It is particularly important to recycle fossil-based plastics rather than incinerating them (thermal recycling) or dumping them in the environment after they have been used once. In many municipalities in Switzerland, we can dispose of our plastic waste – or to describe it more accurately, our mixed household plastics – in one of the many collection bags for plastics, so that it can then be sorted by machine and recycled. 1
However, the recycling process soon reaches its limits. Mechanical recycling is most useful in environmental terms when the recycled material replaces as much primary material as possible. This means that the CO2 emissions from production and incineration can be avoided and the plastic does not make its way into landfill or into the environment. 2 But replacement of new plastics requires high-quality recycled material – and this is precisely where the problem lies.
Chemicals can disrupt the recycling process
It is important to be aware that we produce and use a huge variety of different plastics. They consist of polymer chains that are made up of repeating monomer units and, depending on their intended purpose, contain many additional chemicals, including stabilisers, plasticisers and flame retardants, which give the plastics the necessary properties. In a report for the UN Environment Programme, we identified up to 13,000 chemicals used in plastics. 3 Many of these substances are potentially harmful to human health and to the environment. Nevertheless, in some cases they are not adequately regulated (see ETH News).
