PLA sorting for recycling. Experiments performed at the National Test Centre Circular Plastics (NTCP)
Bioplastic, if produced sustainably, can contribute to the transition to a circular economy, especially when these plastics are recycled as much as possible. BioPE and BioPET are automatically sorted and recycled together with fossil PE and PET in the current recycling system for plastic packaging. After bioPE and bioPET, PLA (polylactic acid) is the third bioplastic on the market in volume. PLA is a bioplastic that can be used for the production of a variety of packaging, for example meat trays and packaging for vegetables and fruit. In the current recycling system for consumer packaging waste in the Netherlands and other countries, PLA is not sorted out and recycled automatically.
It was concluded in a previous study by CE Delft, (2019) that, in theory, sorting out of PLA packaging waste in plastic sorting installations and mechanical or chemical recycling of the sorted out PLA can be interesting, both from an economic and an environmental perspective. CE Delft estimated that the climate impact of mechanical or chemical recycling of PLA is lower than of conventional processing routes like composting or combustion (CE Delft, 2019). The share of PLA in the mix of packaging has to increase to 1 to 5% to make the sorting of PLA economically feasible for industrial sorting installations (CE Delft, 2019).
The main research question
However, these conclusions are somewhat uncertain because the effectivity of sorting out PLA with a Near Infrared (NIR)-installation is not yet tested in Dutch sorting installations with Dutch packaging waste. To tackle these uncertainties, a PLA sorting experiment is performed in the National Test Centre for Circular Plastics (NTCP) in Heerenveen.
This installation is built as a model for Dutch sorting installations. The experiment focused on 3D PLA materials, so no PLA foils are investigated.
The main research question for the experiment is: How well can 3D PLA be sorted out of Dutch PMD waste with a higher share of PLA and how does this affect other sorted out plastic streams (especially PET)? Based on stakeholder interviews and literature research we also looked at the possibilities for actual recycling of the sorted PLA.
Main results experiment
Several results are interesting: the PLA yield (share of PLA, which is sorted out correctly), the purity of the PLA stream (share of PLA in the PLA stream) and the pollution of PLA in the PET stream (share of PLA in the PET stream). The results for these parameters are summarised in Table 1.
The PLA yield depends on the type of packaging. The yield is lower for lids and higher for cups and trays. A large share of lids and the trays (10-19%) end up in the lights stream since it is blown out by the wind shifter. Furthermore, a large share of the lids and cups (19-28%) are not sorted out and end up in the residual stream. The colour of the packaging appears to make no difference in this experiment.