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Sorting of co-mingled light packaging waste to maximise recycling yields for high-quality output

In many parts of Europe, packaging waste is collected together in order to ease the waste separation task for consumers and to reduce collection costs. In these situations, a high level of recycling is needed and an advanced sorting of the co-mingled packaging waste in a material recovery facility (MRF) is considered best practice. A number of sorting technologies are used to achieve the high segregation level that enables the recycling of a very high share of the mixed packaging waste collected from households.

There is a large variation of MRF process configurations due to regional differences such as plant size, number and type of packaging waste, availability and regulatory frameworks etc. However, relevant differences exist based on the inclusion or exclusion of fibres and the types of plastics managed. In spite of the different process layouts, different sections or modules in the plants that have a standard main function can be identified.

A state of the art plant must have sufficient flexibility to efficiently accommodate these variations and typically consists of five main technical sections:

  • Feeding and preconditioning: this includes opening bags and feeding a constant flow of input material.
  • Pre-sorting: this involves removing unsuitable items.
  • Sorting: this includes several steps, e.g. separating fibre from containers; sorting fibre; sorting metal containers by using magnets, eddy currents or X-ray; first sorting of plastic containers by polymer (e.g. separation of PET bottles from other plastic containers).
  • Refining: this consists of additional sorting steps, such as further sorting of polymers by type (e.g. HDPE, PP) and colour in order for the material output quality to meet market requirements. Quality control is performed by automatic or manual sorting.
  • Product handling: this section consists of the baling processes and product storage as bales, loose material or in containers; product handling can also include loading operations for further downstream processes.

The efficiency of the MRFs is highly dependent on the in place waste collection system and the availability of markets for the sorted materials. However, an important factor for its efficient operation is the careful sizing of the plant and precise determination of its capacity.

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