research paper plastic pollution

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Plastic pollution and potential solutions

• PMID: 30025551
• PMCID: PMC10365157
• DOI: 10.3184/003685018X15294876706211

A review is presented of the manufacture and use of different types of plastic, and the effects of pollution by these materials on animal, human and environmental health, insofar as this is known. Since 2004, the world has made as much plastic as it did in the previous half century, and it has been reckoned that the total mass of virgin plastics ever made amounts to 8.3 billion tonnes, mainly derived from natural gas and crude oil, used as chemical feedstocks and fuel sources. Between 1950 and 2015, a total of 6.3 billion tonnes of primary and secondary (recycled) plastic waste was generated, of which around 9% has been recycled, and 12% incinerated, with the remaining 79% either being stored in landfills or having been released directly into the natural environment. In 2015, 407 million tonnes (Mt) of plastic was produced, of which 164 Mt was consumed by packaging (36% of the total). Although quoted values vary, packaging probably accounts for around one third of all plastics used, of which approximately 40% goes to landfill, while 32% escapes the collection system. It has been deduced that around 9 Mt of plastic entered the oceans in 2010, as a result of mismanaged waste, along with up to 0.5 Mt each of microplastics from washing synthetic textiles, and from the abrasion of tyres on road surfaces. However, the amount of plastics actually measured in the oceans represents less than 1% of the (at least) 150 Mt reckoned to have been released into the oceans over time. Plastic accounts for around 10% by mass of municipal waste, but up to 85% of marine debris items - most of which arrive from land-based sources. Geographically, the five heaviest plastic polluters are P. R. China, Indonesia, Philippines, Vietnam and Sri Lanka, which between them contribute 56% of global plastic waste. Larger, primary plastic items can undergo progressive fragmentation to yield a greater number of increasingly smaller 'secondary' microplastic particles, thus increasing the overall surface area of the plastic material, which enhances its ability to absorb, and concentrate, persistent organic pollutants (POPs) such as dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs), with the potential to transfer them to the tissues of animals that ingest the microplastic particles, particularly in marine environments. Although fears that such microparticles and their toxins may be passed via food webs to humans are not as yet substantiated, the direct ingestion of microplastics by humans via drinking water is a distinct possibility - since 92% of samples taken in the USA and 72% in Europe showed their presence - although any consequent health effects are as yet unclear. Foodstuffs may also become contaminated by microplastics from the air, although any consequent health effects are also unknown. In regard to such airborne sources, it is noteworthy that small plastic particles have been found in human lung tissue, which might prove an adverse health issue under given circumstances. It is also very striking that microplastics have been detected in mountain soils in Switzerland, which are most likely windborne in origin. Arctic ice core samples too have revealed the presence of microplastics, which were most likely carried on ocean currents from the Pacific garbage patch, and from local pollution from shipping and fishing. Thus, sea ice traps large amounts of microplastics and transports them across the Arctic Ocean, but these particles will be released into the global environment when the ice melts, particularly under the influence of a rising mean global temperature. While there is a growing emphasis toward the substitution of petrochemically derived plastics by bioplastics, controversy has arisen in regard to how biodegradable the latter actually are in the open environment, and they presently only account for 0.5% of the total mass of plastics manufactured globally. Since the majority of bioplastics are made from sugar and starch materials, to expand their use significantly raises the prospect of competition between growing crops to supply food or plastics, similarly to the diversion of food crops for the manufacture of primary biofuels. The use of oxo-plastics, which contain additives that assist the material to degrade, is also a matter of concern, since it is claimed that they merely fragment and add to the environmental burden of microplastics; hence, the European Union has moved to restrict their use. Since 6% of the current global oil (including natural gas liquids, NGLs) production is used to manufacture plastic commodities - predicted to rise to 20% by 2050 - the current approaches for the manufacture and use of plastics (including their end-use) demand immediate revision. More extensive collection and recycling of plastic items at the end of their life, for re-use in new production, to offset the use of virgin plastic, is a critical aspect both for reducing the amount of plastic waste entering the environment, and in improving the efficiency of fossil resource use. This is central to the ideology underpinning the circular economy, which has common elements with permaculture, the latter being a regenerative design system based on 'nature as teacher', which could help optimise the use of resources in town and city environments, while minimising and repurposing 'waste'. Thus, food might be produced more on the local than the global scale, with smaller inputs of fuels (including transportation fuels for importing and distributing food), water and fertilisers, and with a marked reduction in the use of plastic packaging. Such an approach, adopted by billions of individuals, could prove of immense significance in ensuring future food security, and in reducing waste and pollution - of all kinds.

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Plastic Waste Management Strategies and Their Environmental Aspects: A Scientometric Analysis and Comprehensive Review

Saimin huang.

1 College of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China; moc.anis@59967686081yljn

Hongchang Wang

Waqas ahmad.

2 Department of Civil Engineering, COMSATS University Islamabad, Abbottabad 22060, Pakistan; kp.ude.dtaiuc@damhazaya

Nikolai Ivanovich Vatin

3 Peter the Great St. Petersburg Polytechnic University, 195291 St. Petersburg, Russia; ur.liam@nitav

Abdeliazim Mustafa Mohamed

4 Department of Civil Engineering, College of Engineering in Al-Kharj, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia; [email protected]

5 Building & Construction Technology Department, Bayan College of Science and Technology, Khartoum 11115, Sudan

Ahmed Farouk Deifalla

6 Structural Engineering Department, Structural Engineering and Construction Management, Future University in Egypt, Cairo 11835, Cairo Governorate, Egypt; [email protected]

Imran Mehmood

7 Department of Building and Real Estate, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong 999077, China; [email protected]

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Not applicable.

Plastic consumption increases with the growing population worldwide and results in increased quantities of plastic waste. There are various plastic waste management strategies; however, the present management progress is not sustainable, and plastic waste dumping in landfills is still the most commonly employed strategy. Being nonbiodegradable, plastic waste dumping in landfills creates several environmental and human health problems. Numerous research studies have been conducted recently to determine safe and ecologically beneficial methods of plastic waste handling. This article performed a bibliographic analysis of the available literature on plastic waste management using a computational approach. The highly used keywords, most frequently cited papers and authors, actively participating countries, and sources of publications were analyzed during the bibliographic analysis. In addition, the various plastic waste management strategies and their environmental benefits have been discussed. It has been concluded that among the six plastic waste management techniques (landfills, recycling, pyrolysis, liquefaction, road construction and tar, and concrete production), road construction and tar and concrete production are the two most effective strategies. This is due to significant benefits, such as ease of localization, decreased greenhouse gas emissions, and increased durability and sustainability of manufactured materials, structures, and roadways. Conversely, using landfills is the most undesirable strategy because of the associated environmental and human health concerns. Recycling has equal benefits and drawbacks. In comparison, pyrolysis and liquefaction are favorable due to the production of char and fuel, but high energy requirements limit their benefits. Hence, the use of plastic waste for construction applications is recommended.

1. Introduction

Industrial growth results in a huge number of goods for human activities and a massive quantity of waste in the environment as a result of used items being discarded following human activities. These wastes include gaseous, liquid, and solid wastes [ 1 , 2 , 3 ]. Plastic waste (PW) is a typical industrial waste, and its disposal into landfills creates serious environmental concerns [ 4 , 5 , 6 ]. Plastic items have become an essential part of people’s everyday lives and are utilized in a variety of sectors, including construction, healthcare, electronics, agriculture, the automotive industry, and packaging [ 7 ]. Plastic demand continues to grow due to its numerous advantages, including resistance to erosion, durability, convenience, simplicity of production, and cheap cost [ 8 , 9 ]. Worldwide plastic output has increased at an annually compounded rate of 8.4% since 1950; plastic manufacture reached 0.36 billion tons in 2018 and is expected to surpass 0.50 billion tons in 2025 [ 10 , 11 , 12 ]. Around 60% of PW is not recycled and encounters the environment [ 13 ]. The primary plastics in demand include polyvinyl chloride (PVC), polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyurethane (PUR), and polystyrene (PS) [ 14 ]. Similarly, PW is derived from the aforementioned key plastic types. For instance, the packaging sector consumes the most plastics produced and is the primary source of PW due to the extensive usage of disposable items [ 12 ]. PW discarded by the packaging industry is mostly composed of PET, PS, PE, and PP [ 15 ]. PW degrades slowly and can persist in the environment for hundreds of years; it is thus referred to as nonbiodegradable waste. These industries contribute to the ever-growing quantity of global nonbiodegradable PW, resulting in a variety of environmental challenges [ 16 ].

Recycling is a promising option for lowering the demand for new raw materials and reducing waste in landfills [ 17 , 18 , 19 ]. Additionally, waste recycling benefits the environment by minimizing pollution caused by raw material extraction, conserving energy, and even providing domestic jobs [ 20 ]. Figure 1 shows the life cycle of plastic products from consumption to recycling/disposal. Numerous approaches have been developed and utilized in the management of nonbiodegradable PW to date. These technologies may be classified into two categories: traditional PW and advanced PW treatment. The conventional methods of PW disposal are incineration and landfilling, both of which are constrained by a specific bottleneck. Incinerating PW consumes substantial energy and produces harmful by-products [ 21 ]. CO 2 , persistent organic compounds, particulate matter, acidic gases, and heavy metals are all extremely hazardous by-products that contribute to global warming and a variety of health issues, including lung function problems, respiratory symptoms, and an increased risk of cancer [ 22 , 23 ]. Landfilling has historically been used to handle PW, and even today, the majority of PW is disposed of in landfills [ 24 , 25 ]. Nonbiodegradable PW, on the other hand, decomposes slowly under landfill settings, requiring a growing quantity of land due to the rising volume of PW disposal. Additionally, the contact of PW with groundwater and harmful compounds soluble in water in landfills can result in the production of toxic leachate, which can cause the deterioration of the surrounding soil [ 26 ]. As a result, landfilling has been deemed an extremely adverse managing option and has been subject to a variety of restrictions [ 27 ]. To address the limitations of conventional methods, such as incineration and landfilling, a variety of innovative plastic management strategies have been established, including pyrolysis, liquefaction, and construction applications [ 28 , 29 , 30 , 31 ].

Plastic products’ life cycle [ 32 ].

As research on PW management expands due to the growing trend towards environmental protection, scholars confront information burdens that could hinder creative exploration and academic partnerships. It is therefore necessary to devise and implement a technique that enables scholars to obtain crucial information from the most dependable sources possible. A scientometric approach may aid in alleviating this weakness via a software application. The goal of this study is to undertake a scientometric analysis of bibliographic data published up to 2021 on PW management and a review of the different management strategies for PW that help reduce environmental pollution. A scientometric analysis can perform the quantitative evaluation of vast bibliometric data using a suitable software application. Conventional review studies are deficient in providing a complete and correct connection between disparate portions of the literature. Science mapping, co-occurrence, and co-citation are among the extremely difficult aspects of current exploration. The scientometric study includes the detection of the sources with the most articles, keyword concurrence, the leading authors in terms of papers and citations, and the regions actively participating in researching PW management. The Scopus database was used to extract bibliometric data for 6,101 relevant papers, which were then analyzed using VOSviewer software. Furthermore, the impact of various management strategies for PW on the environment was discussed. The aim was to analyze the benefits and drawbacks of each management technique from the literature and suggest the most desirable ones.

2. Scientometric Analysis Methods

This study employed scientometric analysis [ 33 , 34 , 35 , 36 , 37 ] along with a traditional review for the quantitative evaluation of the different aspects of the bibliographic data. Numerous articles have been published on the subject matter, and it is very important to pick a highly reliable search engine. Scopus and the Web of Science are two highly accurate search engines for that purpose [ 38 , 39 ]. The bibliographic data for the present study on PW management was collected from Scopus, as it is commonly recommended by scholars [ 38 , 40 , 41 ]. The search term “plastic waste management” returned 7756 articles in the Scopus database as of March 2022. To exclude unnecessary papers, various filter preferences were employed. The classifications “article”, “review”, “conference paper”, and “conference review” were chosen as the “document types”. The “source kind” was selected as “journal” and “conference proceeding”. The “publishing year” constraint was chosen to include papers published up through “2021”, and the selected “language” was “English”. Subsequent to the application of these conditions, 6,101 records were retained. The same procedure was also reported by various scholars [ 42 , 43 , 44 , 45 ].

Scientometric studies use science mapping, a method invented by researchers for interpreting bibliometric records for a number of reasons [ 46 ]. Data from Scopus was stored in the comma separated values (CSV) format for further assessment by employing compatible software. For further analysis, VOSviewer (version 1.6.17, Leiden University, Leiden, The Netherlands) was utilized to construct the scientific visualization and quantitative assessment of the literature. VOSviewer is an open-source and freely available visualization product that is broadly employed in a range of disciplines and well-reviewed by scholars [ 47 , 48 , 49 , 50 , 51 ]. Thus, the current study’s objectives were met by utilizing VOSviewer. In VOSviewer, the retrieved CSV files were imported, and further analysis was carried out while keeping data consistency and reliability. The sources of publications, the most frequently used keywords, the authors with the most citations, and countries’ participation were evaluated during the bibliographic evaluation. The several aspects, their associations, and co-occurrence were visualized through diagrams, while their statistical values were listed in tables. Figure 2 demonstrates the flowchart of the scientometric review.

Flowchart of the analysis procedure.

3. Results and Discussions

3.1. subject areas and annual publication pattern.

The Scopus analyzer was employed to perform such analysis as to determine the most relevant research areas. The three leading document-producing areas were found to be Environmental Science, Engineering, and Materials Science, as displayed in Figure 3 . For the searched terms “plastic waste management”, publications of the Environmental Science, Engineering, and Materials Science disciplines comprised around 38%, 10%, and 6% of the documents, respectively, accounting for a total of 54% contribution based on the document count. Furthermore, the type of documents was also analyzed for the searched keywords in the Scopus database, as depicted in Figure 4 . This analysis revealed that, for “plastic waste management”, journal articles, conference papers, journal reviews, and conference reviews comprised nearly 75%, 14%, 10%, and 1% of the total documents, respectively. Figure 5 illustrates the annual trend of publications in the present study area from 1965 to 2021, as the first document on the subject research area was found to have been published in 1965. Steady growth in the publication count was noticed, with an average of around 19 articles annually up to 2000. This annual average of publications rose to about 129 from 2001 to 2015. The number of publications rose substantially in the last six years (2016–2021), with an average of around 592 publications per year.

The subject areas of the articles.

Various types of documents published in related fields of study.

Annual publication trend for articles.

3.2. Publication Sources

This investigation was carried out on the retrieved bibliometric data with the VOSviewer. The “analysis type” was selected as “bibliographic coupling”, and the “analysis unit” was kept as “sources”. A threshold of at least 50 papers per source was established, and 17 of the 1555 sources satisfied these constraints. The publication sources (journals) that published a minimum of 71 papers, including data on PW recycling from up to 2021, are displayed in Table 1 , together with their number of citations received in that time period. Waste Management; Resources, Conservation and Recycling, and Science of the Total Environment are the leading three sources/journals in terms of the number of papers, with 548, 270, and 227 papers published, respectively. Moreover, the aforementioned journals also received the most citations in the related research area with 25,171, 13,142, and 11,555 citations, respectively. Notably, this analysis would provide a basis for forthcoming scientometric studies in this subject area. In addition, past manual evaluations were unable to provide science mapping visualization maps. Figure 6 represents a visualization map of the journals that have published at least 71 documents. The box size is proportional to the journal’s article count in the current research; a bigger box size implies a larger role. As an example, Waste Management has larger box dimensions than the others, denoting that it is a highly significant journal in that area. Two clusters were generated, each represented by a different color (red and green) in the illustration. Clusters are constructed depending on the extent of research sources or the frequency with which they are cited together [ 52 ]. In this analysis, clusters are formed based on the frequency with which they are cited together. The VOSviewer constructed clusters of journals identified by varying colors based on co-citation patterns in the published articles. For example, the green cluster comprises eight journals that are repeatedly cited in similar articles. Moreover, closely-spaced frames (journals) have stronger connections than widely spread frames. As an example, Waste Management is more directly related to Resources, Conservation and Recycling than it is to the Journal of Environmental Management.

Science mapping of publication sources with a minimum of 50 articles in the relevant study area. Box size is proportional to the number of articles published in a particular journal, and color refers to the clustering of journals based on co-citation patterns in the published articles.

Sources of publications with a minimum of 71 papers in the related field up through 2021.

3.3. Keywords

Keywords are crucial in research as they define and indicate the basic topic of the study domain [ 53 ]. For the analysis, the “analytical type” was selected as “co-occurrence” and the “analysis unit” as “all keywords”. The lowest number of occurrences for a keyword was kept 100. As a result of these limits, 221 of the 36,091 keywords satisfied the condition. The leading 20 keywords that were employed frequently in the published papers in the subject area are displayed in Table 2 . The top five most frequently occurring keywords on the subject topic include “waste management”, “plastic”, “recycling”, “plastics”, and “plastic waste”. “Plastics” and “plastic” are the same keywords and need to be considered as a single keyword. However, no such option in the VOSviewer is available to merge the “plastic” and “plastics” keywords. So, they were treated separately. We might add their numerical values manually (2290 + 1548 = 3838), but they will not be displayed in the figure. This analysis revealed that PW recycling has been under study most often for waste management and sustainable development. Figure 7 shows the visualization map of keywords in terms of their co-occurrences, their links, and the density connected with their rate of recurrence. The dimension of a keyword circle in Figure 7 a reflects its frequency, while its position implies its co-occurrence in articles. Furthermore, the image demonstrates that the specified keywords have greater circles than the others, signifying that they are vital keywords in the research of PW management. Clusters of keywords have been highlighted distinctively in the graph to reflect their co-occurrence across a variety of publications. Clustering by color is based on patterns of co-occurrence among multiple keywords in the published articles. Green, red, blue, and yellow suggest the presence of four clusters ( Figure 7 a). As seen in Figure 7 b, diverse colors correspond to different levels of keyword density. The colors are ordered by their density, with red having the maximum and blue having the minimum density. “Waste management”, “plastic”, “recycling”, and “plastics” have red areas, suggesting a greater density. This finding will assist future writers in picking keywords that will expedite the discovery of published data in a specific area.

Co-occurrence of keywords: ( a ) Scientific mapping: circle size is proportional to the number of co-occurrences of a particular keyword; different colors show distinct clusters (red: cluster 1, green: cluster 2, blue: cluster 3, and yellow: cluster 4), and clustering by color is based on patterns of co-occurrence among multiple keywords in the published articles; ( b ) Density mapping.

The leading 20 most utilized keyword combinations in the related study area.

3.4. Authors

Citation numbers show how influential a researcher is in a given research domain [ 54 ]. In the VOSviewer, “co-authorship” was chosen as the “analysis kind”, and “authors” as the “analysis unit”. The fewest number of papers required for a writer was set at 10, and 60 of the 18,236 writers satisfied this criterion. Table 3 displays the leading writers in terms of publications and total citations in the research of PW management, as assessed by data obtained from the Scopus search engine. The average number of citations for each author was computed by dividing the total number of citations by the total number of papers. It was complicated to measure a scientist’s efficacy considering all aspects, such as the number of publications, total citations, and average number of citations. Conversely, the writer’s evaluation was defined by equating each aspect independently, i.e., total publications, total citations, and average citations. When it comes to overall papers, the leading three authors are Li, J. with 39; Wang, H. with 36; and Zhang Y. with 34 papers. When it comes to total citations, Thompson, R.C. takes the lead with 7055; Wilcox, C. is second with 5130; and Li, J. is third with 1964 total citations in the present study area. Furthermore, when comparing average numbers of citations, the following authors come out on top: Thompson, R.C. has about 588; Wilcox, C. has about 395; and Al-Salem, S.M. has about 140 average citations. The visualization of writers with at least 10 papers and the connection of the most notable authors is shown in Figure 8 . It was noticed that 41 of the 60 authors were connected based on citations. This analysis disclosed that several authors are interconnected based on citations in the research of PW management.

Science mapping of authors: ( a ) With a minimum of 10 publications; ( b ) Linked authors based on citations. Box size is proportional to the number of publications by a particular author, and color refers to the clustering of authors based on patterns of co-citation in the publications.

Authors with at least 10 publications in the related study field up through 2021.

3.5. Documents

The number of citations a document receives indicates its influence within a specific field of research. Citation-dense papers are often regarded as pioneers in their respective fields of research. For this assessment, “analysis kind” was set as “bibliographic coupling” and “analysis unit” as “documents”. The limit for the lowest number of citations set to 100, and 384 of the 6101 documents met this criterion. The leading 10 articles based on citations in the field of PW management are given in Table 4 , along with their writers and citations details. Jambeck, J.R. [ 55 ] obtained 4313 citations for their publication “Plastic waste inputs from land into the ocean”. Geyer, R. [ 13 ] and Hidalgo-Ruz, V. [ 56 ] received 3675 and 2007 citations, respectively, for their particular works and were rated in the leading 3. However, only 10 articles received more than 1000 citations up through 2021. Additionally, Figure 9 demonstrates the writer’s mapping of documents, connections based on citations, and the density of the connected documents in the current study topic. The VOSviewer study determined that 286 of 384 documents were connected based on citations. Figure 9 a illustrates the scientific visualization of the contributors to the study of the topic under study whereas Figure 9 b represents the mapping of connected documents based on citations. Furthermore, the density mapping ( Figure 9 c) demonstrates the increased density concentration of the top articles.

Scientific visualization of documents: ( a ) Documents with a minimum of 100 citations; ( b ) Linked documents based on citations: circle size is proportional to the number of co-occurrences of a particular keyword, and different colors show distinct clusters formed based on the pattern of co-citations; ( c ) Density of linked documents.

Leading 10 most cited articles up through 2021 in the related study area.

3.6. Countries

Different nations have provided more to the current research area than others have and intend to. The network mapping was established to enable readers to view locations dedicated to eco-friendly construction. The “analysis type” was selected as “bibliographic coupling”, and the “analysis unit” as “countries”. The lowest document limit for a nation was set 30, and 48 countries satisfied this condition. Table 5 shows the top 20 countries based on publications in the current research area. The United States, India, and China presented the most papers with 871, 581, and 551 documents, respectively. However, the United States has the highest total number of citations at 42,924, then the United Kingdom with 30,071, and China with 19,944 total citations. Figure 10 depicts the science mapping visualization as well as the density of nations connected by citations. The size of a box is comparative to the impact of a nation on the subject topic ( Figure 10 a). According to the density visualization, the nations with the highest involvement had a greater density ( Figure 10 b).

Science mapping of the top contributing countries: ( a ) Network visualization: box size is proportional to the number of publications by a particular country, and different colors show distinct clusters created based on the pattern of co-citations of countries in published articles; ( b ) Density visualization.

Leading 20 countries based on published documents in the present research area through 2021.

4. Management Techniques for Plastic Waste

The management techniques for PW are broadly classified into six categories, namely landfills, recycling, pyrolysis, liquefaction, road construction and tar, and concrete production [ 63 ], as displayed in Figure 11 . These techniques are briefly discussed in the subsequent subsections.

Various management techniques for plastic waste.

4.1. Landfills

Landfilling is the most rudimentary technique of PW disposal. Landfills contain a great deal of garbage and have been linked to a number of issues. It is not a sustainable means of disposing of PW [ 64 ]. The process of landfilling PW from generation to disposal is shown in Figure 12 , and Figure 13 illustrates the issues connected with the disposal of PW based on a review of the literature. Disposing of PW in landfills may exacerbate land shortages and hinder the operations of waste management organizations [ 5 , 65 , 66 ]. Additionally, when PW encounters bodies of water, it contaminates them [ 67 , 68 ]. Hence, dumping PW creates concerns for human health and the environment [ 69 ]. Landfills have long been recognized as contaminating the soil [ 68 , 70 ]. Thus, landfilling PW must be avoided, and other management techniques should be followed as described in the following sections to help protect the environment.

Flowchart of plastic waste management from generation to landfill/shredding [ 63 ].

Disadvantages of plastic waste disposal in landfills.

4.2. Recycling

Generally, recycling is the procedure through which PW is re-extruded. PW is mostly recycled mechanically, which is one of the most cost-effective methods [ 71 , 72 ]. The first phase is shredding or cutting, which involves cutting PW using saws or shears into tiny fragments that are simpler to carry. In the contaminant-separation process, paper pieces, dirt, and smaller particles are removed from PW with the help of a cyclone separator. PW with varying densities is separated using a flotation method in order to manage plastic with varying densities. The next step is milling, which collects and mills the individual polymers. Without the pre-processing phases stated prior to milling, the plant’s efficiency is reduced. Following that, the milled PW is cleaned with water. Chemical washing is also useful for some types of material handling (most notably for removing adhesive from PW), where caustic soda and wetting agents are utilized. The materials are then collected and kept or transferred for further processing during the agglutination process. Extrusion of the plastic results in the formation of strands, which are subsequently pelletized to create a single-polymer plastic. The items are quenched by cooling them with room temperature water. Granulated plastic is then offered on the market as grocery bags, blinds, shutters, and other home items [ 63 ].

Recycling is based on the notion of remolding plastic material. It is difficult to turn the full amount of PW into a reusable product. This mass reduction throughout the recycling process is accounted for as plastic emission [ 73 ]. Another downside of recycling is the significant amount of energy consumed throughout the process [ 74 ]. In comparison to the initial product, the durability of these items is significantly reduced. However, the most prudent course of action regarding plastic is to drastically minimize its usage and reliance. Guidelines limiting the usage of recycled materials have been enacted. For example, used PET containers cannot be utilized to package drinks [ 75 ]. The manufacture of wood–plastic composites is one recycling process that has gained increasing interest [ 76 ]. This approach of PW management entails the creation of novel materials by mixing PW with woody waste biomass in various amounts. The primary advantages of this technology are the capacity to regulate the characteristics of the materials generated and the efficiency with which two distinct forms of waste may be removed in the same process.

Panels made using a mixture of macadamia shells and automotive PW have exhibited more strength and resistance to fire than panels made entirely of automotive PW [ 77 ]. Similarly, it was discovered that when PW was combined with straw flour, its mechanical characteristics greatly improved [ 78 ]. It was also reported that the field of PW and woody biomass composites is still in its initial stages and needs additional investigations before its long-term viability can be determined.

4.3. Pyrolysis

The pyrolysis of PW has been investigated as a method for converting home and industrial PW to fuel by subjecting it to severe process conditions, most notably elevated temperature [ 79 ]. It entails the degradation of polymeric plastic molecules with a high molecular weight into light gas and liquid hydrocarbons in the absence of oxygen to avoid the creation of oxygen-containing by-products, such as sulfur and carbon oxides, in a reactor devised to endure severe conditions [ 79 ]. There are two primary ways by which it is carried out, which are characterized by the presence or absence of a catalyst. Thermal pyrolysis comprises the application of high temperatures and pressure to PW, resulting in the destruction of the molecule by a mixture of scission, in which the carbon chain is cracked around the center, chain crosslinking, and cyclization of linear structures [ 80 ]. On the other hand, catalytic pyrolysis utilizes a catalyst to boost the efficiency of the degradation and decrease the energy needs. The outputs of PW pyrolysis vary according to the kind and amount of feedstock utilized and the reactor employed. These may be classified into three distinct classes, including gaseous and liquid hydrocarbons and char. The pyrolysis liquid products are essential and can be utilized as a direct fuel or after mixing with gasoline, motor oil, or diesel, provided they sustain necessary characteristics [ 81 ].

The most-often obtained liquid products are paraffin (octane, heptane, and butane), olefins, isoparaffins, propane, and aromatics [ 82 ]. Char is a carbonaceous, solid substance that is produced as a by-product of the manufacturing of liquid oil and natural gas. Increases in the proportion of char generated were found to be associated with increases in the pyrolysis temperature [ 83 ]. Pyrolysis produces gaseous products mostly composed of lighter hydrocarbons formed by successive successful cracking, as well as some volatile impurities from char. The yield of gaseous products from the pyrolysis of PW, including low-density polyethylene (LDPE) and polystyrene and is much less than that of liquid products, with an increase in gaseous yield being proportional to a rise in temperature [ 84 ]. In comparison, polyvinyl chloride and polyethylene terephthalate-based PW yielded substantial gases (>75% by weight) because of their different processes and low energy requirements [ 85 ] These gaseous products (methane, butane, ethane, and propane) can be used to generate electricity.

Temperature has the greatest effect on a pyrolysis reaction of PW, with the endothermic characteristic of pyrolysis resulting in enhanced rates of conversion [ 86 ], as well as considerations for extreme operating settings [ 87 ]. Additionally, high temperatures were shown to be favorable for cyclization reactions between the products [ 88 ] but detrimental to the yield of waxes [ 89 ]. Residence time also influences the products, with greater residence time being associated with an increase in the fraction of linear hydrocarbon products and the conversion rate [ 8 ]. Pyrolysis of PW can also be carried out in conjunction with biomass, with a range of synergistic effects on the type and yield of the products, including a decrease in the formation of tar and an increase in the liquid yield [ 82 , 90 ]. Microwave pyrolysis is another method that has gained popularity. It entails causing the breakdown of polymeric molecules using high-intensity microwaves that raise the molecules’ surface temperature [ 91 ]. The plastic material is turned into a fuel made up of a mixture of hydrocarbons during the pyrolysis of PW.

4.4. Liquefaction

Hydrothermal liquefaction has a prolonged history of being used to convert biomass, primarily of algal origin, to bio-oil. It entails the transformation of cellular material into valuable liquid fuel. The method has been adapted to absorb PW and is particularly appealing since it allows for the recovery of plastic for reuse alongside liquid gasoline [ 92 ]. Typically, PW is liquefied in the presence of a biomass source, a process known as co-liquefaction. In comparison to alternative waste to value technologies, liquefaction of biomass results in a more even distribution of components among the products. Higher carbon content in the products should naturally result in improved fuel performance [ 93 ]. It is worth noting that polymers may be liquefied in the absence of biomass although this is a less popular process than co-liquefaction. For any liquefaction method, catalyst choice is critical and has a significant impact on the process’s efficiency. In most situations, heterogeneous catalysts are used in the liquefaction process to reduce the likelihood of corrosion and to optimize the reaction’s interactions [ 94 ].

Depolymerization, disassociation, and recombination are the three processes in the operation of a hydrothermal liquefaction system. Depolymerization of the three major components found in biomass into smaller molecules such as proteins, tiny carbohydrates, and amino acids occurs when a solvent and/or catalyst are added, as well as in high temperature and high pressure conditions [ 95 ]. The smaller molecules dissociate further to produce components in their native state, which then recombine to form the product. Bio-oil is created when recombination is combined with a polymerization event. The creation of char and coke arises from further polymerization and degradation of the bio-oil. The lack of a polymerization step leads to the production of biogas [ 96 ]. The use of polymers in liquefaction tends to reduce the amount of coke produced. As a result, using plastics in liquefaction can be thought of as having two benefits: recycling PW and improving existing liquefaction products [ 97 ]. It has been shown that liquefaction requires a huge amount of water, which might be considered a drawback. Liquefaction is likewise a high-temperature process that consumes a lot of energy [ 98 ].

4.5. Road Construction and Tar

Tar is an organic compound with a variety of different structures and compositions. Tar is produced in significant amounts when PW is co-gasified or co-pyrolyzed with other compounds such as heavy metals [ 99 , 100 ]. The extremely condensable behavior of the organic components of tar makes its existence in gas-manufacturing facilities an onerous prospect, owing to its proclivity for slagging and inhibiting catalysts [ 99 ]. While tar has a detrimental influence on gas-manufacturing facilities, it is widely employed in other sectors and adds value. It is used to treat plant and human diseases and has a wide range of applications in the coatings industry [ 101 ]. The most prevalent use of liquid tar is in road construction [ 102 ]. In several states, especially developing ones, roads are constructed using a bitumen base and successive layers over it [ 103 ]. These layers get compressed over time, forming a robust and sturdy structure. These layers eventually erode and are replenished over time. The use of PW to coat bitumen is a technology that has seen a recent spike in popularity [ 104 , 105 ]. The benefits are twofold: non-biodegradable PW may be disposed of efficiently, and roads using PW have demonstrated greater performance than regular tar roads [ 106 ]. Nearly one ton of PW is used to pave one kilometer of road, resolving the complicated issue of garbage disposal and subsequent emissions [ 107 ]. It was discovered that using PW in the road construction process saves about $40,000 per kilometer of road [ 108 ]. India is the most vocal proponent of this technique, followed by the Netherlands and the United Kingdom. Other developing nations, such as Malaysia and Ghana, are also embracing the usage of PW in road construction [ 63 ].

The addition of PW results in a higher melting point for bitumen as well as greater flexibility. Roads with plastic in them have also been found to have a higher rainfall tolerance. Furthermore, the possibility of using a mixed plastic feed decreases the possible costs associated with PW segregation. Plastic roads have a higher level of ultraviolet resistance and have a longer lifespan. The stiffening effect of PW in bitumen is due to a gradual rise in the attraction forces among the bitumen and the PW over time. Furthermore, the application of oxidizing and linking agents improved the bonding forces even more [ 109 ]. In addition, the PW-modified road has been shown to carry heavier loads for lengthy periods of time [ 110 ].

4.6. Concrete Production

Concrete is widely used in the building sector and hence serves as a cornerstone of industrial advancement [ 111 , 112 , 113 , 114 , 115 , 116 , 117 ]. Recent concrete research has emphasized the use of various ingredients, with a focus on lighter materials, as alternatives to natural aggregates in concrete [ 118 , 119 ]. PW has the potential to be employed in the manufacture of concrete as an aggregate substitute [ 120 , 121 , 122 , 123 ]. Incorporating PW has a detrimental influence on concrete strength properties [ 124 ]. These recycled plastic aggregates, on the other hand, have the potential to enhance a variety of material characteristics and may be used in sound-insulating, thermal, and lightweight materials [ 25 ]. In structural concrete applications where lesser stresses are applied and durability is less crucial, a particular proportion of PW may be used [ 125 ]. Gu and Ozbakkaloglu [ 126 ] reported that PW is preferable for lightweight concrete manufacture. Additionally, because of its better functional performance, concrete comprising PW is suitable for thermal and soundproofing applications [ 127 , 128 , 129 ]. Due to the reduced conductivity of plastic and the higher porosity of composites containing PW as an aggregate, it was observed that composites manufactured with PW had a thermal conductivity five times less than normal composites [ 130 ]. Thermal conductivity reduced with increasing content due to the hydrophobicity of plastic, resulting in the creation of voids in the mixtures [ 131 ]. Numerous studies have revealed that PW, due to its porous nature, has the potential to be used as a sound-absorbing material in concrete [ 128 ].

The use of PW in concrete will decrease not just dependency on natural resources but also manufacturing costs. However, using PW in large quantities in concrete is not recommended due to the considerable loss of strength. Usually, a replacement ratio of 10–15% of PW can result in a material with acceptable mechanical properties [ 132 , 133 , 134 , 135 ]. The increased air content and lower bonding capacity of plastic aggregates in concrete are the major causes of decreased strength. As a result, it is recommended that more research be conducted on the long-term behavior of plastic aggregates in concrete and their impact on the environment and service life. Various researchers have explored further usage of PW in construction, including plastic bottles in concrete blocks [ 136 ], plastic bottle bricks [ 137 ], and plastic fibers in concrete [ 138 ]. The management strategies for PW other than landfilling and their applications in various products are shown in Figure 14 .

Flowchart of various management strategies for shredded plastic [ 63 ].

5. Discussion and Environmental Aspects

This study aimed to carry out a scientometric analysis of the different aspects of the literature on PW management up through 2021 and a review of the various management strategies for PW. The study identified six broad categories of PW management, i.e., landfilling, recycling, pyrolysis, liquefaction, road construction and tar manufacture, and concrete production. The impact of each management strategy on various aspects, such as land requirements, carbon emissions, energy requirements, costs, skilled labor requirements, localization, sustainability of the products, and impacts on society, was compared by constructing Table 6 . After comparing all of the aspects, it was noted that landfilling is the least desirable method due to its negative impact on the environment and human health. On the other hand, the other methods benefit both waste management and the environment. Recycling, the other prominent current strategy of PW handling, was found to have nearly equal benefits and drawbacks. Pyrolysis and liquefaction are favorable since they produce important by-products like char and fuel and the prospect of energy recovery. When plastic-to-fuel methods are used, the reliance on fossil fuels for energy can be significantly decreased. However, the detrimental impact of the high energy needs and challenges with process localization raises concerns. The most effective methods of PW handling have been determined to be the conversion of PW into tar for road construction and into concrete for building construction. This is due to significant benefits, such as ease of localization, reduced greenhouse gas emissions, and the increased durability and sustainability of manufactured materials and constructed structures and roads, the existence of which considerably overcomes disadvantages like the inability to recover expended energy. Due to their extremely effective and sustainable advantages, these two strategies should be prioritized as alternatives to present strategies for future applications and research.

The impact of various plastic waste management strategies on different aspects.

As previously stated, a substantial amount of PW is created on a global scale. Currently, PW is dumped in landfills, burnt, or recycled, but present recycling processes are unsustainable, and PW dumping continues to be the most extensively utilized approach [ 139 ]. Additionally, the combustion of PW emits a significant quantity of CO 2 into the environment [ 140 ]. On the other hand, recycling PW for various applications might alleviate the aforementioned difficulties related to its disposal in landfills. The benefits of reusing PW are illustrated in Figure 15 . By decreasing the quantity of PW discarded in landfills, challenges for waste management may be mitigated while also safeguarding the natural environment. Due to the minimal or total lack of value of PW, its usage in the manufacture of various products decreases the expenditure of raw materials, thereby reducing the cost [ 141 , 142 ]. In addition, natural resources can be protected with the use of recycled PW. Thus, sustainable products might be manufactured at a cheaper cost by utilizing recycled PW.

Advantages of plastic waste recycling and reuse.

6. Future Recommendations

This study discussed the various PW management strategies, their benefits and drawbacks, and environmental aspects associated with each strategy. After a comprehensive review, this study suggests the following:

• To control landfilling PW, local governments can promote closed-loop recycling of PW through a variety of initiatives and campaigns, as well as by imposing restrictions and fines on landfilling and incineration, while simultaneously lowering taxes on recyclable materials.
• Waste management techniques should be considered when designing plastics, mixes, and mechanical recycling processes. If the continuous use of plastics is required, it is better to understand their material life cycle and develop solutions that can sustain their worth over repeated uses and reprocessing. This uniformity will result in increased recycling rates, increased recycled content in products, and a reduction in the amount of plastic we export, landfill, and burn.
• Several aspects, including the state of the PW, the presence of impurities in the PW, and the type of reactor, influence the mechanism of catalytic pyrolysis and, therefore, the yield and distribution of the products. Thus, the effects of all these variables must be carefully known and regulated to assure the process’s viability. Another problem is developing standards for post-consumer PW processes and products, as well as adopting more complex pyrolysis technologies. Additionally, while it is possible to get a suitable product yield and composition at the laboratory scale, industrial producers will face difficulties maintaining the desired result while scaling up PW pyrolysis. If these obstacles are overcome, it will be possible to accomplish a low-cost, partial replacement of dwindling fossil fuels, as well as a reduction in PW, which is currently the primary source of environmental contamination, and a reduction in crude oil imports.
• Liquefaction of PW is a viable alternative to pyrolysis for resolving the problem of excess PW due to its gentler processing conditions [ 143 ]. Although the generation of oil from this process offers an alternative to the transportation industry’s reliance on fossil fuels, additional research is required to properly optimize the approach and determine the oil’s efficiency in engines.
• The use of PW in construction materials will reduce not only dependency on natural resources but also material costs. However, using PW as an aggregate in large quantities in construction materials is not recommended due to a significant loss of material strength. In general, a replacement ratio of 10–15% of PW may yield material with adequate mechanical properties [ 132 , 133 , 134 , 135 ]. The increased air content and lower bonding capacity of PW in concrete are the primary causes of decreased strength. Further research is required in this domain to optimize these aspects. By modifying the shape, size, and surface of PW particles, the material properties can be considerably improved. Additionally, guidelines for the use of PW in construction materials are crucial for reliable design and construction since they describe the appropriate content, allowable size and shape, and structural types. Indeed, standards are often formed over a period of several years after collecting sufficient, reliable information and an understanding of the subject has been achieved. As a result, it is advised that further research be conducted on the long-term performance of PW in construction materials, as well as tits impact on the environment and service life.

7. Conclusions

This study adopted a scientometric analysis strategy to assess various parameters of the available literature on plastic waste (PW) management. Bibliometric data of 6101 relevant articles were retrieved from the Scopus database, and analysis was carried out in VOSviewer software. Moreover, various management strategies for PW are discussed, along with their environmental aspects. The aim was to compare the benefits and drawbacks of all management strategies so as to recommend the most desirable ones. This study reached the following conclusions:

• (1) The analysis of publication sources containing documents on the research of PW management revealed that the leading 3 sources are Waste Management; Resources, Conservation and Recycling; and Science of the Total Environment with 548, 270, and 227 papers, respectively. Moreover, the aforementioned journals also received the most citations in the related research area with 25,171, 13,142, and 11,555 citations, respectively.
• (2) The evaluation of keywords in the subject research area disclosed that the top five most frequently occurring keyword combinations on the subject topic included “waste management”, “plastic, recycling”, “plastics”, and “plastic waste”. It was noticed that PW recycling has been under study mostly for waste management and sustainable development.
• (3) The analysis of authors showed that only 60 authors had published at least 10 articles on PW management. The top authors, with respect to the number of articles, citations, and average citations, were categorized. In terms of total publications, the top 3 writers are Li, J. with 39; Wang, H. with 36; and Zhang, Y. with 34 publications. Thompson, R.C. leads the field in terms of citations with 7055; Wilcox, C. is second with 5130; and Li, J. is third with 1964 citations up through 2021. Additionally, when comparing average citations, the following writers stand out: Thompson, R.C. has about 588; Wilcox, C. has about 395; and Al-Salem, S.M. has about 140 average citations.
• (4) The assessment of documents containing data on PW management showed that Jambeck, J.R. [ 55 ] obtained 4313 citations for their publication “Plastic waste inputs from land into the ocean”. Geyer, R. [ 13 ] and Hidalgo-Ruz, V. [ 56 ] received 3675 and 2007 citations, respectively, for their particular works and were rated in the leading 3. In addition, it was found that only 10 articles received more than 1000 citations on the subject through 2021.
• (5) The leading countries, based on their participation in the research of PW management, were analyzed, and we discovered that only 48 countries produced at least 30 articles. The United States, India, and China each presented 871, 581, and 551 papers, respectively. However, the United States had the most citations (42,924), followed by the United Kingdom (30,071), and China (19,944).
• (6) According to past studies, PW management strategies are broadly classified into six categories: landfills, recycling, pyrolysis, liquefaction, road construction and tar, and concrete production. Among these, landfilling is the most undesirable strategy as it causes environmental and human health concerns. On the other hand, recycling has equal merits and demerits; pyrolysis and liquefaction have more significant by-products, such as fuel and char, but they demand high energy. However, the use of PW for road construction and concrete production were found to be the most effective methods.
• (7) Recycling PW to produce various products will result in sustainable solutions due to the prevention of the use of natural resources, the minimizing of waste management problems, the reduction of environmental pollution, and the production of eco-friendly materials at a lower cost.

Acknowledgments

The authors acknowledge the support of COMSATS University, Islamabad, Abbottabad Campus, Pakistan.

Author Contributions

S.H.: data curation, investigation, and writing—original draft; H.W.: methodology, supervision, and writing—reviewing and editing; W.A.: conceptualization, data curation, software, methodology, project administration, supervision, and writing—original draft; A.A.: methodology, investigation, and writing—reviewing and editing; N.I.V.: funding acquisition, investigation, formal analysis, and writing—reviewing and editing; A.M.M.: resources and writing—reviewing and editing; A.F.D.: validation and writing—reviewing and editing; I.M.: visualization, formal analysis, and writing—reviewing and editing. All authors have read and agreed to the published version of the manuscript.

This research is partially funded by the Ministry of Science and Higher Education of the Russian Federation under the strategic academic leadership program ‘Priority 2030′ (Agreement 075-15-2021-1333 dated 30 September 2021).

Institutional Review Board Statement

Informed consent statement, data availability statement, conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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What is the life-cycle approach and how can it help tackle plastic pollution?

Later this year, negotiators will gather in the Republic of Korea for a fifth round of discussions aimed at developing a legally binding international agreement to end plastic pollution.   

The negotiations are designed to help counter the mounting toll plastic pollution is taking on the planet. Every year, the world produces around 430 million tonnes of plastic, most of which soon becomes waste. This rising tide of plastic debris damages fragile ecosystems, stokes climate change and can result in human exposure to harmful chemicals .  

Central to any solution to plastic pollution is a concept known as the life-cycle approach . It aims to go beyond recycling and reduce the environmental toll that plastic pollution takes at every stage of the life cycle of plastics, from production to its use and disposal. In March 2022, UN Member States agreed to forge an international agreement on plastic pollution embracing the approach .   

“Plastic pollution is a wide-ranging problem and there are many solutions that include shifting away from single-use and short-lived plastic, to ensuring the prolonged use of plastic through reuse systems, to better waste management and recycling,” said Sheila Aggarwal-Khan, the director of the Industry and Economy Division with the United Nations Environment Programme (UNEP). “Recycling alone will not get us out of the plastic pollution crisis. We need a combination of approaches working in tandem across the life cycle of plastic to have a world free of plastic pollution.”  

So, what exactly is the life-cycle approach and how can it help the world deal with plastic pollution in a systemic way? Read on to find out. 

Why is plastic pollution so damaging?  

Plastic products often need to have chemicals added to them to give them their functionality. Some of these are harmful chemicals and may enter the environment or human bodies depending on the production practices, use and disposal. As a result, there is a risk of pollution to the soil, groundwater, the marine environment, or harm to human health. The production of plastic is also responsible for more than 3 per cent of global greenhouse gas emissions, contributing to the climate crisis. This all makes plastic pollution a driver of the triple planetary crisis of climate change , nature and biodiversity loss , and pollution and waste .  

When people talk about the life cycle of plastic, what do they mean?  

Experts refer to the extraction of raw materials, their conversion into products, and use and disposal of a product as its life cycle. In the case of plastic, the story usually begins in the ground . For most of plastic that is fossil fuel based, oil and gas are extracted from the earth and sent to refineries. There, they are transformed into plastic polymers, which are then moulded into products from water bottles and other single-use packaging material—including containers for food and beverage commodities—to fishing gear and products for use in agriculture or in transportation . After they have served their purpose, such products usually find their way to one of four places: a landfill (although often an uncontrolled dumpsite), an incinerator, a recycling or re-use centre and, most damagingly, the environment. 

What is the life-cycle approach to plastic pollution?  

The life-cycle approach looks to limit the potential problems caused by plastic products at every stage of their life, from their production to their disposal. UNEP research has found there are dozens of things that governments and businesses can do to accomplish that goal.  

For example, countries could ban or restrict single-use plastic products or incentivize the development of plastic alternatives. Governments could provide the necessary regulation to send the signal to manufacturers to reduce and eliminate single-use plastic products, and change the product design to ensure plastic products are made of materials that are reusable, prolong their useful life, and that can be recycled at the end of their use. This means having plastic products designed to reduce environmental and human exposure to harmful chemicals across the life cycle of these products.   

Since the plastics sector depends on legions of people around the world, including millions of informal waste pickers , the life-cycle approach also aims to balance socio-economic needs with concerns over plastic pollution.  

Why is the life-cycle approach important?  

Plastic is deeply embedded in our lives and our economies – and plastic pollution continues to mount. Research shows the life-cycle approach could save governments US$70 billion in waste management expenses, and save society US$4.5 trillion in social and environmental costs by 2040. It could also massively reduce the volume of plastics entering the ocean.  

These benefits could be achieved by using the life-cycle approach to inform common design standards, create market incentives and disincentives, and expand reuse schemes, among other things. 

The life-cycle approach is also essential to delivering on key multilateral environmental agreements, such as the Paris Agreement on climate change, and to achieving the United Nations Sustainable Development Goals.  

Why can’t we solve plastic pollution with recycling?  

Recycling is important but it alone isn’t enough to end the plastic pollution crisis. For a start, close to 80 per cent of the plastic in single-use plastic products is not economically viable to recycle . This can be due to design decisions for a plastic product, such as the type of polymer used, and absence of adequate recycling infrastructure, the use of colour additives and combination of materials in a single product, or the use of additives that if harmful, can also pose a health threat to workers in waste management and recycling.  

Additionally, more than 2.7 billion people do not have access to solid waste collection and scaling up recycling infrastructure is challenging.  

“To phase out and ultimately end plastic pollution, there needs to be a combination of solutions across the life cycle of plastics,” said Aggarwal-Khan. “The only way to do that, is with the life-cycle approach.” 

To fight the pervasive impact of pollution on society, UNEP launched #BeatPollution , a strategy for rapid, large-scale and coordinated action against air, land and water pollution. The strategy highlights the impact of pollution on climate change, nature and biodiversity loss, and human health. Through science-based messaging, the campaign showcases how transitioning to a pollution-free planet is vital for future generations.

• Chemicals & pollution action
• Circular economy

Further Resources

• UNEP’s work on chemicals and pollution
• The Life-Cycle Initiative
• Circularity, Explained
• Financing Circularity: Demystifying Finance for the Circular Economy
• Intergovernmental Negotiating Committee on Plastic Pollution

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The Chesapeake Bay Plastic Survey is intended to assess the necessity and to generate a baseline for a future monitoring effort for plastics pollution trends in the Chesapeake Bay watershed. Awarded the Woodward and Curran’s Impact Grant, Ocean Research Project will assess bay-wide plastic pollution by exploring plastic particle count as a water quality indicator for monitoring future bay health. In cooperation with its partners, ORP hopes to repeat this project biannually to enrich understanding of the Bay-wide magnitude of plastic pollution, export to the ocean, and how that is changing relative to Bay improvements and climate change.

ORP’s study will be the first to determine particle concentration of plastic pollution across the United States’ largest estuary, the Chesapeake Bay. The information from this pilot project will be used to inform a dedicated multi-year sampling program by the Chesapeake Bay Program partners at the federal, state, and local levels.

The abundance of plastic garbage created by modern human civilization has infiltrated the deepest trenches of the world’s oceans and concentrated in huge areas on its surface. An estimated 5.5 trillion pieces of plastic debris are in the world’s oceans. There are countless sources of this plastic debris, but virtually all of it originates on land through the overuse of plastics in our daily lives and improper waste disposal. Once plastic trash enters the Ocean, nature’s forces and the migration of marine species and birds determine how the plastic material and chemical compounds move and accumulate through the complex marine environment, including the food chain and the Plastisphere. Much of this plastic debris is concentrated at the centers of enormous oceanic current circulation regions, called gyres.

We know a little more about chemical transfer risk in the sea food chain. Check out our collaborative publication in Marine Pollution Bulletin to find out more… Here

To better understand the nature of plastic debris in the Ocean, ORP has conducted multiple research expeditions in the Atlantic, Pacific, and Arctic Oceans. ORP completed its first marine debris research expedition in 2013. During this trip, its crew spent 70 days sailing in the Atlantic Ocean, collecting samples of plastic trash in the water and mapping out the eastern side of the North Atlantic garbage patch. The following year, ORP embarked upon a second expedition to research microplastic pollution in the Pacific Ocean. During this trip, ORP’s crew sailed 6,800 miles nonstop from San Francisco to Yokohama, Japan, collecting microplastic samples along the trans-pacific route.

Due to the flexibility offered by doing research from a sailboat, ORP’s expeditions could dedicate more time to collecting data samples across a much broader area than other similar types of marine research expeditions would typically cover. ORP’s research has provided an essential baseline for marine surface debris data and improved knowledge of the concentration, composition, and extent of plastic debris in the Ocean. ORP conducted its research to ensure the samples could be used to support further research being done as part of plastic pellet toxicity studies at the University of Tokyo’s Pelletwatch program. In addition, ORP’s research was designed to allow ORP and participating scientists to define further the diversity of the Plastisphere, specifically the roles played by bacteria and viruses in their evolving relationships with plastic debris in the Ocean.

ORP’s research expeditions targeting the investigation of northern hemisphere subtropical gyres of the Atlantic and Pacific Ocean and well as the western Arctic’s plastic pollution in the marine environment have helped increase the scientific community’s understanding of plastic’s pollution’s pervasive distribution across oceans from the sea ice to the seabed. The extensive datasets and that ORP collected, processed and regional interpretation during these expeditions contributed to the following publications:

• Plastic Pollution in the World’s Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea  
• PCBs and PBDEs in microplastic particles and zooplankton in open water in the Pacific Ocean and around the coast of Japan
• Mitigation strategies to reverse the rising trend of plastics in Polar Regions

To date, ORP has sailed tens of thousands of miles, spent many months at sea, and a considerable amount of time in labs back on land sorting the samples and data. During our extended periods of time at sea, there was not one day that went by where we did not see foraging birds mistaking marine debris for food. The fight to prevent pollution from plastic debris in the ocean is best fought at the primary source, on land. Education is a critical element of this effort to increase public awareness and encourage proper disposal of plastic trash along with reduced use of plastics ( link to ORP’s education page ).

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Plastic vaporising process could recycle bags and bottles indefinitely

A new process uses cheap catalysts to break down polyethylene and polypropylene into their building blocks, enabling common plastic objects to be turned into new products

By Matthew Sparkes

29 August 2024

Polyethylene plastic bags are challenging to recycle

Robert Sanders/UC Berkeley

Plastic bottles and bags can be vaporised into chemical building blocks and turned into new plastics with all the properties of virgin material. There are hurdles still to overcome, but the new process is a big step towards a truly circular economy for plastic.

Around 5 billion tonnes of plastic has gone to landfill since the 1950s, and recycling efforts have only tackled 9 per cent of what we’ve produced. With current techniques, plastics degrade in each recycling round and end up in landfill after only a few cycles through this process.

The incredible new tech that can recycle all plastics, forever

John Hartwig at the University of California, Berkeley, and his colleagues had previously developed a process that breaks down waste plastic into its constituent parts, but it relied on expensive metal catalysts iridium, ruthenium and palladium, which were irrecoverably lost as part of the process. Hartwig says that the technique was “OK for an academic paper, for demonstration purposes, but nowhere near what you would need for something that could be conceived of ever becoming industrial.”

Now, his team has discovered an improved process that works on both polyethylene, from which most plastic bags are made, and polypropylene, which is used to make harder objects, and it relies only on catalysts considered so common that they are essentially “dirt”, says Hartwig.

Plastics consist of large molecules called polymers, which are made up of smaller units called monomers bonded together. The catalysts break the chemical bonds of polymers, turning them into gaseous monomers from which new plastics can be pieced together with all the properties of virgin material that has never been recycled.

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In experiments, the team used two catalysts, sodium on aluminium oxide and tungsten oxide on silica, to turn a mixture of polyethylene and polypropylene into the monomers propylene and isobutylene with an efficiency of nearly 90 per cent.

Benjamin Ward at Cardiff University, UK, who wasn’t involved in the research, says recycling plastics is made harder by thousands of additives such as dyes, fire retardants and plasticisers, which can make up as much as a third of a finished product and contaminate the end product after recycling. “It defers the landfill. It defers the environmental problem. But it doesn’t prevent it altogether,” he says.

Ward believes this new process solves the additive problem, as stripping material down to its constituent gaseous monomers also removes the additives.

Hartwig warns that there are still many hurdles to overcome, and that the process has only been tested in the presence of a small number of common additives. “There will be additives that… will poison, will inhibit the catalyst,” he says. “We need to either find a way to separate those, which is maybe not optimal, or to find different catalyst structures or compositions that will be more resistant to some of those additives. That is absolutely a challenge.”

Cressida Bowyer at the University of Portsmouth, UK, says that even when we have a process that can split waste plastic into constituent parts and withstand additives, there are still additional concerns. “Toxicity and disposal of recycling end products [such as catalysts and additives] must be taken into account. These could outweigh any perceived benefits of recycling technologies,” she says. “Recycling should not be seen as any kind of solution or rationale to maintaining or increasing production of single-use and unnecessary plastics and continuing the current prevailing take-make-waste culture.”

Journal reference:

Science DOI: 10.1126/science.adq7316

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