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Review article
Bibliographic mapping of post-consumer plastic waste based on hierarchical
circular principles across the system perspective
Dania Sitadewi
*
, Gatot Yudoko, Liane Okdinawati
School of Business and Management, Institut Teknologi Bandung (ITB), Bandung, Indonesia
ARTICLE INFO
Keywords:
Circular economy
9R framework
System perspective
Plastic
Circular strategy
ABSTRACT
The current dominating production and consumption model is based on the linear economy (LE) model, within
which raw materials are extracted-processed-consumed-discarded. A circular economy (CE) constitutes a regen-
erative systemic approach to economic development which views waste as a valuable resource to be reprocessed
back into the economy. In order to understand the circular strategy for a systemic change from an LE to a CE as a
means of resolving the issue of plastic waste, this research aims to map current circular strategy trends across the
system perspective contained in the literature relating to plastic CE literature. The novelty of the research lies in
the mapping and review of the distribution of comprehensive circular strategies within the 9R framework across
the entire system perspective (e.g. micro-meso-macro) down to its sub-levels in the literature on a plastic CE. The
bibliographic mapping and systematic literature review iindicateed that the majority of the research focused on
recycle (R8), followed by refuse (R0), reuse (R3), and reduce (R2). Certain circular strategies are more appro-
priate to handling certain plastic materials, despite CE's favoring of prevention and recycling over incineration.
Recover (R9) is often used to process mixed and contaminated plastic. Recycling (R8) is the most popular circular
strategy and the most applicable to plastic material with three recycle trends, namely; mechanical recycling,
chemical recycling and DRAM (Distributed-Recycling-and-Additive-Manufacturing). Prolonging the product life
through refurbishing (R5) is not applicable to plastic due to its material limitations. Reduce (R2) popularity as
circular strategy reflects the preference to reduce consumption, either by launching campaigns to prevent waste or
increasing production efficiency. Research on Rethink (R1) has largely focused on rethinking product design,
consumer and organization behavior and perceptions of CE. Refuse (R0) strategy is an adoption of bio-based
plastics which have a similar function to fossil-based plastics.
1. Introduction
The current dominating production and consumption model is based
on the linear economy (LE) model, within which raw materials are
extracted from the environment, processed to become products, used
and, finally, discarded [148]. In 2016, between 19 to 23 million metric
tons of plastic waste were estimated to have entered the global aquatic
ecosystem which represented an increase on the previous estimate of
4.8–12.7 million metric tons in 2010 [103]. It is, therefore, important to
transform the current linear economy into a closed-loop circular system
[20].
A circular economy (CE) constitutes a regenerative systemic approach
to economic development which views waste as a valuable resource to be
reprocessed back into the economy to the potential benefit of business,
environment, and society [49,246]. Failure in implementing systemic
change could result in the misunderstanding and subversion of CE
principals resulting in stakeholders implementing nothing more than
minimum change [114]. One example would be a company that adopts
waste recycling practice rather than rethinking its product design; or
refusing to use fossil-based plastic, thereby preventing waste generation,
as a means of preserving the status-quo vis-
a-vis modes of production and
consumption.
The transition from an LE to a CE requires the implementation of a
strategy across the production chain culminating in systemic change.
Circularity strategies, or the R framework, represents the core principle
and know-how through which a CE [20,73,113] minimizes resource
consumption and waste generation [179]. There are several known R
frameworks or circular strategies, namely; 3R, 4R and 9R. The 3R
framework consists of reduce-reuse-recycle [20,73,113], while the 4R
framework comprises reduce-reuse-recycle-recover [58]. Of all the R
* Corresponding author.
E-mail address: dania_sitadewi@sbm-itb.ac.id (D. Sitadewi).
Contents lists available at ScienceDirect
Heliyon
journal homepage: www.cell.com/heliyon
https://doi.org/10.1016/j.heliyon.2021.e07154
Received 28 December 2020; Received in revised form 24 March 2021; Accepted 24 May 2021
2405-8440/©2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-
nc-nd/4.0/).
Heliyon 7 (2021) e07154
frameworks, the most comprehensive collection strategy is the 9R
Framework, or Circular Strategy [175], which is a hierarchical collection
of circular principles with the closest state to LE being recover (R9),
followed by recycle (R8), repurpose (R7), remanufacture (R6), refurbish
(R5), repair (R4), reuse (R3), reduce (R2), rethink (R1), and, finally,
refuse (R0). The last mentioned is the state closest to a CE [175]. With
regard to systemic change, the implementation of a CE occurs at three
levels, referred to as the micro-meso-macro system perspectives [60,102,
204].
A review of the previous research into the literature on CE confirmed
that it focuses on only one aspect of systemic change (micro-meso-
macro). Previous literature reviews focused solely on one aspect of the
micro system such as the product level [24,223] or the company level
[78,162,173,196,208,226]. Other literature reviews centred on the
meso system at the industrial level [126,141]. Certain literature included
all levels of systemic change (micro-meso-macro) but only incorporated
limited circular strategies such as maintain, reuse, remanufacture, and
recycle [202] or reduce-reuse-recycle-recover (4R Framework) [114].
In order to understand the circular strategy for a systemic change
from an LE to a CE as a means of resolving the issue of plastic waste, this
research aims to map current circular strategy trends across the system
perspective contained in the literature relating to plastic CE literature.
This study proposes the systemic change perspective as the combination
of the research by Saidani (2018) and Kirchherr (2017), while the cir-
cular strategy will employ the 9R framework [175]. The novelty of the
research lies in the mapping and review of the distribution of compre-
hensive circular strategies within the 9R framework across the entire
system perspective (e.g. micro-meso-macro) down to its sub-levels in the
literature on a plastic CE.
Within this study, bibliographic mapping involving the use of a
VOSviewer complemented by a systematic literature review. The
emerging research trend initially identified by bibliographic mapping
can be used to design a detailed in-depth analysis of this systematic re-
view through the use of a system perspective and 9R framework as part of
a Circular Strategy. Widely used CE strategies can be identified and
employed to determine the level of transition from an LE to a CE at the
micro-meso-macro levels down to their sub-levels. The distribution of
circular strategy within the system perspective in the literature will use
9R frameworks.
This study is organized into five parts. Section 1highlights the
background and contains a literature review. Section 2contains the
research methodology and iterative approach employed to categorize the
literature on plastic CE. Section 3presents the visualization results of the
VOSviewer-generated bibliographic map. Section 4elaborates the find-
ings of the systemic literature review. Section 5features the conclusion,
while Section 6outlines the research limits and suggests possible areas
for future research.
2. Methodology
The research was conducted using bibliographic mapping and com-
plemented by a systematic literature review. Bibliographic mapping tools
can enable the processing of the abundant information produced by the
rapid pace of research by facilitating the tracking of research evolution
and emerging trends [214]. However, despite further advances in text
mining and machine learning techniques, bibliographic mapping is
limited as far as providing in-depth analysis is concerned. Consequently,
a systematic literature review was also undertaken to complement
bibliographic mapping. The emerging trend initially identified by
bibliographic mapping can be used to design a detailed in-depth analysis
of the systematic review.
The bibliographic analysis is based on a general methodological
flowchart [179] which involves three steps, namely; data acquisition,
followed by data processing, and, finally, visual output. The justification
for following the flows contained in this framework is that they are
reproducible, flexible and appear in other bibliographical mapping pa-
pers using the same method [97,251].
Figure 1 shows the methodological framework of the literature re-
view undertaken for this paper. The first step consisted of conducting a
search of an online database using a general keyword. Initial data
acquisition involved accessing Goggle Scholar, ProQuest, and Science-
Direct. Using a combination of the keywords “Circular Economy”and
“Plastic”, an initial 42,412 articles were screened on the basis of having
been published between 2009 and 2020 to produce a reduced total of
36,431 articles.
The second step involved data processing and screening conducted on
the basis of the type of academic article written in English which further
reduced the total number to one of 4,082 articles. In order to avoid the
inclusion of redundant articles from various online sources another
screening process was completed based on title, redundancy and source
type (Scopus index of peer-reviewed journals). The justification for
making exclusive use of Scopus-indexed journals lay in the fact that the
VOSviewer can only process articles from either Scopus or Web of Sci-
ence. This fact constitutes one of the limitations of this research. The
screening resulted in a total of 315 articles whose abstracts, keywords,
authors, years of publications, and source journals were downloaded
from the Scopus website in CSV downloadable format. Each article ab-
stract was manually checked for relevance with redundant studies on
such topics as biogas, bioreactors and microbiota being removed. Articles
with no abstract, keywords, or author names were also removed from the
literature database. This process resulted in the final data amounting to
207 articles.
The third step, visualization output of the final data, involved
descriptive analysis and bibliographic mapping using a VOSviewer.
Descriptive analysis was conducted to enable comprehension of the data
distribution by constructing a histogram based on the year of publication
and journal source. Bibliographic mapping was conducted using the final
article database that had been checked, corrected and screened by the
VOSviewer using in-app algorithms to create the output visual file. The
justification for using the VOSviewer lay in its being an open-source Java-
based package allowing the user to visualize in the form of bibliometric
maps which enable trend analysis [235]. The visualization employed a
co-occurrence analysis of the articles' keywords to identify research
clusters and, subsequently, investigate the emerging research trend. The
use of keywords reflected each article's core content and research topic
development [225].
The fourth step was a systematic review of article abstracts and a
content analysis of the literature abstracts to identify and classify those
which are state-of-the-art. The database was subsequently classified
using a classification framework based on the system perspective and 9R
Framework (or Circular Strategy) contained in Figure 2. A systematic
literature review was also conducted to complement bibliographic
mapping. The emerging trend initially highlighted by this means can be
used to design a detailed in-depth analysis of systematic reviews to
identify research gaps requiring further work in addition to the direction
of future research. This study employs the circular strategy of the 9R
Framework [175] across the systemic change perspective [202].
2.1. System perspective within the circular economy
The system perspective, or systemic change, within the CE pertains to
those system levels that will be fundamentally changed when tran-
sitioning from an LE to a CE [114]. A business or region striving to
achieve sustainable development and enhance its circularity can do so by
means of transition stages. The transition to a CE as a system occurs at
three levels: micro-meso-macro system perspectives [60,102,114,204].
The macro-system focuses on the fundamental change in the entire
economic structure. The meso-system highlights the transition and
adjustment to the CE at the industrial level [92,216]. The micro-system
seeks to improve the circularity of the product or consumer levels [102,
204] (see Table 1).
D. Sitadewi et al. Heliyon 7 (2021) e07154
2
Figure 1. Methodology framework used to review the plastic circular economy literature.
D. Sitadewi et al. Heliyon 7 (2021) e07154
3
Two previous literature reviews classified system perspectives in the
CE; one based on the 114 definitions of the CE [114], the other on the
taxonomy of CE indicators [202]. Table 2 displays the system perspec-
tives of previous research and that presented here, both of which classify
the system perspectives as micro-meso-macro, yet which differ at the
sub-level.
Micro-system perspective sub-levels based on the 114 CE definitions
[114] consist of product, company and customer levels [99,204]. The
meso-system consists of eco-industrial parks [92,216] and the regional
level [70,125]. The macro-system consists of global, national, and in-
dustrial structure levels. Meanwhile, based on the CE indicator taxonomy
[202], micro-system perspective sub-levels consisting of product,
component, and material levels [202]. The meso-system comprises
business and industrial symbiotic levels. The macro-system includes city,
regional and national levels. Certain sub-levels are mentioned only in one
literature source, while others are contained in both sources. The dif-
ferences are due to the various sources of classification within the system
perspective: some based on the circular indicators identified in both the
academic and grey literature developed by scholars, governmental
agencies, and consulting companies [202]; others based solely on the 114
CE definitions [114].
Based on the background above, this research will combine both
system perspectives [114,202] and add a new production chain sub-level
to review the distribution of CE implementation across the plastics in-
dustry from a system perspective within the current CE literature. The
micro-system will consist of material, component, and product levels
Figure 2. The proposed classifications of plastic circular economy literature.
Table 1. Review of previous literature on the plastic circular economy.
# Study Focus
1. Ghisellini et al. (2016) [73] Summary of 155 articles on CE.
2. Lieder and Rashid (2016) [126] CE manufacturing industry.
3. Kirchherr et al. (2017) [114] Analysis of 114 definitions of CE.
4 Gregorio et al. (2018) [78] Trends of bio, green, and CE.
5 Okorie et al. (2018) [162] Digitalization in CE.
6 Saidani et al. (2018) [202] Taxonomy of CE indicators.
7 Spierling et al. (2019) [224] Bioplastic in CE.
8 Bungaard and Huulgaard (2019) [24] Luxury product and its links to CE.
9 Paes et al. (2019) SWOT (Strength-Weakness-Opportunity-Threat) analysis of organic waste management.
10 Meherishi et al. (2019) [141] Sustainable Packaging for Supply Chain Management in CE.
11 Pieroni et al. (2019) [173] Business model innovation for CE.
12 Rosa et al. (2019) [196] Circular Business Model.
13 Sassanelli et al. (2019) [208] CE performance assessment method.
14 Thorley et al. (2019) [226] CE impact towards SME.
15 Sanchez et al. (2020) [206] Analyzing articles on DRAM (Distributed Recycling and Additive Manufacturing) in CE.
16 Qureshi et al. (2020) [181] Pyrolysis for plastic waste
D. Sitadewi et al. Heliyon 7 (2021) e07154
4
[202], together with the customer level [202]. The material level will
focus on improving circularity of the element's composition. The
component level focuses on adjustment of the CE at the ingredient level.
The product level centers on improving circularity while still satisfying
customer needs. The customer level focuses on the socio-demographic
breakdown of the product's consumers and the nature of sustainable
consumption. The meso-system deals with industrial symbiosis,
eco-industrial parks [202], production chain level and the business level
[114]. The business level focuses on the adjustment to improve circu-
larity at the company level. The production chain level centers on the
transition to a CE at the supply chain level. Industrial symbiosis is the
merger of two or more different industries where each tries to achieve
optimal access to material components and material elements [13,189].
An eco-industrial park is a business that cooperates with locals to share
resources efficiently and reduce waste in order to promote economic
prosperity, improve environmental quality and enhance human re-
sources for the local community [167]. A macro-system will consist of
city, regional and national levels [114] combined with the global level
[202]. City, regional and national levels focus on the fundamental change
to the CE of administration at these levels. The global level focuses on the
transition to the CE at the multi-national level and across borders.
2.2. Circular economy strategies
CE strategies outline the R strategy necessary to transform LE to a CE
[175] and are ordered from R0 to R9 based on their level of priority in the
LE to CE transition as shown in Figure 3. R0 signifies the closest state to
CE,while R9 indicates the closest state to LE. Adopting the circular
recycling strategy (R8) means that the system is predominanttly under
LE. Meanwhile, implementing circular reduction strategies (R2) means
the closer the transition to the CE model.
The circular strategies of smarter product use and manufacturing
framework comprise recovery (R9) and recycling (R8) [175]. The CE
principle is that of extracting the maximum value from material at the
end-of-life (EoL) [48]. Recycling is the most widely-known circular
strategy, although it represents only one of the options and is closer to the
LE after recovery (R9) than the CE [175]. The recycling strategy includes
mechanical recycling, chemical recycling and DRAM. DRAM involves
producing objects from 3D models by joining materials layer-by -ayer
using 3D manufacturing processes [206]. Mechanical recycling involves
the application of physical treatment to reduce a product to its material
level, thereby enabling it to be remade [7,175]. Chemical recycling
produces chemical feedstock in the form of solid, liquid, and gaseous
fuels [7].
Extending the lifespan of the product and its parts requires circular
strategies of repurpose (R7), remanufacture (R6), refurbish (R5), repair
(R4), and reuse (R3). Reuse and remanufacture are two of the circularity
loops in the CE butterfly diagram of the technical materials produced by
the practitioner [49]. However, there is a limit to prolonging the product
life of items manufactured from plastic and it cannot constitute a main-
stream practice [85].
Smarter product use and manufacturing frameworks apply circular
strategies of refuse (R0), rethink (R1), and reduce (R2). Refuse (R0) is the
closest circular strategy in the production chain to CE [175]. In this
research, the use of bio-based plastic as the CE strategy of “refuse”(R0) is
included since the adoption of such plastic, which performs a similar
function, can render conventional plastic redundant. Degradable
bio-based plastic can be manufactured from renewable materials,
including plant materials [88], thus allowing microbes to break down the
bioplastic complex molecular structure and produce CO
2
. Examples of
biodegradable bio-based plastics are PLA (Polylactic acid), PHA (Poly-
hydroxyalkanoates), PBS (Polybutylene succinate), and starch blends.
Biodegradable plastic can also be produced solely from petrochemicals
using additives to facilitate its breaking down, but it remains a
fossil-based plastic [57]. Examples of petrochemical-based biodegrad-
able plastics include PBAT (Polybutylene Adipate Terephthalate) and
PCL (Polycaprolactone).
3. Analysis
3.1. Descriptive analysis of the data
Descriptive analysis of bibliographic data can promote an under-
standing of data distribution. Figure 4 contains the distribution of articles
from 2009 to 2020. Initially, between 2009 and 2013, only one or two
articles were published. However, from 2014 to 2016, there was an in-
crease in the number of articles in line with the European Union's new
Circular Economy Package [59]. Furthermore, it is important to note the
exponential increase in 2017 when the number of articles on the plastic
circular economy almost trebled. This increased research interest might
Table 2. CE system perspectives for this research.
Authors Macro-System Perspective/Levels Meso-System Perspective/Levels Micro-System Perspective/Levels
Kirchherr et al. (2017) 114 ☆Global level
☆National level
☆Industrial structure level
☆Eco-industrial parks level
☆Regional level
☆Product level
☆Company level
☆Customer level
Saidani et al. (2018) 202 ☆City level
☆Regional level
☆National level
☆Businesses level
☆Industrial symbiosis
☆Product level
☆Company level
☆Customer level
This research ☆City level
☆Regional level
☆National level
☆Global level
☆Business level
☆Production chain level
☆Industrial symbiosis
☆Eco-industrial parks
☆Material level
☆Component level
☆Product level
☆Customer level
Figure 3. Framework for CE strategies [175].
D. Sitadewi et al. Heliyon 7 (2021) e07154
5
be due, in part, to the New Plastic Economy project and Ellen MacArthur
Foundation initiatives which aim to develop a more circular economic
model [246]. The upward trend continued until 2019 when the number
of published articles rose to the unprecedented annual total of 103.
China's new regulation of July 2017 banning solid waste imports
(including plastics, paper products, and textiles, among others) from
foreign countries and its impact on the global plastic waste trade [22]
might have contributed to the increased interest in plastic CE as a
research topic. Analyzing the trend retrospectively, there is a possibility
that, in subsequent years, more articles will be published on the plastic
circular economy since the topic is new and relevant to current events.
However, the sharp decline in yearly publication in 2020 might be in part
due to the shifting research interest moving into the topic of pandemic. In
addition, not all publication in 2020 are considered with the research on
the end of 2019 and throughout 2020 are presented as projection.
Figure 5 contains a quantitative measurement of the top six journal
sources. The leading journal for plastic CE research is Resources, Con-
servation, and Recycling with 24 articles, followed by the Journal of Cleaner
Production with 23 articles and Waste Management with 18 articles,
respectively. Meanwhile, Plastic Engineering,Waste Management*, as well
as Research and Science of the Total Environment each have an average of
eight articles. The journals Resources; Conservation and Recycling; and
Journal of Cleaner Production contain more topics on the CE compared to
other journals. This is due to both journals addressing a wide variety of
topics on sustainability and their high Scopus ranking. Resources, Con-
servation and Recycling, in particular, emphasizes the transitional process
towards sustainable production and consumption systems in line with the
definition used within the Circular Economy. The Journal of Cleaner
Production addresses the issues of preventing waste production,
improving resource use efficiency and promoting a more sustainable
society which are similar to Circular Economy principles. In addition, the
Scopus ranking of both journals is very high at Q1 which explains the
preference of numerous researchers for submitting articles to these
journals compared to others such as Plastic Engineering (Q4) and Waste
management and Research (Q2).
3.2. Bibliographic mapping using VOSviewer keywords co-occurrence
analysis
A keyword co-occurrence network is useful for the purposes of
knowledge mapping [182] since keywords reflect the research topic
development and core content of an article [225]. The author's keywords
in the literature database determine the co-occurrence frequencies in the
VOSviewer. Table 3 shows that of 823 keywords, only 22 satisfied the
condition of appearing in a minimum of five publications which,
expressed statistically, represents a frequency of 2.67% (22/823*100%).
The justification for adopting this minimum occurrence level for the
keyword is that the more frequently it occurred, the more popular the
research topic.
This study found "Circular Economy" to be the most important
keyword with a total link strength of 134 and the largest circle size at 135
co-occurrences in the dataset. The "Circular Economy" keyword links all
the keywords in the map, thereby justifying its large total link strength.
The vast array of networks for this keyword is justified since both it is
used as one of the research keyword during online literature data
acquisition. The second most important is "Recycling", with a total link
strength of 67 and 42 co-occurrences. The keyword "recycling" has links
to most map keywords except for the following: plastic recycling,
contamination, life cycle assessment, and bioplastic.
VOSviewer visualization resulted in two different maps, namely: the
network and overlay visualization maps. Both visualizations incorporate
the use of a two-dimensional distance-based map that indicates the
strength of the items' relationship based on their distance [235]. A larger
distance indicates a weak association and vice-versa. In contrast, a
shorter distance signifies greater strength of the relationship. A keyword
is indicated by a label and a circle whose size signifies its importance
[235]. The bibliographic mapping of overlay visualization is identical to
network visualization, although different colors are used to indicate
distinct information. The network visualization conveys the information
of keywords cluster groups, while the overlay visualization conveys the
information of average annual publication of each keyword.
Figure 6 contains network visualization groups of closely related
keywords shown in different colors indicating the cluster to which they
belong. It identifies four keyword network clusters from the network
visualization. Meanwhile, within overlay visualization (Figure 7), the
circle labels are colored according to the average annual publication of
the keyword. To represent the average publication year, purple was used
for 2017 and yellow for 2020. Figure 7 contains the keywords mentioned
in the average number of articles published between 2018 and 2019.
The following constitutes an analysis of the identified research clus-
ters within network visualization. The first cluster (shown in red) con-
tains certain keywords including “bioplastic”,“LCA”,“packaging”,
“plastic”,“sustainability”, and “waste”. This cluster pertains to reviewing
the life cycle assessments of plastic material and its substitution by bio-
plastic to render it more sustainable. Bioplastics perform a similar func-
tion, thereby rendering conventional plastic unnecessary. Substitution of
conventional plastic by bioplastics is similar to the circular strategy
relating to refuse (R0) of offering similar functions but with different
products. “Refuse”is the closest circular strategy in the production chain
to the CE [175]. Overlay visualization shows the publication year (2018)
for this cluster when the keywords “LCA”,“sustainability”and “plastic”
were trending, followed by “bioplastic”and “packaging”which did so in
the following year. This phenomenon is reflected in the more intense
focus on the issue of plastic waste in the marine environment during
2018 and 2019.
The second cluster (shown in green) contained the keywords “3D
printing”,“additive manufacturing”,“polymers”,“recycling”,“upcycle”,
and “waste plastic”and is concerned with recycling (R8), either through
downcycling or upcycling. In the recycling process, material value is
often partially lost or downgraded, while the upcycling process increases
value by upgrading the product used [219]. Additive manufacturing is a
process of producing objects from 3D models [206]. In upcycling, using
the latest technology in 3D printing, the plastic waste is recycled into
added-value products through additive manufacturing. In overlay visu-
alization, the keyword “recycle”was trending in 2018 with additive
manufacturing, while those of “3D printer”and “upcycle”gradually
gained popularity in publications during in the following year.
Figure 4. The annual number of publications from 2009 to 2020.
Figure 5. Quantitative measurements of the six leading journal sources from
2009 to 2020.
D. Sitadewi et al. Heliyon 7 (2021) e07154
6
Table 3. Co-occurrence and total link strength of the most common keywords.
# Selected Keywords Cluster Number Occurrences Total link strength Average Publication Year
1 Circular economy 3 135 134 2018
2 Recycling 2 42 67 2018
3 Waste plastic 2 6 27 2019
4 Polymers 2 5 25 2019
5 Upcycle 2 5 25 2019
6 Plastic waste 4 12 24 2019
7 Additive manufacturing 2 6 21 2019
8 Plastic 1 10 20 2018
9 Plastics 4 12 19 2017
10 Waste 1 10 18 2017
11 Plastic recycling 4 9 17 2019
12 Sustainability 1 14 16 2018
13 Life cycle assessment 3 10 14 2018
14 Waste management 3 11 14 2018
15 Bioplastics 1 8 13 2019
16 Packaging 1 6 13 2019
17 3d printing 2 5 12 2019
18 Pyrolysis 4 8 11 2019
19 Recovery 4 5 8 2017
20 Contamination 3 5 7 2019
21 LCA 1 5 7 2018
22 Municipal solid waste 3 6 6 2017
Figure 6. Co-occurrence of keyword network visualization.
Figure 7. Co-occurrence of keyword overlay visualization based on average publications per year.
D. Sitadewi et al. Heliyon 7 (2021) e07154
7
The third cluster (shown in blue), containing the keywords “circular
economy”,“contamination”,“life cycle assessment”,“municipal solid
waste”, and “waste management”, concerns the management of munic-
ipal solid waste to reduce contamination using a CE. Reduce (R2) con-
stitutes a circular strategy to decrease resource consumption [175] which
is achievable through waste prevention campaigns or greater production
efficiency. Overlay visualization shows this cluster to contain multiple
trending research topics emerging in 2018, one of which is “circular
economy”, in addition to “recycling”,“sustainability”,“life cycle assess-
ment”, and “waste management”.
The fourth cluster (shown in yellow) contained “plastic recycling”,
“plastic waste”,“plastics”,“pyrolysis”, and “recovery”and concerned
“plastic waste recovery”and “treatment through chemical recycling”
such as pyrolysis. Pyrolysis is one form of chemical recycling that con-
verts plastic waste into energy in the form of solid, liquid, and gaseous
fuels [145]. Recovery (R9), another popular circular principle in the
management of post-consumer plastic-waste, was based on energy re-
covery through material oxidation [228] to produce heat, power, oils,
and disposable by-products [7]. Therefore, incineration for energy is
classified as the recovery strategy. Overlay visualization shows that one
of the earliest core topics of plastic CE articles in 2017 pertains to
municipal solid waste, plastic waste and recovery.
4. Result
This section contains the result of the systematic literature review
relating to the distribution of circular strategy within the whole system
perspective contained in the plastic CE literature which is classified in the
SOTA (State-of-The-Art) table. This table enables researchers to identify
gaps in the existing research and the need for further future investigation.
Widely-used CE strategies can be identified and employed to determine
the level of transition from the LE to the CE in the system perspective.
Table 4 shows the distribution of circular strategy across the system
perspective in the existing literature.
For classification of this systemic literature review, a source can only
be classified as falling within one of the CE system perspectives. The total
number (n) of works was 207. Statistically, most previous literature re-
views focused on the microsystem at 59% (122/207*100%). The second
most common theme was the macro-system at 23% (47/207*100%),
while the meso-system occupied third place at 18% (38/207*100%).
Overall, the meso-system accounted for the smallest share of the litera-
ture compared to other system perspectives.
Based on the dimension with the least amount of reviews, the meso-
system perspective suffered from a research gap (Figure 8). A further
breakdown in the system perspective categorization sub-levels is as
follows.
a. From the micro-system perspective, the distribution of literature was
one of 54 texts at the material level, 7 texts at the component level, 47
texts at the product level, and 14 texts at the consumer level.
Furthermore, the product level represented the largest proportion of
system perspective literature, while the component level was the
smallest (Figure 9).
b. From the meso-system perspective, the distribution of literature
consists of 12 texts at the business level, 16 texts at the production
chain level, 6 texts at the industrial symbiosis level, and 4 texts at the
eco-industrial park level. The industrial symbiosis level represented
the largest proportion of texts, while the eco-industrial park was the
smallest (Figure 10).
c. From the macro-system perspective, the distribution of literature
consists of 8 texts at city level, 10 texts at regional level, 11 texts at
national level, and 18 texts at the global level. The national level
represented the largest proportion of texts, while the city level rep-
resented the smallest (Figure 11).
The component, eco-industrial park, and city levels had the smallest
proportion of texts in their respective system perspectives. Therefore,
they constitute research gaps in the literature on plastic CE which could
be the focus of future investigation.
For the purposes of classification into the circular strategy, a total
population (n) of 253 was arrived at after adding all the identified 9R
framework in each text (13 þ141 þ3þ2þ0þ2þ21 þ22 þ11 þ38).
A text can use one or more circular strategies. Statistically, it was found
that the most common circular strategy was recycle (R8) at 55.73% (141/
253), followed by refuse (R0) at 15.02% (38/253), reduce (R2) at 8.70%
(22/253), reuse (R3) at 8.30% (21/253), recovery (R9) at 5.14% (13/
253), rethink (R1) at 4.35% (11/253), repurpose (R7) at 1.19% (3/253),
remanufacture (R6) at 0.79% (2/253), and repair (R4) at 0.79% (2/253).
Meanwhile, the least popular strategy was refurbish (R5) at 0% (0/253).
Figure 12 displays the identified circular strategies in the texts.
4.1. Micro-system perspective circular strategy for plastic
4.1.1. Material level
Research into plastic CE at the material level mostly consists of cir-
cular strategies with the majority focusing on refuse (R0) with 23 articles,
and recycle (R8) with 30 articles. In the articles relating to rethink (R1)
reduce (R2), and reuse (R3) strategies are sparsely implemented, while
no research was found on repair (R4), refurbish (R5) and remanufacture
(R6) at the plastic material level. Table 5 shown the distribution of
literature of circular strategy at the material level.
Refuse (R0) is the second most popular strategy due to the adoption of
bioplastics with many texts on the subject published in 2019. Two texts
focused on bioplastic as a substitute for fossil-based materials in terms of
its chemical functionalities [170], upcycling process [16], and low
environmental impact with particular regard to the food packaging ap-
plications of PLA material [194]. Extensive research into bioplastics fo-
cuses on the development of bioplastic production, namely; bio-derived
Table 4. State of the art system perspective of the transition towards a plastic circular economy.
Circular Strategies (9R Framework) Micro-system perspective Meso-system perspective Macro-system perspective
Material Component Product Consumer Businesses Production Chain Industrial Symbiosis Eco-Industrial Park City Regional National Global
Recover (R9) 2 1 1 1 2 - 1 - 1 2 2 -
Recycle (R8) 31 6 35 6 11 12 3 4 6 7 12 8
Repurpose (R7) 1 - 1 - - - - 1 - - - -
Remanufacture (R6) - 1 - - - - - - - 1 - -
Refurbish (R5) - - - - - - - - - - - -
Repair (R4) - - 2 - - - - - - - - -
Reuse (R3) 5 1 4 1 1 1 1 - 2 2 2 1
Reduce (R2) 2 - 1 2 1 1 1 1 1 2 2 8
Rethink (R1) 1 - 2 2 2 - - 1 1 - - 2
Refuse (R0) 22 1 6 4 - 3 - - - - - 2
D. Sitadewi et al. Heliyon 7 (2021) e07154
8
Table 5. Circular strategy at the material level.
Material Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[8] X X PHAs production technical feasibility.
[10] X BPA MFA in Norway.
[11] X Polymer recycling technology
[14] X Microwave-assisted recycling LDPE.
[16]X Improving biotechnological upcycling processes.
[17]X PHA-production technical and economic feasibility.
[29]X Compounding food waste with PLA.
[30]X Material design for bio-based Polymer Cosmetic packaging.
[38] X Different blend ratios of PP/mixed post-consumer recycled polyolefin materials.
[40] X Polymeric blends design.
[41] X PET depolymerization using enzymes.
[42] X PET recycling with enzymes as catalyst.
[47]X Bio-derived polymer from citrus waste.
[55] X Household plastic contamination.
[79] X CO2-based monomers &polymers transformation routes.
[90] X X Performance and recyclability improvement strategy in bio-based plastics.
[93] X Innovative process to recycle hydrocarbon polymer.
[98] X Multilayer EVOH/HDPE rigid packaging.
[99] X Variational effects in mixed recycled material.
[119] X Utilization potential of Polyolefin-rich from wet mechanical processing pilot plants.
[128] X Reimagining green chemistry towards circular material.
[130]X Review of industrial enzymes within the sustainable approach to chemical synthesis.
[142] X X CF life cycle cost model.
[143] X X PA-12 reprocessing by injection molding.
[144] X X Cement kiln incineration and chemical recycling for PET, HDPE, LDPE, PP and PS.
[156]X Modification of natural polymer with thermoplastic properties.
[159]X Possibility of biotransformation and biodegradation of fossil-plastics.
[163] X Agricultural and plastic waste for affordable homes.
[164]X Integrated biodegradation strategy of waste-to-wealth.
[166]X PLA production technologies, challenge and future opportunities.
[168] X Hydrothermal processing chemical recycling.
[170]X Bioplastic as a substitute to fossil based on its chemical functionalities.
[177]X Bio-based plastic standardized labelling, sorting, and coordinated regulation.
[181] X Opportunities and challenges of pyrolysis for plastic waste.
[186] X X Trade of feedstock material model
[187] X Recycled polymers 3D printing.
[194]X PLA as substitute for fossil-plastics
[199]X Degradation characteristics of bioplastic material.
[207] X X Development of bioplastic with full-chemical recyclability.
[211] X X Rethink material recycling of flame retardant additives.
[212] X Challenges of recovering plastic from electronic waste.
[213] X X X Material efficiency in manufacturing and waste segregation.
[215] X X Converting biomass into fuels, commodity chemicals and bioplastics.
[217]X Substitute capacity and commercial viability of bio-based plastics.
[218] X Framework for polymeric material reuse.
[222] X Multi-step pyrolysis to recover energy and chemicals.
[232]X Bioplastics derived from microalgae cultivation.
[238]X Combining 3D printing with biomaterials.
[249] X Gigabot to optimize recycled material.
[250]X RepRapable Recyclebot.
[253] X Recovering materials from pharmaceutical blister packaging.
[255] X Fiber-reinforced polymer manufacturing.
[258]X Novel development of SPC.
TOTAL 221250001312
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
D. Sitadewi et al. Heliyon 7 (2021) e07154
9
polymer extracted from citrus waste [47] and sludge cellulose plastic
composite (SPC) [258]. Furthermore, bioplastic from microalgae culti-
vation exploits agricultural run-off and urban wastewater as feedstock
[232], cosmetic packaging made from bio-based polymer [30], converts
biomass into bio-plastic [215], and combines 3D printing with bio-
materials [238]. Several pieces of research have investigated the biode-
gradability [164] and degradation characteristics of bio-plastics [199]. A
considerable body of literature covers the development of bio-based
plastic polylactic acid (PLA) and polyhydroxyalkanoates (PHA),
focusing on its substitution and commercial viability [217], PHA pro-
duction feasibility [8], PHA economic feasibility [17], and the com-
pounding of food waste with PLA [29]. Moreover, its standardized
labeling, sorting, and coordinated regulation [177], production tech-
nologies, challenge and future opportunities [166] have also been
covered. The remaining literature at the material level has focused on
improving bioplastic polymer performance [90], chemical recyclability
[207], and chemical synthesis [130]. One article described the potential
processing and modification of natural polymer with thermoplastic
properties [156].
Other strategies utilized at the material level include rethink (R1)
reduce (R2), and reuse (R3). The main focus of the rethink (R1) strategy
lies in rethinking the recycling of material additives to produce second-
ary material [211]. The Reduce (R2) strategy can be achieved through
production efficiency to reduce resource consumption during material
manufacturing [255] and segregate waste into high quality circulated
raw material [213]. The focus on reuse (R3) covers an array of topics
from polymeric material reuse [218], through the carbon fibre (CF) life
cycle cost model [142], to feedstock material trade modelling to
encourage private investment [186].
Recover (R9) is also used as a circular strategy at the material level.
Certain plastic types PET (Polyethylene Terephthalate), HDPE (High-
density Polyethylene), LDPE (Low-density Polyethylene), PP (Poly-
propylene), and PS (Polystyrene) are incompatible with chemical recy-
cling. Therefore, incineration and mechanical recycling are preferred due
to their lower global warming impact [144]. Contaminants such as
bisphenol A (BPA) can be destroyed during incineration making it the
form of waste-handling causing the least environmental emissions [10].
Thus, despite CE's favoring of prevention and recycling over incineration
or landfilling, some circular strategies are more appropriate to managing
certain plastic waste materials.
The articles on recycling (R8) form the majority of research into the
material level. The topics focus on polymer recycling [11], wet me-
chanical processing pilot plants [119], and pharmaceutical waste [253].
Recovering materials for recycling includes transforming electronical
waste and compounded polycarbonate into pellets [212] and pharma-
ceutical blister packaging using switchable hydrophilicity solvents [253].
Two pieces of research investigated polymeric blend properties that
include the design of polymeric blends [40] and polypropylene/mixed
post-consumer recycled polyolefin materials at different blend ratios
[38]. Regarding physical contaminants, metal substances should be
removed during the recycling process as increasing recycling rates may
lead to higher metal concentrations in recycled materials [55].
The literature proposed a variety of chemical recycling and DRAM
options at the material level. The chemical recycling options include
multi-step pyrolysis [222], using enzymes as catalyst for disseminating
PET [41], and PET depolymerization using enzymes via glycolysis re-
actions [42]. Other topics include chemical recycling by means of hy-
drothermal processing of waste plastic fractions [168], reimagining
green chemistry in relation to its circular material [128], the opportu-
nities for and challenges of plastic waste pyrolysis [181]. One article
discussed microwave-assisted recycling LDPE waste into value-added
chemicals [14]. Another option is to process high-density plastic waste
using hydrothermal processing [169]. DRAM at the material level covers
the topics of: recycled 3D printing polymers [187]; polyamide 12 (PA-12)
reprocessing by injection moulding [143]; combining 3D printing with
biomaterials to produce bioplastics [238]; gigabot development to opti-
mize recycled material [249]; exploring potential, design, fabrication
and operation of a RepRapable Recyclebot [250].
4.1.2. Component level
The component level overwhelmingly focuses on the recycle (R8)
strategy in six articles. Refuse (R0), reuse (R3), remanufacture (R6) and
recover (R9) strategies each only appear in one article. No research was
found relating to rethink (R1), reduce (R2) and remanufacture (R4) (R5)
and (R7) at the plastic component level. Refuse (R0) strategy is used in
the bio-composite market for biodegradable polymeric matrices from
agriculture waste [6]. Table 6 shown the distribution of literature of
circular strategy at the component level. Reuse (R3) strategy is applied to
glass fibre reinforced plastic waste treatment technology and the reuse
potential of composites [105]. Remanufacture (R6) is evidently used for
composite performance analysis of remanufacturing involving recycled
short carbon fibres with the HiPerDif method [134]. Recycling (R8)
strategy is largely used to process composites as follows. Plastic com-
posite evaluation based on multiple properties [81]; automated plastic
sorting using miniaturized handheld near-infra red (NIR) spectrometers
[185], recycling strategies employing SWOT analyses of component
recycling for WEEE (Waste from Electrical and Electronic Equipment)
plastic [243]; Recover (R9) primarily used for wood-plastic composites
(WPC) end-life treatment rather than recycling (R8) due to the lack of
secondary material markets [220].
4.1.3. Product level
Most of the circular strategies are present in the research into plastic
CE at the product level. The limitation in this case is that no research on
refurbish (R5) and remanufacture (R6) was found to exist. The majority
are on recycle (R8) with 35 articles, followed by refuse (R0) with six
articles, and reuse (R3) with four articles. The remaining articles cover
circular strategies of rethink (R1) reduce (R2), repair (R4), repurpose
(R7) and recover (R9). Table 7 shown the distribution of literature of
circular strategy at the product level.
Table 6. Circular strategy at the component level.
Circular Strategy at the Component Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[6] X Bio-composite market for biodegradable polymeric matrices from agriculture waste.
[81] X Plastic composite evaluation based on multiple properties.
[105] X X Glass fibre reinforced plastic waste treatment technology and reuse potential of composites.
[134] X X Analyse performance of composites remanufactured from recycled short carbon fibres with the HiPerDif method.
[185] X Urban automated plastic sorting.
[220] X X WPC incinerated end-life treatment.
[243] X Recycling strategies SWOT analysis for component recycling for WEEE plastic.
TOTAL 1001001061
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
D. Sitadewi et al. Heliyon 7 (2021) e07154
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At the product level, Refuse (R0) strategy addresses mainly the
replacing of fossil-plastics with bioplastics having a similar function. Two
pieces focused on the performance comparison between a fossil-based
plastic product and biodegradable single-use tableware [35,67]. Two
articles focus on novel products as an innovative approach to a more
circular cosmetic dermatology and packaging [153] and PLA for novel
consumer packaging application [76]. The literature on bioplastic
focused on the issue of risks associated with its use [4,223].
Rethink (R1) strategy at the main product level focuses on rethinking
product design to render it more sustainable. Rethinking product design
innovation can involve the use of waste [66], sharing economy and the
internet of things concept to enable CE [140]. Reduce (R2) strategy re-
flects the circular preference to reduce raw material consumption during
production through innovative plastic packaging design [210]. At
product level, the topic focuses on reuse (R3) of recycled plastic to pro-
duce bricks [146], and reusable plastic crates [229]. Other topics include
the consideration of product reusability throughout its lifecycle when
designing products for helicopter canopies [109].
Repair (R4) involves making defective products useable and has its
original function in maintenance [175]. Research at the product level
Table 7. Circular strategy at the product level.
Product Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[4] X X Bioplastic risk.
[9] X LCA recycled plastic diesel fuel filter
[26] X LCA of 3D printer FPF.
[27] X Thermochemical conversion from landfill.
[33] X Product design &eco-design packaging
[35] X X Single-use tableware.
[50] X Agricultural polymer container pesticide residue.
[53] X Thermal degradation of resource-separated plastics HHW.
[54] X Thermal degradation of HHW in Denmark.
[61] X Recycling potential in Denmark.
[66]X Product design made from waste
[67]X Biodegradable tableware
[72] X Recycled product chemical safety on food packaging.
[76]X PLA for novel packaging application.
[89] X Cotton polyester textile recycling into a novel cellulose fibres.
[96] X X X Comparison with upcycling plastic scrap.
[101] X X Typology to measuring recyclates feedstock quality.
[109] X X Helicopter canopy lifecycle.
[122] X Single-use infant feeding bottle.
[127] X Biodegradable plastic product design.
[138] X Thermo-chemical exploitation of plastic.
[140]X Product design using sharing economy and IoT concept.
[146] X Reusing secondary material from landfills to manufature bricks in Italy.
[151] X Bricks made from plastic waste.
[152] X Sequential pyrolysis and catalytic chemical vapour deposition of plastic waste.
[153]X Bioplastic used in circular cosmetic dermatology and packaging.
[157] X Chemical-ultrasonic treatment of Multilayer Flexible Packaging Waste (MFPW).
[161] X Product policy and design measures of ICT.
[172] X Decontamination of agrochemical.
[183] X New products made from recycled polymer.
[184] X Different approaches to recycled polymer use.
[192] X Guidance to incorporate recycled plastics into new E&EE.
[195] X X Leveraging waste reclaimed from water.
[197] X Construction products made from plastic.
[203] X Societal challenge of plastic packaging.
[210] X Innovative plastic product development for food packaging design.
[221] X Car door material LCA.audit
[223]X Literature review of bioplastic.
[229] X Reusable plastic crates in Italy.
[230] X Single-use black LCA plastic life cycle.
[231] X Plastic food packaging development.
[239] X eDIM (ease of disassembly matrix) using LCD Monitor.
[240] X Circular construct on product implementation.
[245] X Recycling plastic used in air purifiers.
[257] X Upcycling using recyclebot.
TOTAL 62142001351
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
D. Sitadewi et al. Heliyon 7 (2021) e07154
11
focuses on product design disassembly evaluation using ease of Disas-
sembly Metrics through the case study of LCD Monitor [239]. The other
article measuring recyclates feedstock quality employed the example of a
single-use plastic bottle [101]. There is one piece of research which
compares remanufacture (R6), recycle (R8), and recover (R9) in upcy-
cling plastic scrap [96].
Recycle (R8) forms the largest portion of circular strategy at the
product level with the topics encompassing recycled products, chemical
recycling, DRAM, decontamination, product lifecycle and product
design. Three articles focused on recycled products: recycled polymers
[184], bricks made from plastic waste [151], air purifiers [245], and
construction products made from plastic [197]. Another article provides
guidance to manufacturers looking to incorporate recycled plastics in
new electrical and electronic equipment (E&EE) [192]. The articles on
household waste (HHW) focused on HHW recycling in Denmark [54],
thermal degradation, and the mechanical properties of
resource-separated plastic HHW [53]. One article assess CE of plastic
bottle in the USA at a product systemic level [133].
Chemical recycling options at the product level encompass thermo-
chemical exploitation of plastic [138], thermochemical conversion
from landfill [27], chemical-ultrasonic treatment of different types of
Multilayer Flexible Packaging Waste [157], sequential pyrolysis and
catalytic chemical vapor deposition [152]. The DRAM option at the
product level include; upcycling using recyclebot, an open-source waste
plastic extruder [257] and 3D printer FPF (Fused Particle Fabrication)
lifecycle [26]. The articles on plastic decontamination of secondary
material comprise agrochemical decontamination [172], pesticide res-
idue in agricultural polymer containers [50], and recycled product
chemical safety relating to food packaging [72]. Three articles focused on
the product lifecycle of single-use black plastic [230], car door material
[221], and plastic diesel fuel filters made from recycled polymide [9].
Articles of product design include topics such as single use feeding
bottles [122], plastic food packaging development 231], biodegradable
plastic product design [127], and product policy and design measures of
information and communication technologies (ICT) [161]. Product
design and eco-design packaging replaces eucalyptus wood sheets with
plastic compound alternatives composed of virgin and recycled PP [33].
Other articles focus on cotton polyester textile recycling to produce a
novel cellulose fibre [89]. The articles on PCPW (Post-Consumer Plastic
Waste) product design focused on large-scale industrial trials of new
products [183] and the plastic waste recyclability characteristics of
Danish recycling centers [61]. The rest of the articles on product
recycling cover topics such as societal challenges from plastic packaging
[203], implementing circular construction of products [240], and
leveraging waste reclaimed or diverted from water for products and
marketing [195].
4.1.4. Customer level
At the customer level the circular strategy of Refuse (R0) largely re-
lates to the customer perception of using bioplastics as opposed to fossil
plastic with the following focus. users' emotional experiences resulting
from interaction with sustainable materials [14]; psychological drivers of
market acceptance of bioplastics [36]; consumer perceptions of bio-
plastic [200]; a bioplastic market review and the latest solution resulting
from the use of bioplastic packaging materials [45]. Table 8 shown the
distribution of literature of circular strategy at the customer level.
Rethink (R1) strategy focuses on raising awareness of the research
focus on consumers’perceptions of environmentally sustainable
beverage containers and comparing it with LCA [18]. Raising awareness
of plastic waste is undertaken through practical sessions involving
interdisciplinary participants [82].
Reduce (R2) strategy highlights the following initiatives to prevent
waste generation: university-based plastic bottle reduce-reuse-recycle
campaigns [205]; behavioral change in terms of reducing marine pollu-
tion [248]; and effecting changed behavior with regard to plastic bottle
waste prevention [259].
Recycling (R8) strategy at the customer level focuses on recycled
product impact on health with particular reference to the following:
recycling limitations and impacts on health and safety [15]; waste sorting
manuals vs. technical and health risks for workers [31], mass flow
analysis of plastic and paper in relation to childhood exposure to haz-
ardous chemicals in recycled material [120]; behavioral response to
plastic products in the Netherlands [135]; and stakeholder perceptions
and viability of 3D printing as a CE enabler at the local level [137]. To
reduce the adverse effect on human health from the increase adoption of
recycling, the CE should be based on sustainable and clean resource flows
[121].
4.2. Meso-system perspective circular strategy for plastic
4.2.1. Business level
The main focus of the circular strategy at the business level is on
recycling (R8) with research gaps in the areas of refuse (R0), and stra-
tegies aimed at extending product lifespan. Table 9 shown the
Table 8. Circular strategy at the consumer level.
Circular Strategy at the Consumer Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[14] X X Users' emotional experiences resulting from interaction with sustainable materials.
[15] X Recycling limitation and impacts to health and safety.
[18] X Consumer's perception of environmentally sustainable beverage containers and compared it with LCA.
[31] X Waste sorting manual vs. technical and health risk for workers
[36] X Psychological driver for market acceptance for bioplastic.
[45] X Bioplastic market review and the latest solution bioplastic packaging materials
[82] X Raising awareness of plastic waste through practical session among interdisciplinary audience.
[120] X Mass flow analysis of plastic &paper for childhood exposure to hazardo us chemical in recycled material.
[135] X Behavioral response to plastic produces in Dutch.
[137] X Stakeholders' perception and viability of 3D printing as a CE enabler at the local level.
[158] X Value-adding by informal waste collector in developing economies.
[200] X Consumer perception to bioplastic.
[205] X Plastic bottles reduce-reuse-recycle campaign in university.
[248] X Behavioral change on marine litter mitigation.
[259] X Waste prevention behavior for plastic bottle.
TOTAL 4221000061
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
D. Sitadewi et al. Heliyon 7 (2021) e07154
12
distribution of literature of circular strategy at the business level. One
article reviewied distributed recycling using a 3D process chain [206].
Another dealt with chemical recycling of plastic waste-to-fuel from dis-
used landfills within the EU [65]. The remaining articles covered the
following topics related to mechanical recycling: healthcare waste anal-
ysis using the case study of a general public hospital in Pakistan [5]; an
analysis of the life cycle of agricultural plastic waste (APW) [28]; the
framework integrating an AI/DB (Artificial Intelligence Database)
interface into the DSC-TGA (Differential Scanning
Calorimetry-Thermogravimetric Analysis) system with a virgin-recycled
mixing ratio database beneficial to the manufacturer [71]; optimizing
recycling management in terms of emptying holding containers [129];
and plant bottle packaging company programs in China [188].
A discussion of Rethinking (R1) organization behavior with regard to
CE can be found in these articles. Indicators for Circular Business Model
are used in a case study of companies in Brazil [198], while the rela-
tionship between Organization behaviour and CE draws on an example
from Belgium [112]. Waste reduction (R2) represents the research focus
of a composition analysis of waste produced during commercial flights
using a case study of 27 such journeys to and from Cyprus [227]. Reuse
(R3) and recycle (R8) appear in the research on municipal household
waste, where the largest value creation potential (economic, social, and
environmental) is that of waste reuse [254]. Several papers refer to the
use of energy recovery (R9) to process unrecyclable, contaminated, and
mixed plastic waste [100,117] and propose improvements in Recycla-
bility Benefit Rate and the Recycled Content Benefit Rate indicators
[100] and use of a fuel mixture containing contaminated plastic for
incineration [117].
4.2.2. Production chain level
Refuse (R0) strategy is covered in three articles relating to the pro-
duction chain level with the following focus: designing for Recycling
(DfR) to address bio-based polymers and recycling infrastructure system
constraints [95]; a collaborative value chain for circular business models
[111]; investigations into the structure of potential Organic Fraction of
Municipal Solid Waste (OFMSW) supply chains to identify bottlenecks
(bioplastic) [178], the role of Reduce (R2) strategy in the optimization of
end-to-end supply network design to reduce waste in Scottish agriculture
[190]; and Reuse (R3) strategy in relation to the legacy additives in the
plastic waste stream resulting from improper disposal, treatment option
and regulation [244]. Table 10 shown the distribution of literature of
circular strategy at the production chain level.
Recycle (R8) constituted the predominant strategy of at the produc-
tion chain level with the following topics: innovative value co-creation
through a collaboration model in market garden plastic films [19];
eco-design throughout the production chain [32]; “Waste-to-resources”
opportunities using plastic and food supply chain waste [34]; the
value-adding of informal waste collectors in developing economies
[158]; distributed plastic recycling using 3D printers within a closed
supply chain network [165]; industrial circular plastic consumption cy-
cles in Islamabad and Rawalpindi [233]; mathematical modelling of
supply chain complexity to identify potential optimum recycling centres
[139]; research focus on three PCPW topics - PCPW Recycling network
levels, types and materials [23]; PCPW focus on stakeholder value chains
[85]; and integrating systemic thinking in the value chain of stakeholders
for PCPW [86].
4.2.3. Industrial symbiosis level
Industrial symbiosis is a merger of two or more different industries
to find optimal access to material components and process waste [12],
similar to CE. Research at the industrial symbiosis level covers only
reduce (R2), reuse (R3), recycle (R8) and recover (R9) within the
following topics: the UK Plastic Pact for recycling collective initiative
[74]; PCPW material flow analysis of the Swiss waste management
system's industrial ecology [91]; an industrial symbiosis model of
electrical cable reuse [136]; the life cycle assessment of household
waste collected at eight recycling centers in Denmark [65]; an exami-
nation of Extended Producer Responsibility (EPR) in South Korea
[104]; organization behaviour relating to CE in Belgium [112]; and
Chinese plastic recycling industries (CPRI) [131]. Table 11 shown the
distribution of literature of circular strategy at the industrial symbiosis
level.
4.2.4. Eco-industrial park level
Mechanical recycling dominates circular strategy at the eco-industrial
level; PCPW industrial park construction [252] and pilot CE imple-
mentation in suburban steel plants recycling plastic waste in China [256].
One text examines locally-managed chemical recycling using appropriate
technology within rural communities in Uganda [107]. The article out-
lining the New Plastics Economy and launching a Circular Design guide
to help industry transition from LE to CE uses the
reduce-reuse-remanufacture-recycle strategy [75]. Table 12 shown the
distribution of literature of circular strategy at the eco-industrial park
level.
Table 9. Circular strategy at the business level.
Circular Strategy at the Business Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[5] X Healthcare waste analysis using case study of general public hospital in Pakistan.
[28] X APW life cycle analysis.
[34]X“Waste-to-resources”opportunities in plastic and food supply chain waste.
[65] X Plastic waste-to-fuel recycling from old landfills in EU.
[71] X Framework combines AI/DB interface into DSC-TGA system with database of mix virgin-recycled ratio.
[100] X X Propose improvement of Recyclability Benefit Rate and the Recycled Content Benefit Rate indicators.
[112] X Organization behaviour to CE in Belgium.
[117] X X Fuel mixture using contaminated plastic for incinerator.
[129] X Optimize recycling management in terms of emptying containers holding.
[188] X Plant bottle packaging company program in China.
[198] X Indicators for Circular Business Model using case study of companies in Brazil.
[206] X Review of DRAM using a 3D process chain.
[227] X Composition analysis of waste produced during a flight using case study of 27 flights in Cyprus.
[254] X X For municipal household waste, the largest value creation potential is at waste reuse (economically, socially, and environmentally).
TOTAL 02110000112
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
D. Sitadewi et al. Heliyon 7 (2021) e07154
13
4.3. Macro-system perspective circular strategy for plastic
4.3.1. City level
The research at the city level predominantly uses a recycling strategy.
Examples include: waste-to-wealth of post-war communities in Sri Lanka
based on recycling plastic [37]; 3D printing disruption to the existing
material value chain in the London Metropolitan Area [69]; and a
Multi-Waste plant established to process municipal waste by means of
pyrolysis and anaerobic digestion [94]. Rethink (R1) strategy is applied
as part of the urban assessment of historical circular cities [77]. Reuse
(R3) and recycle (R8) are used with the urban waste circular business
model by integrating 4.0 technology and 3D printing technology [160].
Waste reduce (R2) depends on the socio-demographic characteristics that
affect the plastic waste generation within a Czech municipality [201].
The design of urban biorefinery in Bangkok [209] incorporates both
recycling (R8) and energy recovery through incineration (R9). Table 13
shown the distribution of literature of circular strategy at the city level.
4.3.2. Regional level
Reduce (R2) strategy at the regional level is identified in two articles,
namely; Landfill mining (LFM) in the Baltic region to reduce disposed waste
[25] and South Italy Farmers' attitudes towards policy, subsidies, and tax
credits to reduce plastic waste [43]. A Reuse (R3) and Recycle (R8) com-
bination is available at part of the "Pay-as-you-throw" (PAYT) scheme in
the County of Aschaffenburg, Germany [154]. Table 14 shown the dis-
tribution of literature of circular strategy at the regional level.
The most common strategy at the regional level is recycling (R8)
featuring various topics. These include Three different collection schemes
which affect quantity and quality of recycling in England [87]; Exploratory
study of Abloradgei dumpsite in Ghana [1]; Collection process of recyclable
Table 10. Circular strategy at the production chain level.
Circular Strategy at the Production Chain Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[19] X Innovative value co-creation through collaboration model in garden market plastic films.
[23] X PCPW Recycling network level of types &material.
[32] X Eco-design along the production chain.
[85] X PCPW focus on stakeholders' value chain.
[86] X Integrating systemic thinking in value chain of stakeholders for PCPW.
[95] X Designing for Recycling (DfR) for bio-based polymers and recycling infrastructure system constraints.
[111] X X Collaborative value chain for circular business model.
[165] X Distributed plastic recycling using 3D printer using closed supply chain network.
[178] X X Investigate the structure of potential supply chain of OFMSW to identify bottlenecks (bioplastic)
[190] X X Optimization on end-to-end supply network design to reduce waste in Scotland agriculture.
[233] X Islamabad and Rawalpindi industrial circular plastic consumption cycle.
[244] X X Legacy additives in the plastic waste stream from improper disposal, treatment option and regulation.
[139] X Mathematical modelling of supply chain complexity to identify possible optimum recycling centres.
TOTAL 30110000120
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
Table 11. Circular strategy at the industrial symbiosis level.
Circular Strategy at the Industrial Symbiosis Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[65] X Life cycle assessment of residential household waste collected at 8 recycling centers in Denmark.
[74] X UK Plastic Pact for recycling collective initiative.
[91] X PCPW material flow analysis of Swiss waste management system industrial ecology.
[104] X Examines extended producer responsibility in South Korea.
[131] X CPRI
[136] X Industrial symbiosis model of electrical cable reuse.
TOTAL 0011000031
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
Table 12. Circular strategy at the eco-industrial park level.
Circular Strategy at the Eco-Industrial Park Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[75] X X X X Outline for New Plastics Economy &launch a Circular Design guide to help industry transition from LE to CE.
[107] X Locally produced waste-to-fuel using appropriate technology in rural communities in Uganda.
[252] X PCPW Industrial park construction.
[256] X Pilot CE implementation in suburban steel plant recycles including plastic waste in China.
TOTAL 0011000140
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
D. Sitadewi et al. Heliyon 7 (2021) e07154
14
materials between 2004 and 2011 in 103 Italian provinces [3]; and Lower
Austrian waste management system involving the introduction of a 'catch--
all-plastics-bin' [116].
The combination of Recover (R9) and Recycle (R8) strategies can be
found in two articles at the regional level; Nordic Region plastic value chain
and mapping major actors, interactions and barriers to material flow [147]
and In P€
aij€
at-H€
ame region, Finland, significant portion of plastic material
flows to energy production instead of recycling [242].
4.3.3. National level
The plastic circular strategy at the national level consists mainly of
recycling (R8) which covers various topics, including: Recycling potential
of PCPW in Finland [39]. Development of German waste legislation "Pay As
You Throw" to achieve its recycling rates [46]; Multi-scale system modelling
approach to alternative resource recovery methods in UK [83]; Material flow
analysis in Trinidad and Togabo [149]; Modelling municipal solid waste
(MSW) characteristics in the USA [176]; and Activities of polymer industry in
Bulgaria [241]. Another articles review the Life cycle assessment of
Table 13. Circular strategy at the city level.
Circular Strategy at the City Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[37] X Waste-to-wealth of post-war communities in Sri Lanka by recycling plastic.
[69] X 3D printing disruption to the existing material value chain in London Metropolitan Area.
[77] X Urban assessment of historical circular cities
[87] X Three different collection schemes which affect quantity and quality of recycling in England.
[94] X Multi-Waste plant to process municip al waste through pyrolysis and anaerobic digestion.
[160] X X Urban waste circular business model by integrating industry 4.0 technologies and 3D printing technology.
[201] X socio-demographic characteristics that affect plastic waste generation in Czech municipality.
[209] X X Design of urban biorefinery in Bangkok by integrating plastic and paper recycling processes.
TOTAL 0111000061
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
Table 14. Circular strategy at the regional level.
Circular Strategy at the Regional Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[1] X Exploratory study of Abloradgei dumpsite in Ghana.
[3] X Collection process of recyclable materials in year 2004–2011 in 103 Italian provinces.
[25] X LFM in the Baltic region to reduce disposed waste.
[43] X Farmers' attitudes towards policy, subsidies, and tax credits to reduce plastic waste.
[116] X Lower Austrian waste management system by introducing 'catch-all-plastics-bin'.
[124] X X X Extent of toxic chemical BDEs (Brominated Diphenyl Ether flame retardants) enter secondary product chains.
[147] X X Nordic Region plastic value chain and mapping major actors, interactions and barriers to material flow.
[154] X X "Pay-as-you-throw" scheme contributes to material reuse and recycling in German county.
[242]XXInP
€
aij€
at-H€
ame region, significant portion of plastic material flows to energy production instead of recycling.
TOTAL 0022001072
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
Table 15. Circular strategy at the national level.
Circular Strategy at the National Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[10] X Contaminant BPA material flow analysis in Norway during waste handling.
[39] X Recycling potential of post-consumer plastic packaging waste in Finland.
[46] X Development of German waste legislation "Pay As You Throw" to achieve its recycling rates.
[83] X Multi-scale system modelling approach to alternative resource recovery methods in UK.
[84] X Plastic recovery status and existing recycling infrastructure in Qatar.
[108] X X X Big data analytics to identify countries to potentially benefit from locally managed decentralized CE in Uganda.
[115] X Waste management system for plastic packaging in 2013 Austria using material flow analysis.
[149] X Material flow analysis in Trinidad and Togabo.
[176] X Modelling USA municipal solid waste characteristics.
[236] X Assessment waste management system of plastic packaging in 1994 Austria.
[241] X Activities of polymer industry in Bulgaria.
[247] X X X X Review of Thailand national waste management using energy recovery and 3R framework.
TOTAL 00220000112
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
D. Sitadewi et al. Heliyon 7 (2021) e07154
15
Denmark residential household waste collected at recycling centers [63]
and transition to CE at national level in Hungary business environment
[68].
Only two articles dealt with reduce-reuse-recycle strategies. One
was a review of Thailand's national waste management using energy
recovery and 3R framework [247]. The other involved the use of big
data analytics to identify countries which could potentially benefit
from locally managed decentralized CE such as operated in Uganda
[108]. Two further articles reviewed Austria's waste management
assessment in different periods; one relating to plastic packaging in
1994 [236], the other to material flow analysis (MFA) in 2013 [115].
Table 15 shown the distribution of literature of circular strategy at the
national level.
Table 16. Circular strategy at the global level.
Circular Strategy at the Global Level
References R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 Research
[2] X Impacts of marine debris (microplastics): 1) marine organism; 2) merine environment; 3) human health &economy.
[21] X Bio-based plastics EU recirculation routes
[22] X Commodity trade data illustrate export plasic waste from higher-income countries to lower-income countries
[44] X Initiative rethink and redesign future of plastic.
[51] X Europe household waste quality &quantity performance based on 84 recovery scenarios
[62] X Life cycle assessment of Denmark residential household waste collected at recycling centers.
[63] X X Fair-trading systems for waste reutilization across countries globally to reduce waste.
[80] X EU's RISKCYCLE summary and issues.
[103] X Waste sources and solutions to waste management in several countries around Africa.
[106] X X X Legislation and adopt 3R framework to reduce marine microplastic.
[110] X Green sustainable chemistry trends of waste valorisation.
[118] X Value proposition of polymer molecule via plant-biomass photosynthesis.
[150] X Global perspective of LE for CE.
[171] X EU regulatory measures across multiple economic sectors of individua l countries in the EU.
[180] X Impact of China waste import ban.
[191] X Production deglobalization to reduce plastic waste.
[193] X Process efficiencies of plastic EoL (end-of-life) in EU.
[237] X EU mechanical recycling technical assessment of post-consumer plastic packaging waste.
[63] X X Fair-trading systems for waste reutilization across countries globally to reduce waste.
TOTAL 2281000080
LEGEND: R0 ¼Refuse; R1 ¼Rethink; R2 ¼Reduce; R3 ¼Reuse; R4 ¼Repair; R5 ¼Refurbish; R6 ¼Remanufacture; R7 ¼Repurpose; R8 ¼Recycle; R9 ¼Recover.
Figure 8. Distribution of texts across all system perspective of plastic CE.
Figure 9. Distribution of texts across micro-system sub-levels.
Figure 10. Distribution of texts across meso-system sub-levels.
Figure 11. Distribution of texts across macro-system sublevels.
Figure 12. Bar chart of circular strategies identified in texts.
D. Sitadewi et al. Heliyon 7 (2021) e07154
16
4.3.4. Global level
Reuse (R0) at the global level is analyzed in two pieces of research.
One investigated replacing fossil-plastic with bio-based carbon plastics
and industrial products in China, EU, NAFTA, USA, Canada, Mexico
[118]. The other looked at the adopting of bio-based plastic in EU
recirculation routes [21]. A Reduce-Reuse-Recycle strategy was adopted
in an effort to reduce marine microplastics [106]. Table 16 shown the
distribution of literature of circular strategy at the global level.
Rethink (R1) applied to the topic of New Plastic Economy initiative by
bringing together key stakeholders to rethink and redesign the future of
plastics [44] and the global trend towards the green sustainable chem-
istry of waste valorisation [110].
Reduce (R2) research covers reducing marine microplastics [2] and
EU regulatory measures across multiple economic sectors of EU indi-
vidual countries [171]. Other topics include production deglobalization
to reduce plastic waste [191]; fair-trading systems for waste reutilization
across countries globally to reduce waste [132]; and process efficiencies
of plastic EoL in EU [193].
Recycle (R8) accounts for the majority of research at the global level.
Two pieces of research focus on the impact of China's waste import ban
[180] and the export of plastic waste from higher-to-lower income
countries [22]. Three focus on EU countries. European household waste
quality and quantity performance based on 84 recovery scenarios [51];
the EU's RISKCYCLE (Risk-based management of chemicals &products in
CE) summary and issues [80]; and the EU's mechanical recycling tech-
nical assessment of post-consumer plastic packaging waste [237]. The
rest of the articles cover various topics including; Life cycle assessment
(LCA) of Denmark residential household waste collected at recycling
centers [62]; Waste sources and solutions to waste management in
several countries around Africa [103] and Value proposition of polymer
molecule via plant-biomass photosynthesis. Global perspectives on LE for
CE [150].
5. Summary
The finding proves that failure in implementing systemic change
could result in the subversion and misunderstanding of the CE principal
resulting in stakeholders only implementing minimal change in order to
preserve the status-quo [114]. The bibliographic mapping and systematic
literature review indicated that the majority of the research focused on
recycle (R8), followed by refuse (R0), reuse (R3), and reduce (R2).
Certain circular strategies are more appropriate to handling certain
plastic materials, despite CE's favoring of prevention and recycling over
incineration [10].
Recover (R8) is often used to process mixed and contaminated plastic
[100,117] at the business level. Plastics that are mixed with other ma-
terials during disposal, including other types of plastics, can lead to the
contamination and deterioration of polymeric properties due to their
permeable nature [87]. Recovery (R8) has already been adopted by the
national waste management systems of countries such as South Korea
[104], Finland [147,242], Thailand [209,247], and Norway [10]. The
academic literature on recovery (R9) strategy is comparably limited due
to its relative lack of circularity importance since recovery is closer to LE
[175]. This fact accounts for it having the lowest research priority.
However, the recover (R9) strategy can destroy the contaminants present
in plastic waste and, consequently, produces the lowest environmental
emissions.
This research found that recycling is the most popular circular strat-
egy and the most applicable to plastic material either through upcycling
or downcycling. Furthermore, there are three recycle trends, namely;
mechanical recycling, chemical recycling and DRAM. DRAM and chem-
ical recycling constitute recent topics of interest to researchers from 2018
and 2017 respectively. In addition, mechanical recycling is the most
widely known and oldest form of recycling with research into the subject
dating back as far as 2011. The popularity of recycling enables the pre-
serving of current industrial and consumption models [123], even though
it is close to the linear economy model [175]. Lemile (2019) believed
that, in order to truly move to a circular economy, recycling has to be
discontinued. Recycle only serves to preserve the status-quo of LE since it
can devalue material (downcycle) and, instead, investment should be
made in the CE strategies that maintain or increase value. Rather than
adopting recycling practice to preserve the status-quo through down-
cycling (devalue material), investment should be made in circular prin-
ciples such as upcycling that maintain or increase value. The CE should
be aimed to be able to resolve resource scarcity and regeneration instead
of only creating products from recycled products [56]. In upcycling, the
latest technology in 3D printing is employed to turn plastic waste into
added-value products through additive manufacturing.
Research using repurpose (R7) is not widely available across all sys-
tem perspectives. The research at material level focused on developing
upcycled material to construct affordable homes for Nigeria's low-income
community [163]. The product level deals with comparisons with
upcycling plastic scrap [96], while the eco-industrial park level is con-
cerned with guiding circular design [75]. No article was identified which
analyzed both the meso and macro-system perspective.
Remanufacture (R6) research is limited to the component and
production-chain levels. The research at component level investigated
the performance of plastic composites remanufactured from short carbon
fibers [134]. The other focus was on the extent to which the banned toxic
chemical BDEs entered remanufactured product chains [124]. No article
dealing with the macro-system perspective was identified.
Refurbish (R5) represents the circular strategy for which the least
academic literature for plastic CE has been produced with no article
discovered at any system perspective level. Prolonging the product life
through refurbishing is not applicable to plastic due to its material lim-
itations [85].
Research on repair (R4) can be found at the product level. The topics
covered comprise product design disassembly evaluation [239] and
measuring recyclate feedstock quality through the example of a
single-use plastic bottle [101]. No article was discovered dealing with the
meso and macro system-perspective.
Research utilizing the reuse strategy (R3) can be found across all
system perspectives. The relative popularity of the reuse strategy in the
literature can be due to the increasing adoption of 3R framework [20,
247]. No research exists on reuse strategy at the company level (micro)
and eco-industrial park (meso).
Reduce (R2) is the second most popular circular strategy after recy-
cling and is comparatively highly prioritized with the third highest
number of articles at 21 (9.91%). It reflects the circular preference to
reduce consumption, either by launching campaigns to prevent waste or
increasing production efficiency. The frequent appearance of the macro-
system in the published literature is due to the increasing adoption of 3R
framework as the form of national waste management in such countries
as Thailand [247] and globally to reduce ocean-borne microplastics
[106]. The Reduce strategy can also be implemented through production
efficiency which reduces resource consumption [213,255]; enhances
process efficiency at EoL [2,193]; optimizes supply network design
[190]; and innovative plastic packaging design [210]. Several pieces of
research focus on the behaviorial aspects of waste reduction with a focus
on waste prevention activities during flights [227]; socio-demographic
characteristics that affect waste generation [201]; and farmer attitudes
to plastic waste reduction policies in agriculture [43].
Research on Rethink (R1) has largely focused on rethinking product
design, consumer and organization behavior and perceptions of CE.
Rethinking product design innovation comprises made from waste [66],
flame retardant additive material [211], and using sharing economy and
D. Sitadewi et al. Heliyon 7 (2021) e07154
17
internet of things concepts to enable CE [140]. Rethinking consumer
behavior encompasses consumer perception of environmentally sus-
tainable beverage containers [18]; and raising awareness of plastic waste
through interdisciplinary study [82]. Other topics include rethinking
organizational behavior towards CE [112] and cultural paradigm shift
and collaboration as means off transitioning to a circular city [77].
Refuse (R0) constitutes the second most popular strategy after recycle.
Its popularity is due to the adoption of bio-based plastics which have a
similar function to fossil-based plastics. The literature on the development
of bio-based plastic polylactic acid (PLA) and polyhydroxyalkanoates
(PHA) focused on its substitution and commercial viability [217]; com-
pounding food waste with PLA [29]; together with its standardized la-
beling; sorting; coordinated regulation [177]; production technologies;
challenge; and future opportunities [166]. Popular research bioplastic
research focuses on the development of bioplastic production, namely;
bio-derived polymer from citrus waste [47]; PLA from agricultural waste
[6] and sludge cellulose plastic composite (SPC) [142]. Other topics
include: bioplastic produced by microalgae cultivation using agricultural
runoff and urban wastewater as feedstock [232]; cosmetic packaging
made from bio-based polymer [30]; converting biomass into bio-plastic
[215]; and combining 3D printing with biomaterials [238]. Several
pieces of research explore bio-plastic biodegradability [159,164,223]
and degradation characteristics [199]. The remainder of the literature at
the material level focused on improving bioplastic polymer performance
[90]; chemical recyclability [207]; chemical synthesis [130]; and con-
structing a low-cost small building using biogenic materials [64]. Two
articles focused on bioplastic as a substitute for fossil-based materials due
to its chemical functionalities [170] and its upcycling process [16]. One
article described the potential processing and modification of natural
polymer with thermoplastic properties [156].
6. Limitation and future research
Plastic is very popular for various applications due to its durability,
lightweight nature, low cost, and flexibility, which makes it convenient
for single-use packaging in business-to-customer applications [174,246].
The current plastic economy is highly fragmented which leads to waste
leaking into the environment. Therefore, it is necessary to transform the
existing LE into a more closed-loop CE [246]. A fundamental shift in the
current system and understanding of CE is required for the transition to
avoid stakeholders possibly implementing minimal change in order to
preserve the existing state of affairs [114]. From the praxis of gover-
nance, CE strategies can be used to steer the transition in the CE [155].
The current literature is extensive but fragmented and numerous po-
tential strategies can be incorporated across the system perspective.
Therefore, this study mapped the combination of a comprehensive CE
strategy with a system perspective which is currently lacking in the
existing literature. Moreover, the aims unify the fragmented literature
and understand the current state of the art.
The limitation of this study is that data collection was that it was
confined to the Scopus database. Therefore, the findings can be viewed as
a starting point to further the CE research agenda. Bibliographical visu-
alization by means of VOSviewer using keyword co-occurrence is limited
in its capacity to map the entirety of system perspectives and circular
strategies contained in the literature. This limitation is due to the use of
VOSviewer co-occurrence analysis being restricted to either of the iter-
ature keywords, author or nation, to create a bibliographical map. This is
where systematic literature can be used to cover the limitation by
manually classifying the literature based on system perspectives and
circular strategies. Based on the state-of-the-art classification, the
following future research topics can be proposed.
6.1. Transitioning from LE to a CE at the urban level (circular city)
This study found that not all circular principles are applied at
every sub-level of system perspectives for plastic. Furthermore, there
are gaps in both meso-system and macro-system perspectives across
the repurpose, remanufacture, refurbish and repair categories. Of all
the circular principles, the material level of the micro-system has
the strongest literary focus. Meanwhile, there is very little literature
relating to the urban level of the macro-system perspective. There-
fore, future research can be conducted on transforming the current
linear economy into a circular one by incorporating all circular
principles at the city level.
6.2. Further research into the meso-system perspective
A review of the previous literature indicated that the lowest number
of academic papers have investigated the Meso-system perspective
compared to other perspectives across all strategies. Therefore, more
studies need to be conducted at the meso-system perspective in the
future.
6.3. Developing research on extending product life for post-consumer
plastic waste
The CE strategy of extending the life of a product and its parts
consists of repurpose, remanufacture, refurbish, and repair. Evidently,
there is limited research on extending product life using these circular
principles, with the exception of reuse. The lack of academic literature
highlights the interpretation of circular strategy priorities within the
academic and business landscapes. Contrasting business environments
may result in a varying circular priority [67]. Reuse is a popular cir-
cular strategy within the second-hand business in Western Europe,
leading to the comparatively larger body of literature on this subject. In
addition, the popularity of reuse is due to the increasing adoption of 3R
framework into waste management and reuse of products and mate-
rials. This study found that refurbish is the least popular strategy fol-
lowed by repair, remanufacture, and repurpose. Since Refurbish
involves restoring old products, it applicability to single-use plastics
and plastic packaging is questionable. However, it might be applicable
to other plastic-based products.
6.4. Developing plastic CE research in developing country contexts
Previous literature on developing countries is relatively less extensive
than that relating to developed countries, thereby constituting a research
gap. Meanwhile, plastic waste leakage into the environment is a signif-
icant challenge currently faced by many developing countries exacer-
bated by changing patterns such as increased consumption, especially of
plastic, and poor waste management [234]. Therefore, it is important to
conduct further study into plastic CE and the characteristics uniquely
evident in developing countries. Researcher should act as honest broker
and also need to include unheard stakeholders such as waste pickers in
developing countries to find solution on plastic waste from a social justice
context [52].
Declarations
Author contribution statement
Dania Sitadewi, Gatot Yudoko and Liane Okdinawati: Conceived and
designed the experiments; Performed the experiments; Analyzed and
interpreted the data; Contributed reagents, materials, analysis tools or
data; Wrote the paper.
Funding statement
This study was funded by a P3MI research grant 2020 from Institut
Teknologi Bandung (ITB), Indonesia.
D. Sitadewi et al. Heliyon 7 (2021) e07154
18
Data availability statement
Data included in article/supplementary material/referenced in
article.
Declaration of interests statement
The authors declare no conflict of interest.
Additional information
No additional information is available for this paper.
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