The big fear of every plastics recycler is that biobased materials or plastics containing degradable/compostable additives will inadvertently get into the recycling stream and ruin the recycled materials, making them unfit for re-processing into other products.
According to Plastics Recycling Europe (PRE; Brussels), even small quantities of degradable plastics that end up in the traditional waste streams have a significant, negative impact on recycled plastics. The recycling organization recently reported that waste streams in the south of Europe pose a quality issue in films because of a higher share of degradable plastics.
A trial done on 1,000 tons of equally purchased quantities of waste from northern and southern Europe showed substantial quality discrepancies in the recycled film. The tests were performed on industrial lines: Recycled plastics were first produced from 98/2 post-consumer quality waste—PE film that contains 98% natural and 2% colored material—and then converted into a 50-micron-thick film. The extrusion worked normally with the recycled plastics coming from northern Europe. However, holes and specks appeared regularly in film produced with recycled waste coming from southern Europe.
Besides the qualitative analysis of holes and specs, abrasion of the supply lines turned out to be a useful indicator, since they are batch-independent and, thus, could be used as a statistical average. To understand the defects and ruptures of the film, samples were analyzed by infrared, thermal analysis as well as via gas chromatography mass spectrometry. These analyses determined that most of the degradation was coming from substances used in the production of degradable plastics, such as starch, polylactide (PLA) and polybutylene adipate terephthalate (PBAT).
The tests showed the impact on functionality of recycled plastics coming from southern Europe waste film flows. Therefore, the PRE concluded, it is necessary to develop separate streams not only for bio-waste but also degradable plastics in order to make sure that the latter do not enter waste streams of conventional plastics.
Although production of thick-walled recycled products (>50 micron) from this highly contaminated material is possible, it will affect their appearance.
The push toward increasing the use of degradable plastics is expected to make this problem more acute in the future. Therefore, the PRE calls on authorities to assess the overall impact of degradable plastics in conventional streams and to develop separate collections for both bio-waste and degradable plastics in order to avoid putting in jeopardy the efforts of moving toward a circular plastics economy.