Plastic Economy Research Articles

Polyurethane with β-Selenocarbonyl Structure Enabling the Combination of Plastic Degradation and Waste Upcycling.

Degradable polymers offer a promising solution to mitigate global plastic pollution, but the degraded products often suffer from diminished value. Upcycling is a more sustainable approach to upgrade polymer waste into value-added products. Herein, we report a β-selenocarbonyl-containing polyurethane (SePU), which can be directly degraded under mild conditions into valuable selenium fertilizers for selenium-rich vegetable cultivation globally, enabling both plastic degradation and waste upcycling. Under oxidation condition, this polymer can be easily and selectively degraded via selenoxide elimination reaction from mixed plastic waste. The degraded product can serve as effective selenium fertilizers to increase selenium content in radish and pak choi. The SePU exhibits excellent mechanical properties. Additionally, we observed the formation of spherulites-like selenium particles within the materials during degradation for the first time. Our research offers a successful application of selenoxide elimination reaction in the field of plastic degradation for the first time, endowing plastics with both degradability and high reusable value. This strategy provides a promising solution to reduce pollution and improve economy and sustainability of plastics.

Selectively self-recyclable, highly transparent and fire-safe polycarbonate plastic enabled by thermally responsive phosphonium-phosphate.

Both the circular economy and fire-safety of polymer plastics have become a global consensus. Herein, an integrated strategy for selectively self-recyclable, highly-transparent and fire-safe polycarbonate plastic is proposed by thermally responsive phosphonium-phosphate (DP). During its service life, DP, as a flame-retardant with good compatibility, enables polycarbonate plastic with high transparency in visible light, excellent self-extinguishing and high fire-safety. After consumption, DP, as a catalyst, triggers the selective self-recycling of DP-containing polycarbonate in mixed plastics and even in same-kind polycarbonate plastics without an external catalyst. Importantly, the oxygen-consuming mechanism at high temperature in fire accidents (>350 °C) and the double hydrogen bond catalysis mechanism at a lower temperature (180 °C) of DP are key to the life cycle management of polycarbonate from use-stage to post-consumption. This work inspires a new solution to plastic pollution by designing sustainable plastics that satisfy both service-stage and end-of-life criteria, striving towards a zero-waste circular economy.

Ni-based catalysts supported on Hbeta zeolite for the hydrocracking of waste polyolefins.

Polyolefin plastics are the most popular polymer materials worldwide, and the catalytic degradation of post-consumer polyolefins has attracted increased attention as a viable process. In this study, two types of Ni-based catalysts supported on Hbeta zeolite, Ni-Hbeta and NiS2-Hbeta, have been successfully synthesized for the hydrocracking of waste polyolefin. The experimental results indicated that the synergistic effect between Ni or NiS2 and the acidic sites of Hbeta zeolites can significantly enhance the tandem cracking and hydrogenation of polyolefin plastics, which suppresses the formation of gas products and coke. Ni-Hbeta employed as a catalyst can effectively degrade HDPE into high value liquid and gas products with high yield of 94% under 523 K and 3 MPa H2, while also exhibiting excellent cycle stability. In particular, Ni-Hbeta shows better catalytic performance than NiS2-Hbeta during the hydrocracking of HDPE at a relatively low temperature of 523 K. Furthermore, Ni-Hbeta catalyst also exhibits a remarkable capability for efficient depolymerization of unsorted post-consumer polyolefin plastics (HDPE, LDPE, PP) containing various additives and pollutants. These findings underscore the application potential of employing noble metal-free and recyclable catalysts for hydrocracking plastic waste, thereby facilitating the realization of a circular economy for plastics.

Dynamics in the evolution of circular sourcing strategies: Evidence from German frontrunners sourcing for recycled plastics

Firms’ circular sourcing strategies are essential for the transition to a circular economy as they enhance circularity both within individual firms and across industries. A key barrier to the implementation of such strategies is that many approaches still offer a static perspective on resource use without addressing its evolutionary characteristics and dynamic interdependencies over time. Based on the assumption that companies’ strategic procurement decisions on recyclate markets show temporal patterns depending on the development of these markets (“marketness”), the dynamics in the complex cause-and-effect structures of circular procurement strategies are analysed longitudinally with the help of causal loop diagrams. Employing a comparative case-study design with the example of German frontrunners sourcing recycled plastics, the paper addresses three recyclate markets at various stages of development, ranging from the emerging market of recovered plastic litter, through the developing market of plastic recyclate from mixed post-consumer packaging waste, towards the well-established market of recycled deposit bottles. The results reveal ideal-typical longitudinal patterns of company leaders’ strong commitment to sustainability, facilitated by flexible organisational structures, significant investment in product development, sound supplier relationship management and brand building to sway consumer preferences towards circular products, indicating that market-shaping activities are key in long-term shifts towards circular market transitions. By understanding the dynamics of circular sourcing and their relationship with the development stage of recyclate markets, the study sheds light on potential governance measures to scale-up plastic recyclate markets for a circular plastics economy. It concludes that overall dynamics point to a steady development of firms’ circular sourcing strategies and a rapid growth in recyclate application, involving complex challenges of resource circularity that call for carefully targeted regulatory policies.

Materials designed to degrade: structure, properties, processing, and performance relationships in polyhydroxyalkanoate biopolymers.

Conventional plastics pose significant environmental and health risks across their life cycle, driving intense interest in sustainable alternatives. Among these, polyhydroxyalkanoates (PHAs) stand out for their biocompatibility, degradation characteristics, and diverse applications. Yet, challenges like production cost, scalability, and limited chemical variety hinder their widespread adoption, impacting material selection and design. This review examines PHA research through the lens of the classical materials tetrahedron, exploring property-structure-processing-performance (PSPP) relationships. By analyzing recent literature and addressing current limitations, we gain valuable insights into PHA development. Despite challenges, we remain optimistic about the role of PHAs in transitioning towards a circular plastic economy, emphasizing the need for further research to unlock their full potential.

Electrocatalytic upgrading of polyethylene terephthalate plastic to formic acid at an industrial-scale current density via Ni-MOF@MnCo-OH catalyst

Electrocatalytic polyethylene terephthalate (PET) waste upgrading is crucial for developing a circular plastics economy and solving the energy crisis, but achieving efficient PET upgrading at an industrial-scale current density remains a formidable challenge. In our work, Ni-MOF@MnCo-OH catalyst was prepared by designing hierarchical heterostructure and incorporating the concept of multi-metal sites, wherein the Ni-MOF can be derived from PET plastic. Benefiting from the advantages of material design, the catalyst demonstrates excellent adsorption capabilities for both OHad and ethylene glycol (EG), while also enhancing the electron transfer capability of Ni-MOF. We achieve a high Faradaic efficiency (∼80 %) during PET plastic upgrading at industrial-scale current density (300 mA·cm−2 at 1.43 V vs. RHE) with Ni-MOF@MnCo-OH. Moreover, through theoretical calculations and in situ Fourier transform infrared (FTIR) spectroscopy, we have further elucidated the mechanism of ethylene glycol oxidation reaction (EGOR). Notably, glycolic acid has been identified as a vital intermediate during the electrical oxidation of EG. This work provides a viable and eco-friendly approach to enhance the value of PET waste through sustainable means.

Applications of plastics in the automotive industry: Current trends and future perspectives

AbstractPlastics have transformed the automotive industry, contributing substantially to automobile design, weight reduction, fuel efficiency, safety, and sustainability. This review paper examines the applications of plastics in the automotive sector, evaluates the present trends, and describes the future plastic consumption possibilities, emphasizing emerging technology and sustainable practices. The paper delineates how plastics have become an essential component of automotive innovation and illustrates the possibilities for additional breakthroughs in this dynamic industry.Highlights Advances in plastics, bioplastics, and smart materials in the auto industry. Plastic role in design, safety, and sustainability in the auto industry. Recycling and the circular economy of plastics in the auto industry. Collaboration of stakeholders to drive change in the auto industry.

Mitigation approach of plastic and microplastic pollution through recycling of fishing nets at the end of life

Plastic and microplastic pollution in the marine environment is a global issue and lost or discarded fishing nets (FNs) represent a relevant part of the marine litter. This type of waste is very harmful to marine organisms due to ghost fishing and microplastics release. Furthermore, nets are difficult to dispose because they take up a lot of space at landfill sites and are expensive to transport. Therefore, the development of recovery and recycling strategies represents one of the solutions for this problem. In the present work, a multifilament, knotted, twisted waste FN, composed of nylon 6,6, was recycled realizing composite materials in combination with recycled expanded polystyrene (EPS) or poly(acrylonitrile-butadiene-styrene) (ABS) matrices. The composites were realized exploiting a cold mixing approach, mixing the FN, either as a pre-ground short fiber filler or as mats, with the polymers swollen in an organic solvent. Several compositions were explored by these approaches and the composites were characterized by means of thermal, spectroscopic, mechanical and morphological analyses. Finally, a qualitative assessment of the economic impact of fishing net recycling was conducted. Results showed that the proposed recycling approaches allow to realize composite materials with interesting properties, opening new routes for recycling the FNs at the end of life improving the circular economy of plastics and reducing their ecological, ecosystem service and social and economic impacts.

Sustainable production and degradation of plastics using microbes.

Plastics are indispensable in everyday life and industry, but the environmental impact of plastic waste on ecosystems and human health is a huge concern. Microbial biotechnology offers sustainable routes to plastic production and waste management. Bacteria and fungi can produce plastics, as well as their constituent monomers, from renewable biomass, such as crops, agricultural residues, wood and organic waste. Bacteria and fungi can also degrade plastics. We review state-of-the-art microbial technologies for sustainable production and degradation of bio-based plastics and highlight the potential contributions of microorganisms to a circular economy for plastics.

Evaluating Heterodinuclear Mg(II)M(II) (M = Mn, Fe, Ni, Cu, and Zn) Catalysts for the Chemical Recycling of Poly(cyclohexene carbonate).

Polymer chemical recycling to monomers (CRM) is important to help achieve a circular plastic economy, but the "rules" governing catalyst design for such processes remain unclear. Here, carbon dioxide-derived polycarbonates undergo CRM to produce epoxides and carbon dioxide. A series of dinuclear catalysts, Mg(II)M(II) where M(II) = Mg, Mn, Fe, Co, Ni, Cu, and Zn, are compared for poly(cyclohexene carbonate) depolymerizations. The recycling is conducted in the solid state, at 140 °C monitored using thermal gravimetric analyses, or performed at larger-scale using laboratory glassware. The most active catalysts are, in order of decreasing rate, Mg(II)Co(II), Mg(II)Ni(II), and Mg(II)Zn(II), with the highest activity reaching 8100 h-1 and with >99% selectivity for cyclohexene oxide. Both the activity and selectivity values are the highest yet reported in this field, and the catalysts operate at low loadings and moderate temperatures (from 1:300 to 1:5000, 140 °C). For the best heterodinuclear catalysts, the depolymerization kinetics and activation barriers are determined. The rates in both reverse depolymerization and forward CHO/CO2 polymerization catalysis show broadly similar trends, but the processes feature different intermediates; forward polymerization depends upon a metal-carbonate intermediate, while reverse depolymerization depends upon a metal-alkoxide intermediate. These dinuclear catalysts are attractive for the chemical recycling of carbon dioxide-derived plastics and should be prioritized for recycling of other oxygenated polymers and copolymers, including polyesters and polyethers. This work provides insights into the factors controlling depolymerization catalysis and steers future recycling catalyst design toward exploitation of lightweight and abundant s-block metals, such as Mg(II).

Enzymatic Upcycling of PET Waste to Calcium Terephthalate for Battery Anodes.

Biotechnological recycling offers a promising solution to address the environmental concerns associated with waste plastics, particularly polyethylene terephthalate (PET), widely utilized in packaging materials and textiles. To advance the development of a bio-based circular plastic economy, innovative upcycling strategies capable of generating higher-value products are needed. In this study, we enhanced the enzymatic depolymerization of waste PET by incorporating highly concentrated calcium ions (up to 1 m) to the hydrolytic reaction catalyzed by the best currently known enzyme LCCICCG . The presence of calcium ions not only improved the thermal stability and activity of the biocatalyst but also significantly reduced the consumption of base required to maintain optimal pH levels. Employing optimized conditions at 80 °C for 12 h, we successfully converted ≈84 % of the waste PET (200 g L-1 ) into solid hydrated calcium terephthalate (CaTP ⋅ 3H2 O) as the primary product instead of soluble terephthalate salt. CaTP ⋅ 3H2 O was easily purified and employed as a raw material for battery electrode production, exhibiting an initial reversible specific capacity of 164.2 mAh g-1 . Through techno-economic analysis, we conclusively demonstrated that the one-pot biocatalysis-based synthesis of CaTP is a superior PET upcycling strategy than the secondary synthesis method employing recycled terephthalic acid.

Enzymatisches Upcycling von PET‐Abfällen zu Calcium‐Terephthalat für Batterieanoden

AbstractBiotechnologisches Recycling bietet eine vielversprechende Lösung für die Umweltprobleme im Zusammenhang mit Kunststoffabfällen, insbesondere für Polyethylenterephthalat (PET), das häufig in Verpackungsmaterialien und Textilien verwendet wird. Um die Entwicklung einer biobasierten Kreislaufwirtschaft für Kunststoffe voranzutreiben, sind innovative Upcycling‐Strategien erforderlich, mit denen höherwertige Produkte erzeugt werden können. In dieser Studie verbesserten wir die enzymatische Depolymerisation von PET‐Abfall, indem wir hochkonzentrierte Kalziumionen (bis zu 1 m) in die hydrolytische Reaktion einbrachten, die durch das beste derzeit bekannte Enzym LCCICCG katalysiert wird. Das Vorhandensein von Kalziumionen verbesserte nicht nur die thermische Stabilität und Aktivität des Biokatalysators, sondern verringerte auch den Basenverbrauch, der zur Aufrechterhaltung eines optimalen pH‐Wertes erforderlich ist, erheblich. Unter optimierten Bedingungen bei 80 °C für 12 Stunden konnten wir ≈84 % des PET‐Abfalls (200 g L−1) erfolgreich in festes hydratisiertes Kalziumterephthalat (CaTP ⋅ 3H2O) als Hauptprodukt anstelle von löslichem Terephthalatsalz umwandeln. CaTP ⋅ 3H2O konnte leicht gereinigt und als Rohstoff für die Herstellung von Batterieelektroden verwendet werden und wies eine anfängliche reversible spezifische Kapazität von 164.2 mAh g−1 auf. Durch eine techno‐ökonomische Analyse konnten wir schlüssig nachweisen, dass die auf Biokatalyse basierende Eintopfsynthese von CaTP eine bessere PET‐Upcycling‐Strategie ist als die sekundäre Synthesemethode, bei der recycelte Terephthalsäure verwendet wird.

Advancing the material performance of chemically recyclable polythioesters via copolymerization

Developing new chemically recyclable polymers provides an opportunity for establishing a circular plastic economy. However, it is still challenging to reconcile both polymer recyclability and material properties. Herein, we aimed to exploit copolymerization of 3-methyl-dithian-2-one (Me-DTO) and thiovalerolactone (TVL) to access chemically recyclable polythioesters with high-performance material properties. Adjusting the copolymer compositions allowed to modulate the thermal and mechanical properties of the resulting copolymers extensively. Ultimately, polyolefin-like mechanical properties was achieved for P[(Me-DTO)100-co-(TVL)900] (σB = 33.87 ± 4.79MPa and εB = 638 % ± 112 %). These copolymers were capable of depolymerizing into their monomers in solution or bulk efficiently with high yields of >95 %, thus establishing their circular life cycle.

Organocatalytic depolymerization of poly(3-hydroxybutyrate) to crotonic acid

Utilizing end-of-life poly(3-hydroxybutyrate) (PHB) as a carbon source for the production of value-added chemicals has attracted increasing interest in recent years. In this report, an organocatalytic pyrolysis method was explored for chemical recycling of PHB into trans-crotonic acid (CA). Under relatively mild conditions and through the promotion of organic base catalysts, the CA was recovered with high efficiency and yield. The effect of reaction conditions on the depolymerization process, such as types of catalysts, solvent polarity, temperature, and molar equivalents of PHB to catalyst, was investigated in detail. This work is the first to achieve the pyrolysis of PHB using organic base catalysts, which provides a green and efficient option for plastic degradation and promotes the development of circular plastic economy.

New study on brominated flame retardants by BSEF

On November 7, BSEF presented a new study on brominated flame retardants in WEEE plastics and their integration into Europe's Circular Economy, called “Brominated Flame Retardants and the Circular Economy of WEEE Plastics”.

Enzymatic hydrolysis of single-use bioplastic items by improved recombinant yeast strains

Single-use bioplastic items pose new challenges for a circular plastics economy as they require different processing than petroleum-based plastics items. Microbial and enzymatic recycling approaches could address some of the pitfalls created by the influx of bioplastic waste. In this study, the recombinant expression of a cutinase-like-enzyme (CLE1) was improved in the yeast Saccharomyces cerevisiae to efficiently hydrolyse several commercial single-use bioplastic items constituting blends of poly(lactic acid), poly(1,4-butylene adipate-co-terephthalate), poly(butylene succinate) and mineral fillers. The hydrolysis process was optimised in controlled bioreactor configurations to deliver substantial monomer concentrations and, ultimately, 29 to 78% weight loss. Product inhibition studies and molecular docking provided insights into potential bottlenecks of the enzymatic hydrolysis process, while FT-IR analysis showed the preferential breakdown of specific polymers in blended commercial bioplastic items. This work constitutes a step towards implementing enzymatic hydrolysis as a circular economy approach for the valorisation of end-of-life single-use bioplastic items.

Biotechnological Plastic Degradation and Valorization Using Systems Metabolic Engineering.

Various kinds of plastics have been developed over the past century, vastly improving the quality of life. However, the indiscriminate production and irresponsible management of plastics have led to the accumulation of plastic waste, emerging as a pressing environmental concern. To establish a clean and sustainable plastic economy, plastic recycling becomes imperative to mitigate resource depletion and replace non-eco-friendly processes, such as incineration. Although chemical and mechanical recycling technologies exist, the prevalence of composite plastics in product manufacturing complicates recycling efforts. In recent years, the biodegradation of plastics using enzymes and microorganisms has been reported, opening a new possibility for biotechnological plastic degradation and bio-upcycling. This review provides an overview of microbial strains capable of degrading various plastics, highlighting key enzymes and their role. In addition, recent advances in plastic waste valorization technology based on systems metabolic engineering are explored in detail. Finally, future perspectives on systems metabolic engineering strategies to develop a circular plastic bioeconomy are discussed.

The role of chemical and solvent-based recycling within a sustainable circular economy for plastics

Chemical and solvent-based recycling of plastic waste may help overcome some of the challenges faced by predominantly applied mechanical recycling techniques. This study quantifies the environmental impacts of chemical and solvent-based recycling as a function of varying process parameters and product composition using life cycle assessment. Furthermore, potential benefits and impacts on a system level are determined. To that end, a high-resolution material flow analysis is conducted for the reference system of Switzerland, covering all main plastic types and applications. In a scenario for the year 2040, we employ environmentally beneficial mechanical recycling where possible and convey suitable remaining waste streams to chemical or solvent-based recycling processes. Applying chemical or solvent-based recycling as a complement to maximum mechanical recycling, instead of thermal treatment with energy recovery, may achieve a reduction in the climate change impact of the system ranging from less than 10 % to almost 40 %. For achieving high environmental benefits, proper process choice and configuration are crucial. Dissolution or depolymerization provide higher benefits relative to other chemical recycling processes, but can only treat certain waste streams and require prior sorting into plastic types. Pyrolysis and gasification appeared to only have the ability to achieve substantial benefits over incineration if their output products can substitute high-impact chemicals and provided that efficient heat transfer and recovery is warranted when implemented on a large scale. As industrial-scale plants for chemical or solvent-based plastic recycling are still lacking, the upscaling potential and the environmental benefits achievable in practice are highly uncertain today.

Upcycling plastic polymers into single-walled carbon nanotubes from a magnesia supported iron catalyst

Plastic waste has posed an ever-growing environmental threat to the United Nations’ sustainable development goals. Converting plastic polymers into high value chemicals like carbon nanotubes is a promising approach for recycling without carbon dioxide emission. Using a two-stage pyrolysis-catalytic reactor, we herein report the transformation of five types of plastic polymers into high-quality single-walled carbon nanotubes (SWNTs) with the assistance of a rationally designed heterogeneous catalyst, i.e., an iron metal catalyst supported by porous magnesia. Because of the high metal dispersion and the large carbon solubility of the active component, the heterogeneous catalyst affords the formation of uniform metal particles which can sustain high carbon fluxes, resulting in the synthesis of high quality SWNTs. More importantly, the approach is also demonstrated with mixtures of plastic polymers. This work helps gain deep insights into the mechanisms of plastic polymer conversion to SWNTs, accelerating the progress toward a sustainable plastic economy.

Structure-Property Relationship and Multiple Processing Studies of Novel Bio-Based Thermoplastic Polyurethane Elastomers.

Currently, the growing demand for polymeric materials has led to an increased need to develop effective recycling methods. This study focuses on the multiple processing of bio-based thermoplastic polyurethane elastomers (bio-TPUs) as a sustainable approach for polymeric waste management through mechanical recycling. The main objective is to investigate the influence of two reprocessing cycles on selected properties of bio-TPUs. Two series of bio-based TPUs were synthesized via a solvent-free two-step method with the use of hexamethylene diisocyanate or hexamethylene diisocyanate/partially bio-based diisocyanate mixtures, bio-based poly(triamethylene ether) glycol, and bio-based 1,3 propanediol. Both the raw bio-TPUs and those subjected to two reprocessing cycles were examined with respect to their chemical, physical, thermal, thermomechanical, and mechanical properties. The conducted research revealed that reprocessing led to changes in the phase separation between the hard and soft segments, thereby affecting the bio-TPUs' properties. Both series of materials showed similar chemical structures regardless of reprocessing (slight changes were observed in the range of carbonyl peak). The thermal properties of TPUs exhibited slight differences after each reprocessing cycle, but generally, the non-processed and reprocessed bio-TPUs were thermally stable up to about 300 °C. However, significant differences were observed in their mechanical properties. The tensile strength increased to 34% for the twice-reprocessed bio-TPUs, while the elongation at break increased by ca. 200%. On the other hand, the processing cycles resulted in a decrease in the hardness of both bio-TPU series (ca. 3-4 °ShA). As a result, the prepared bio-TPUs exhibited characteristics that were closer to those of the sustainable materials model, promoting the circular economy of plastics, with environmental benefits arising from their recyclability and their high content of bio-based monomers (78.4-78.8 wt.%).