Closed-Loop Recycling of Mixed Plastics of Polyester and CO2-Based Polycarbonate to a Single Monomer.

Physical blending is an effective strategy for tailoring polymeric materials to specific application requirements. However, physically blended mixed plastics waste adds additional barriers in mechanical or chemical recycling. This difficulty arises from the intricate requirement for meticulous sorting and separation of the various polymers in the inherent incompatibility of mixed polymers during recycling. To overcome this impediment, this work furthers the emerging single-monomer - multiple-materials approach through the design of a bifunctional monomer that can not only orthogonally polymerize into two different types of polymers - specifically lactone-based polyester and CO2-based polycarbonate - but the resultant polymers and their mixture can also be depolymerized back to the single, original monomer when facilitated by catalysis. Specifically, the lactone/epoxide hybrid bifunctional monomer (BiLO) undergoes ring-opening polymerization through the lactone manifold to produce polyester, PE(BiLO), and is also applied to ring-opening copolymerization with CO2, via the epoxide manifold, to yield polycarbonate, PC(BiLO). Remarkably, a one-pot recycling process of a BiLO-derived PE/PC blend back to the constituent monomer BiLO in >99 % selectivity was achieved with a superbase catalyst at 150 °C, thereby effectively obviating the requirement for sorting and separation typically required for recycling of mixed polymers.

Global plastic waste recycling and extended producer responsibility laws.

In the USA, 8.66% of municipal solid waste (MSW) plastic was recycled and 75.9% landfilled (2018). Some critical challenges in widespread adoption of post-consumer recycled (PCR) plastic include high collection costs, sortation complexity, inconsistent feedstock properties, and unknown contamination leading to safety considerations. The objective of this review is to discuss global Extended Producer Responsibility (EPR) policies/regulations and their ability to facilitate coordination of domestic/international policies and business to overcome critical recycling complications. Global EPR and recycling laws were examined to compare and contrast initiatives to increase recycling and avoid plastic waste generation. EPR laws increase producers' liability towards product generation, marketing, and disposal by applying fees and taxes on products depending on product recyclability and volume generation. Countries with established plastic EPR regulations and landfill bans often possess higher recycling rates. The results of this research can facilitate development of local regulatory mandates to increase recycling rates.

Impact of plastic pollution on outdoor recreation in the existence of bearing capacity and perspective management.

Large-scale increases in plastic waste, greenhouse gas emissions, and fossil fuel depletion all have negative consequences for the environment. Plastic pollution can lead towards negative impacts on outdoor recreational activities. China and the European Union, as world leader in recycling and reuse, are tackling this issue by putting in place measures to counteract this trend for better outdoor recreational activities. As China and EU nations are most attracted by the tourists it is possible that recreational spot can have harmful effects upon wild and human life. So, we analyze the impacts of plastic waste recycling and reuse on outdoor recreation. It is possible to speed up the circular process if industry reduces its resource and energy consumption while also being able to handle plastic waste responsibly, utilize renewable energy sources, generate jobs, and contribute to economic growth, among other things. This research investigates the transition to sustainability in the European Union nations and China between 2000 and 2020 via the prism of resource and energy productivity in the EU nations and China. The Autoregressive Distributed Lag (ARDL) Model, as well as the estimator Driscool Kraay, are employed in this study. There is a statistically significant relationship between plastic recycling and valorization because of plastic pollution leads toward negative impacts on outdoor recreation, as well as resource productivity, according to the data. Increased energy tariffs, insufficient investment in research and development, a lack of job opportunities, and other factors all act as roadblocks to the implementation of circular growth strategies.

Characterization and engineering of a plastic-degrading aromatic polyesterase.

Poly(ethylene terephthalate) (PET) is one of the most abundantly produced synthetic polymers and is accumulating in the environment at a staggering rate as discarded packaging and textiles. The properties that make PET so useful also endow it with an alarming resistance to biodegradation, likely lasting centuries in the environment. Our collective reliance on PET and other plastics means that this buildup will continue unless solutions are found. Recently, a newly discovered bacterium, Ideonella sakaiensis 201-F6, was shown to exhibit the rare ability to grow on PET as a major carbon and energy source. Central to its PET biodegradation capability is a secreted PETase (PET-digesting enzyme). Here, we present a 0.92 Å resolution X-ray crystal structure of PETase, which reveals features common to both cutinases and lipases. PETase retains the ancestral α/ß-hydrolase fold but exhibits a more open active-site cleft than homologous cutinases. By narrowing the binding cleft via mutation of two active-site residues to conserved amino acids in cutinases, we surprisingly observe improved PET degradation, suggesting that PETase is not fully optimized for crystalline PET degradation, despite presumably evolving in a PET-rich environment. Additionally, we show that PETase degrades another semiaromatic polyester, polyethylene-2,5-furandicarboxylate (PEF), which is an emerging, bioderived PET replacement with improved barrier properties. In contrast, PETase does not degrade aliphatic polyesters, suggesting that it is generally an aromatic polyesterase. These findings suggest that additional protein engineering to increase PETase performance is realistic and highlight the need for further developments of structure/activity relationships for biodegradation of synthetic polyesters.

Decomposing the decoupling of plastics consumption and economic growth in G7 and China: Evidence from 2001 to 2020 based on China's import ban.

Plastic recycling is critical for dematerializing of plastics. It has a profound implication on decoupling economic growth from environmental pressure and advancing waste plastic governance domestically and internationally while identifying drivers that might improve decoupling. In this study, plastic consumption and recycling patterns are presented, and the factors influencing the acceleration of dematerialization subsequent to the ban were investigated in the G7 countries and China. The results show that plastic consumption increases from 7.60 million metric tons (mt) to 12.60 mt between 2017 and 2019, and subsequently rapidly decreases to 6.84 mt in 2020. The plastic recycling rate drastically decreased by 21.3% in 2017, and decreased slightly from 2017 to 2020, at an annual rate of 2.9% on average. China's ban shocked the decoupling trends, which showed resilience and motivated the development of robust plastic recycling, and the global recycling transformation pattern accelerated the dematerialization of plastics. Decoupling performances of the G7 and China gradually stabilized in 2019, and all the countries were strongly decoupled in 2020, although decoupling index (DI) fluctuates from 2017 to 2020. Among the recycling-trading drivers, the improvement of waste plastic quality in recycling contributes more to decoupling, the recycling rate shows a more negative decoupling effect on China before the ban, and the population effect is weak relative to other influencing factors. The factors revealed the mechanism of decoupling of plastic consumption in the recycling-trading process, and the recyclability improvement in terms of plastic quality is important for dematerialization.

Assessment of the Electrostatic Separation Effectiveness of Plastic Waste Using a Vision System.

The work presented here describes the first results of an effective method of assessing the quality of electrostatic separation of mixtures of polymer materials. The motivation for the research was to find an effective method of mechanical separation of plastic materials and a quick assessment of the effectiveness of the method itself. The proposed method is based on the application of a dedicated vision system developed for needs of research on electrostatic separation. The effectiveness of the elaborated system has been demonstrated by evaluating the quality of the separation of mixtures of poly (methyl methacrylate) (PMMA) and polystyrene (PS). The obtained results show that the developed vision system can be successfully employed in the research on plastic separation, providing a fast and accurate method of assessing the purity and effectiveness of the separation process.

Output-oriented analysis of the wet mechanical processing of polyolefin-rich waste for feedstock recycling.

In recent years, an increasing number of studies have revealed that plastics and their components (e.g. plasticisers) pose an environmental risk. However, it is hard to imagine how our industrialised society could do without these materials, since the fields of application are manifold. One possible approach to tackle this mounting problem is the implementation of a comprehensive and well-functioning collection and recycling system. An international comparison shows that only a small proportion of the total plastics in circulation is collected and recycled. The investigations conducted under the present research project, 'Plastic Reborn', focused on both identification and analysis of the discharge paths of polyolefin-rich waste streams, under the Austrian waste management system. Another objective was determining the utilisation potential of the output fractions of these polyolefin-rich waste streams, generated from a wet mechanical processing pilot plant. Experiments have shown that the polyolefins are successfully separated from the waste streams and that a total polyolefin potential of 429,000 t y-1 remains unexploited in the Austrian waste management system. Thus, these separated plastic fractions can make a significant contribution to the implementation of the European Circular Economy Directive. The residual fractions meet the legal and company-specific requirements for their use as solid recovered fuels in co-combustion plants.

Exposing the pitfalls of plastics mechanical recycling through cost calculation.

The plastic industry needs to match the recycling goals set by the EU. Next to technological hurdles, the cost of plastics mechanical recycling is an important modality in this transition. This paper reveals how business economic cost calculation can expose significant pitfalls in the recycling process, by unravelling limitations and boundary conditions, such as scale. By combining the business economic methodology with a Material Flow Analysis, this paper shows the influence of mass retention of products, the capacity of the processing lines, scaling of input capacity, and waste composition on the recycling process and associated costs. Two cases were investigated: (i) the Initial Sorting in a medium size Material Recovery Facility and (ii) an improved mechanical recycling process for flexibles - known as the Quality Recycling Process - consisting of Additional Sorting and Improved Recycling. Assessing the whole recycling chain gives a more holistic insight into the influences of choices and operating parameters on subsequent costs in other parts of the chain and results in a more accurate cost of recycled plastic products. This research concluded that the cost of Initial Sorting of flexibles is 110,08-122,53 EUR/t, while the cost of subsequent Additional Sorting and Improved Recycling ranges from 566,26 EUR/t for rPE Flex to 735,47 EUR/t for rPP Film, these insights can be used to determine a fair price for plastic products. For the Quality Recycling Process it was shown that rationalisation according to the identified pitfalls can reduce the cost per tonne of product by 15-26%.

Isoconversional Analysis of the Catalytic Pyrolysis of ABS, HIPS, PC and Their Blends with PP and PVC.

Thermochemical recycling of plastics in the presence of catalysts is often employed to facilitate the degradation of polymers. The choice of the catalyst is polymer-oriented, while its selection becomes more difficult in the case of polymeric blends. The present investigation studies the catalytic pyrolysis of polymers abundant in waste electric and electronic equipment (WEEE), including poly(acrylonitrile-butadiene-styrene) (ABS), high-impact polystyrene (HIPS) and poly(bisphenol-A carbonate) (PC), along with their blends with polypropylene (PP) and poly(vinyl chloride) (PVC). The aim is to study the kinetic mechanism and estimate the catalysts' effect on the activation energy of the degradation. The chosen catalysts were Fe2O3 for ABS, Al-MCM-41 for HIPS, Al2O3 for PC, CaO for Blend A (comprising ABS, HIPS, PC and PP) and silicalite for Blend B (comprising ABS, HIPS, PC, PP and PVC). Thermogravimetric experiments were performed in a N2 atmosphere at several heating rates. Information on the degradation mechanism (degradation steps, initial and final degradation temperature, etc.) was attained. It was found that for pure (co)polymers, the catalytic degradation occurred in one-step, whereas in the case of the blends, two steps were required. For the estimation of the activation energy of those degradations, isoconversional kinetic models (integral and differential) were employed. In all cases, the catalysts used were efficient in reducing the estimated Eα, compared to the values of Eα obtained from conventional pyrolysis.

Environmental-friendly extraction of di(2-ethylhexyl) phthalate from poly(vinyl chloride) using liquefied dimethyl ether.

Poly(vinyl chloride) (PVC) is one of the most widely used plastics. However, a major challenge in recycling PVC is that there is no economical method to separate and remove its toxic phthalate plasticizers. This research made a breakthrough by extracting PVC with liquefied dimethyl ether (DME) and successfully separating the plasticizer components. Nearly all (97.1 %) of the di(2-ethylhexyl) phthalate plasticizer was extracted within 30 min by passing liquefied DME (285 g) through PVC at 25 °C. The compatibility of PVC with organic solvents, including liquefied DME, was derived theoretically from their Hansen solubility parameters (HSP), and actual dissolution experiments were conducted to determine the optimal PVC solvents. A liquefied DME mixture was used to dissolve PVC, and the extract was diluted with ethanol to precipitate the dissolved PVC. We demonstrated that liquefied DME is a promising method for producing high quality recycled products and that the process retains the fundamental properties of plasticizers and PVC without inducing degradation or depolymerization. Because of its low boiling point, DME can be easily separated from the solute after extraction, allowing for efficient reuse of the solvent, extracted plasticizer, and PVC. DME does not require heat and produces little harmful wastewater, which significantly reduces the energy consumption of the plasticizer additive separation process.

How the Digital Product Passport Can Lead the Plastics Industry towards a Circular Economy-A Case Study from Bottle Caps to Frisbees.

The Digital Product Passport (DPP) as a product-specific data set is a powerful tool that provides information on the origin or composition of products and increases transparency and traceability. This recycling case study accompanies the production of 2192 frisbees, which originated from collected beverage bottle caps. In total, 486.7 kg of feedstock was collected and transformed into 363.2 kg of final product with verified traceability through all process steps via a DPP, provided by the R-Cycle initiative and based on the GS1 standard. This demanded a generally agreed dataset, the availability of technical infrastructure, and additional effort in the processing steps to collect and process the data. R-Cycle offers a one-layer DPP where the data structure is lean and information is visible to everyone. This is beneficial to a variety of stakeholders in terms of transparency. However, it does not allow the sharing of sensitive information. On the one hand, the DPP has a high potential to be an enabler for customer engagement, origin verification, or as a starting point for more efficient and advanced recycling of plastics. On the other hand, the DPP involves a certain effort in data generation and handling, which must be justified by the benefits. For small, simple packaging items, the DPP may not be the perfect solution for all problems. However, with a broader societal mindset and legislative push, the DPP can become a widely used and trusted declaration tool. This can support the plastics industry in its journey towards a circular economy.

Evaluation of mixed #3-7 plastic waste from material recovery facilities (MRFs) in the United States.

Plastic recycling rates are still low in the United States (U.S.), with less than 10% of municipal solid waste (MSW) plastic being recycled. Most unrecycled plastics are identified by Resin Identification Codes (RIC) from #3-7, which are commonly destined for landfill or waste-to-energy facilities (WTE). Therefore, the composition and quality of outbound bales containing #3-7 plastics were assessed to understand the potential to increase recycling rates. Three bales were sourced from three different Material Recovery Facilities (MRFs) located in the United States. Each bale was manually sorted and characterized for quality and performance via multiple plastic characterization techniques. Considerable differences in bale composition were observed between MRFs, which correlated with the technology used by each MRF in the sorting process. The differences were substantial in the residual levels of poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE), which are highly desired for mechanical recycling processes and not expected in #3-7 plastics bales. Traditional recycling processes including washing, extrusion, and injection molding of the sorted material were employed prior to the physical, thermal, and molecular characterization. Despite differences in bale composition by plastic type, some polymer properties were similar across MRFs. This research suggests that landfill-diverted mixed plastic waste can be utilized in the mechanical recycling of currently unrecycled materials, as processes can be designed to work with consistent polymer properties. It also highlights the need to upgrade the sorting systems to prevent waste feedstocks, which can be recycled with current technologies, from contaminating other plastic streams or reach landfills.

Graphene Oxide Facilitates Transformation of Waste PET into MOF Nanorods in Ionic Liquids.

Although though ionic liquids (IL) are rapidly emerging as highly efficient reagents for the depolymerization of waste plastics, their high cost and adverse impact on the environment make the overall process not only expensive but also environmentally harmful. In this manuscript, we report that graphene oxide (GO) facilitates the transformation of waste polyethylene terephthalate (PET) to Ni-MOF (metal organic framework) nanorods anchored on reduced graphene oxide (Ni-MOF@rGO) through NMP (N-Methyl-2-pyrrolidone)-based coordination in ionic liquids. Morphological studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed mesoporous three-dimensional structures of micrometer-long Ni-MOF nanorods anchored on reduced graphene substrates (Ni-MOF@rGO ), whereas structural studies using XRD and Raman spectra demonstrated the crystallinity of Ni-MOF nanorods. Chemical analysis of Ni-MOF@rGO carried out using X-ray photoelectron spectroscopy demonstrated that nickel moieties exist in an electroactive OH-Ni-OH state, which was further confirmed by nanoscale elemental maps recorded using energy-dispersive X-ray spectroscopy (EDS). The applicability of Ni-MOF@rGO as an electro-catalyst in a urea-enhanced water oxidation reaction (UOR) is reported. Furthermore, the ability of our newly developed NMP-based IL to grow MOF nanocubes on carbon nanotubes and MOF nano-islands on carbon fibers is also reported.

Colombian Sustainability Perspective on Fused Deposition Modeling Technology: Opportunity to Develop Recycled and Biobased 3D Printing Filaments.

In the context of the preservation of natural resources, researchers show a growing interest in developing eco-friendly materials based on recycled polymers and natural fiber biocomposites to minimize plastic and agroindustrial waste pollution. The development of new materials must be integrated within the circular economy concepts to guarantee sustainable production. In parallel, fused deposition modeling, an additive manufacturing technology, provides the opportunity to use these new materials in an efficient and sustainable manner. This review presents the context of plastics and agro-industrial fiber pollution, followed by the opportunity to give them added value by applying circular economy concepts and implementing these residues to develop new materials for the manufacture of fused deposition modeling 3D printing technique feedstock. Colombian perspective is highlighted since 3D printing technology is growing there, and Colombian biodiversity represents a high reservoir of materials. Also, recycling in Colombia promotes compliance with the 2030 Agenda and the Sustainable Development Goals.

Photo-Modulating CO2 Uptake of Hypercross-linked Polymers Upcycled from Polystyrene Waste.

Incorporating photo-switches into skeletal structures of microporous materials or as guest molecules yield photo-responsive materials for low-energy CO2 capture but at the expense of lower CO2 uptake. Here, we overcome this limitation by exploiting trans-cis photoisomerization of azobenzene loaded into the micropores of hypercross-linked polymers (HCPs) derived from waste polystyrene. Azobenzene in HCP pores reduced CO2 uptake by 19 %, reaching 37.7 cm3 g-1 , but this loss in CO2 uptake was not only recovered by trans-cis photoisomerization of azobenzene, but also increased by 22 %, reaching 56.9 cm3 g-1 , when compared to as-prepared HCPs. Computational simulations show that this increase in CO2 uptake is due to photo-controlled increments in 10-20 Šmicropore volume, i. e., adsorption sites and a photo-reversible positive dipole moment. Irradiating these HCPs with visual-range light reverted CO2 uptake to 33 cm3 g-1 . This shows that it is feasible to recycle waste polystyrene into advanced materials for low-energy carbon capture.

From Bottle Caps to Frisbee-A Case Study on Mechanical Recycling of Plastic Waste towards a Circular Economy.

This study demonstrates an open-loop recycling process of a specific post-consumer plastic waste stream. The targeted input waste material was defined as high-density polyethylene beverage bottle caps. Two methods of waste collection, informal and formal, were employed. Thereafter, materials were hand-sorted, shredded, regranulated, and then injection-molded into a flying disc (i.e., frisbee) as a pilot product. To observe the potential changes in the material throughout the entire recycling process, eight different test methods including melt mass-flow rate (MFR), differential scanning calorimetry (DSC), and mechanical tests were carried out on the various material states. The study showed that the informal collection led to a relatively higher purity in the input stream, which also appeared to have a 23% lower MFR value compared to that of the formally collected materials. The DSC measurements revealed a cross-contamination by polypropylene, which clearly affected the properties of all investigated materials. The cross-contamination led to a slightly higher tensile modulus in the recyclate, while the Charpy notched impact strength declined after processing by approximately 15% and 8% compared to those of the informal and formal input materials, respectively. All materials and the processing data were documented and stored online as a practical implementation of a digital product passport as a potential digital traceability tool. Furthermore, the suitability of the resulting recyclate to be used in transport packaging applications was also investigated. It was found that a direct replacement of virgin materials for this specific application is not possible without proper material modification.

Recycling of polystyrene-based external thermal insulation composite systems - Application of combined mechanical and chemical recycling.

The material recycling of complex waste streams such as external thermal insulation composite systems (ETICS) is challenging, which is why their recycling in the sense of a circular economy is currently hardly established. Therefore, the combined mechanical and thermochemical recycling of ETICS based on expanded polystyrene (EPS) is investigated experimentally and by simulating full process chains in order to evaluate circular economy opportunities. Model ETICS as example for building and construction waste is pretreated mechanically, followed by either pyrolysis and / or gasification steps, and full mass and energy balances are derived. By the combined recycling, inorganic compounds can be separated to a large extent allowing a pre-concentrate generation. The plastic-rich pre-concentrate is converted into either pyrolysis oil with a high styrene monomer content of 51 wt% or to synthesis gas in the subsequent thermochemical conversions. The holistic approach enables a high carbon recycling rate between 53 and 68 wt%. In addition, the investigation reveals technology limitations and opportunities to be further developed and optimized.

A sustainable recycling process for end-of-life vehicle plastics: A case study on waste bumpers.

End-of-life vehicle (ELV) recycling has considerable potential value and a wide range of applications. Plastics form an increasing percentage of the total weight of automobiles as their lightweight. Recycling plastics from automobiles is important for achieving the overall recycling goal from a sustainability standpoint. In this study, the whole recycling process of automotive plastic parts was explored, using waste bumpers as an example, in which paint removal and recycled polypropylene (RPP) modification were the important links. First, LS-Dyna was used to run simulations to determine the best paint removal process parameters for surface coating treatment, and experiments were then conducted to confirm the paint removal effect. Second, component, morphological, and Gel Permeation Chromatography (GPC) analyses were conducted. As per the results, the degradation was primarily caused by surface oxidation of the ELV bumper, and the molecular weight of RPP was lower than that of new PP. Finally, the thermal and mechanical properties of RPP, modified RPP, and the new bumper were compared. The addition of nano-montmorillonite(nano-MMT), virgin PP, and a compatibilizer could improve the thermal and mechanical properties of RPP while satisfying the application requirements of the new bumper. This process provides a valuable idea for the sustainable recycling of used ELV plastics.

Short- and Long-Term Performance of Pipe Compounds Containing Polyethylene Post-Consumer Recyclates from Packaging Waste.

The polymer industry is pushed to present solutions that lead to a circular plastics economy. High plastic packaging waste recycling targets will eventually lead to a high availability of packaging material recyclates. Although the use of polyethylene terephthalate (PET) recyclates is prescribed by regulations to be used in new PET bottles, no such regulation prescribes the use of polyethylene recyclate (rPE) in new products. One possibility of using rPE, which is considered by the European Union, is the use within pipe materials. Pipe applications demand a certain property profile, most prominently a high slow crack growth (SCG) resistance, which is not met by most packaging materials or recyclates made from it. Hence, this work investigates the use of commercially available post-consumer recyclates out of high-density polyethylene from packaging applications in compounds together with high SCG-resistant virgin PE pipe material with a PE100-RC specification. Two rPEs were acquired from German producers and blended to compounds consisting of 25 m%, 50 m% and 75 m% recyclate. These compounds, together with the pure recyclates and several virgin pipe materials acting as benchmarks were tested in terms of short- and long-term mechanical performance and with other basic characterization methods. Several compounds exceeded the performance of one tested virgin PE pipe material, an injection molding PE80 grade, in several categories. The content of recyclate needed to outperform this benchmark grade was mostly dependent on the resulting melt flow rate (MFR) of the compound and thus also of the MFR of the pure recyclate. Furthermore, different levels of polypropylene contaminations within the recyclates resulted in differently contaminated compounds. This is proved to influence the SCG resistance too, as compounds of similar MFRs but with different SCG resistances were found.

Sampling Scheme Conception for Pretreated Polyolefin Waste Based on a Review of the Available Standard Procedures.

Given the rapid development of plastics recycling in recent years, the need for guidelines for sampling and material characterization is steadily emerging. However, there still exists a considerable scarcity of methods that enable proper material data acquisition. This paper consists of two parts. The first part provides a critical review of the available sampling techniques that can be utilized in the field of plastics recycling. Several sampling studies were covered in the review alongside the prominent standardization institutions. It was found that neither the literature nor the standards provide a comprehensive practice that considers the distinctive characteristics of plastic waste and applies it to different situations along the value chain. In the second part, a proposal of a sampling plan for pretreated rigid plastic waste is conceptualized based on selected information from the reviewed methods. Two variants of the proposed plan were evaluated based on the flake size distribution and the apparent density of four different pretreated polyolefin (PO) waste materials. The results of the study showed that combining stratified random sampling with composite sampling yields a good sampling technique for rigid PO waste. Moreover, the analysis of a composite sample adequately conveys the true material properties of a sublot or lot.