In the past few years, Wageningen Food & Biobased Research has carried out several projects to analyse material flows. The emphasis was on plastic packaging because of the inefficiency of this value-chain and the multiple questions that this sparks. Many of the material flow analyses focused on how diverse types of packaging have been introduced onto the Dutch market and which of these have been collected, mechanically recovered, sorted and recycled. These analyses were used to understand the contribution of each player to the value chain, to calculate the recycling rate and to analyse options for improvement.
The first chain model of the recycling chain for plastic packaging in 2014
The recycling chains for plastic packaging are notoriously complicated because there are so many different types of packaging, with different material compositions, that are all collected, sorted and recycled differently. In order to describe these value chains, dozens of samples were taken of separated, collected plastic packaging, residual waste, mechanically recovered concentrates, sorted products and recycling products. These samples were studied with respect to the type of packaging, moisture content and amount of attached dirt. Although this gave a rough sketch of how the types of packaging are collected, mechanically recovered and sorted, these material flow analyses can never be fully accurate based only on the data from the samples. But with advanced mathematics, the best possible description of the types of packaging in the chain from households through the sorting products and waste streams could be created.
A second challenge was to connect this chain description with the mechanical recycling step. To this end, the composition of the sorted products in types of packaging was first translated into a description in terms of the materials present. Then transfer coefficients were used to calculate the composition of the mechanically recycled products and by-products. This showed that in 2014, when household plastic packaging waste was still being collected separately, the net recycling percentage was 22%. There were also large differences in the Sorting fates and End-of-Life fates with respect to the types of packaging present in the diverse recycled plastics and waste streams. About 40% of the PE bottles and flasks ended up in the PE sorted product, 5% ended up in the wrong sorted products and the rest was not recycled but incinerated. It was also possible to calculate the average polymer purity of the recycled plastics, which turned out to be 91%. That seems high, but it is actually much too low for the most demanding applications, which often require a purity of more than 98%. It also appeared that most of the contaminants in the recycled plastics originated from the packaging itself, from components such as labels, caps, sealing foil, etc.
This first model clearly showed that a lot of improvements could still be made in the recycling system for post-consumer plastic packaging. Two points were immediately apparent. First, the low collection rates result in low recycling rates; and second, the complex material composition of many types of packaging, results in impure recycled plastics.
The second chain model for 2017
Hardly had the model for 2014 been completed when it appeared to be outdated. Municipalities had switched en masse from the separate collection of plastic packaging to collecting lightweight packaging (LWP) in Dutch abbreviated with PMD. The model was thus substantially expanded with new data from samples. This showed that the recycling rates for post-consumer plastic packaging had risen to 26% and that the average polymeric purity of the recycled plastics was still 91%. Thus, the new collection method had increased the amount of recycled plastics in particular.
New calculation rules
In 2019 the European Commission announced new calculation rules to calculate the recycling rate for packaging. Our model is very suitable for calculating the effect of these new rules on the recycling rate of plastic packaging. However, we were required to expand the model to include post-industrial plastic packaging. This expansion resulted in a recycling rate for Dutch plastic packaging of between 35-39% in 2017.
How can we better retain plastic packaging in recycling loops?
Our current recycling system for plastic packaging is characterised by a large inflow of virgin plastics, a limited number of partially closed material recycle loops (like PET in the deposit system) and an outflow to diverse non-food consumables. As such, it is primarily an ‘open-loop’ recycling system that is dependent on the inflow of oil and the outflow to consumables. This is not what our politicians envision to be a circular economy. It is therefore interesting to explore how we could improve our recycling system with current technology. The material stream models of plastic packaging are extremely suitable to carry out this investigation. It appeared that if all interested parties do their utmost, a recycling rate of 72% is feasible as well as an average polymeric purity of 97%. But to achieve this, unparalleled changes have to be made, especially to designing, collecting, sorting and recycling packaging. And even the most ideal circular economy will still depend on the inflow of crude oil and the outflow to consumables, but then larger amounts of packaging materials will be recycled in closed-loop systems.