Emerging Associates of the Circular Economy: Analysing Interactions and Trends by a Mixed Methods Systematic Review

Abstract

Circular Economy (CE) frameworks augmented multi-dimensional research, including definitions, principles, indicators, history, limitations, enablers, and allied issues. Rethinking the designing strategies requires the exploration of CE associates and their functioning as companions for amplification through multiple suggestions, highlighting the interactions with the overall CE system towards sustainability. This paper focuses on how CE literature concentrates on premeditated areas and solution approaches. A lack of deterministic manifestations critically limits the interpretation and application of CE concepts. The paper contributes to the CE theoretical and practical understanding by for the first time outlining the CE associates, their connotation, progression, positioning in architecture, and their current state. These associates support individualization of a CE concept. The coherently applied methodology attempts to reduce the knowledge gap by following a systematic quantitative literature review process to screen 76 articles and 122 CE definitions, referencing one decade of literature. Application of comprehensive morphological mining facilitated the extraction of CE associates and later analysis. On application of Bibliometric Analysis, Text Analysis, Semantic Analysis, and Relation Mapping to the literature, 49 associates emerged. They were further validated by application of Content Analysis and Weighted Average Priority Ranking on extracted article content and definitions for deriving the most prominent associates. Subsequently, Association Rules Data Mining and K-Means Clustering were deployed in exploring the relations, ranking, and significance of CE associates. The findings consistently state that business actions (virtualize, exchange); sustainability pillars (society); and R strategies (refuse, refill, and repurpose) are unexplored CE associates, whereas Business, Economics, Environment, Measurement, Product, Industry, Resource, System, Waste, and Recycle are the most explored associates of the CE ecosystem.

1. Introduction

The linear growth model of the take–make–use–dispose tradition is primarily causing the climate change hazard with an extraordinary rate of environmental pollution, which threatens planetary boundaries, creating uncertainties in the Linear economy-based world [1]. Rapid extraction and overexploitation of resources vis-à-vis the planet’s ability to regenerate or reverse the cycle is the main reason for recent deliberations on responsible production and consumption among stakeholders [2]. The Circular Economy (CE) is emerging as an advanced alternate model by designing environmentally integrated systems to balance the sustainable pillars coupled with industrial progression. It involves the replication of lean systems with minimal or zero waste with highly optimized bundling of resources to foster natural cycles into production as well as consumption processes. Transition towards CE in today’s society requires dedicated policies, frameworks, and social changes to create a value chain not only for products and materials but also for processes and consumer behaviour. Beyond policies, directives, and regulations, a more crucial aspect is shifting from the pure profit maximization tendency by firms/industries while simultaneously departing from a highly price-sensitive mind-set and switching over by consumers. Co-integration of the two sectors will build a conducive atmosphere, leading to proper and faster implementation of CE models. CE fundamentals aim to maintain the long-term value of materials/products by reducing wastes and to further preserve resources by refurbishing or recycling or reusing them into another product/raw material [3].

Enabling such transformations requires an in-depth understanding of the CE systems aligning with its principles, schools of thought, frameworks, etc., with the inter-operating associates. In the given context, the identification of these associates of CE systems is pertinent, and how they potentially interact and integrate. Their manifestation helps in demonstrating optimal strategies and innovative solutions for sectors. Limited transformation towards CE ranges from various intrinsic barriers stemming from cultural, regulatory, market, and technological aspects [4]. Manufacturers in linear industries find it incomprehensible as to how and why to change their current processes and practices in terms of cost-benefit analysis [5].

In 2015, the “Sustainable Development Goal” (SDG) emerged to provide the blueprint to address the world’s critical environmental, political, and economic challenges collectively for a sustainable future. The confidence behind the optimism was due to a global attention, effort, approach, and motive to address the inconvenience. However, the literature pointed out three constraints in the overarching program of SDGs, which have hindered the desired progress around SDGs till now. These challenges were (a) stability, i.e., not being able to put the correct stakeholders at the correct time in the correct place, (b) implementation, i.e., not being able to ensure programmes that fit the local context and make difficult trade-offs, and lastly, (c) governance, i.e., not been able to build accountability for actions [6,7]. In a similar period, CE emerged as a toolbox for achieving sizeable SDGs in several geographic regions, especially in countries like the United Kingdom and China [8]. Conversely, economists, environmentalists, and other experts flagged ambiguity around the term Sustainability and CE. Among all discourses, netizens’ traction toward the topics “Sustainability” (Figure A1) and “Circular Economy” (Figure A2) gradually increased from 2015 to 2019. The Google trend search results reveal this fact, and this result also signifies that with the inception of the SDGs programme from the United Nations General Assembly, public curiosity around the terms Sustainability and CE grew immensely. However, the growth rate of curiosity towards the topics were not uniform. The traction rate towards CE was more rapid compared to the relatively old concept of Sustainability.

CE’s concept received much attention from diverse stakeholders across the globe, including scholars, companies, governments, and citizens [9]. Facts reveal that the traction was due to the concept’s ability to attain 21 targets associated with SDGs directly and to influence the following SDGs’ progress [8]:

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SDG 6: the Goal on Clean Water and Sanitation,

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SDG 7: the Goal on Affordable and Clean Energy,

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SDG 8: the Goal on Decent Work and Economic Growth,

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SDG 12: the Goal on Responsible Consumption and Production, and

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SDG 15: the Goal on Life on Land

This traction astounded the academic propagators yet motivated them for more significant action with practitioners for the applied execution of the concept [10]. However, sufficient exploration of CE’s associates and their relations remains unexplored to date, which is essential to achieving the above goal [11].

To illustrate the whole scenario, Simon Sinek’s Golden Circle structure with the CE framework explained that “what” stands for the results, “how” for the process, and “why” for the purpose, cause, or belief. Current exploration of CE is around “how”, i.e., changing the way we do things by following the three principles of CE, viz., design out waste and pollution; keep products and materials in use; regenerate natural systems [12]. The “what” part describes that CE’s propagators aimed for a thriving economy benefiting everyone within the planet’s limits. However, sustaining the “why” necessities further exploration and explanation as it communicates the intention, behaviour, and define-specific value proposition. An in-depth investigation and explicit working of the “why” part in a CE context is needed at this time.

This research work aims to bridge that gap and therefore aims to perform a systematic literature review to detect, extract, and explore the ‘associates’ emerging from analysis of identified critical keywords stated in one decade of literature and definitions of CE. The authors have conceptually defined the term ‘associates’ as relative connectedness having shared function by occurring together with the potential to individuate or establish the concept of CE. They interact and integrate in the system to translate the core principles of CE effectively in practice beyond a merely theoretical approach. Ideologically, they connect with CE core principles, amplifying it, providing the direction to adopt appropriate practices and further create a sustainable CE system through dynamic mutual interaction. The term “associate” has been chosen judiciously because it represents practical implications with interactions of the Circular Economy. Further, it can be expressed in an objective manner beyond pure subjective exemplification with an element of quantification. “Associates” are different from keywords, as the latter highlight the significance only while the former observe multi-directional linkage with significant properties. Hence, an associate plays a key role in the diffusion and adoption of the CE concept here. The study is novel as for the first time it introduces and reports the conceptualization of ‘associates’ in the context of CE by deploying in-depth analysis using a unique approach of combination methods. Further, a framework of CE system architecture is proposed to demonstrate the robustness and interaction of the emerged associates.

The present study attempts to contribute to the literature by bridging the knowledge gap on CE associates and their interactions within a system. Exploration of CE associates was considered through a literature review, examining definitions that emerged and further mapping and affirming them from identified journal articles/definitions. In the second phase, various CE associates were reviewed, analysed, and ranked based on the calculated significance score, applying a robust statistical methodology. The grey areas of the topic were extrapolated at the end of the study with illustration of a comprehensive framework of CE associates. By mapping the current status of CE, including identification of CE associates, and calculating their significance scores, the paper makes a crucial contribution to the subject.

Moreover, the adopted Systematic Quantitative Literature Review (SQLR) method separates this study from similar review works due to its comprehensive as well as integrated methodological approach, and novelty in bridging knowledge gap. It undertakes critical analysis and a review to direct actual diffusion and absorption of the CE concept. A number of reviews of CE literature have appeared as of now, but to our knowledge, identification of associates, and exploring their significance to generate the research gap, applying the SQLR method, were not incorporated. Previous studies applied mostly descriptive, and qualitative method in a systematic manner to narrate the developments of CE [13,14]. The findings are comprehended later in the article in Summary Table of Literature Review. This highlights that 71.05% of (i.e., 54) article samples considered in the study adopted a qualitative method to describe and conceptualize the fundamentals of CE.

A comprehensive exploration of the subject can only help establish growth, loyalty, inspiration and decision-making with flexibility and innovation [15]. At present, the missing belief in the concept seems to hinder the desired progress of the subject, i.e., an ambiguous fraction of the propagated idea. Hence, exploration should also address issues on spheres such as overconsumption and the social dimension [16]. Recent research on CE literature focuses on the conceptualization, development of knowledge, strategies, measuring indicators, enabler-barriers, themes, limitations, models, and cases characterized by fragmented studies [17,18]. A comprehensive understanding and interpretation of the operation of underlying CE core principles is lacking, besides an understanding of interactions or operations within the CE ecosystem. Thus, this study attempts to explore the CE literature from a different perspective, as to how the concept evolves, becomes operational, and achieves a system level of dynamics. Accordingly, the main research question is: What are the associates of CE and how do they interact to build a sustainable CE system?

The following structure is adopted for the paper: Section 2 describes the process and methodology for article selection, data extraction and assessment; Section 3 outlines the SQLR-based analysis; Section 4 highlights the results and outcome of the analyses performed; Section 5 provides discussion and insights; and Section 6 concludes with major research takeaways.

2. Material and Research Methodology

Studies on understanding definitions of CE [13], exploration of CE history [10], analysis of core evaluation of CE with novel definitions [19], identification and understanding of limitations and challenges the CE [20], identification of the frameworks for literature categorization [21], identification of the C(Circular)-indicators [22], and a few more studies along similar lines exist but with different lenses. This includes a human need approach [23], a waste and resource management approach [24], a quantification approach [18], etc.; but no author has explored associates of CE with their significance score and neither have previous authors used the SQLR method for their review studies. Moreover, researchers have welcomed more scientific studies to strengthen CE’s theoretical framework and remove ambiguities [21,25,26].

Therefore, to explicitly comprehend the different dimensions of CE, the following research questions (RQ) were designed.

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RQ 1: Which keywords are manifested from one-decade literature on CE and over a hundred definitions of CE?

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RQ 2: Which keywords are ontologically allied with CE and meet the definition of an associate?

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RQ 3: Which associates are significant as per one decade of CE literature?

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RQ 4: What can be the holistic CE framework with emerged associates demonstrating individuation of the concept of CE?

The study aimed to address the aforementioned issues around CE literature.

The main objectives of this study are as follows:

• To explore and map common keywords from literature and CE definitions.
• To explore the ontological connection of emerged keywords with CE and generate a list of associates.
• To examine associates with respect to CE and rank them to understand their current state.
• To develop a holistic framework with associates of CE and demonstrate the ontological connections.

An SQLR was planned and preferred over narrative or Systematic Literature Review (SLR) because this technique enables new researchers to smoothly analyse the current academic literature systematically and generate a structured quantitative overview of the field [27]. During the review, the prime focus of the study was on the identification of CE associates.

To conduct the exploratory research study, the SQLR process was adopted with a hybrid analytical method followed by the inductive method to recognize CE associates’ patterns and trends [28] and considering secondary data sources at every stage. Besides, a mixed approach was utilized inclusive of both quantitative and qualitative methods to maximize the information gain and furnish a holistic view [29].

A paper screening exercise based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was performed following flow diagram steps (Figure 1) [30,31]. The authors gave preference to the replicable, reliable, robust, and impartial technique in the study [29]. The flow diagram in Figure 1 demonstrates the screening process of articles. Since the study is exploratory, therefore, deployment of purposive sampling of publications was followed to shepherd the study. The authors considered a mixed approach to analyse the literature’s content and generate facts from it. A few statistical tools, such as Bibliometric Analysis, Semantic Analysis (semantic signifies relating to meaning in language or logic), and a few other analytical tools were applied at different stages of the study to analyse the content and facts that emerged from the literature, such as keywords, definitions, and conclusions. The next section of the article describes each step and application of statistical tools in detail.

The search results from research papers, articles on the “Circular Economy”, led to extraction of 6309 and 3201 papers from the most preferred academic search engines, i.e., Scopus and Web of Science (WoS), respectively, as of 25 May 2020, using a comprehensive screening process.

2.1. Article Screening Process for Literature Review

The study considered the following criteria:

(a)

English journal articles published between 2010 and 2019, a decade, because a decent amount of published research in the field emerged from 2010.

(b)

The journal article’s concept and subject area, as demonstrated in the flowchart. The final step of screening was based on its title, abstract, keywords, and citation score.

(c)

Further, it includes the availability of complete articles in the website’s database [32] and the citation index score [33].

A snowballing technique was deployed as per the requirement from the articles’ references or bibliography of most cited research papers.

This study set Bibliometric indicators [34] for selecting research papers. These indicators were a minimum of five and a maximum of the thirteen most cited articles per year, depending on the availability of relevant published items on the topic in that year. The other criteria considered for selection were [35]:

• the conceptual nature of the paper,
• high citation score,
• at least published in quartiles 1 or 2 journals,
• non-repetitive or no duplicate contents, and
• in the English language

Figure A3 highlights a complete graphical view of the exact number of publications considered each year versus the precise number of published articles available in a given year on CE and total citation values as of 25 May 2020, according to Scopus online research database statistics. Citation score for every considered article was available in Scopus, but it was not the same for WoS. Fifty-five articles were common between the two databases. Therefore, each year’s average citation value was calculated based on the citation score of 25 May 2020 from the Scopus database. The reason for considering the Scopus database for average calculation is that all regarded articles of WoS were available in the Scopus database as well. We compared the overall citation score for each year’s considered papers in the study to the average Scopus citation score for the same articles. We believed that citation score usage could be vital to ensure screened documents’ quality and verify the most active years in citations (Figure A3), though it is not the sole criterion as it may not always reflect quality. Here, the assumption lies in the fact that, as per Bibliometric Analysis (a statistical method to analyse published journal articles, book chapters, etc., on numerous dimensions), a scientific publication has been the indicator of research output [36], and citations received by them are considered as the proxy of their scientific impact [37]. Figure A3 illustrates that 2017 was the most productive year, followed by 2016 in citation score. Simultaneously, it is observed that since 2015, citation scores for articles have improved; the reason seems to be more traction towards the subject since then onwards, as illustrated in Figure A1 and Figure A2. The Bibliometric review supported the robust mechanism for identifying quality articles that described the subject’s conceptual nature and proceeded with this study [2].

Journal-wise, article count was conducted during the study to highlight the most relevant journals in CE within the considered timeframe. On analysing the publications of 76 articles, statistics showed that the Journal of Cleaner Production (JoCP) is at the forefront of publishing articles on CE, and the Journal of Industrial Ecology (JoIE), and Resources, Conservation & Recycling (ReCR) remained at the second and third spot, respectively. All considered journals for the study have been abbreviated at the appendix of the article for reference (

Table A2. Abbreviations used in the manuscript.

Abbreviation	Full Form	Abbreviation	Full Form
ANOVA	Analysis of Variance	PRISMA	Preferred Reporting Items for Systematic Reviews and Meta-Analyses
CBM	Circular Business Model	SC	Supply Chain
CE	Circular Economy	SCI	Sustainable Circular Index
CSCM	Circular Supply Chain Management	SD	Sustainable Development
EMF	Ellen MacArthur Foundation	SDG	Sustainable Development Goals
GDP	Gross Domestic Product	SLR	Systematic Literature Review
GRI	Global Reporting Initiative	SQLR	Systematic Quantitative Literature Review
LCA	Life Cycle assessment	TBL	Triple Bottom Line
MFA	Material Flow Analysis	WAPR	Weighted Average Priority Ranking
NDF	Normalize Definition Frequency	WoS	Web of Science
NDO	Normalize Definition Occurrence	UN	United Nation

).

2.2. Applications Rationale and Methods

After screening and analysing relevant journal articles on CE, we apprehended CE’s present-day epistemology from multiple literature works by capturing the narrative description of facts. Next, a quantitative analysis of associates extracted from the contents was conducted while the relation between Sustainability and CE was arrested with the revelation of other CE associates. These revelations include the significance of CE associates emerging from keywords and content analysis. It includes confirmatory test results using the statistical tool, Text Analysis, Semantic Analysis, Weighted Average Priority Ranking (WAPR), Association Mapping, and Cluster Analysis, on compiled definitions of CE. These analysis results also present the subject’s current state of the art and the research gaps.

Earlier in 1980, author Robert Frederick Lorch from the University of Massachusetts Amherst, in a study entitled, “Priming Processes in Semantic Memory”, mentioned that the associate of a concept plays a crucial role in disseminating the value of a concept with its strength. Therefore, exploring the associates with their significance score is essential for developing the concept of CE. The study here bridges that gap and is conducted using secondary data. In the context of CE, a Text Analysis, Semantic Analysis exercise was conducted, followed by clubbing synonymous words during the study to highlight CE’s main associates. In addition, Bibliometric Analysis, Network Analysis, and Content Analysis were also observed to investigate the CE model’s trends and gaps. Findings showed a lack of consensus on CE terminologies and definitions [19]. Therefore, researchers sought more advanced methods/tools to explore the subject [25,26].

Next, weighted average and generated priority rank are calculated for CE’s associates based on occurrence and frequency map score against the contents of 76 articles. The extracted 122 definitions of CE were analysed following the same steps and tools adopted earlier for 76 article contents. Further, the adoption of Content and Semantic Analysis for CE definitions helped generate CE’s multifaceted associates’ stance. Moreover, to validate the findings of WAPR, association mapping using WEKA and later Cluster Analysis using SPSS were followed. Lastly, a list of the most significant and least significant CE’s associates was generated for future exploration and research around them. Figure 2 and

Table 1. Summary of applied statistical tools with the applications rationale and outcome.

Statistical Tools	Software	Rationale	Outcome
Bibliometric analysis	VoSviewer	A popular research method that enables scholars to examine the past and future growth of scientific work [41,42]	Extensive qualitative analysis of CE articles emerged, quantitative metrics extracting critical keywords in CE literature. It also helped to derive the interactions of critical keywords with CE sequentially.
Text Analysis	TROPES V8.4	Assists in drawing statistical inferences from texts and transcripts [43,44]
Relation Mapping	TROPES V8.4	Relation graph/exercise gives the number of relations (co-occurrence frequency) existing between various equivalent classes
Content Analysis	VOSviewer and Microsoft Excel Coding	Makes inferences by objectively and systematically identifying specified characteristics of messages [45,46]	CE’s multifaceted associates’ stance to promote CE as a facilitator was observed. Generated a frequency map to explore the prominence and significance of extracted CE associates.
Sematic Analysis	TROPES V8.4	Ontological conceptual understanding is revealed from Semantic analysis [47]
Weighted Average Priority Ranking	Microsoft Excel	Provides an order of preference and indicates relative magnitude [48]	Findings showed a lack of consensus on CE terminologies and definitions, so advanced methods are used. Generated a priority rank for CE’s associates and identified the most and least significant CE’s associates for the future research agenda. Validation of findings of WAPR, Association mapping and Cluster analysis was followed, to describe the character of CE and its associates.
Association Rules Data Mining	WEKA	Identify associations in which transactions are distributed across multiple sources [49]
K-Means Clustering	SPSS	Non-hierarchical clustering and iterative partitioning method that divides observations into a predetermined number of clusters. [50]

provide a comprehensive structure and summary, respectively, to demonstrate the entire study methodology. For WAPR calculation, the formula used is:

$$X_{normalized}=\frac{X-X_{minimum}}{X_{maximum}-X_{minimum}}$$

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Text Analysis,Semantic Analysis and Relation Mapping (TROPES V8.4): Tropes V8.4 processes texts to extract relevant information for stylistic, syntactic (syntactic analysis may depend on the types of words, but not their meaning), and semantic equivalents analysis, covering several themes in various graphs, reports, or specific data structures [38]. The application indexes the articles, using a preloaded dictionary, in the citations network, either as citation sources or cited articles. It captures features and precise traits of the scientific discourse. The selection is based on the initial results from text conversion and citations identification [39].

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Bibliometric Analysis (VOSviewer): Bibliometric analysis is often represented as a network visualization, which ranges from entirely graphical user interface-based software such as VOSviewer. It explores the bibliometric networks structured from data mining and keyword selection [40]. Maps are created from keywords co-occurrence and their frequency, finally assigned to clusters, producing set of items and links.

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Content Analysis and WAPR (MS Excel): It is an interpretive technique which is both observational and narrative in nature. It is used to determine, quantify and analyse the presence, meanings, and relationships of keywords or themes in the text. The text is coded into categories to summarise data by generating binary values to create an occurrences or frequency map.

The WAPR process helps in analysing and generating rank for complex strategic initiatives with objective prioritization. The occurrence plus frequency value of each associate is calculated and the average value is computed by setting equal weight for predefined associates for rank generation.

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Association Rules Data Mining (WEKA): The Apriori algorithm is an algorithm in machine learning that discovers plausible associations and creates association rules. It finds out the minimum support and confidence threshold while computing these rules. Apriori works with binary attributes or nominal data. The tool Waikato Environment for Knowledge Analysis (WEKA) allows one to perform frequent pattern mining by implementing Apriori for finding features which occur together or are correlated.

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K-Means Clustering (SPSS): The unsupervised learning algorithm is used to cluster the unlabelled dataset based on a centroid by minimizing the sum of distances between data points and their corresponding clusters having similar properties following an iterative process.

The above deployed tools and techniques helped in systematic analysis of the article’s contents. Text, semantic and relation mapping are used sequentially for identification of prominent keywords from the literature and definitions are based on co-occurrence. This was followed by bibliometric analysis, which provided a visualization network to decipher associations and finally led to the emergence of CE associates. Content analysis, association rule mining, and clustering further validated and established reliability with generalizability of the findings in a robust scientific manner. Moreover, a summary of applied statistical tools with application rationale are provided in Table 1.

An exhaustive and comprehensive process was followed for SQLR study on CE. On analytical examination, 215 keywords emerged through text analysis of “Title, Abstract, Keywords, and Conclusion”, followed by 110 bonds using TROPES V8.4. and VoSviewer software tools. Later, by the relation mapping exercise, 82 prominent relations among CE keywords were obtained. Based on CE’s commonality and relation with multiple keywords, the 49 most prominent associates were identified from described relationships and frameworks of CE in literary narratives. The flow chart describes the complete methodology in a nutshell and a frame (Figure 2). Advanced methods were introduced to explore the relations between associates and to describe their character with CE.

3. Systematic Qualitative Literature Review: Content and Semantic Analysis

3.1. Circular Economy: Epistemology and Origin

The global population has attempted to combat the adverse effects of human activities such as pollution, waste generation, natural resource extraction, and climate change through a balance between social, economic, environmental, and technological orchestration [51]. CE emerged as a promising alternative with an expectation to counter global adverse effects [52] such as climate change, rate of biodiversity loss, changes to the global nitrogen cycle [53], with other associated effects such as unemployment, poverty, and diseases [54]. Many researchers, practitioners, and policymakers perceived the adverse impact as a threat to the Linear Economic model’s stability and natural ecosystems’ veracity, and the survival of humanity [55]. A transition towards CE has been perceived by many as the reference point to harmonize economic growth, environmental issues, and resource scarcity in society [52]. CE’s epistemology exploration and the manifestation of critical literature built a foundation to map different CE associates according to their significance, subsequently comparing and ranking.

CE’s origin and linkage with Sustainability were either narratives or simple SLR; however, ambiguity remained around the origin and CE dimensions [2,10]. Clear evidence of a single source or originator of the CE concept is hard to propose [10]. Literature identified CE’s origin in William Harvey’s work of 1628 on systematic circulation, followed by Marcello Malpighi’s work of 1661 on the bloodstream. François Quesnay’s work of 1758 in his book “Tableau Economique” and later, a speech of the first President of the Royal Chemical Society, Hofman, in 1848, were also attributed by researchers as CE’s origin [56].

Conversely, many authors [34,55,57,58,59,60] have attributed environmentalist economists Pearce and Turner as introducing the term “CE” from an environmental perspective in 1990 through the publication, “Economics of natural resources and the environment.” Pearce and Turner built the theoretical framework with a focus on the published document “The Economics of the Coming Spaceship Earth” by Kenneth E. Boulding in 1966 [10,61]. However, Boulding criticized the “cowboy economy” (open system) over the “spaceman economy” (closed system) [56,62] and acknowledged the environment for four basic welfare economic functions, i.e., amenity values, a resource base for the economy, a sink for residual flows, and a life support system [57].

Further, the notion of CE also has its roots in General Systems Theory [60], a material balance principle, with a focus on Environmental Economics [63], the loop economy, Industrial Economics [64] and Industrial Ecology [65,66].

It is inferred that several contributors-cum-propagators for the inception of CE belonged to multiple “schools of thought” [19,55,56,67]. We found CE as a loosely bounded scientific and non-scientific notion [21]. Different schools of thought varied in their implementation strategies, focusing on intended outcomes [60]. The prominent schools of thought contributing to the inception and propagation of CE include Laws of Ecology [68], Regenerative Design [69], Biomimicry [70], Cradle-to-Cradle [71], Industrial Ecology [72], Looped and Performance Economy [73], and The Blue Economy [74]. The Ellen MacArthur Foundation (EMAF), in its publication in 2013, also acknowledged the presence of multiple schools of thought in CE [24]. Besides, the literature also recognized CE as an umbrella concept with multiple disciplines that illustrate its roots [52,59].

This study attempts to analyse CE’s associates’ significance and current trend. CE’s growth was reviewed in two halves, i.e., pre- and post-inception of the SDG-focused programme globally. The study also clarifies CE’s interaction with numerous associates to promote CE as a facilitator for improving the economy, environment, and society simultaneously [75]. We identified CE’s associates, mapped them from screened articles using code, and compared the global scenario around the SDGs. Further, we generated a frequency map based on semantic analysis to explore the strength and significance of associates. The present study attempts the identification, consolidation, and significance of associates of CE which may be attributed to diverse backgrounds and origins. Research on consolidation and analysis of those associates of CE are missing. Therefore, further exploration around multiple associates, testing the strength and significance of those associates, along with pillars of Sustainability, are necessary to eliminate indistinctness.

3.2. Circular Economy: Definitions, Principles, Strategies

The study revealed that a commonly accepted definition of CE does not exist to date [21,76]. Kirchherr [13] consolidated the maximum number of CE definitions and has defined CE “as an economic system that replaces the ‘end-of-life’ concept with reducing, alternatively reusing, recycling and recovering materials in production/distribution and consumption processes.” However, EMAF proposed the most accepted definition, linking focal points of different schools of thought [67]; in 2013, EMAF defined CE as “an industrial economy that is restorative or regenerative by intention and design” [2]. Conversely, the study highlighted that authors formerly aimed at compilation of CE definitions consolidation: 114 by Kirchherr, 11 by Korhonen, and 25 by Homrich [13,19,21].

Content analysis of these definitions derived from secondary sources, i.e., journal articles, extracts numerous dimensions associated with CE lacking earlier. Rather than attempting one more definition, the authors have analysed consolidated definitions to throw light on different dimensions associated with CE.

Observations from numerous literature items explained that authors favoured assorted and broader definitions over inflexible ones in the last five years. However, the literature suggested that both kinds of CE definitions are valued. Researchers described the first kind of definitions and implementation as sensu strict, having a narrow focus [77], followed by the second kind as sensu latu, having a broader focus [56]. Contrarily, EMAF, in 2015, attempted to tighten the loose theories and suggested three core principles of CE, i.e., Waste elimination, Product continuation, and Resource conservation [34].

“Reduce, Reuse, Recycle”, i.e., the three R strategy, were claimed as matching the EMAF’s principle on CE [78]. R-imperative literature demonstrated its origin in the disciplines [79]. These include a range of “Re” strategies ranging from 3R to 10R and describing the essence of CE. Different author groups have assigned different R -imperatives to conceptualize the way forward to attend to circularity in the environment, economy, and society. Therefore, R-imperatives have a robust utility and presence in the principles of CE. In

Table 2. R strategies framework description.

R Framework	Strategies	Studies
3R	Reduce, Reuse, Recycle	[80,81]
4R	3R + Recover	[82,83,84]
5R	3R + Refurbish + Repair	[85]
6R	5R + Remanufacture	[86,87]
7R	6R + Refuse	[88]
8R	7R + Repurpose	[89]
9R	8R + Rethink	[90]
10R	9R + Recover	[13,91,92]

, different R-imperatives are discussed:

The three common R-strategies among all R-imperatives were Reduce, Reuse, and Recycle. Based on R-strategies, the size of the Loop is defined. For example, R0–R3 defines the Shortest Loop; R4–R6 defines the Medium Loop; and R7–R9 defines the Long Loop [79].

The present study recognized three existing noticeable implementation frameworks. Firstly, a business-oriented framework of EMAF [3] for systematic CE implementation [56]. Secondly, a relatively balanced framework by Lieder and Rashid [93], which attempted an orchestration between the three pillars of Sustainability; and lastly, the most straightforward, by author Bocken [77], who valued Original Equipment Manufacturers (OEMs) over others in the model. However, on the comparison, these models have been criticized considering inherent weakness. EMAF’s model disregarded the environmental aspects over economic characteristics. Similarly, Bocken’s model integrated product design and business models but ignored the legislative landscape. Lastly, Lieder and Rashid’s model, which was the most comprehensive out of the three due to inclusion of institutions and individuals for CE implementation, neglected the financial viability of initiatives [78].

Further, the literature also revealed that the way a firm conducts a business defines circularity or linearity in a model. The transition to a CE model is an example of a radical change, which requires a new way of thinking and doing business [77]. From the literature, 26 Circular Business Models (CBM) under six classified criteria became known. These criteria were six business actions implementing the principles of CE [94]. The first business action, Regenerates (Re), signifies shifting to renewable, followed by the second, Share (S), that signifies reusing products as long as possible, and the third, optimize (O), signifies the performance of a product. Similarly, the fourth action, Virtualize (V), signifies the delivery of a particular utility virtually, and the last business action, Exchange (E), signifies replacing old materials with advanced ones. These business actions are considered the parts of the ReSOLVE framework [12]. Discussions around R-strategies and business actions reflected in the literature were observed to be leveraging on application of digital technologies such as Industry 4.0 in business model innovation to enable CE [95,96].

In addition, while exploring the CBM’s effectiveness over other models and reasons for the vacillating concept of CBM, EMAF analysis in 2014 highlighted the customer’s irrationality, conflict of interest within companies, uneven profit-share along the Supply Chain (SC), and geographical outreach as underlying explanations [97].

Recently, in the Circular Supply Chain (CSC), the concept of CE has been integrated into the supply chain operation of an organization. This integration in a system provides new scope for ameliorating Sustainability in operations. However, such implementation is scarce due to the complexity and risk of the process [98,99]. The authors emphasize the linkage between the Circular Business Model (CBM) and Circular Supply Chain Management (CSCM). The supply chain’s design and coordination to close, narrow, slow, intensify, and dematerialize resource loops are classified as CSCM attributes [100]. Later, consolidated Circular Design Strategies—Design for circular supply, resource conservation, long-life use products, multiple cycles, and system change—received tremendous traction. [101].

Previous research studies emphasized CE’s association with multifaceted issues influencing multiple stakeholders’ performance. Actors, such as seminal thinkers, think tanks, advisory and legislative institutions, academics, and businesses, were found to interpret waste and resource management frameworks in their way [59]. These interpretations at times have glued and occasionally have unglued the theoretical ideas [102].

To measure circularity, authors debated and questioned the methods, validity, and efficiency of company-level metrics. They also argued on the effectiveness of those measurement tools for product manufacturing and transition in a system.

Authors have also analysed the potential use of circularity metrics as key performance indicators for product or regulatory label transition-related issues [103]. However, the composite indicator, Sustainable Circular Index (SCI) [104], Circular Economy Index (CEI), Triple Bottom Line (TBL), Global Reporting Initiative (GRI) [105], and Global Resource Indicator (GRI) [106], are in use to evaluate CE with qualitative and quantitative pieces of information. Besides, lifecycle thinking and a wide variety of life cycle assessment (LCA) approaches were noticed as determining the environmental impacts of a product, service, organization, policy, or procedure [102]. The literature on circularity measurement also threw light on the Material Circularity Indicator (MCI) and criticized the method because of its ambitious attempt [3]. Authors were found to mention (i) material flow analysis; (ii) life cycle assessment; and (iii) evaluation and monitoring indicators as the three significant categories of loop assessment methodology [22]. In the same section on the measurement of circularity, the authors also discussed the measurement units. Those were mass, energy, and time, depending on the fundamental aspect of any circularity metric. Conversely, the problematic issue here is the method of selecting a unit, which has been questioned time and again [103].

Literature further revealed that CE followed different patterns globally. In China, CE has emerged as a direct outcome of national political strategy. Therefore, the CE implementation strategy in China remained top-down and structured. In contrast, within Europe, Japan, and the USA, CE’s transition occurred organically as bottom-up environmental and waste management policies with assistance from civil societies and NGOs [55].

Based on a comprehensive review of CE, the narratives mentioned above on CE’s epistemology emerged. This section helped build a base for content analysis and a scenario for semantic analysis using the fundamentals of CE in the study. The study’s different statistical analysis results are shown below in the next section of the research study, i.e., results and discussion for a detailed examination and argument. These statistical analysis results may be considered as a confirmatory test to establish facts based on emerging trends on the CE associates and interactions within them. This section addresses issue of insufficient confirmatory researches in CE literature [19].

4. Statistical Analysis and Results

The screening process in the study selected 76 English journal articles for review, constituting 60.53% review study articles, 38.16% case studies, and 1.31% mixed studies (

Table 3. Table describing characteristics of 76 reviewed articles.

Sl	Title	Authors	WoS	SoP	Year	Journal	Type	Method	Contribution	DOI	Major Associates	Country	Category
1	A circular economy model of economic growth	George, Donald A. R.; Lin, Brian Chi-ang; Chen, Yunmin	41	54	2015	Environmental Modelling & Software	Conceptual, Fundamental and Descriptive	Qualitative	Identified CE model with two types of economic resource, i.e., polluting input and recyclable input.	dx.doi.org/10.1016/j.envsoft.2015.06.014	Recycle and Economy	China	Review
2	A conceptual framework for circular design	Moreno M., De los Rios C., Rowe Z., Charnley F.		98	2016	Sustainability (Switzerland)	Conceptual, Fundamental and Descriptive	Qualitative	Conceptual framework for circular economy design strategy incorporation.	doi:10.3390/su8090937	Design and Innovation	United Kingdom	Review
3	A Review and Typology of Circular Economy Business Model Patterns	Lüdeke-Freund F., Gold S., Bocken N.M.P.	41	53	2019	Journal of Industrial Ecology	Conceptual, Fundamental and Descriptive	Qualitative	Proposed six major CE Business Model patterns with potential to support closing of resource flows.	10.1111/jiec.12763	Business and Resource	Germany	Review
4	A review of the circular economy in China: Moving from rhetoric to implementation	Su, Biwei; Heshmati, Almas; Geng, Yong; Yu, Xiaoman	280	333	2013	Journal of Cleaner Production	Analytical, Empirical, and Applied	Quantitative and Qualitative	Current development of CE and policy recommendations.	dx.doi.org/10.1016/j.jclepro.2012.11.020	Implementation and Policy	China	Review
5	A review on circular economy: The expected transition to a balanced interplay of environmental and economic systems	Ghisellini P., Cialani C., Ulgiati S.	692	856	2016	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Demonstrated CE’s reliability as a solution to environmental issues emerging of current businesses.	dx.doi.org/10.1016/j.jclepro.2015.09.007	Environment and Business	China	Review
6	A systematic review on drivers, barriers, and practices towards circular economy: a supply chain perspective	Govindan K., Hasanagic M.	57	83	2018	International Journal of Production Research	Conceptual, Fundamental and Descriptive	Qualitative	Consolidated and described the factors influencing CE adoption in organizations.	doi.org/10.1080/00207543.2017.1402141	Driver, and Barrier	Denmark	Review
7	A taxonomy of circular economy indicators	Saidani M., Yannou B., Leroy Y., Cluzel F., Kendall A.		47	2019	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Illustrated multiple dimensions of C-indicators and comprehended their application in Industry.	10.1016/j.jclepro.2018.10.014	Measurement and Implementation	France	Review
8	Circular economy as an essentially contested concept	Korhonen J., Nuur C., Feldmann A., Birkie S.E.	90	117	2018	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Illustrated methodological models on conducting researches on CE.	doi.org/10.1016/j.jclepro.2017.12.111	Policy and Product	Swede	Review
9	Circular economy in China-The environmental dimension of the harmonious society	Naustdalslid J.	40	52	2014	International Journal of Sustainable Development & World Ecology	Conceptual, Fundamental and Descriptive	Qualitative	Comprehended Chinese version of CE, and its implementation.	10.1080/13504509.2014.914599	Implementation and Society	China	Review
10	An exploration of firms’ awareness and behavior of developing circular economy: An empirical research in China	Liu Y., Bai Y.	67	73	2014	Resources, Conservation and Recycling	Analytical, Empirical, and Applied	Quantitative	Identified contextual, and cultural factors creating gaps in awareness generation and actual behaviour	dx.doi.org/10.1016/j.resconrec.2014.04.002	Environment and Behaviour	China	Case Study
11	Business models and supply chains for the circular economy	Geissdoerfer M., Morioka S.N., de Carvalho M.M., Evans S.	70	92	2018	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Developed a framework to integrate circular business models and circular supply chain management for Sustainable Development.	doi.org/10.1016/j.jclepro.2018.04.159	Business and Supply Chain	India	Case Study
12	Circular Business Model Innovation: Inherent Uncertainties	Linder M., Williander M.	112	140	2017	Business Strategy and the Environment	Conceptual, Fundamental and Descriptive	Qualitative	Identified the characteristics and challenges of circular business models (CBMs).	10.1002/bse.1906	Remanufacture and Reuse	Sweden	Review
13	Business model innovation to create and capture resource value in future circular material chains	Roos G.		44	2014	Resources	Conceptual, Fundamental and Descriptive	Qualitative	Compiled the process of business model development for ensuring innovative circular value chain	10.3390/resources3010248	Business and Industry	Australia	Case Study
14	Circular economy practices among Chinese manufacturers varying in environmental-oriented supply chain cooperation and the performance implications	Zhu, Qinghua; Geng, Yong; Lai, Kee-hung	136	165	2010	Journal of Environmental Management	Analytical, Empirical, and Applied	Quantitative	Identified and exhibited causal relation between environmental-oriented supply chain cooperation practices and CE	10.1016/j.jenvman.2010.02.013	Environment and Supply Chain	China	Review
15	Circular Economy Rebound	Zink, Trevor; Geyer, Roland	91	117	2017	Journal of Industrial Ecology	Conceptual, Fundamental and Descriptive	Qualitative	Compiled the potential environmental rebound of the circular economy.	10.1111/jiec.12545	Reuse, Refurbish, and Recycle	USA	Review
16	Development pattern and enhancing system of automotive components remanufacturing industry in China	Zhang, Tongzhu; Chu, Jiangwei; Wang, Xueping; Liu, Xianghai; Cui, Pengfei	111	126	2011	Resources, Conservation and Recycling	Conceptual, Fundamental and Descriptive	Qualitative	Brought to light three barriers of remanufacturing sector.	10.1016/j.resconrec.2010.09.015	Remanufacture and Technology	China	Case Study
17	Circular economy-From review of theories and practices to development of implementation tools	Kalmykova Y., Sadagopan M., Rosado L.	120	148	2018	Resources, Conservation and Recycling	Conceptual, Fundamental and Descriptive	Qualitative	Generated two sets of data-driven tools for implementing CE.	doi.org/10.1016/j.resconrec.2017.10.034	Raw Material and Measurement	Sweden	Review
18	Circular Integration of processes, industries, and economies	Walmsley T.G., Ong B.H.Y., Klemeš J.J., Tan R.R., Varbanov P.S.	22	25	2019	Renewable and Sustainable Energy Reviews	Conceptual, Fundamental and Descriptive	Qualitative	Brought to light a unified framework of Circular Integration (CI) to stimulate large transdisciplinary research.	doi.org/10.1016/j.rser.2019.03.039	Business and Industry	Czech Republic	Case Study
19	Do circular economy business models capture intended environmental value propositions?	Manninen K., Koskela S., Antikainen R., Bocken N., Dahlbo H., Aminoff A.	63	77	2018	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Generated a framework for evaluating the environmental value propositions for CE-driven business models,	doi.org/10.1016/j.jclepro.2017.10.003	Business and Environment	Finland	Case Study
20	Product/Service-Systems for a Circular Economy: The Route to Decoupling Economic Growth from Resource Consumption?	Kjaer L.L., Pigosso D.C.A., Niero M., Bech N.M., McAloone T.C.		34	2019	Journal of Industrial Ecology	Conceptual, Fundamental and Descriptive	Qualitative	A two-step framework to support analyses of Product/Service-System and their potential to lead to absolute resource decoupling.	10.1111/jiec.12747	Product and Business	Denmark	Review
21	Conceptualizing the circular economy: An analysis of 114 definitions	Kirchherr, Julian; Reike, Denise; Hekkert, Marko	356	452	2017	Resources, Conservation and Recycling	Fundamental, Empirical, Analytical	Quantitative and Qualitative	Compiled much conceptual information around the Circular Economy to bring coherence.	dx.doi.org/10.1016/j.resconrec.2017.09.005	System and Business	Netherland	Review
22	Closed-loop production systems-A sustainable supply chain approach	Winkler H.		88	2011	CIRP Journal of Manufacturing Science and Technology	Conceptual, Fundamental and Descriptive	Qualitative	Brought to light the importance of integrating environmental goals into the production system, with sustainable supply chain networks (SSCN).	10.1016/j.cirpj.2011.05.001	Economy and Environment	Austria	Review
23	Closing the loop or squaring the circle? Locating generative spaces for the circular economy	Kersty Hobson		72	2016	Progress in Human Geography	Conceptual, Fundamental and Descriptive	Qualitative	Revealed scope and purpose of conducting critical analysis on socio-political and economic mechanisms with respect to Circular Economy.	10.1177/0309132514566342	Product and Society	United Kingdom	Review
24	Constructivism scenario evolutionary analysis of zero emission regional planning: A case of Qaidam Circular Economy Pilot Area in China	Liu D., Li H., Wang W., Dong Y.		27	2012	International Journal of Production Economics	Analytical, Empirical, Conceptual, and Applied	Quantitative and Qualitative	Revealed important policy implications on China’s regional development plan due to evolutionary constructivism.	10.1016/j.ijpe.2011.04.008	Sustainable and Industry	China	Case Study
25	Towards a national circular economy indicator system in China: An evaluation and critical analysis	Geng Y., Fu J., Sarkis J., Xue B.	235	277	2012	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Brought to light a national level sustainability indicator system for developing countries.	10.1016/j.jclepro.2011.07.005	Government and Policy	China	Case Study
26	Who is in charge? A review and a research agenda on the ‘human side’ of the circular economy	Chiappetta Jabbour C.J., Sarkis J., Lopes de Sousa Jabbour A.B., Scott Renwick D.W., Singh S.K., Grebinevych O., Kruglianskas I., Filho M.G.		36	2019	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Supplemented conceptual foundations on CE business models by integrating green human resource management theory and practices.	doi.org/10.1016/j.jclepro.2019.03.038	Business and Resource	France	Review
27	Process engineering in circular economy	Reh, Lothar	41	48	2013	Particuology	Analytical, Empirical, and Applied	Quantitative	Compiled progress and challenges of recycling industry.	dx.doi.org/10.1016/j.partic.2012.11.001	Energy and Recycle	China	Case Study
28	Product design and business model strategies for a circular economy	Bocken N.M.P., de Pauw I., Bakker C., van der Grinten B.		357	2016	Journal of Industrial and Production Engineering	Conceptual, Fundamental and Descriptive	Qualitative	Generated insights on the current product design and business model strategies suited embracing circular economy.	dx.doi.org/10.1080/21681015.2016.1172124	Product and Design	Netherlands	Review
29	Business model innovation for circular economy and sustainability: A review of approaches	Pieroni, Marina P. P.; McAloone, Tim C.; Pigosso, Daniela C. A.	38	52	2019	Journal of Cleaner Production	Analytical, Empirical, and Applied	Quantitative and Qualitative	Compiled and presented different approaches on circular or sustainable business model innovation process.	doi.org/10.1016/j.jclepro.2019.01.036	Innovation and Business	Denmark	Review
30	Diversifying and de-growing the circular economy: Radical social transformation in a resource-scarce world	Hobson K., Lynch N.		69	2016	Futures	Conceptual, Fundamental and Descriptive	Qualitative	Described the social and political implications of CE-driven transformations in a system.	dx.doi.org/10.1016/j.futures.2016.05.012	ReSOLVE and Technology	United Kingdom	Review
31	Methodological Aspects of Applying Life Cycle Assessment to Industrial Symbioses	Mattila T., Lehtoranta S., Sokka L., Melanen M., Nissinen A.	63	72	2012	Journal of Industrial Ecology	Conceptual, Fundamental and Descriptive	Qualitative	Comprehended the methodological issues encountered while applying life cycle assessment, besides historical development and current status of industrial symbiosis (IS)	10.1111/j.1530-9290.2011.00443.x	Life Cycle Assessment and Industry	Finland	Review
32	Effectiveness of the policy of circular economy in China: A DEA-based analysis for the period of 11th five-year-plan	Wu H.-Q., Shi Y., Xia Q., Zhu W.-D.	88	102	2014	Resources, Conservation and Recycling	Analytical, Empirical, and Applied	Quantitative	Described data envelopment analysis to measure efficiency of CE development in China.	dx.doi.org/10.1016/j.resconrec.2013.10.003	Policy and Implementation	China	Case Study
33	Green, circular, bio economy: A comparative analysis of sustainability avenues	D’Amato, D.; Droste, N.; Allen, B.; Kettunen, M.; Laehtinen, K.; Korhonen, J.; Leskinen, P.; Matthies, B. D.; Toppinen, A.	104	117	2017	Journal of Cleaner Production	Analytical, Empirical, and Applied	Quantitative and Qualitative	Elaborated the conceptual differences between Circular Economy and Bio-economy and Green Economy.	dx.doi.org/10.1016/j.jclepro.2017.09.053	Economy and Environment	Finland	Review
34	Lost in Transition? Drivers and Barriers in the Eco-innovation Road to the Circular Economy	de Jesus A., Mendonça S.	65	83	2018	Ecological Economics	Conceptual, Fundamental and Descriptive	Qualitative	Brought to light the insights of soft and hard factors in generating eco-innovation (EI) during transition to circular economy (CE)	dx.doi.org/10.1016/j.ecolecon.2017.08.001	Driver and Barrier	Portugal	Review
35	The Emergence of Circular Economy A New Framing Around Prolonging Resource Productivity	Blomsma, Fenna; Brennan, Geraldine	125	165	2017	Journal of Industrial Ecology	Conceptual, Fundamental and Descriptive	Qualitative	Described the potentially catalytic function the CE performs in waste and resource management	doi.org/10.1111/jiec.12603	Waste and Resource	United Kingdom	Review
36	The Relevance of Circular Economy Practices to the Sustainable Development Goals	Schroeder, Patrick; Anggraeni, Kartika; Weber, Uwe	36	47	2019	Journal of Industrial Ecology	Conceptual, Fundamental and Descriptive	Qualitative	Presented the relationship of CE practices and the SDGs, as well as highlighting CE practices that can help to achieve the SDG targets.	10.1111/jiec.12732	Sustainable and Business	United Kingdom	Review
37	Strategies on implementation of waste-to-energy (WTE) supply chain for circular economy system: a review	Pan, Shu-Yuan; Du, Michael Alex; Huang, I-Te; Liu, I-Hung; Chang, E-E; Chiang, Pen-Chi	140	171	2015	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Presented several cases in the waste-to-energy supply chain to assess the level of circularity.	dx.doi.org/10.1016/j.jclepro.2015.06.124	Waste and Energy	China	Case Study
38	The Circular Economy A new sustainability paradigm?	Geissdoerfer, Martin; Savaget, Paulo; Bocken, Nancy M. P.; Hultink, Erik Jan	544	654	2017	Journal of Cleaner Production	Analytical, Empirical, and Applied	Quantitative and Qualitative	Illustrated conceptual trends of CE using bibliometric analysis and semi-structured snowballing technique.	dx.doi.org/10.1016/j.jclepro.2016.12.048	Sustainable and Economy	United Kingdom	Review
39	Towards a new taxonomy of circular economy business models	Andrea Urbinati, Davide Chiaroni, Vittorio Chiesa	84	112	2017	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Presented the strengths and weakness of the classification framework to assess the method besides the agenda.	doi.org/10.1016/j.resconrec.2019.03.045	Life Cycle, and Recycle	Belgium	Review
40	Products that go round: Exploring product life extension through design	Bakker C., Wang F., Huisman J., Den Hollander M.	172	188	2014	Journal of Cleaner Production	Analytical, Empirical, and Applied	Quantitative	Brought to light the number of product life extension strategies besides showing the requirement for tailored approaches.	dx.doi.org/10.1016/j.jclepro.2014.01.028	Design and Product	Dutch	Case Study
41	Progress Toward a Circular Economy in China The Drivers (and Inhibitors) of Eco-industrial Initiative	Mathews, John A.; Tan, Hao	164	178	2011	Journal of Industrial Ecology	Conceptual, Fundamental and Descriptive	Qualitative	Demonstrated common themes across case studies on eco-industrial aspects.	10.1111/j.1530-9290.2011.00332.x	Driver and Industry	China	Case Study
42	Circular economy indicators: What do they measure?	Moraga G., Huysveld S., Mathieux F., Blengini G.A., Alaerts L., Van Acker K., de Meester S., Dewulf J.		29	2019	Resources, Conservation and Recycling	Conceptual, Fundamental and Descriptive	Qualitative	Generated a classification framework for CE indicators and used it to evaluate quantitative indicators to measure CE and its process.	doi.org/10.1016/j.resconrec.2019.03.045	Measurement and Implementation	Belgium	Review
43	Energy conservation and circular economy in China’s process industries	Li, Huiquan; Bao, Weijun; Xiu, Caihong; Zhang, Yi; Xu, Hongbin	87	104	2010	Energy	Conceptual, Fundamental and Descriptive	Qualitative	Described the energy conservation method of China’s process industry for the learning of other nations.	doi:10.1016/j.energy.2009.04.021	Waste and Energy	China	Case Study
44	The circular economy, design thinking and education for sustainability	Andrews D.		54	2015	Local Economy	Conceptual, Fundamental and Descriptive	Qualitative	Illustrated the necessity for inclusion of design thinking and practice in education curricula.	10.1177/0269094215578226	Design and Product	United Kingdom	Review
45	Operational principles of circular economy for sustainable development: Linking theory and practice	Suárez-Eiroa B., Fernández E., Méndez-Martínez G., Soto-Oñate D.		26	2019	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Identified seven operational principles to emphasize the role of design and education as transversal elements, besides introducing a new definition of CE.	doi.org/10.1016/j.jclepro.2018.12.271	Sustainable and System	Spain	Review
46	Product services for a resource-efficient and circular economy-a review	Tukker, Arnold	443	542	2015	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Elaborated the process of implementation of Product Service Systems (PSS), besides identification of factors enabling implementation seeking attention.	dx.doi.org/10.1016/j.jclepro.2013.11.049	Product and System	Netherlands	Review
47	Unlocking the circular economy through new business models based on large-scale data: An integrative framework and research agenda	Jabbour C.J.C., Jabbour A.B.L.D.S., Sarkis J., Filho M.G.		46	2019	Technological Forecasting & Social Change	Conceptual, Fundamental and Descriptive	Qualitative	Generated an integrative framework for illustrating the nexus between CE and large-scale data (LD).	dx.doi.org/10.1016/j.techfore.2017.09.010	ReSOLVE and Society	France	Review
48	Consumer product knowledge and intention to purchase remanufactured products	Wang Y., Hazen B.T.	73	88	2016	International Journal of Production Economics	Analytical, Empirical, and Applied	Quantitative	Comprehended remanufacturing and closed-loop supply chain managing policies besides marketing strategies.	dx.doi.org/10.1016/j.ijpe.2015.08.031	Remanufacture and Supply chain	China	Case Study
49	Creating integrated business and environmental value within the context of China’s circular economy and ecological modernization	Park, Jacob; Sarkis, Joseph; Wu, Zhaohui	122	144	2010	Journal of Cleaner Production	Conceptual, Fundamental, and Descriptive	Qualitative	Illustrated emerging integration of business value and environmental returns in the context of CE in China applying the theoretical lens.	10.1016/j.jclepro.2010.06.001	Environment and Economy	China	Case Study
50	Green chemistry and green engineering in China: Drivers, policies and barriers to innovation	Matus K.J.M., Xiao X., Zimmerman J.B.		58	2012	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Described the crucial barriers to and enablers of green chemistry and engineering innovations in China.	10.1016/j.jclepro.2012.03.033	Innovation and Policy	China	Case Study
51	How Circular is the Global Economy?: An Assessment of Material Flows, Waste Production, and Recycling in the European Union and the World in 2005	Haas, Willi; Krausmann, Fridolin; Wiedenhofer, Dominik; Heinz, Markus	198	237	2015	Journal of Industrial Ecology	Fundamental, Empirical, Analytical	Quantitative and Qualitative	Revealed the necessity for review, new definition, and measurement of circularity.	10.1111/jiec.12244	Production, and Recycle	United Kingdom	Case Study
52	How do scholars approach the circular economy? A systematic literature review	Merli R., Preziosi M., Acampora A.	90	112	2018	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Brought to light the best practices and solutions from several schools of thoughts to execute CE.	doi.org/10.1016/j.jclepro.2017.12.112	Innovation and Environment	Italy	Review
53	Implementation of circular economy business models by small and medium-sized enterprises (SMEs): Barriers and enablers	Rizos V., Behrens A., van der Gaast W., Hofman E., Ioannou A., Kafyeke T., Flamos A., Rinaldi R., Papadelis S., Hirschnitz-Garbers M., Topi C.	84	99	2016	Sustainability (Switzerland)	Conceptual, Fundamental and Descriptive	Qualitative	Presented the understanding around requirement of sufficient knowledge and technical knowhow to execute circular economy in small and medium-sized enterprises	10.3390/su8111212	Barrier and Risk	United Kingdom	Case Study
54	The Circular Economy: An Interdisciplinary Exploration of the Concept and Application in a Global Context	Murray A., Skene K., Haynes K.		357	2017	Journal of Business Ethics	Conceptual, Fundamental and Descriptive	Qualitative	Demonstrated CE’s relation with sustainable business and applications, besides policy implications.	10.1007/s10551-015-2693-2	Business and policy	United Kingdom	Review
55	The circular economy: New or Refurbished as CE 3.0?—Exploring Controversies in the Conceptualization of the Circular Economy through a Focus on History and Resource Value Retention Options	Reike D., Vermeulen W.J.V., Witjes S.	66	90	2018	Resources, Conservation and Recycling	Conceptual, Fundamental and Descriptive	Quantitative and Qualitative	Illustrated numerous R-imperatives and their attributes for conceptualizing the key CE principle.	doi.org/10.1016/j.resconrec.2017.08.027	R-imperatives	Netherlands	Review
56	Towards a consensus on the circular economy	Prieto-Sandoval V., Jaca C., Ormazabal M.	87	107	2018	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Revealed the three eco-innovation determinants after their application in CE was regulated and policy was framed for the supply side and demand side.	doi.org/10.1016/j.jclepro.2017.12.224	Innovation and Environment	Spain	Review
57	Reutilisation-extended material flows and circular economy in China	Li N., Zhang T., Liang S.		21	2013	Waste Management	Analytical, Empirical, Conceptual, and Applied	Quantitative and Qualitative	Introduced readers to reutilisation-related laws and regulations with respect to CE.	10.1016/j.wasman.2013.01.029	Measurement and Raw Material	China	Review
58	Introduction of the circular economy within developing regions: A comparative analysis of advantages and opportunities for waste valorization	Ferronato N., Rada E.C., Gorritty Portillo M.A., Cioca L.I., Ragazzi M., Torretta V.	24	27	2019	Journal of Environmental Management	Conceptual, Fundamental and Descriptive	Qualitative	Presented the main opportunities for improving the current state of solid waste management in upcoming big cities.	doi.org/10.1016/j.jenvman.2018.09.095	Recycle and Raw Material	Romania & Bolivia	Case Study
59	Measuring circular economy strategies through index methods: A critical analysis	Valerio EliaMaria, GraziaGnoni, FabianaTornese	84	101	2017	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Proposed and demonstrated a four-level framework to support the assessment during monitoring of multiple stages of CE.	dx.doi.org/10.1016/j.jclepro.2016.10.196	Measurement and Implementation	Italy	Review
60	Food packaging in the circular economy: Overview of chemical safety aspects for commonly used materials	Birgit Geueke, Ksenia Groh, Jane Muncke	35	41	2018	Journal of Cleaner Production	Conceptual, Fundamental and Descriptive	Qualitative	Brought to light the important properties of food packaging materials affecting their recyclability and safety aspects.	doi.org/10.1016/j.jclepro.2018.05.005	Recycle, Reduce and Reuse	Switzerland	Case Study
61	Environmental Supply Chain Cooperation and Its Effect on the Circular Economy Practice-Performance Relationship Among Chinese Manufacturers	Zhu, Qinghua; Geng, Yong; Lai, Kee-hung	61	66	2011	Journal of Industrial Ecology	Analytical, Empirical, and Applied	Quantitative	Brought to notice the facts on leading manufacturers with higher levels of implementation of Environmental Supply Chain Cooperation practices.	doi.org/10.1111/j.1530-9290.2011.00329.x	Environment and Supply chain	China	Case Study
62	The Impact of Scale, Recycling Boundary, and Type of Waste on Symbiosis and Recycling	Chen, Xudong; Fujita, Tsuyoshi; Ohnishi, Satoshi; Fujii, Minoru; Geng, Yong	42	46	2012	Journal of Industrial Ecology	Analytical, Empirical, Conceptual, and Applied	Quantitative and Qualitative	Revealed the relationships between recycling boundary, project scale, and performance of each eco-town besides the recycling facility in eco-towns with regard to the types of waste treated.	10.1111/j.1530-9290.2011.00422.x	Waste and Recycle	Japan	Case Study
63	The Circular Economy: Swings and Roundabouts?	Millar N., McLaughlin E., Börger T.		28	2019	Ecological Economics	Conceptual, Fundamental and Descriptive	Qualitative	Presented literature once and Sustainable Development to demonstrate their potential for economic growth.	doi.org/10.1016/j.ecolecon.2018.12.012	Development and Economy	Ireland	Review
64	Designing the business models for circular economy-towards the conceptual framework	Lewandowski M.	211	227	2016	Sustainability (Switzerland)	Conceptual, Fundamental and Descriptive	Qualitative	Illuminated the researchers of CE with classifications, characteristic, and integration processes for circular business models.	doi:10.3390/su8010043	Business and Principle	Poland	Review
65	Developing country experience with eco-industrial parks: a case study of the Tianjin Economic-Technological Development Area in China	Shi, Han; Chertow, Marian; Song, Yuyan	180	196	2010	Journal of Cleaner Production	Analytical, Empirical, and Applied	Quantitative and Qualitative	Elucidated the process Tianjin Economic-Technological Development Area adopted to form a complex industrial symbiosis network in a mixed industrial park besides examining the features and patterns of existing and discontinued IS exchanges.	doi.org/10.1016/j.jclepro.2009.10.002	Industry and Economy	China	Case Study
66	Environmental sciences, sustainable development and circular economy: Alternative concepts for trans-disciplinary research	Sauvé S., Bernard S., Sloan P.	152	182	2016	Environmental Development	Conceptual, Fundamental and Descriptive	Qualitative	Elucidated three alternative concepts on transdisciplinary research, and showcased the opportunities besides associated challenges.	dx.doi.org/10.1016/j.envdev.2015.09.002	Environment and Sustainable	Canada	Review
67	The history and current applications of the circular economy concept	Winans, K.; Kendall, A.; Deng, H.	132	154	2017	Renewable and Sustainable Energy Reviews	Conceptual, Fundamental and Descriptive	Qualitative	Illustrated assessment of ongoing CE initiatives and highlighted barriers to sustained circularity due to material flows that exceeded or did not meet demand, and transport and infrastructure.	dx.doi.org/10.1016/j.rser.2016.09.123	Policy and Infrastructure	Denmark	Review
68	New business models for a radical change in resource efficiency	Schulte U.G.		43	2013	Environmental Innovation and Societal Transitions	Conceptual, Fundamental and Descriptive	Qualitative	Highlighted new businesses which cropped up with the notion of serving as an intermediary, because they own the material content of products and sell back the materials to the producer at the end of the life cycle.	dx.doi.org/10.1016/j.eist.2013.09.006	Business and Resource	Netherland	Case Study
69	Challenges in supply chain redesign for the Circular Economy: a literature review and a multiple case study	Bressanelli G., Perona M., Saccani N.		25	2019	International Journal of Production Research	Conceptual, Emperical, Fundamental and Descriptive	Qualitative	Identified and classified challenges about CE supply chain redesign based on analysis of previous literature.	doi.org/10.1080/00207543.2018.1542176	Supply chain and Design	Italy	Review & Case Study
70	Survey of officials’ awareness on circular economy development in China: Based on municipal and county level	Xue, Bing; Chen, Xing-peng; Geng, Yong; Guo, Xiao-jia; Lu, Cheng-peng; Zhang, Zi-long; Lu, Chen-yu	62	81	2010	Resources, Conservation and Recycling	Analytical, Empirical, and Applied	Quantitative	Revealed facts on awareness of the concept of CE in government and the public.	doi:10.1016/j.resconrec.2010.05.010	Policy and Government	China	Case Study
71	The circular economy umbrella: Trends and gaps on integrating pathways	Homrich A.S., Galvão G., Abadia L.G., Carvalho M.M.	67	84	2018	Journal of Cleaner Production	Analytical, Empirical, and Applied	Quantitative and Qualitative	Presented definition of CE, besides highlighting the main trends, research gaps.	doi.org/10.1016/j.jclepro.2017.11.064	Economy and Business	Brazil	Review
72	Towards a more Circular Economy: Proposing a framework linking sustainable public procurement and sustainable business models	Witjes S., Lozano R.	160	136	2016	Resources, Conservation and Recycling	Conceptual, Fundamental and Descriptive	Qualitative	Generated a framework with socio-cultural specifications besides physical and social proximity between the stakeholders to include technical and non-technical aspects of product/service combinations to improve resource usage efficiency through recovery.	doi.org/10.1016/j.resconrec.2016.04.015	Collaborate and Business	Netherlands	Review
73	Sustainable supply chain management and the transition towards a circular economy: Evidence and some applications	Genovese, Andrea; Acquaye, Adolf A.; Figueroa, Alejandro; Koh, S. C. Lenny	198	229	2017	Omega (United Kingdom)	Analytical, Empirical, and Applied	Quantitative	Elucidated the environmental implications related to implementation of circular production systems, comparing performances of traditional and circular production systems across a range of indicators.	dx.doi.org/10.1016/j.omega.2015.05.015	Environment and Supply Chain	United Kingdom	Case Study
74	Circular Economy: The Concept and its Limitations	Korhonen J., Honkasalo A., Seppälä J.	224	281	2018	Ecological Economics	Conceptual, Fundamental and Descriptive	Qualitative	Demonstrated the scientific basis for the CE concept and assessed the CE concept critically to describe high value and high quality material cycles and show the possibilities of the sharing economy besides sustainable production for a more sustainable production and consumption.	10.1016/j.ecolecon.2017.06.041	Environment and Sustainable	Finland	Review
75	Policy for material efficiency-Sustainable taxation as a departure from the throwaway society	Stahel W.R.		57	2013	Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences	Conceptual, Fundamental and Descriptive	Qualitative	Highlighted the finding that taxing materials and energies may promote low-carbon and low-resource solutions and may stimulate a move towards a ‘circular’ regional economy.	dx.doi.org/10.1098/rsta.2011.0567	Society and Policy	United Kingdom	Case Study
76	International comparative study of 3R and waste management policy developments	Shin-ichi Sakai, Hideto Yoshida, Yasuhiro Hirai, Misuzu Asari, Hidetaka Takigami, Shin Takahashi, Keijirou Tomoda, Maria Victoria Peeler, Jakub Wejchert, Thomas Schmid-Unterseh, Aldo Ravazzi Douvan, Roy Hathaway, Lars D. Hylander, Christian Fischer, Gil Jong Oh, Li Jinhui & Ngo Kim Chi	70	83	2011	Journal of Material Cycles and Waste Management volume	Analytical, Empirical, Conceptual, and Applied	Quantitative and Qualitative	Described the current situation, historical background, and effectiveness of 3R policies within one specific region.	10.1007/s10163-011-0009-x	R-imperatives and Countries	USA, Korea, Japan, China, and Vietnam	Case Study

). The study also found that out of 76 articles, 46% have either come up with a new definition of CE or analysed CE definitions. The correlation between authors revealed 14 instances among the 76 reviewed papers. Further, the author-wise count of screened journal papers validated the credibility of articles included in the study. While analysing screened articles, we observed that the top ten primary focused CE associates are “Business”, followed by “Economic, Environment, Sustainability, Supply Chain, Design, Innovation, Measurement, Policy, and Implementation”. Each paper comprised primary associates followed by secondary and tertiary associates. The role of these associates is pivotal in implementing CE on account of their frequency and appearance in literature.

4.1. Text Analysis, Bibliometric Analysis, Relation Mapping from Syntactic Analysis of Keywords and Associate Mapping

While conducting the analytical exercise, we identified the most prominent CE associates using a statistical tool, TROPES V8.4, which is a text analysis software assisting in text mining, qualitative analysis, semantic categorization, and keyword extraction. A total of 215 words emerged from the tool application, describing CE’s association with multiple subjects. To pinpoint CE’s associates, a bibliometric analysis was conducted using the VoSviewer statistical tool. During this exercise, we analysed the articles’ titles, keywords, and abstracts. The results showed 110 associations or bonds (Figure 3). Keyword co-occurrence network visualization represents nodes and links wherein node size, link signals among nodes, and each colour determine distinct CE associates with their associations while explaining network effect with their manifestation.

Next was extraction of the most significant associations from the contents of screened articles, and 82 prominent bonds were identified based on the frequency of appearances using TROPES. A frequency map emerged out of that for associates of CE for analysing lexical items. This exercise further strengthened the selection of associates from several keywords. The top three promising emerging associations of CE are “Strategy, Implementation, and Policy”. Similarly, the least preferred CE interactions were amongst “Environment” and “Economics”, demonstrated in the relation mapping (Figure 4). Above illustrated steps addressed, RQ1. Further, the section also illustrated the ontology of keywords, and later extrapolated associates.

The ontology of each associate may be observed from the Bibliometric analysis result of Figure 3, relation map plotting of keywords using the VoSviewer application in Figure 4, and finally, the

Table A1. Identification of 49 keywords or Associates of CE.

	List of Keywords	The Word, Other Allied and Associated Words
Sustainability Pillar	Sustainable	Sustainable, Sustainability, Sustainable Development Goal, SDG
	Society	Society, Social, Societal, Culture, Access, Community, Corporate Social Responsibility (CSR), Tradition, Job, Employment, Recruitment, Wellbeing, Equality, People
	Economy	Profit, Growth, Development, Consumption, Production, and Gross Domestic Product (GDP), National Income
	Environment	Environment, Environmental, Climate, Weather, Planet, Carbon, Footprint, Ecology, Eco, Ecosystem, Global Warming, Emission, Organic, Biodegradable, Biology, Pollution, Natural, Nature, Conserve, Green House Gas (GHG), Preserve, Anaerobic
	List of Keywords	Allied and Similar Words
Other Similar Keywords (Part of Business Model Canvas, Other R-imperative, Influencers, and Regulation and Standardization)	Barrier	Barrier, Challenge, Difficult, Hinder, Negative
	Behaviour	Behaviour, Habit, Customer Behaviour, Leader, Nudge, Steward, Decision
	Business	Business, Business Management, Circular Business Model, Lease, Rent, Share, Business Model Canvas, Start-up, Value Chain, Value Proposition, Enterprise, Company, Corporate, Fund, Producer, Consumer, Cost, Investment, Market, Gain, Loss, Solution, Competition, Resale, Similar Words
	Collaborate	Collaborate, Partnership, Joint
	Countries	Country, America, Brazil, China, Japan, Europe, Korea, Switzerland, Germany, India
	Design	Design, Cradle, Process Design, Product Design, Cradle to Cradle
	Driver	Driver, Enabler, Positive, Scope, Hope, Opportunity, Positive
	Energy	Energy, Renewable, Biomass, Solar, Hydro
	Government	Government, Govern, Governance, Governmental
	Implementation	Implementation, Meso, Micro, Macro, Local, Global
	Industry	Industrial, Symbiosis, Agriculture, Chemical, Construction, Education, Electrical, Electronics, Fashion, Food, Water, Glass, Rubber, Plastic, Package, Wood, Transport, Tourism, Operation, Health, Similar Words
	Infrastructure	Infrastructure, Infrastructural, Private and Public Infrastructure
	Innovation	Innovation, Disruptive Innovation, Frugal Innovation, Job to Be Done Theory, Nudge Theory, Radical
	Institute	Institute, Bank, Educational Institute, Institution, Organization
	Life Cycle	Lifecycle
	Measurement	Measure, Assess, Indicator, Life Cycle Assessment (LCA), Material Flow Analysis (MFA), Efficiency, Impact, Perform, Rate, Ratio, Allied Words
	Policy	Policy, Act, Law, Legal, Regulation
	Principle	Principle, Fundamental
	Product	Product, Durable, Longevity, Goods, Product Service System, Maintenance, Price, Other Allied Words
	Raw Material	Raw Material
	Refill	Refill, Refillable
	Replace	Replace, Replacing, and Replacement
	Resource	Resource, Resources
	Return	Return, Returning
	Risk	Risk, Uncertain, Uncertainty, Shock, and Insurance
	Supply Chain	Supply Chain, SC, Reverse Logistic
	System	System, Systematic
	Technology	Technology, Tech, Artificial Intelligence (AI), Internet of Things (IoT), Automation, Big Data
	Waste	Waste, Garbage, Waste Management, Collection, Disposal, E-Waste, Segregation, Landfill
	List of Keywords	The Word, Other Allied and Similar Words
10 R Framework (R-imperatives)	Recycle	Recycle, Recycled, Recyclability, Recycling
	Refuse	Refuse, Refusal, Deny
	Rethink	Rethink, Rethinking
	Reduce	Reduce, Reduction, Reduced
	Reuse	Reuse, Reused
	Repair	Repair, Repaired, Repairing
	Refurbish	Refurbish, Refurbished, Refurbishment
	Remanufacture	Remanufacture, Remanufacturing
	Repurpose	Repurpose, Repurposing
	Recover	Recover, Recovery
	List of Keywords	The Word, Other Allied and Similar Words
ReSOLVE Framework	Regenerate	Regenerate, Regeneration, Regenerative
	Share	Share, Sharing
	Optimize	Optimize, Optimization, Optimal
	Loop	Loop, Close, Slow, Narrow, Dematerialize, Intensify
	Virtualize	Virtualize, Internet, Online, Virtual
	Exchange	Exchange, Exchanged

. This section supports RQ2 of the study.

Similar words or intending phrases were clubbed based on commonalities with context for the last three exercises, helping to reduce the essential associates of CE to 49. We identified Lexical items and counted them in the process. These identified keywords describe CE’s association with multiple sectors and the current state of the art. While extrapolating and clubbing the keywords, it was observed that the representation of the Sustainability pillar, R-strategies, and ReSOLVE framework governs from the literature pieces, as 19 CE associates appeared from these three frameworks, highlighting their implications. Besides, three R-imperatives, though not considered one of the 10 R-framework strategies, emerged during the analysis and discussion. The narrative literature review on systematically selected research papers followed by applying statistical tools to analyse the selected research content made this study unique. The indexing process is demonstrated for finally emerged keywords extracted as CE associates (Table A1).

The following groups of CE associates appeared from the above analysis: R-strategies (10R, Replace, Return, Refill); Business actions (ReSOLVE framework); Sustainability pillars (Sustainable, Economy, Environment, Society); Regulation and Standardization (Government, Policy, System, Implementation, Measurement, Institute, Countries, Infrastructure, Collaborate); Business model canvas (Business, Supply chain, Resource, Innovation, Behaviour, Raw material, Design, Technology, Principles, Industry, Life cycle assessment, Product, Energy, Waste, Risk); and Influencers (Barrier, Driver).

This is the unique contribution which led to the emergence of 49 critical associates from the CE literature. It represents the identification of associates from diversified perspectives and inclusivity with a strength of linkages and a direction towards understanding the structures of CE implementation from both a practice and theory orientation (Figure 4).

4.2. Semantic Analysis of 76 Articles and 122 Definitions

Screened CE associates were validated using code and statistical tools.

▪

Occurrence and frequency mapping of 76 articles

In this section, we conducted an occurrence mapping exercise, and 49 keywords cum associates were mapped for two different time intervals of the studied period, i.e., 2010 to 2019. Two different time intervals helped analyse the subject from the perspective pre (2010–2015) and post (2016–2019) the appearance of the SDG concept and its targets. The result of this exercise generated an exciting result. The result presented 25 associates getting more attention in the second phase compared to the first phase time frame of 2010–2015 due to the inception of the idea of SDGs. The top ten impacted CE associates were considered for discussion to eliminate overlapping scopes between negligible transition and noticeable transition due to the SDG’s inception in 2016. The top ten CE associates during 2016–19 vis-à-vis 2010–15 are: “Enabler, Loop, Principle, Society, Innovation, Collaboration, System, Regeneration, Design, Supply Chain” (Figure 5). Thus, Section 4.1 followed by 4.2, Table A1, and Figure 5 collectively addresses RQ2 in all respects.

Transiting in CE associates focus is clear in 2016–19 over 2010–15, where building blocks of the business model canvas receive more emphasis at firm level decisions to translate into consumer behaviour profitably with niche value creation. However, this requires shared modalities with effective strategic planning actions.

Besides, based on the understanding and built scenario of CE’s current state from the previous literature, a semantic analysis was conducted. A frequency map emerged for associates of CE on considering syntactic structures and textual context to analyse abstracts and conclusions applying TROPES V8.4 [38] (Figure 6). However, on comparing both occurrence and frequency semantic analysis, similar associates have been extracted, though with varying preferential order. This validates the prior analysis with high reliability.

Further, to explore CE’s theoretical perceptions, CE’s multifaceted definitions, which emerged in 76 articles from academicians of CE, were analysed. During the exercise, we extracted 122 definitions from 76 articles. Multiple authors have defined CE with multiple perspectives at different periods. We conducted an Occurrence Mapping and Semantic Analysis for identified definitions based on a built scenario from the reflection of narratives, understanding of literature, and identified associates of this study mentioned in the previous literature review section.

▪

Occurrence and frequency mapping of 122 definitions

On analysing the occurrence of a keyword from the considered literature, it was observed that the most prioritized CE associate identified from the contents of 122 definitions after performing occurrence mapping was: “Product, Measurement, Environment, Economic, Resource, Waste, Industry, Recycle, Reuse”, and so forth, as illustrated in Figure 7. “Repurpose, Virtualize, Collaborate, Refuse, Refill” are the least occurred CE associates in the contents of the 122 definitions dataset.

On applying semantic analysis to 122 definitions, it was observed that “Economy, Resource, Environment, Industry, Product” are eminent CE associates while “Repurpose, Virtualize, Collaboration” are discreet (Figure 8). Comparing graphs in Figure 7 and Figure 8, i.e., graphs mapping the occurrence and frequency of 49 associates from 122 definitions, 23 positioned associates matched each other. The similar associates in two graphs are positioned at the lower end, signifying low preference over top associates. It refers to how this exercise concludes a consensus among academicians towards the mentioned associates receiving less attention. Hence, CE literature for these associates is still underdeveloped while the focus has been heavily on other broader aspects connected to policy level, sustainability pillars, few R-strategies, etc.

4.3. Weighted Average Priority Ranking (WAPR) on ARTICLES and Definitions

Prior analyses have revealed the 49 most critical CE associates and their significance based on network connectedness, relevance, occurrence, and frequency mapping; however, the preferential order of these associates is not clearly depicted. It is imperative to understand their ranking, which will characterize their existing strength of bonding. Therefore, WAPR is adopted as this process helps to incorporate opinions or results of multiple techniques or experts based on subjective weights [107]. Most importantly, the analysis provides an order of preference and indicates relative magnitude [48]. While calculating WAPR, weightage was equally distributed for associates, i.e., 0.25 for all 10R considered strategies under different circumstances. WAPR for associates based on analysis of content and definitions combined and shown in Figure 9.

Findings depicts that the ranking of 49 associates ranges from a minimum of zero to a maximum of 0.89. These rankings may be interpreted by categorizing them into three broad ranges of high (value from 0.89 to 0.40); medium (value from 0.39 to 0.20); and low (value from 0.19 to zero). This suggests that highly ranked associates represent core principles of CE: i.e., retention of resources in the system; elimination of wastes; resource recovery via recycling; industry focus on circular products in consideration with economic/business and environmental impact; whereas the medium ranking associates show a diverse approach in the context of macrolevel associates like policy, country, societal perception, influencers having a positive or negative impact, technology advancement, etc. These primarily operate to create a proactive collaborative CE ecosystem. Lastly, the low rankers clearly reinforce earlier findings also regarding the least focus on the business actions with newly integrated R-strategies like recover, regenerate, remanufacture, rethink, etc. Less academic focus suggests that empirical evidences of practising such strategies and business actions is lacking for CE implementation in practice.

4.4. Association Rule Mining and K-Means Clustering

The WEKA tool was applied to highlight the top associates in terms of their strong association with CE for association rule mining deploying the Apriori algorithm. To analyse CE associates’ pattern of association within a CE definition database, Apriori is the most compatible algorithm in place [108]. On mining the definition dataset, the ten best rules were generated as the output with the minimum metric <confidence> value at 0.99. On the application of Association Rule Mining on a database of CE definitions, 48 attributes interacted. We set minimum support of 0.40 (59 instances), and 12 cycles were performed algorithmically (Figure 10).

K-means Cluster Analysis was applied to segregate the most significant, moderately significant, and insignificant associates and CE associations. Insignificant associates are those that appeared extremely less in articles. The primary reason for considering the K-means Cluster Analysis method is that the technique is non-hierarchical. It uses simple unsupervised learning algorithms to offer a solution to the problem of Clustering [109]. Besides, the K-means clustering analysis process is also an iterative partitioning method that divides observations into a predetermined number of clusters [110]. The value of K is determined as eight using the Elbow method to execute the K-means Clustering algorithm considering centroid value to define cluster centres (Figure 11) [111].

On conducting Cluster Analysis on SPSS using the K-means clustering algorithm at K-value 8, we obtained cluster numbers six, two, one, and five with the most definitions. In contrast, clusters number three and eight included the lowest number of CE definitions followed by cluster seven and four.

Table 4. Clustering 122 definitions.

Cluster	1	2	3	4	5	6	7	8
Definitions	8, 9, 11, 12, 15, 16, 18, 22, 27, 43, 46, 51, 52, 66, 75, 77, 86, 108, 114	2, 4, 14, 17, 23, 24, 25, 26, 28, 31, 33, 37, 42, 45, 70, 71, 72, 74, 85, 98, 103, 111, 115, 116, 121	5, 68, 105	6, 13, 30, 35, 36, 47, 62, 63, 79, 81, 99, 113	3, 7, 10, 41, 48, 49, 53, 54, 59, 60, 76, 84, 88, 95, 97, 106, 107, 110	1, 19, 20, 21, 29, 32, 39, 40, 50, 56, 57, 58, 61, 64, 65, 67, 78, 80, 82, 89, 90, 91, 92, 93, 94, 96, 101, 109, 117, 118, 119, 120, 122	34, 38, 44, 55, 73, 83, 87, 100, 102, 112	69, 104
Number	19	25	3	12	18	33	10	2

shows cluster-wise definition details.

Clusters six and second have a differential focus whereby former aggregates definitions highlight positive environmental impact by practicing strategies promoting recycling and reuse of existing products to initiate circularity; while the latter emphasizes waste management, energy conservation, resource retention business applications supported by development process in some specific nation contexts. Cluster one and five demonstrate definitions concerning both environment and economy while implementing the strategies and approaches of circular model from linearity. Simultaneously, similar aspects are produced from cluster four; however, no R-strategies are observed, so it primarily encompasses aspects related to energy harnessing with environment considerations, resource acquisition, and retention in a closed or open loop system. Conversely, clusters three, seven, and eight tend to be widespread, ranging in covering themes which are distant but intertwined like a nexus of R-imperatives with business modelling aspects to realize economic and environmental impact. On generalization, environment is the broad theme across the clusters with a focus on a circular product/process/model through strategic execution for resource conservation.

Further, definitions were analysed through cluster analysis using SPSS to extract CE associates’ significance value based on the ANOVA and distributing them into three groups, viz., highly significant, moderately significant, and insignificant, derived from the p-value (

Table 5. Segregation of CE associates based on ANOVA table score.

Highly Significant (Sig. < 0.05)	Moderately Significant (0.05 < Sig. ≤ 0.10)	Insignificant (Sig. > 0.10 or No Value)
Waste, Policy, Industry, Energy, Risk, Raw Material, Product, Design, Technology, Business, Driver, Barrier, Environmental, Social, Measurement, Sustainable, Country, Infrastructure, Rethink, Replace, Reuse, Recycle, Reduce, Return, Regenerate, Resource, Optimize, Economy, System, Principle, Loop	Institute	Behaviour, Implementation, Innovation, Life Cycle, Refuse, Refurbish, Refill, Recover, Repair, Remanufacture, Share, Exchange, Government, Collaborate, Supply Chain, Repurpose, Virtualize

). Analysis conducted in Section 4.3 and Section 4.4 addressed RQ3. This shows the focus of emerging associates towards regulation and standardization; sustainability; influencers; and certain aspects of business model canvasing, with a negligible effect from business actions (ReSOLVE) and majority niche R-strategic resource planning and execution. Hence, reinforcement of core CE principles in practice gained interest by integration of various associates from a different context operating in an environment at macro (regulatory/policy, national/regional, institutional, industry), meso (intrinsic/extrinsic business actions/strategies), and micro (entire value chain and production processes) levels interactively (Figure 12).

4.5. Development of an Integrated CE System

CE research is characterized by interdisciplinary areas and multifaceted themes, creating opportunities for cross-sector linkages, while some associates are more active and others passive. The analysis shows that a wide range of CE associates operate within the CE eco-system; however, it is fragmented in nature. Interestingly, the majority of them originate from R-strategies, ReSOLVE framework, and Sustainability pillars, highlighting their leading role. So far, CE literature’s main focus over the initial years was on conceptualizing CE while other new trajectories later are emerging related to social embeddedness, value chain underpinning, and business modelling. The analysis varies from reporting the associates at a macro and meso level, specifically investigating specific industries and policy guidelines which are now proliferating at a micro level for every production unit along with innovative processes including product disposal efficiently.

Previous analysis aided in establishing relations among 49 associates resulting in a comprehensive framework of CE associates (Figure 12). The proposed framework coherently depicts that CE is diffused in a system with extracted associates operating at three diverse levels applications i.e., micro, meso, and macro. The micro-level implies CE’s application at a company or consumer-level; the meso-level suggests CE at an eco-industrial park. Lastly, the macro-level means applying CE in cities, provinces, and regional levels [55,112].

The application of design principles stimulates existing widespread R strategies while some contemporary strategies appear inconsequential. These strategies further ensure the execution of business actions through innovative applications. Perpetual integration of CE with associates occurs by appropriate regulatory policies governing the CE implementation through enablers, barriers, risk mitigation actions, collaborations, new infrastructures, technologies, and institutions. Further associates showed in the framework also try to influence production and consumption behaviour through a transition in the supply chain, the energy required for production, and bring in a change in the life cycle of produce. All steps are intended to either diffuse or ensure absorption of CE in the system with proper measurement, and finally, achieve sustainability through the attainment of three pillars, further augmenting sustainable development in an economy. Section 4.5 and Figure 12 address the RQ 4.

5. Discussion

Based on the consolidated findings from varied analysis, it is remarkable that 82 bonds leading to 49 associates were uncovered as evident from the growing CE literature. Although CE development had been analysed through several theoretical approaches and domains, a holistic, common view is lacking to interpret the network effect and connectedness with relevant associates for its implementation from both theoretical and practical insights. The study sheds light on the current state of the art of CE, in terms of the associates linked with CE, and adds itself to the valuable emerging literature on the subject. These associates are responsible for stimulating CE directionally. The study explores, evaluates, and defines the concept of CE ‘associates’ with an attempt to merge the present knowledge. The focus systematically transits from a generic to a specific conception by outlining influencers (barriers/drivers), product innovation and design, business models around circularity, further extending to advanced business actions supporting current digital technologies, responsible production as well as consumption, societal issues, though sporadically. Another pattern appearing is the strong connect between CE and sustainability, particularly for two of its pillars, i.e., economy and environment. It implies that CE is potentially responding to climate change concerns with absorption for economic transactions; however, due to deficient projections, the societal stimulus is meagre in addressing sustainability issues. A cause-and-effect relation is also noted from previous literature that pointed towards the attainment of SDGs with CE associates. Content analysis of one-decade literature perceives that the significant associates are contributing to attaining five SDGs directly, viz., Goal 6, 7, 8, 12, and 15 [8]. However, the empirical evidence to investigate CE from a sustainable development prototype is still lacking to establish CE associates as multi-structural and multi-layered to achieve CE goals.

In addition, cluster analysis reveals the statistically highly/moderately significant and insignificant associates, signifying not only their mere association but also the strength of the network effect on CE. Current analysis revealed Business, Economics, Environment, Measurement, Product, Industry, Resource, System, Waste, and Recycle are the top ten significant associates of the CE ecosystem. This study may be further elaborated to define the magnitude and direction (positive, negative, neutral) of these bonds on the associates with CE and mutually. Hence, it may provide the understanding of whether nodes are affecting each other as per expectation or any deviation is happening; moreover, of what are the cause–effect relations among the associates to influence CE. Hence, calibration of the system can be achieved by identifying best CE practices, key performing associates (KPAs), benchmarking, testing, and training the system with different scenario generation.

Further, the complete architecture of the existing scenario of CE is another main contribution of this study. Proliferation of CE core principles in conjugation with its associates seem to be trickling from macro to meso and micro levels. This may open a new area of research trends to further inspect such transitions assisted by identified CE associates. Such studies may help to delineate their boundaries and practical handbook for CE implementation across sectors and designing national policy/regulations for CE under a wide institutional context. Other avenues may include providing strategic planning to incumbents and new entrants for balancing trade-offs from CE compliances with profitability in the initial stages, thereby supporting green investments and financing in the long run to sustain profitability. The CE system architecture illustrated the interaction of all 49 associates of CE and their implications in one frame. The architecture depicts how to achieve Sustainability using CE principles, applying R-imperatives, and the ReSOLVE framework in a consensus of government through favourable policies promoting waste elimination, innovation, technologies, and stakeholder collaborations (Figure 12). Hence, associates like Product, System, Supply chain, Energy, Raw material, Resources, Waste at micro-level require in-depth analysis to understand the significance of serving customers (with high utility) and their role for generating profitability. The acceptance with responsible behaviour of customers’ needs to be implanted to develop a virtuous loop. It is imperative to successfully establish CE initiatives in the firms not only from a dynamic business models view but also from innate environment, governance, and ownership organization.

The three associates—Raw Material, Resource, and Waste—explores resource efficiency, raw material productivity and waste management in an organization. A plethora of research and development (R&D) and innovations are directed for conservative resource mining, biodegradable raw material, new technologies, and waste management to reduce carbon emissions and zero wastage. To enhance end-to-end value creation, a green supply chain coupled with green energy is required by logically identifying and planning actors’ and stakeholder’s engagement. At the intra-organizational level (beyond sectors/industry/regional/national level), new research and case studies may bring forward the role of innovation and underpinning policies in enabling development of the CE system architecture. Quantification of performance metrics may aid to validate the framework; hence, new insights are to be measured by new indices/tools at a micro level.

At the meso/micro level, the findings reveal more interesting associates with an emphasis upon the ReSOLVE framework and R-strategies. However, research has exhibited a consensus for both these categories of associates, as the former is almost a very novel associate, while the latter has a few established strategies and others less in practice. In-depth studies may lead to another CE domain whereby the implications based on longitudinal dataset mining can open new research spaces. With the recent introduction of the Metaverse and the wide use of Artificial Intelligence, the Internet of Things, Blockchain, etc., in new business models and transactions, the ReSOLVE framework may offer novel contributions: particularly, with respect to the associates “Virtualize” (replacing physical products with virtual and dematerialized ones, implying customer satisfaction) and “Exchange” (transfer old and non-renewable produce into superior and renewable ones [113]). However, this scope is yet to receive substantial attention for executing the transformation process. Similarly, the associate “Refuse, Refill, Repurpose” lack traction from academics from the R-strategies list. The associate “Refuse” (denial usage of non-renewable items); “Refill” (using an existing storage box to stock an object); and lastly, “Repurpose” (using a product for an alternate purpose) are catching the interest of commercial/social start-ups and entrepreneurs to offer new value to informed customers. Though these customers are often fragmented and are concentrated in small pockets, serving them is tapping the Blue Ocean with low competition and a reduced threat to profitability.

Before execution, further exploration from academicians and practitioners is expected to strategize more significant as well as practical applicability across the globe. The reference of the abovementioned currently insignificant associates implies that a few authors expressed their beliefs, so it has appeared during analysis with time that the significance may be accomplished as well. All five most insignificant CE associates are relatively new introductions. All propagators are expecting a worthwhile contribution from these associates soon because they see potential in those associates. So, new research may be planned and executed on the abovementioned associates to remove the research gap.

One more fact that emerged out of the past ten years’ literature is the visibility of the application of principles of CE in a system and not in isolation. That signifies CE’s inclination towards industrial applications and practices. The emerging triggering point for industries seems to be the scarcity of resources for product development due to over-extraction and exploitation that directly impacted the business profit generation and margin. Hence, CE warned producers to explore alternatives, such as converting waste to wealth and pushing consumers for circular products or services for continuing business, but by adopting circular processes that include slowing, narrowing, and closing loops.

Therefore, the study is justified because of the usage of unique lenses to review the vast literature of CE, and getting into the depth of absolutely new findings by not only exploring the associates of CE but also finding their significances scores and generating a comprehensive framework for future direction.

6. Conclusions

The paper presents a comprehensive systematic literature review of CE by adopting a robust article-screening process from various databases. The study identified CE associates, comprehended the relations as well as interactions from the literature and definitions, as well as generating a comprehensive architecture of CE associates’ interaction. No study of CE to date has demonstrated such a review. The study establishes the contribution of CE associates methodically from the existing vast literature of one decade by bridging the knowledge gap on CE associates and their relations in the current ecosystem. Multiple quantitative tools, algorithms, and software were applied, resulting in the appearance and portrayal of CE associates over time. The study is also novel because of the application of the unique Systematic Quantitative Literature Review method combining PRISMA guidelines with 27-item checklist [114] as described in Supplementary Material and statistical tools as elaborated above in rational literature analysis. The research study facilitated generating the novel first-ever comprehensive architecture of CE with its associates. Thereby, a future research agenda is proposed by the dynamic advancement of the topic.

The paper contributes to the CE theoretical and practical understanding by outlining the CE associates progression, their connotation, architecture, and the current state of the art. Although research is in its nascent stage, the emerging research trends reflect that CE enthusiasts across the globe are following R-strategy imperatives, ReSOLVE business actions, and Sustainability pillars. Yet, the significance of the content of strategies, actions, and pillars varies with their actual application in literature and the ecosystem, focusing on environmental impacts, economic costs with energy harnessing, in comparison to the managerial perspectives. Therefore, scholars need to contribute in this area by exploring feasibility issues, decision-making practices, and the profitability of CE strategies. Accordingly, there is a need to theoretically examine the CE association phenomenon while concurrently advancing its diversity and system dynamics by scholars.

The study adds significant value to the existing list of vast literature on CE, and it creates scope to explore CE with new lenses in some prominent ways, by adopting similar methodologies focusing on analysing surveys, case studies, practitioners’ versus academics’ perspectives, sectoral differentiations, multi-level associates interaction (Figure 12), empirical research, exploring the most/least significant associates further and drawing inferences around those associates. There is a great potential in investigating the extent of models, framework implementation, longitudinal studies, and causality analysis. Moreover, this research is an introductory initiative proposing levels of the CE associates system (i.e., micro, meso, and macro); hence, new studies focused on the intersection and interdependencies between levels may be undertaken to develop a universal eco-system. This calls for multiple stakeholder engagement, actors’ network, including units beyond companies and customers and an institutional role for CE transition. Hence, the impact of CE transition at the managerial level, conflict, and change management would be motivating to investigate.

This research presents some practical implications, since it is the first study focused on the concept of CE associates. It updates both business and policymakers about the current knowledge of CE. The study provides a foundation for a roadmap and planning actions by real-time decision-making towards scalable CE transition and implementation. Business goals can be better aligned with CE models in view of this study with a supportive legal framework and body. The framework for three levels—micro, meso, and macro—further indicates that organizations are neglecting the intersection of levels for CE tools and principles execution. Designing strategic and business actions adjusting the internal requirement will be guided by the emerged associates at three levels. Thus, organizations can focus on the specific associates for CE transition and compliances effectively.

In conclusion, it may be stated that the study contributes to the knowledge of CE literature in three dimensions. Firstly, the study identifies 49 CE associates based on an extensive literature review and their findings’ analysis (RQ1 & RQ2). Secondly, the study shows the significance of those associates using qualitative and quantitative tools, and later, illustrates the priority ranks for CE associates besides highlighting the unexplored associates for research: viz., Repurpose and Virtualize (from the business action framework), Society (from the sustainability framework), Refill and Refuse (from the R-imperative strategies) are unexplored (RQ3). Lastly, the study proposes a CE system architecture framework that has been conceptualized from the significance of identified CE associates, and maps critical interactions for successful CE implementation and sustainability (RQ4). In future, researchers can address the methodological limitations of the study by considering other scientific contributions/journal articles and multiple languages for the study. One more important limitation that may also be addressed is consideration of a few pertinent associates such as citizens, property, etc., that might have an influence on the diffusion of CE in the system, but due to insufficient reflection or appearances of those associates in the considered decade’s articles, it did not emerge as a prominent associate during analysis and study. Lastly, future researchers can incorporate attributes of the PESTEL (Political, Economic, Social, Technological, Environmental, and Legal) framework and restructure the CE architecture, and explore how CE would diffuse with the inclusion of such associates. So, the study has not only thrown light on the new avenues of research from the findings of the current research study but also from the limitations.