
represents a viable technology for a transition period of about ten years, until the new Technical
Regulation for Municipal Waste as an amendment of the Waste Act in Germany will be fully in
force. Beginning from 2005, at the latest, only waste with an ignition loss less than 5% can be
disposed of. However, realization times of thermal treatment plants are very long. The biological
stabilization of waste to be disposed of is therefore a practical approach to reduce the hazard potential of landfills during this transition period.
Much experience could be collected for the biological stabilization of waste, after the first
tests beginning 1994. A process description and first results were already reported.1 The biological stabilization is accomplished by biological-mechanical treatment. The steps of this process
are: shredding, mixing/homogenization, composting and, optionally, subsequent separation. The
composting is performed in open windrows directly upon the landfill area.
AERATION OPTIMIZATION
One of the limiting parameters for the composting process is the supply of fresh air. This is especially important during the initial period of the composting process:
(a) to keep the oxygen content high enough for a sufficient process progress (which
determines degradation rate and final organic content) and
(b) to avoid overheating of (purely vented) portions of the composting material (with
possible critical consequences for the microflora).
Although in the former investigations,1 main attention was given to the effective aeration of
these windrows, there is still a great potential for developments. This is especially true for a sufficient air supply for the composting process by passive (free thermic) aeration. Therefore, special
improved self aeration systems were developed and optimized. Additional active aeration means
are not necessary. Focus was and is on the easy and low-cost applicability directly at landfill sites.
Various Aeration Methods
For an effective aeration, the following methods could be applied:
(1) multiple turning of the windrow (improvement of free convection);
51st Purdue Industrial Waste Conference Proceedings, 1996, Ann Arbor Press, Inc., Chelsea, Michigan 48118.
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