Mechanical-Biological Treatment

Humification processes and fate of humic substancesduring pretreatment and landfilling of residual municipal solid waste

Investigations confirm that compliance with the limiting values for loss on ignition and total carbon content defined in the Technical Instruction on Municipal Waste is not possible where mechanically-biologically pre-treated residual waste is used as landfill. At the same time, the limited microbial degradation and conversion processes observed are reflected in the minimal emissions generated.

Summary

The Technical Instruction on Municipal Waste will be brought into force in Germany on 1st June 2005.  After this date, residual wastes which are to be used as landfill will need to be pre-treated by thermal or mechanical-biological processes in order to ensure compliance with limiting values of <5% of dry material and <105 mg/m3 for loss on ignition and total carbon content (TOC) respectively.

Since these limiting values do not provide an adequate representation of biological degradation processes and emission behaviour during mechanical-biological pre-treatment, alternative parameters and associated limiting values have been investigated as a means of ensuring the ecologically harmless dumping of landfill material in accordance with the terms of the Technical Instruction on Municipal Waste.

To this end, this project involved the investigation of nine samples of mechanically-biologically pre-treated residual waste, which have been compared with residual waste samples from landfill simulation trials.

Results:

  • As expected, none of the mechanically-biologically pre-treated samples was able to achieve compliance with the landfill values defined in the Technical Instruction on Municipal Waste for loss on ignition and TOC content in the solid.
  • The cellulose/lignin ratio and the basal/potential respiratory activity have proved to be suitable alternative parameters.
  • The carbon nitrogen (C/N) ratio was only suitable for the description of aerobic processes.
  • The comparison with landfill simulation samples produced the following maximum degradation rates for mechanically-biologically pre-treated residual waste: 99% TOC, 90% carbohydrates, 90% of the alkyl-/O-alkyl-C-ratio and 93% respiratory activity.

Conclusion:

Notwithstanding a synthetic material content of 20 – 40% (TOC), microbial humification processes and associated emissions will only be anticipated to a limited extent where mechanically-biologically pre-treated residual waste is used as landfill.

Project Participants

Implementing Institutions

TU München (Lehrstuhl für Bodenkunde)

More Project Information

Project title: Humification processes and fate of humic substancesduring pretreatment and landfilling of residual municipal solid waste

Project number: 1471054/9

Project period: 1996 - 1999

Project region: Germany (Bavaria)

Project contact:

Frau Prof. Dr. Kögel-Knabner

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Source: German National Library of Science and Technology Hannover (TIB)