The distinction between mechanical recycling and feedstock (or chemical) recycling is that mechanical requires physical separation, whereas feedstock recycling converts mixed PE/PP/PS/PVC into basic hydrocarbon building blocks. Thus, mechanical recycling is appropriate for the primary and secondary recycling routes discussed above, through the grinding of plastic products into pellets or flakes. Feedstock recycling technologies, whilst they can handle contaminated and mixed material, are relatively expensive.
Mechanical recycling is primarily a method of treating single polymer waste. The waste is converted into pellets or granules for extrusion into new products. This allows the addition of virgin polymer materials, pigments and stabilisers. Feedstock recycling is a relatively new recycling technology, which can be used to treat mixed polymer waste. The method used depends on the nature of the waste. For example, thermolysis is used to convert mixed plastic wastes back into the component monomers. Feedstock recycling plants require major capital investment but can handle relatively high tonnages of plastics.
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