Eggo Ulphard Thoden van Velzen

The management of plastic packaging waste needs to be optimized to improve recycling rates. In this article, fourteen categories of non-bottle polyethylene terephthalate (PET) packages were mechanically recycled at laboratory bench scale; the generated data were assessed using a multi-criteria decision analysis (MCDA) approach to identify the categories most suited for the mechanical recycling process from social, technical and legislative viewpoints. Recycling yields varied between 75% and 92% across the 14 categories. The intrinsic viscosity (IV) values of the produced recycled PET (rPET) corresponded to molecular weights ranging from 28,000 to 35,000 g/mol. The MCDA recyclability assessment showed that 7 of the 14 categories (accounting for 72% of the sorted products by mass flow) are often composed of multiple, inseparable materials, resulting in the lowest-quality rPET. Furthermore, only 4 categories (approximately 28% of the categories) were found suitable for closed-loop mechanical recycling. The stakeholders involved in the PET packaging value chain could use these results to support decision-making and the development of a well-organized framework to valorize even the most complex types of plastic waste.

The transition to a sustainable, circular economy requires more plastic waste to be recycled into high-quality recycled plastics. However, it is challenging to recycle mixed waste fractions or common multilayer materials by using current mechanical recycling technology. Enzymatic hydrolysis potentially offers a solution because of its mild conditions and selectivity. In this study, we show that polyester hydrolases can be applied to recycle PET-PE multilayer packaging waste without costly amorphization pretreatment. Polyester hydrolases were produced by recombinant Pichia pastoris yeast and used to efficiently depolymerize the PET layer of PET-PE multilayer trays. High yields were obtained at laboratory scale with unpurified enzyme and high PET-PE loading (10–20% w/w PET-PE, ≥94% PET depolymerization, and ≥80% terephthalic acid recovery). The enzymatic reaction was scaled up to 4.5 kg of PET-PE production waste. After depolymerization (≥95% PET depolymerized), terephthalic acid was isolated and repolymerized into rPET. The remaining PE layer was recovered, treated with an alkaline cleaning step to remove residual PET contamination, and successfully reprocessed into rPE films with similar properties to virgin low-density PE. This study demonstrates the applicability of enzymatic hydrolysis for the recycling of PET-PE multilayer materials and highlights its general potential for the recycling of polyesters in mixed post-consumer waste.

Adverse impacts of plastic can be reduced by shifting to a circular bioeconomy with biobased plastics. Incumbents face barriers, including the alleged “recycling lock-in”, hindering the adoption of new polymers due to the current plastic packaging system. Corporate power is crucial in promoting this shift. This study focuses on corporate power in the Dutch plastic packaging sector, analyzing conflicts of interest and barriers in transitioning to a circular bioeconomy. Market-based Instruments’ effectiveness in promoting circularity among food companies is explored. Fifteen incumbents in Dutch plastic food packaging sector were interviewed. Reasons for not widely using biobased polymers are: technical performance issues, higher prices, limited availability and lack of recycling infrastructure. Moreover, existing recycling infrastructure, regulations, and practices are optimized for fossil-based polymers, creating lock-ins for the inclusion of new materials. Despite no legal barriers, companies are hesitant to use biobased plastics due to system challenges. They struggle to transition from fossil-based to biobased plastic packaging due to resistance to change. Power dynamics analysis shows that the petrochemical industry, Fast-Moving Consumer Goods (FMCG) sector, and retail dominance has decreased in the past decade, with governmental measures increasing the influence of non-governmental organizations (NGOs) and recyclers. No single entity controls the system.

The recycling of PET trays is highly challenging. The aim of this paper was to investigate the issues related to the mechanical recycling process and, the correlation between feedstock composition and the quality of the produced rPET. Four feedstocks with different degrees of impurity were mechanically recycled at a laboratory pilot scale. The optical and thermal properties of the rPET products were examined to determine the quality and to seek relations with the starting level of impurities. The final products of the PET trays’ mechanical recycling were found to be affected by the presence of impurities (organics) and multi-material (non-PET) elements in the feedstocks. The rPET products crystallised faster for contaminated feedstocks showed lower molecular mass and higher yellow index values due to thermal degradation. Yellowing is a crucial parameter in assessing the thermal degradation of rPET. Injection moulded samples corresponding to higher contamination levels, reported values of Yellow Index equal to 179 and 177 compared to 15 of mono-PET sample. The intrinsic viscosity decreased from 0.60 dL/g to just above 0.30 dL/g, and losses were more significant for soiled or multi-material feedstocks. A method of improving the final quality would involve the purification of the starting feedstock from impurities.