Polymer Waste Management

By Johannes Karl Fink

With the huge amount of plastics floating in the oceans, fish and other sea creatures are directly suffering the consequences. On land, city leaders and planners are banning one-use plastics as well as plastic bags from grocery stores in an effort to stem the use.  Many countries have made official announcements and warnings concerning the pollution caused from plastic wastes.  These urgent developments have stimulated the author to study the problem and write Polymer Waste Management.   

Plastic recycling refers to a method that retrieves the original plastic material. However, there are many sophisticated methods available for the treatment and management of waste plastics such as basic primary recycling, where the materials are sorted and collected individually. In chemical recycling, the monomers and related compounds are processed by special chemical treatments. Other methods, such as pyrolysis, can produce fuels from waste plastics. These methods and others are treated comprehensively in the book

This ground-breaking book also discusses:

• General aspects, such as amount of plastics production, types of waste plastics, analysis procedures for identification of waste plastic types, standards for waste treatment, contaminants in recycled plastics.
• Environmental aspects, such as pollution in the marine environment and landfills.
• The advantages of the use of bio-based plastics.
• Recycling methods for individual plastic types and special catalysts.

• Language: English
• Publisher: Wiley
• Release date: Aug 28, 2018
• ISBN: 9781119536390

Johannes Karl Fink

Dr. Fink is a Professor of Macromolecular Chemistry at Montanuniversit Leoben, Austria.

Book preview

Preface

The scientific literature with respect to plastic recycling increased dramatically after the mid-1970s and remains a growing field, since the production of polymers, and thus the problems concerning the disposal of these materials after their life cycle, are continuously growing.

Recently, in several countries, official announcements and warnings concerning the pollution caused by plastic wastes have been published.

For these reasons, the problems of plastic waste management have been collected from several recent scientific publications in this monograph.

Plastic recycling refers to a method that can regain the original plastic material. However, there are still more sophisticated methods available for the treatment and management of waste plastics.

These methods include the following:

Basic primary recycling, where the materials are sorted as such and collected individually. In chemical recycling, the monomers and related compounds are sampled by special chemical treatments. Other methods, such as pyrolysis can produce fuels from waste plastics, etc. These methods and others are treated in one of the chapters.

The book starts with general aspects, such as amount of plastics production, types of waste plastics, analysis procedures for identification of waste plastic types, standards for waste treatment and contaminants in recycled plastics.

Then, in another chapter, environmental aspects, such as pollution in the marine environment, such as ingestion of plastics by marine animals, and pollution in landfills are dealt with.

Furthermore, the recycling methods for plastics and then the methods for the recovery of monomers are reported in detail. Also, the advantages of the use of bio-based plastics are discussed.

Another chapter deals with the recovery into fuels, since this has also become an important aspect.

Finally, specific materials are detailed, including recycling methods for individual plastic types, and special catalysts. Here, special uses are also reported, such as the use of plastic fibers in concrete and others.

This textmay be of importance for scientists engaged in the problems of plastics waste management and also for the education of students that are interested in the current problems of plastics recycling.

The text focuses on the basic issues and also the literature of the past decade. The book provides a broad overview of plastic recycling procedures and waste management.

How to Use This Book

Utmost care has been taken to present reliable data. Because of the vast variety of material presented here, however, the text cannot be complete in all aspects, and it is recommended that the reader study the original literature for more complete information.

Index

There are three indices: an index of acronyms, an index of chemicals, and a general index. In the index of chemicals, compounds that occur extensively are not included at every occurrence, but rather when they appear in an important context. When a compound is found in a figure, the entry is marked in boldface letters in the chemical index.

Acknowledgements

I am indebted to our university librarians, Dr. Christian Hasenhüttl, Dr. Johann Delanoy, Franz Jurek, Margit Keshmiri, Dolores Knabl Steinhäufl, Friedrich Scheer, Christian Slamenik, Renate Tschabuschnig, and Elisabeth Groß for their support in literature acquisition. In addition, many thanks to the head of my department, ProfessorWolfgang Kern, for his interest and permission to prepare this text.

I also want to express my gratitude to all the scientists who have carefully published their results concerning the topics dealt with herein. This book could not have been otherwise compiled.

Last, but not least, I want to thank the publisher, Martin Scrivener, for his abiding interest and help in the preparation of the text. In addition, my thanks go to Jean Markovic, who made the final copyedit with utmost care.

Johannes Fink

Leoben, 11th July 2018

Chapter 1

General Aspects

Economic, ecological, and technical aspects of plastic waste handling have been summarized in monographs (1–4).

Plastics have become an indispensable ingredient of human life. They are non-biodegradable polymers mostly containing carbon, hydrogen, and a few other elements such as chlorine, nitrogen, etc. Rapid growth of the world population has led to increased demand for commodity plastics (5).

The total plastics production in the world is shown in Table 1.1.

Table 1.1 Plastics production in the world (6).

A list of acronyms and initials used in the waste management industry has been published (7).

1.1 History of the Literature

The issue of recycling of plastics was not important for scientists before the 1970s. The amount of literature concerning plastics recycling is collected in Table 1.2.

Table 1.2 The literature with plastics recycling in the title of the papers found in Google Scholar in March 2018.

As can be seen from Table 1.2, the boom started in the mid-1980s.

1.2 Amount of Wastes

The plastic wastes produced in the European Union in 2007 was about 52.5 Mt (8, 9). In 2008, 60 Mt were produced in Europe and the global production in 2008 was 245 Mt (10). In 2007 the amount of post-consumer plastic wastes obtained in the EU that year was 24.6 Mt, which is similar to that in 2008 (8, 10).

The total waste generated per year in 2010 in Pakistan was about 31 Mt per. In big Pakistani cities such as Karachi, about 7 to 8 Mt of solid waste is generated. It is estimated that about 6% to 8% of solid waste is post-consumer plastic waste, while only 10% of this amount is recycled (11).

The quantities of recycled poly(vinyl chloride) (PVC) in Europe are shown in Table 1.3.

Table 1.3 Quantities of recycled PVC in Europe (12).

Also, the problems of plastics wastes in other countries have been highlighted, such as, in India (13) and Bangladesh (14, 15).

Consequently, there is a growing social concern related to the management of the plastic wastes, which should proceed according to a hierarchical approach in agreement with the following order: waste minimization, reuse, recycling, energy recovery and landfilling (16).

In 2014, nine countries in Europe reached a recovery ratio of more than 95% of the post-consumer plastic waste (6). The amounts are shown in Table 1.4.

Table 1.4 Plastics recycling in European countries (6).

1.3 Metal Content in Wastes

1.3.1 Waste Poly(ethylene) and Pure High Density Poly(ethylene)

The metal content of both waste poly(ethylene) (PE) and pure high density poly(ethylene) (HDPE) used in a specific study (9) is shown in Table 1.5.

Table 1.5 Metal content of poly(ethylene) samples (9).

In pure HDPE, the total metal content is very low and accounts for less than 0.03%. In contrast, the metal content in waste PE is much higher and accounts for roughly 0.4%. The main metals present are Cu and Ti with a share of 0.162% and 0.151%, respectively (9).

1.4 Analysis Procedures

1.4.1 Fluorescence Labeling

The demand for polymers in combination with their high durability following rather short life phases ensures the flow of plastic waste into landfills (17). Therefore, plastic recycling has become indispensable. In order to produce economically attractive products based on recycled plastics, mono-fractional compositions of waste polymers are required.

However, existing measurement technologies, such as near infrared spectroscopy used in sorting facilities, show limitations with regard to the separation of complex mixtures of plastic flakes, especially when dark and black plastics are part of them. An innovative approach to overcome these obstacles and provide high sorting purities is to label different types of plastics with unique combinations of fluorescence markers, also known as tracers, which can be considered as optical fingerprints. They are incorporated into the virgin plastic resins at ppm levels during the production process and do not affect either the visual appearance nor the structural and mechanical integrity of the materials.

The goal is to realize the practical use of this concept in industrial processes. An industrial applicable spectroscopic measurement system has been designed and implemented that can identify polymer flakes with a size of a few millimeters transported on a conveyor belt in real time based on the emitted fluorescence of incorporated organic markers. In addition to the implementation of the opto-electrical measurement system, a multi-threading software application has been developed and realized which controls the hardware and collects the measured data and finally classifies the data (17).

In recent years, great effort has been expended in the development of the automated identification and sorting methods for post-consumer plastics in the waste streams that are reaching recycling processes (18). The final properties of the recycled materials largely depend on the purity of the plastic residue.

The use of fluorescence spectroscopy has been explored as a technique to identify certain waste polymers. In particular, the use of fluorescent markers for removing, for technical or safety related issues, selected HDPE containers from the waste stream has been studied. The results of this study indicate that identification by extrinsic fluorescence can be easily achieved even with a small proportion of markers of 10–3% without a significant change to the polymer structure.

The effect of thermal, hygrothermal and photochemical degradation on the fluorescence emission has been analyzed. Although the signal intensity decreases during the accelerated degradation, distinguishable fluorescent emission can be recorded even after sample exposure to aggressive conditions, thus enabling the correct identification of the marked plastics (18).

1.4.2 Time-Gated Fluorescence Spectroscopy

For the production of high-quality parts from recycled plastics, a very high purity of the plastic waste to be recycled is mandatory (19).

The incorporation of fluorescent tracers, i.e., markers, into plastics during the manufacturing process helps overcome the typical problems of non-tracer based optical classification methods.

Despite the unique emission spectra of fluorescent markers, the classification may become difficult when the host plastics show a strong autofluorescence that may spectrally overlap the fluorescence of the marker. Increasing the marker concentration is not a good option from an economic perspective and might also adversely affect the properties of the plastics.

A method that can suppress the autofluorescence in the needed signals is time-gated fluorescence spectroscopy. However, time-gated fluorescence spectroscopy is associated with a lower signal-to-noise ratio, which may result in larger classification errors.

In order to optimize the signal-to-noise ratio, the best time-gated fluorescence spectroscopy parameters were investigated and validated. A model for the fluorescence signal for plastics labeled with four specifically designed fluorescent markers was used. The implementation of time-gated fluorescence spectroscopy on a measurement and classification prototype system has also been demonstrated.

Mean values for a sensitivity of 99.93% and a precision of 99.80% could be achieved in this study. This shows that a highly reliable classification of plastics can be achieved in practice (19).

1.4.3 Content of Flame Retardants

The process of disassembling large plastic components from waste electrical and electronic equipment can increase the recovered value (20).

A higher quality and significantly higher mechanical properties can be achieved by the proposed process compared to post-shredder recycling. Today, the application of infrared spectroscopy and X-ray fluorescence in the sorting step enables the recycling of unrecovered plastics by the determination of their chemical structure and flame retardant content (20).

1.4.4 Identification of Black Plastics

Black polymers represent a much wider variety of materials than household plastic waste since they are mostly used for technical applications with special requirements (21). Various additives and filler materials, which are added in order to achieve specific properties of the plastics, complicate the identification, since spectra of the same kind of plastic can vary dramatically if different types or amounts of additives, e.g., flame retardants, fibers, or soot, are contained in the plastic parts.

Even lacquer films on the plastic part surface prevent any spectral identification and have to be removed before measurement. The importance of characterizing black polymers has led to a wide range of IR techniques, e.g., attenuated total reflection (22, 23), infrared transmission (24), emission spectroscopy (25), and photoacoustic spectroscopy (26).

Photoacoustic spectroscopy is the measurement of the effect of absorbed electromagnetic energy, particularly of light, on matter by means of acoustic detection (27).

Also, the use of reflectance measurements was demonstrated for characterizing soot filled polymers (28, 29).

1.4.4.1 Terahertz Spectroscopy

For a modern recycling cycle, a 100% mono-fraction sorting of plastic waste is needed. The final stage in most sorting machines is based on optical sensors like hyperspectral optical camera systems. These systems cannot detect black plastics because the reflectance is too low for stable detection.

THz systems offer the possibility of a spectroscopy analysis of shredded plastics (30, 31). From an economic viewpoint, full spectroscopy systems which cover a large area of the THz region are too expensive.

Test measurements have shown the possibility to separate plastics with electronic THz systems. The limitations in bandwidth can be compensated by external height sensors and sophisticated mathematic methods.

The system operates between 84 GHz and 96 GHz (31). Since the relevant plastics exhibit no specific absorption lines in this frequency range, a broadband approach is necessary to accumulate slight differences in dielectric properties. Using this technique, enough entropy can be gathered so that a machine learning algorithm can be trained to differentiate between different materials.

1.4.4.2 Middle Infrared Spectroscopy

The identification of black polymers which contain about 0.5% to 3% mass percent soot or black master batch is still a problem in recycling sorting processes (21).

Near infrared spectroscopy of non-black polymers offers reliable and fast identification, and is therefore suitable for industrial application. However, this method cannot be used for black polymers, because small amounts of carbon black or soot absorb all light in the near infrared spectral region.

However, a spectroscopy in the mid-infrared spectral region offers a possibility to identify black polymers. Mid-infrared spectral measurements can be carried out with Fourier transform infrared (FTIR) spectrometry, but the measurements are not fast enough to meet the economic requirements in sorting plants.

In contrast, spectrometer systems based on the photon up-conversion technique are fast and sensitive enough and can be applied to sort black polymer parts. Such systems are able to measure several thousand spectra per second. Hence, they are suitable for industrial applications (21).

In the middle infrared spectral region from 2.5 µm to about 16 µm wavelength, which corresponds to a wave number range from 4000 to about 600 cm–1, the different kinds of plastic material show additional vibrational modes, like deformation, rocking, and twisting modes, due to their molecular structure (21). In addition to the C–H group, other molecule groups, like O–H, N–H and O–C also contribute with their fundamental vibrations to the spectral features.

The various molecular groups with their different vibrational modes generate a unique spectrum of each polymer in the spectral range between 2500 cm–1 and 600 cm–1. This allows a definite identification of the polymer type. Therefore, this spectral range is called the fingerprint region, and middle infrared spectroscopy is the predominant analytical method for polymer characterization (21). Another important advantage of this spectral range is that reflectance spectra can be measured which allow the identification of black polymers. The reflectance spectra of a black poly(propylene) (PP) polymer part and a non-black part are compared in Figure 1.1.

Figure 1.1 Reflectance spectra of a black Poly(propylene) and a non-black Poly(propylene), reproduced from an open access article (21).

In the study, the results of the measurements were collected and analyzed by a principal component analysis method (21).

Principal component analysis is a statistical procedure that uses an orthogonal transformation to convert a set of observations of possibly correlated variables into a set of values of linearly uncorrelated variables called principal components (32, 33).

1.4.5 Raman Spectroscopy

Raman spectroscopy has potential for application in waste plastic recycling when large-scale, accurate sorting processes are required (34).

A high-accuracy rapid system for sorting a plurality of waste products by polymer type has been developed (35).

Raman spectroscopy and other complex identification techniques are used to identify and sort post-consumer plastics for recycling. The procedure reads information unique to the molecular structure of the materials to be sorted to identify their chemical compositions and uses rapid high-volume sorting techniques to sort them into product streams at commercially viable throughput rates.

The system uses a laser diode for irradiating the material sample, a spectrograph is used to determine the Raman spectrum of the material sample and a microprocessor-based controller is employed to identify the polymer type of the material sample (35).

In addition, a high-speed Raman identifier has been developed with a 3 ms measuring time (34). This identifier could be successfully integrated into an online sorting system in a shredded plastic recycling plant. A practical-scale (200–600 kg h–1) demonstration facility was constructed with 50 Raman apparatuses on a 30 cm wide conveyor with a speed of 100 mmin–1. This device also included preprocessing using specific gravity classification and putty removal.

The Raman identification system was used to control air jets to sort PP, poly(styrene) (PS), and an acrylonitrile-butadiene-styrene (ABS) copolymer with high accuracy from shredded plastics from post-consumer electrical appliances. The method of Raman plastic identification can also provide solutions to problems at recycling sites such as the detection of brominated flame retardants and the identification of black plastics (34).

1.4.6 Life Cycle Assessment

Life cycle assessment (LCA) is a technique to assess environmental impacts associated with all the stages of a product’s life from raw material extraction through materials processing, manufacture, distribution, use, repair and maintenance, and disposal or recycling (36, 37).

The basic idea of LCA is that all environmental burdens connected with a product or service should be assessed, back to the raw materials and down to the removal of waste (38). LCA is the only environmental assessment tool which avoids positive ratings for measurements which only consists of the shifting of burdens.

In the years from 1990 to 1993, the development of LCA was presented in a series of workshops at SETAC and SETAC-Europe, which culminated in the Code of Practice of 1993 (39). The basic structure which is now underlying the standardizing activities of ISO (38, 40) is

Goal definition and scoping,

Life cycle inventory analysis,

Impact assessment, and

Improvement assessment.

Also, the limitations of the LCA, the relationship between the LCA phases, and conditions for use of value choices and optional elements are described (40).

There is software available for support of LCA studies (41–43).

The basic issues of LCA have been described in several monographs (44–47).

For example, the Italian system of plastic packaging waste recycling, that collected and mechanically recycled the post-consumer PE and poly(ethylene terephthalate) (PET) liquid containers, has been investigated using this technique (48). The phases of collection, compaction, sorting, reprocessing and refuse disposal were individually analyzed and quantified in terms of energy and material consumptions as well as the emissions into the environment. The main goal of this study was the quantification of the real advantage of plastic container recycling and the definition of criteria, to be environmentally compatible and economically sustainable.

Also, the environmental impacts of lifetime extension versus energy efficiency for video projectors were investigated using LCA (49).

The results of the LCA study showed that the use stage dominates the life cycle impacts of the global warming potential and the primary energy demand. For the metal depletion potential, the production stage accounts for most of the total life cycle load. The highest shares in production emissions were identified for electronic components, i.e., printed wired boards and integrated circuits. Reconditioning and reuse of a secondary projector resulted in minor environmental impacts in comparison to the replacement and use of a primary projector with an energy efficiency increase of 5%. The saving potential of the primary energy demand is higher only in the case of a 10% more efficient device as compared to the secondary projector (49).

1.4.7 Analysis of Contaminated Mixed Waste Plastics

Mixed waste plastics, especially those obtained from municipalities, typically contain many different types of contaminants that must be removed or otherwise dealt with in any effective plastic reclamation process (50). Such contaminants can include, for example, non-melting fillers, pigments, wood, paper or metal, as well as a variety of plastics that may not be suitable for use as a feed material.

Various polymeric materials that may be present in mixed waste plastics may include PE, PP, PS, PET, ethylene-vinyl acetate, poly-(vinylidene chloride) (saran), ABS, and the like.

The ability to use a higher percentage of mixed waste plastics in the manufacture of new products, including composite wood and plastic building materials, is highly desirable.

Although many products have been manufactured successfully using scrap or recycled plastics of various types, the variability that exists in the composition and cleanliness of batches of mixed waste plastics obtained over time from either the same or different sources has previously caused serious problems with raw materials processing and manufacturing.

For example, the reclamation and reuse of a PE film is particularly problematic. In 2005, the U.S. Environmental Protection Agency reported that less than 3% of all PE film was recycled (51). Consequently, millions of tons per year of PE film is buried in landfills and never reused. Such films can include, for example, trash bags, shopping bags, bubble wrap, shrink wrap, meat packing wrap, blood bags, nursery films, and greenhouse films.

Various analytical methods have been used in the past to determine the types and properties of plastic present in mixed waste plastics, but with limited success (50).

For example, batches of mixed, reclaimed plastics have been analyzed by pressing a sample of the material between two hot plates at a suitable temperature to form a test plaque, which is then cut up and repressed several more times to make it more homogeneous. Sometimes the polymers present in such test plaques can be determined by visual inspection, although this method is highly inaccurate and only allows for gross distinctions to be made. At other times the samples may contain contaminant inclusions that are not representative of the entire batch and thus can skew the analysis. Other methods believed to have been tried to characterize mixed reclaimed plastics include, for example, melt filtration and solvent extraction.

More recently, the use of differential scanning calorimetry for various purposes has been described and explained. It has been found that the color contribution to the composite of the component plastic can be characterized by measuring a thoroughly homogenized sample of the plastic, and measuring its color parameters with a reflectance spectrophotometer. Furthermore, more useful information can be obtained by mixing small amounts of known pigments (black and white) with the material prior to homogenization, with subsequent homogenization, and color analysis. Measuring and correlating the results of such testing allow us to predict the effects of their raw material on the subsequent composite board color, which may be pigmented. It is believed that the use of prior known methods that did not thoroughly homogenize the samples would yield unforeseeable results due to small particles of highly pigmented plastic (50).

Such methods of analysis can be used to calculate the properties of materials recycled from a plurality of various batches that can be mixed together, i.e., reformulated, in the final stage (50).

Such methods allow the manufacturers to produce green products with a high percentage of reclaimed plastics without the need for separating the various components of the mixed waste plastics in the manner that has previously been required. Using these methods, manufacturers can now reformulate various batches of mixed waste plastics into feed materials for new products by blending together calculated amounts of various batches that, when combined, either alone or with some portion of virgin resin, yield a feed material having a set of physical properties falling within a desired, predetermined target window (50).

1.4.8 Construction and Household Plastic Waste

The recyclability of construction and household plastic waste collected from local landfills has been studied (52). Samples were processed from mixed plastic waste by injection molding. In addition, blends of pure plastics, PP and PE were processed as a reference set.

Reference samples with known plastic ratio were used as the calibration set for quantitative analysis of plastic fractions in recycled blends. The samples were tested for the tensile properties. Scanning electron microscope-energy-dispersive X-ray spectroscopy was used for elemental analysis of the blend surfaces and FTIR analysis was used for the quantification of the plastics contents (52).

1.4.9 Models for Forecasting the Composition of Waste Materials

Several methods to forecast the amount of waste that will emerge have been developed (53–57). These methods have also been applied to forecast the generation of electronic waste in several regional and national studies.

The material flow analysis (MFA) model can be used to describe, investigate, and evaluate the metabolism of anthropogenic systems (58). This model is based on the principle of mass conservation and can be used to quantify the flow of materials in a system defined by spatial and temporal boundaries. In an MFA model, the flows and the stocks interact with each other. The stocks increase when the inflows exceed the outflows of a system, and the stocks decrease when the outflows exceed the inflows. A flow diagram of a stock-based model is shown in Figure 1.2.

Figure 1.2 Flow diagram of a stock-based model (54).

The principle of the stock-based model can be described by the following equations:

(1.1)

(1.2)

Here, and are the product inflows entering society in year t and year t – k, respectively. is the outflow of obsolete products in year t. St and St–1 are the in-use stocks of product in year t and year t – 1, respectively. M is the maximum lifetime of the product and dk is the lifetime distribution density value (54).

Using this model, forecasts can be made based on information concerning the stock by (54):

Modeling the product lifetime distribution,

Extrapolating the stocks based on past information, and

Determining the initial year.

Substance Flow Analysis (STAN) is a free software that supports the performance of a material flow analysis (MFA) (59). The basic idea behind STAN is the combination of all necessary features of a MFA in one software product: Graphical modeling, data management, calculations and graphical presentation of the results. Application examples of this software have been detailed (59).

Also, an innovative model to forecast the composition of electronic waste materials has been presented (60, 61).

The methodology is based on the distribution delay forecasting method presented by Chancerel (62). A distribution delay forecasting method, also referred to as a market supply model, uses sales and average lifetime distribution data to forecast the amount of waste that will be discarded (60). The challenge to forecast emerging waste streams with a distribution delay method is to obtain detailed and reliable data on the historic numbers of products that were sold. In addition, the number of products that will be placed on the market in the near future should also be taken into account to make a correct forecast.

In order to demonstrate the applicability and of this proposed methodology, it was applied to forecast the evolution of plastic housing waste from flat panel displays and monitors, TVs, cathode ray tube TVs and cathode ray tube monitors. The results of the forecasts indicated that a wide variety of plastic types and additives, such as flame retardants, are found in the housings of similar products.

This case study demonstrates that the proposed methodology allows the identification of the trends in the evolution of the material composition of waste streams (60).

1.5 Standards

The standard ISO 15270:2008 provides guidance for the development of standards and specifications covering plastics waste recovery, including recycling (63). The standard establishes the different options for the recovery of plastics waste arising from pre-consumer and post-consumer sources. It also establishes the quality requirements that should be considered in all steps of the recovery process, and provides general recommendations for inclusion in material standards, test standards and product specifications.

Consequently, the process stages, requirements, recommendations and terminology presented in the standard are intended to be of general applicability (63).

1.5.1 Circular Economy Package

The European Commission recently introduced a circular economy package, setting ambitious recycling targets and identifying waste plastics as a key area where major improvements and focus is necessary (64).

The importance of plastics as a landmark case for the circular economy is denoted by the significant report on the new plastics economy released by the Ellen MacArthur Foundation. The multiple array of challenges facing used plastics has been vividly exemplified in a recent International Solid Waste Association (ISWA) report looking at the PP case.

The collection modalities were detailed. A crucial aspect affecting the quantity and quality of recycling was investigated, using recent empirical serial data from household dry recyclables collection in the United Kingdom, and specifically within the devolved administration of England (64).

In addition, the big challenges and big opportunities in the United Kingdom and other international locations were documented (65).

1.5.2 SPI Codes

The ASTM International Resin Identification Coding System, often abbreviated as the RIC, is a set of symbols