Anaerobic treatment of residual waste using the Schwarting-Uhde process

In a two-stage anaerobic plant using the Schwarting-Uhde process, it has been demonstrated that the biological treatment of organic wastes, even residual wastes, represents an economical and ecologically sound alternative to disposal by combustion. Process residues are suitable for landfill, on the grounds of their low level of respiratory activity.

On the grounds of its variable composition and its relatively high content of organic materials, residual waste is not suitable for direct recycling.  The objective of this project was to improve the efficiency of a specific anaerobic process for the biological treatment of residual waste, and to guarantee the safe disposal of residues in future, in accordance with statutory requirements.  Process stages involving the degradation of lignocellulose have been of particular significance.

Results:

• The cost-effective fermentation of residual waste has been demonstrable, even where it has not been possible to transpose results obtained in the laboratory to a pilot plant, for reasons of licensing or cost.
• In a two-stage anaerobic plant using the Schwarting-Uhde process, 76% of the dry organic material content of residual waste has been converted to biogas, with a gas output of
• 0.4 l/g of dry organic material.
• Through the adjustment of the process technology for the anaerobic fermentation of organic components such as lignin or lignocellulose, it has been possible to improve the degradation performance to 87% at an economically acceptable cost.
• Process energy generated exceeds the energy consumption of the plant.  In consequence, the virtually complete fermentation of residual waste represents an economical and ecologically sound alternative to disposal by combustion.

Process residues will be suitable for use as landfill in future, given a level of respiratory activity (AT4 value) of less than 1 mg O2/g of residual waste.

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