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Many pledges and laws are setting recycling targets without clearly defining quality of recycling. Striving to close this gap, this study presents an operational framework to quantify quality of recycling. The framework comprises three dimensions: the Virgin Displacement Potential (VDP); In-Use Stocks Lifetime (IUSL); and Environmental Impact (EI). The VDP indicates to what extent a secondary material can be used as a substitute for virgin material; the IUSL indicates how much of a certain material is still functional in society over a given time frame, and the EI is a measure of the environmental impact of a recycling process. The three dimensions are aggregated by plotting them in a distance-to-target graph. Two example calculations are included on poly(ethylene terephthalate) (PET) and glass. The results indicate that the recycling of bottle and container glass collected via a deposit-refund system has the lowest distance-to-target, at 1.05, and, thus, the highest quality of recycling. For PET bottles, the highest quality of recycling is achieved in closed-loop mechanical recycling of bottles (distance to optimal quality of 0.96). Furthermore, sensitivity analysis indicates that certain parameters, e.g., the collection rate for PET bottles, can reduce the distance-to-target to 0.75 when all bottles are collected for recycling.

An important impediment to the acceptance of recyclates into a broader market is their unwanted odor after reprocessing. Different types of washing procedures are already in place, but fundamental insights into the deodorization efficiencies of different washing media are still relatively scarce. Therefore, in this study, the deodorization efficiencies of different types of plastics after washing with different media were determined via gas chromatography and mass spectrometry analysis. A total of 169 compounds subdivided into various chemical classes, such as alkanes, terpenes, and oxygenated compounds, were detected across all packaging types. Around 60 compounds were detected on plastic bottles, and around 40 were detected on trays and films. Owing to the differences in physicochemical properties of odor compounds, different deodorization efficiencies were obtained with different washing media. Water and caustic soda were significantly more efficient for poly(ethylene terephthalate) bottles with deodorization efficiencies up to 80%, whereas for polyethylene (PE) and polypropylene bottles, the washing media were relatively inefficient (around 30-40%). Adding a detergent or an organic solvent could increase deodorization efficiencies by up to 70-90% for these packaging types. A similar trend was observed for PE films having deodorization efficiencies in the range of 40-50% when washing with water or caustic soda and around 70-80% when a detergent was added. Polystyrene trays were most effectively deodorized with a detergent, achieving efficiencies up to 67%. Hence, this study shows that optimal washing processes should be tailored to specific packaging types to further improve deodorization and to eventually be able to meet ambitious European recycling targets., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Visualization of the selected odorous components present on the analyzed plastic material in function of their boiling point, molecular weight, and LogP values. The components are projected in blue on the BP/MW plane, in red on the LogP/MW plane, and in green in the LogP/BP plane. • Different washing media for plastic deodorization were compared. • Detergents and organic solvents achieve deodorization efficiencies up to 90%. • Deodorization can accurately be described by an isotherm and kinetic model. • Adsorption and desorption of odor components occur during washing. • Solid/liquid ratio and recirculation rate are important factors. Mechanical recycling is to date the most commonly applied recycling technology. However, mechanical recycling of post-consumer plastics still faces many challenges, such as the presence of odorous constituents. Accordingly, recycling industry is looking for cost-effective solutions to improve the current washing efficiencies. However, scientific literature and basic understanding of deodorization processes are still scarce, which impedes efficient industrial optimization. Therefore, this study aims to obtain more fundamental insights in the deodorization mechanisms of plastic films in different washing media such as water, detergent, caustic soda, and ethyl acetate as organic solvent. The removal efficiencies of 19 odor components with a wide range of physicochemical properties were quantified via GC-MS analysis. The results revealed that deodorization depends on various factors such as temperature and physicochemical properties as polarity, volatility, and molecular weight of the odor components and the washing media. It was shown that polar washing media are less efficient compared to apolar media or media containing a detergent, achieving efficiencies of around 50% and 90%, respectively. The desorption processes can be accurately modeled by the isotherm model of Fritz-Schlunder in combination with a reversible first order kinetic model for the deodorization kinetics. Aspen Plus® process simulations of a water-based washing process reveal that at least 60% fresh water is needed to avoid saturation of the medium and undesired (re-)adsorption of odor components onto the plastics, which results in a substantial ecological footprint. [ABSTRACT FROM AUTHOR]