Search Results (36)

Plastic waste accumulation is one of the most pressing environmental challenges of the 21st century, owing to the widespread use of synthetic polymers and the limitations of conventional recycling methods. Among available strategies, chemical upcycling via depolymerization has emerged as a promising circular approach that converts plastic waste back into valuable monomers and chemical feedstocks. This article provides an in-depth narrative review of recent progress in the upcycling of major plastic types such as PET, PU, PS, and engineering plastics through thermal, chemical, catalytic, biological, and mechanochemical depolymerization methods. Each method is critically assessed in terms of efficiency, scalability, energy input, and environmental impact. Special attention is given to innovative catalyst systems, such as microsized MgO/SiO₂ and Co/CaO composites, and emerging enzymatic systems like engineered PETases and whole-cell biocatalysts that enable low-temperature, selective depolymerization. Furthermore, the conversion pathways of depolymerized products into high-purity monomers such as BHET, TPA, vanillin, and bisphenols are discussed with supporting case studies. The review also examines life cycle assessment (LCA) data, techno-economic analyses, and policy frameworks supporting the adoption of depolymerization-based recycling systems. Collectively, this work outlines the technical viability and sustainability benefits of depolymerization as a core pillar of plastic circularity and monomer recovery, offering a path forward for high-value material recirculation and waste minimization. Full article

The growing global concern over plastic waste accumulation has brought this issue to the forefront of environmental discussions. The increasing demand for plastic materials has led to the widespread production of plastic resins. However, the low cost of plastics, combined with high supply and consumption rates, has resulted in a troubling surge in post-consumer plastic waste. At the same time, the essential role plastics play in ensuring quality, convenience, and modern living has made them indispensable. In this context, the concept of circularity introduces a transformative shift in consumption habits, product design, and the management of raw materials and waste. A central strategy for promoting circularity in the plastics economy is the development of chemical recycling technologies. These processes aim to convert plastic waste into higher-value materials for the chemical industry, often generating liquid and gaseous products that can serve as feedstocks—ideally leading to the recovery of the original monomers. As polyolefins are the most widely used plastics worldwide, efficient recovery of their corresponding monomers is crucial to advancing circular strategies. This review explores current methods for the chemical depolymerization of polyolefins and critically analyzes efforts focused on the direct recovery of olefinic monomers. Full article

Plastic waste accumulation presents critical environmental challenges demanding innovative circular economy solutions. This study developed a comprehensive machine learning framework to systematically identify optimal enzyme combinations for polyester depolymerization. We integrated kinetic parameters from the BRENDA database with sequence-derived features and network topology metrics to train ensemble classifiers predicting enzyme-substrate relationships. A multi-objective optimization algorithm evaluated enzyme combinations across four criteria: prediction confidence, substrate coverage, operational compatibility, and functional diversity. The ensemble classifier achieved 86.3% accuracy across six polymer families, significantly outperforming individual models. Network analysis revealed a modular organization with hub enzymes exhibiting broad substrate specificity. Multi-objective optimization identified 156 Pareto-optimal enzyme combinations, with top-ranked pairs achieving composite scores exceeding 0.89. The Cutinase–PETase combination demonstrated exceptional complementarity (score: $0.875\pm 0.008$), combining complete substrate coverage with high catalytic efficiency. Validation against experimental benchmarks confirmed enhanced depolymerization rates for recommended enzyme cocktails. This framework provides a systematic approach for enzyme prioritization in plastic valorization, advancing biological recycling technologies through data-driven biocatalyst selection while identifying key economic barriers requiring technological innovation. Full article

The increasing market demand and rising costs of raw materials have intensified interest in renewable and sustainable sources. As a result, the production of building-block chemicals from natural products or synthetic feedstocks has driven scientific research toward catalytic strategies for the depolymerization of these materials. Polymer chemistry offers significant opportunities for recycling, as polymer synthesis typically begins with monomeric units. Emerging non-destructive techniques now allow for the recovery of these original reagents. This review summarizes recent advances in catalytic methods for the depolymerization of polymers derived from both natural sources, such as cellulose and lignin, and synthetic sources, including conventional plastics. The review is structured in three main sections: catalytic depolymerization of cellulose, lignin, and plastics. Special emphasis is placed on recent studies that explore innovative methodologies. The raw materials obtained through these processes can be reintegrated into production cycles, contributing to the development of a fully circular economy. Full article

Plastics are widely used in various industries because of their light weight, low cost, and high durability. The mass production and consumption of plastics have led to a rapid increase in plastic waste problem, necessitating the development of effective recycling technologies. The chemical recycling of plastics has emerged as a promising strategy to address these challenges, enabling the conversion of plastic waste into high-purity monomers or oils, even from contaminated or mixed plastic feedstock. This review focuses on the development of catalysts for the chemical recycling of plastics in South Korea, which has one of the highest per capita plastic consumption rates and both academic and industrial efforts in this field. We examine catalytic depolymerization processes for recovering monomers from polymers, such as polyethylene terephthalate (PET) and polycarbonate (PC), as well as catalytic pyrolysis processes for polyolefins, including polyethylene (PE), polypropylene (PP), and polystyrene (PS). By summarizing recent academic research and industrial initiatives in South Korea, this review highlights the strategic role of the country in advancing chemical recycling. Moreover, this review proposes future research directions including the development of reusable catalysts, energy-efficient recycling process, and strategies for recycling mixed or contaminated plastic waste. Full article

This article considers modern approaches to obtaining synthetic oil from unconventional hydrocarbon feedstocks, including plastic waste, tires, biomass, coal, and extra-heavy oil. Particular attention is paid to multi-stage technologies, such as pyrolysis, catalytic depolymerization, gasification followed by Fischer–Tropsch synthesis, and hydrocracking of heavy residues. The important role of catalysts in increasing the selectivity and economic efficiency of processes is noted: nanostructured, bifunctional, and pollution-resistant systems are increasingly used. Economic factors influencing the competitiveness of this industry are considered, including the volatility of prices for traditional oil, government support measures, and the development of waste logistics infrastructure. It is emphasized that the strengthening of the position of synthetic oil is associated with the growth of environmental requirements stimulating the recycling of plastics, tires, and biomass; at the same time, compliance with high environmental standards and transparency of emission control play a critical role in the social aspects of projects. In addition to improving the environmental situation, the development of synthetic oil contributes to the creation of jobs, the resolution of problems of shortage of classical oil fields, and the increase of energy security. It is concluded that further improvement of technologies and integration into industrial clusters can turn this sphere into a significant component of the future energy sector. Full article

Plastics, particularly synthetic organic polymers, have become indispensable in modern life, yet their large-scale production has led to significant environmental challenges due to persistent waste. Traditional mechanical recycling methods have proven insufficient in addressing these issues. This review explores recent advancements in polymer recycling, focusing on chemical and biological processes, such as pyrolysis, depolymerization, and enzyme-based degradation, which offer more efficient and sustainable alternatives. Within the framework of a circular economy, the review also examines strategies like closed-loop and circular plastic economies. These developments represent critical steps toward creating more sustainable plastic recycling practices. The final chapter includes the Quarterly Report 2024 on recycling plastics, providing an up-to-date overview of the current state of plastic recycling and its recent trends. Full article

The chemical conversion of plastic waste has been considered an important subject in terms of the circular economy, and the chemical recycling and upcycling of poly(ethylene terephthalate) (PET) has been considered one of the most important subjects. In this study, the depolymerization of PET with n-hexylamine, n-octylamine, and 3-amino-1-propanol has been explored in the presence of Cp*TiCl₃ (Cp* = C₅Me₅). The reactions of PET with n-hexylamine and n-octylamine at 130 °C afforded the corresponding N,N′-di(n-alkyl) terephthalamides in high yields (>90%), and Cp*TiCl₃ plays a role as the catalyst to facilitate the conversion in exclusive selectivity. The reaction of PET with 3-amino-1-propanol proceeded at 100 °C even in the absence of the Ti catalyst, affording N,N′-bis(3-hydroxy) terephthalamides in high yields. A unique contrast has been demonstrated between the depolymerization of PET by transesterification with alcohol and by aminolysis; the depolymerizations with these amines proceeded without the aid of a catalyst. Full article

While multilayer plastic is difficult for recycling, innovative technologies and tactics are being developed to improve the process. New technologies in chemical recycling show promising results; however, the net improvement brought to the environment, economy, and society should be assessed for their wider adoption and diffusion. This study focuses on a Life Cycle Sustainability Assessment (LCSA) of an innovative process for the sorting and chemical recycling of multilayer plastic packaging waste from post-consumer sources to obtain new packaging for the food industry. The analysis indicated that the packaging made of rPET obtained through depolymerization is environmentally and economically competitive compared to the virgin PET. Packaging made of rPET and rLDPE obtained through delamination usually performed worse (or comparable) than the virgin counterparts. The social impact assessment indicated some areas of concern (e.g., workers’ health and safety risks due to exposure to hazardous substances), as well as potential opportunities (e.g., improved local employment). This paper is the first to present a synergetic approach to the sustainability assessment of chemical recycling technologies to obtain new high-performance packaging solutions. It provides useful insights to academics, managers, and decision makers in the plastic recycling sector whether (and under what conditions) the chemical recycling of multilayer plastic waste is feasible from the environmental, economic, and social perspectives. Despite associated uncertainties, the results are promising as an attractive option for further research, optimization, and upscaling. Full article

This paper highlights the complexity and urgency of addressing plastic pollution, drawing attention to the environmental challenges posed by improperly discarded plastics. Petroleum-based plastic polymers, with their remarkable range of physical properties, have revolutionized industries worldwide. Their versatility—from flexible to rigid and hydrophilic to hydrophobic—has fueled an ever-growing demand. However, their versatility has also contributed to a massive global waste problem as plastics pervade virtually every ecosystem, from the depths of oceans to the most remote terrestrial landscapes. Plastic pollution manifests not just as visible waste—such as fishing nets, bottles, and garbage bags—but also as microplastics, infiltrating food chains and freshwater sources. This crisis is exacerbated by the unsustainable linear model of plastic production and consumption, which prioritizes convenience over long-term environmental health. The mismanagement of plastic waste not only pollutes ecosystems but also releases greenhouse gases like carbon dioxide during degradation and incineration, thereby complicating efforts to achieve global climate and sustainability goals. Given that mechanical recycling only addresses a fraction of macroplastics, innovative approaches are needed to improve this process. Methods like pyrolysis and hydrogenolysis offer promising solutions by enabling the chemical transformation and depolymerization of plastics into reusable materials or valuable chemical feedstocks. These advanced recycling methods can support a circular economy by reducing waste and creating high-value products. In this article, the focus on pyrolysis and hydrogenolysis underscores the need to move beyond traditional recycling. These methods exemplify the potential for science and technology to mitigate plastic pollution while aligning with sustainability objectives. Recent advances in the pyrolysis and hydrogenolysis of polyolefins focus on their potential for advanced recycling, breaking down plastics at a molecular level to create feedstocks for new products or fuels. Pyrolysis produces pyrolysis oil and syngas, with applications in renewable energy and chemicals. However, some challenges of this process include scalability, feedstock variety, and standardization, as well as environmental concerns about emissions. Companies like Shell and ExxonMobil are investing heavily to overcome these barriers and improve recycling efficiencies. By leveraging these transformative strategies, we can reimagine the lifecycle of plastics and address one of the most pressing environmental challenges of our time. This review updates the knowledge of the fields of pyrolysis and hydrogenolysis of plastics derived from polyolefins based on the most recent works available in the literature, highlighting the techniques used, the types of products obtained, and the highest yields. Full article

Increasing plastic waste generation has become a pressing environmental problem. One of the most produced waste plastics originates from post-consumer packaging, of which PET constitutes a significant portion. Despite increasing recycling rates, its accumulation has created a need for the development of new recycling methods that can further expand the possibilities of recycling. In this paper, we present the application of Lewis acid catalysts for the depolymerization of PET waste. The obtained results show the formation of diisodecyl terephthalate (DIDTP), which is used as a PVC plasticizer. For this purpose, several Lewis acid catalysts were tested, including tin, cobalt, manganese, zirconium, zinc, and calcium derivatives, alongside zinc acetate and potassium hydroxide, which were used as reference catalysts. Our results show that tin (II) oxalate is the most effective catalyst, and it was then used to synthesize two application samples (crude and purified). The physicochemical properties of PVC mixtures with the obtained samples were determined and compared to commercial plasticizers, where both plasticizers had similar plasticizing properties to PVC plasticization. Full article

Polycarbonate (PC) is a highly versatile plastic material that is extensively utilized across various industries due to its superior properties, including high impact strength and heat resistance. However, its durability presents significant challenges for recycling and waste management. Polycarbonate is a thermoplastic polymer representative of the class of condensation reaction polymers obtained from the reaction of bisphenol A (BPA) and a carbonyl source, such as phosgene or alkyl and aryl carbonate. The recycling processes for PC waste include mechanical recycling, blending with other materials, pyrolysis, and chemical recycling. The latter is based on the cleavage of carbonate units to their corresponding monomers or derivatives through alcoholysis and/or hydrolysis and ammonolysis, normally under basic conditions and without catalysts. This study investigates the efficacy of the use of several heterogeneous catalysts based on silica gel as a robust support, including Sc(III)silicate (thortveitite), which has been previously reported for the preparation of polyesters, core-shell Si-ILs, and core-shell Si-ILs-ZnO, which has never been used before in the depolymerization of polycarbonate, proposing a sustainable and efficient method for recycling this valuable polymer. We chose to explore core-shell catalysts because these catalysts are robust and recyclable, and have been used in very harsh industrial processes. The core-shell silica catalysts used in this study were characterized by XRD; SEM_EDX, FT-IR, and ICP-OES analysis. In our experimental protocol, polycarbonate samples were exposed to the catalyst under controlled conditions (60–150 °C, for 12–24 h) using both oxygen and nitrogen nucleophiles. The depolymerization process was systematically monitored using advanced analytical techniques (GC/MS and GPC chromatography). The experimental results indicated that core-shell silica catalyst exhibits high efficacy, with up to 75% yield for the ammonolysis reaction, producing monomers of high purity. These monomers can be reused for the synthesis of new polycarbonate materials, contributing to a more sustainable approach to polycarbonate recycling. Full article

Since the 2005 discovery of the first enzyme capable of depolymerizing polyethylene terephthalate (PET), an aromatic polyester once thought to be enzymatically inert, extensive research has been undertaken to identify and engineer new biocatalysts for plastic degradation. This effort was directed toward developing efficient enzymatic recycling technologies that could overcome the limitations of mechanical and chemical methods. These enzymes are versatile molecules obtained from microorganisms living in various environments, including soil, compost, surface seawater, and extreme habitats such as hot springs, hydrothermal vents, deep-sea regions, and Antarctic seawater. Among various plastics, PET and polylactic acid (PLA) have been the primary focus of enzymatic depolymerization research, greatly enhancing our knowledge of enzymes that degrade these specific polymers. They often display unique catalytic properties that reflect their particular ecological niches. This review explores recent advancements in marine-derived enzymes that can depolymerize synthetic plastic polymers, emphasizing their structural and functional features that influence the efficiency of these catalysts in biorecycling processes. Current status and future perspectives of enzymatic plastic depolymerization are also discussed, with a focus on the underexplored marine enzymatic resources. Full article

Synthetic polymers, commonly known as plastics, are currently present in all aspects of our lives. Although they are useful, they present the problem of what to do with them after their lifespan. There are currently mechanical and chemical methods to treat plastics, but these are methods that, among other disadvantages, can be expensive in terms of energy or produce polluting gases. A more environmentally friendly alternative is recycling, although this practice is not widespread. Based on the practice of the so-called circular economy, many studies are focused on the biodegradation of these polymers by enzymes. Using enzymes is a harmless method that can also generate substances with high added value. Novel and enhanced plastic-degrading enzymes have been obtained by modifying the amino acid sequence of existing ones, especially on their active site, using a wide variety of genetic approaches. Currently, many studies focus on the common aim of achieving strains with greater hydrolytic activity toward a different range of plastic polymers. Although in most cases the depolymerization rate is improved, more research is required to develop effective biodegradation strategies for plastic recycling or upcycling. This review focuses on a compilation and discussion of the most important research outcomes carried out on microbial biotechnology to degrade and recycle plastics. Full article

The accumulation of waste plastics has a severe impact on the environment, and therefore, the development of efficient chemical recycling methods has become an extremely important task. In this regard, a new strategy of degradation product-promoted depolymerization process was proposed. Using N,N′-dimethyl-ethylenediamine (DMEDA) as a depolymerization reagent, an efficient chemical recycling of poly(bisphenol A carbonate) (BPA-PC or PC) material was achieved under mild conditions. The degradation product 1,3-dimethyl-2-imidazolidinone (DMI) was proven to be a critical factor in facilitating the depolymerization process. This strategy does not require catalysts or auxiliary solvents, making it a truly green process. This method improves the recycling efficiency of PC and promotes the development of plastic reutilization. Full article