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Study: Possibilities for the release of microplastic during recycling

According to a pilot study from a team of scientists at the Scottish University of Strathclyde in cooperation with universities in Canada, UK and New Zealand, there is a possibility that some of the microplastic in the environment could stem from the recycling of plastic waste. The research team concludes from the results of a study that plastics recycling plants could, alongside road traffic, be a significant cause of the planet’s microplastic contamination, and that the recycling of plastic waste should be fundamentally called into question. In order to evaluate the measurements taken at a Scottish recycling plant as well as the conclusions from the study, BKV’s latest study results concerning pellet losses in the industry in Germany were taken into account.
 

Recycling plants in which the plastic waste is usually washed several times during the processing process represent, according to the pilot study headed by Deonie Allen (which appeared in the Journal of Hazardous Materials Advances), a potential source of the discharge of microplastic particles into the environment. For Allen's study, samples were removed within the examined recycling plant from four drainage channels used by the washing water. Initially, the plant did not have any device to capture small particles. A subsequently installed filtration system consisted of filters that were able to catch small particles with a size of up to 50 micrometres (1 micrometre corresponds to a millionth of a metre). The particle filters were mounted on three of the four outlet and sampling points, and it was also part of the plant's filtration system to manually scrape off the sludge from the surface of the last water tank manually after the water had passed through the particle filters. With a comparison of the microplastic concentration and the particle size distribution in the specimens from the unfiltered and filtered effluent, the researchers also wanted to measure the efficiency of the filtration. To avoid falsely positive results and also to make a contribution to the quality control, investigations were, according to the study, also carried out with so-called blank samples. The samples taken at the washing stations were pretreated and then analysed microscopically (Nile red fluorescent microscopy) with regard to the size and shape of the microplastic particles they contained. According to Allen, although the method used enables a quantification of the particles, it does not allow any statements about the type of polymer. The result was that the researchers found microplastic particles in all the specimens. The comparative analysis before and after filtration of the washing water was carried out for particles larger than 10 micrometres, and showed that the number of microplastic particles more or less halved after filtration. The examined recycling plant could, according to the extrapolations of the research team, emit up to 3.3 million kilograms of microplastic per year without a filtration system, but with filtration, the quantity fell to around 1.4 million kilograms a year.
 
In the pilot study by Deonie Allen and her team, an investigation was carried out of the water pollution attributable to microplastic from a single plastic recycling plant in the UK, in which, according to the figures, around 22,000 tonnes of mixed plastic waste are sorted, shredded and melted into pellets every year. The study does not give the name of the operator of the plant, which is described as highly modern.
 
According to a study from Conversio Market & Strategy GmbH compiled in 2022 on behalf of BKV, around 1.9 million tonnes of recyclate are produced by plastics recycling companies in Germany. Recyclate is offered on the market in the form of regrind, flakes and pellets. Most of the produced recyclate is processed into pellets. Approximately 0.9 million tonnes are not turned into pellets, in other words they are processed into flakes or regrind, or in some cases are reused directly by plastics processing companies. The main discharge pathways for potential pellet losses at recycling companies are the process of filling the materials into transport containers and the subsequent internal logistics, as well as the loading and unloading of transport vehicles.
 
With regard to the discharge into the environment of pellets stemming from German recycling companies, an annual emission potential through internal processes totalling 1,042 tonnes is assumed. This corresponds to a loss rate of approx. 0.1 percent of the produced volume. According to the study, it can be assumed that, through retention measures such as regular sweeping and the use of sewer systems, as well as connection to wastewater cleaning facilities, the majority of the potentially discharged quantity of pellets is collected. Overall, this means that, each year, 58 tonnes of pellets may be emitted on the sites of German plastic recycling plants, and either discharged directly into the environment or into the sewer system. This represents annual pellet emissions at recycling companies in Germany of 0.006 percent in relation to the production volume.
 
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