Plastic Recycling: 3 Reasons It's Failing
Updated: Mar 17
We live in a plastic society. In 2016, 335 million tonnes of plastic were produced globally and this number is expected to reach a staggering 1,124 million tonnes by 2050. Recycling plays an important role in extending the life cycle of materials and subsequently reducing demand for the production and manufacturing of virgin materials, however its application to plastics is limited. This is in part due to the highly heterogeneous nature of plastics – ‘plastic’ is an overarching term that describes thousands of different polymers which differ in chemical structure and therefore physical properties. Adding to this complexity is the diversity in product design and types, rendering recycling of household waste a difficult task.
As a result, virgin materials are often favoured over recycled materials due to their poor quality. If we want to transition to a circular economy, we need to understand the limitations of our current recycling systems and address the challenges that prevent optimal plastic recycling.
Household recycling streams accept mixed recycling. For us consumers, this is fantastic news. Minimal sorting requires minimal brainpower – we just place our plastics into the recycling and don’t give it another thought. However, most plastics are coated with additives and while these chemicals improve the functionality of polymers, their potential to contaminate food is widely documented. As a result, regulatory demands were imposed to control the composition of plastic used to generate recycled material for food packaging. Unfortunately, because our recycling streams create melting pots of plastics, the composition of the recycled end-product cannot be traced back and is too contaminated to come into contact with food.
Several studies have shown that the physical properties, such as tensile strength or elongation to break, of a polymer may be reduced following recycling. These changes in properties may be attributed to thermo-mechanical degradation during reprocessing, photo-oxidative stress during the plastic’s lifetime, contamination with other polymers (e.g. products designed with several immiscible polymers or materials).
Additionally, a same polymer can exhibit different processability properties based on the product design. This is a particularly important feature as it determines which production method to use. For instance, plastics with low processability are typically blow moulded into bottles whereas those with high processability are moulded into tubs and buckets via injection. It is not surprising that mixed recycling hinders closed-loop recycling into similar products.
How can we improve plastic recycling? If we want to address the plastic crisis and reduce the amount lost to landfills and incineration, it is crucial to redesign the current recycling system, keeping in mind the challenges mentioned above. First and foremost, the recycling industry needs to transition away from an oversimplified mixed recycling stream. In order to improve the circularity of plastic waste, separation of plastics based on polymer-type should be encouraged. This effort should initially be focused on isolating the three most common polymers: PET, PE and PP. Another important change worth implementing is the distinction between food and non-food packaging from both a safety and regulatory perspective. And finally, promoting plastic sorting based of product type (e.g. bottles, tubs, etc) can also be beneficial.
Most of the challenges associated with plastic recycling can be traced back to contamination – creating specialised collection streams should theoretically improve the quality of waste and increase recovery rates, thus paving the way to a circular plastic economy.