Recycling is the process of converting waste materials into new materials and objects. The first written records of recycling dates back to the Byzantine era (400BC) and paper recycling was done in Japan in AD 1031.

There are several steps to recycling.


  • (A) waste sorting at user level and collection. We differentiate between (1) mix vs separate waste streams, and (2) residential vs centralised collection;
  • (B) industrial level sorting;
  • (C) rinsing, washing, processing;
  • (D) recycling.

There are more than 1000 types of plastics, mainly derived from petroleum. Plastics have different molecular structures and are not always compatible when it comes to recycling.

Plastics are usually divided in 3 categories:

  • thermosets / thermosetting: plastics retain strength and shape when heated;
  • thermoplastics: plastics become liquid when heated;
  • elastomers: plastics with a high elongation and flexibility capacity;
    • thermoset elastomers
    • thermoplastics elastomers

Recycling Codes

It’s a uniform system developed by the Society of Plastics Industry in 1988. It’s the universal ID card of plastics to facilitate separation and recycling.

  • 1 = polyethylene terephthalate (PET) (beverage bottles, cups, other packaging, etc.)
  • 2 = high-density polyethylene (HDPE) (bottles, cups, milk jugs, etc.)
  • 3 = polyvinyl chloride (PVC) (pipes, siding, flooring, etc.)
  • 4 = low-density polyethylene (LDPE) (plastic bags, six-pack rings, tubing, etc.)
  • 5 = polypropylene (PP) (auto parts, industrial fibres, food containers, etc.)
  • 6  = polystyrene (PS) (plastic utensils, Styrofoam, cafeteria trays, etc.)
  • 7 = other plastics, such as acrylic, nylon, polycarbonate and polylactic acid (PLA).


plastics recycling codes
plastics recycling codes


Plastic Recycling

There are several waste treatment methods for plastic recycling:

  • Mechanical recycling: plastics are processed with physical means: grinding, shredding, melting. Recycled plastics are used to form new objects. Example: PET waste is converted into textiles.
  • Chemical recycling: some polymers can be converted into monomers and re-transformed into new polymers. This process involves the use of chemicals.
  • Backfilling: construction, land reclamation and landscaping engineering. Not universally accepted as recycling.
  • Energy recovery: conversion of polymers into petroleum. Plastics are mostly made from oil / petroleum and are thus high in energy

Products derived from plastic recycling are mostly textiles (duvets), car parts (interior and bumpers), building (isolation) and packaging.

Contamination of plastic waste streams (several types of plastics get mixed up)  may be a problem. It costs too much or it’s too hard to separate the plastics. Clean, large and constant waste stream are necessary to make recycling successful.

Germany is the most advanced country in Europe with regards to plastics recycling. They use a deposit system on plastic bottles.

Some plastics are harder to recycle such as PVC.

The Chinese Recycling Scandal

Western countries export their plastic waste to China for recycling and China dumps the plastics in the Yangtze. This is probably the worse ecological scandal of mankind. The waste that is actually recycled such as steal and aluminium are recycled with energy generated from coal plants.

Cost of Recycling

China recently stopped importing waste from Western countries. Western countries will have to set up their own recycling systems and plants. This will be financed with tax and/or contributions. Taxes will have to be set and collected at national level and redistributed to local governments. There’s a risk that tax money will stick in the national treasury instead of going to local governments.



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