D5.1: Recyclability of biobased plastic and smart food packaging along traditional polyolefin recycling

This report titled as Recyclability of biobased plastic and smart food packaging along traditional polyolefin recycling, corresponds the STOPP project (contract no. 101134958) deliverable D5.1 (M22) led by VTT. The aim of this task was to analyse the impact of bio-based plastic food packaging waste as well as smart packaging (referred to as ‘speciality food packaging’ in STOPP) in the polyolefin (PP and PE) waste recycling streams. Two main scenarios were considered, including: (1) Biobased packaging ending up in polyolefin streams; (2) Biobased and smart packaging ending up in polyolefin streams. The selection of specialty packaging was deemed according to their abundance in the market. It is obvious that the polyolefin materials are not ideally mechanically recyclable with contamination coming from biobased-packaging and smart packaging. Therefore, density-based float-sink separation technique was applied to fractionate the polyolefins and specialty packaging. This technique was chosen due to its simplicity for application at larger scales and abundance in recycling plants to reflect its adoptability by the industry. Swiss partner funded by Funded by the European Union. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or REA. Neither the European Union nor REA can be held responsible for them. For either of PP and PE ground rigid flakes, four different level of contamination with biobased and smart packaging was devised. The purity and composition of these eight different feedstocks were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Fluorescence (XRF) Spectroscopy, Thermogravimetric analysis (TGA), and Differential Scanning Calorimetry (DSC). The compositional analysis with DSC indicated zero sorting efficiency of PPbased specialty smart packaging from rigid HDPE light fraction via float-sink separation technique. DSC results shows that separate collection system and alternative sorting methods is necessary for smart packaging materials. The DSC-based compositional quantification of HDPE-PP (smart packaging) was successful contrary to rigid PP-PP (smart packaging). In case of HDPE-PP, the melting peaks overlapped, but due to higher content of HDPE, the melting peak of HDPE was more pronounce while PP contributes to higher temperature side of the curve. In case of rigid PP-PP (smart packaging) peak deconvolution was not possible due to complete melting peak overlap. There was no melting peak detected in sorted light fraction polyolefin relevant for biobased feedstock. This indicated high sorting efficiency of biobased feedstock from polyolefin through float-sink density separation method. In FTIR Spectroscopy results, there were no peaks attributed to PLA or cellulosic (Woodly) materials, showing that the density-based separation method was successful to separate the selected biobased packaging from HDPE packaging. A trace of PP (smart packaging) was detected from HDPE, showing that smart packaging was also found in the light fraction. In case of densityseparated rigid PP, the FTIR spectra did not reveal distinct peaks related to PPbased smart packaging. This highlights limitation of FTIR method in detecting trace amount of smart packaging elements such as silver (Ag) and tin (Sn) which were detected by XRF method in both PP and HDPE light fraction feedstock. Interestingly, the TGA results revealed residual ash mass of 0.87% for smart packaging combined by rigid HDPE, and zero with rigid PP. The XRF method proved to be an effective method for tracing elemental contaminants in mixed packaging waste streams. Swiss partner funded by Funded by the European Union. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or REA. Neither the European Union nor REA can be held responsible for them. In conclusion, based on the results, biobased packaging could be readily sorted out from the polyolefin streams which enables further recycling and upgrading of the mainstream polyolefins. However, it was impossible to separate PLA and cellulose-based packaging from each other with densitybased sorting technique due to their close density values. Therefore, ideally, these plastics should be labelled with clear disposal instructions and separately collected for value retention and recycling. The high-quality recycling of biobased packaging can be facilitated by applying complementary sorting methods such as elutriation, using biodegradable substrates, or by alternative recycling routes such as accelerated biodegradation techniques (enzymatic, chemoenzymatic) and chemical recycling (depolymerization into monomers). Smart packaging contaminated both the biobased packaging and polyolefin fractions, posing risks to purity and quality of recycled feedstock, especially mechanically recycled polyolefins. The silver-based paste printed onto smart packaging, slightly increased the density of PP film substrates, but it was not sufficient enough to sink and separate from rigid PP and HDPE light fraction. Therefore, smart packaging materials must strictly be separately collected. Polyolefins ending up in the light fraction after density-based separation (except the scenarios where smart packaging are included) can be both mechanically and chemically recycled since they have negligible number of impurities.