Circular Economy and Economic Development in the European Union: A Review and Bibliometric Analysis

Increased changes in the climate and ecosystems call for a sustainable economic development, where economic growth should be compatible with the environment goals. In order to do this, it is urgent to find new ways of life and new production systems that make our ecological footprint compatible with global sustainability. The concept of the circular economy has brought relevant contributions to this problem. The central objective of the study presented here is to highlight the main insights presented through scientific literature about the concept of the circular economy within the European Union. In practice, the intention is to show what has already been done about this topic and what can/should be implemented in the future. To achieve these objectives, 144 articles were considered from the Web of Science (Core Collection) for the topics “circular economy” and “European Union”. These documents were, firstly, analysed through a proper literature review and later explored through bibliometric analysis, considering bibliographic data and the VOSviewer software. As the main findings have revealed, the increased importance of this concept within the European Union is recognized. However, this paper also identifies several challenges in the literature, namely the concentration of the identified publications in certain countries, organizations, and authors.


Introduction
The social, economic, environmental, and technological contexts, amongst others, change at a great velocity around the world, and these frameworks call for new concepts, approaches, and perspectives concerning how multiple stakeholders play their role in society and in economic activities. The concept of circular economy, especially in countries having great environmental impacts, appears to have its importance widely recognized among the policymakers and the scientific community. The number of scientific documents available on the main scientific platforms (WOS, for example) confirms this perspective [1,2].
In fact, the interest shown by the scientific community towards the topics related with the circular economy has increased over the last decades, namely, in domains related with the economy and management. This is highlighted by the number of publications from European, Chinese, and North American authors. On the other hand, new ecological concepts may be interlinked with other new concepts from other socioeconomic fields, such as innovation and entrepreneurship [1].
In any case, the topics associated with the circular economy seem to arouse great curiosity within the Chinese and the European Union scientific community, namely, after changes in related policy instruments [2]. These fields have motivated researchers around the world. On the other hand, it is worth stressing the diversity of realities within each country, as well as inside the European Union. Since the concerns around the circular economy are global, the opportunities and the potential to Public institutions, and their respective policies, play a determinant role in promoting a balanced relationship between socioeconomic activities and the environment, for example in the promotion of a renewable source of resource use [26]. In order to design efficient strategies, it is crucial to identify adjusted models [27] and indicators so as to perform pertinent assessments that support well-structured plans [28]. The indicators may be macro (country level), meso (industrial ecology), and micro (firm level) [29] and should be incorporated into the several policies, including regional strategies [30]. The discussion about the indicators to be considered so as to assess the circular economy is extensive [31]. Approaches which include the several institutions, the several levels of governance, and the complex policy framework, may bring to light relevant insights for policy design in an efficient evolution for a circular economy [32]. In this context, the European Union needs to rethink its policy framework for an effective decarbonisation [33], claiming, in some circumstances, for more robust frameworks [34]. This is also true for external cooperation, namely with developing countries [35]. For example, concerning the use of urban waste as agricultural fertilizers, the European legislation could be more specific about some aspects, namely those related with the potential contaminants [36]. The same deeper specificity could be helpful for plastics recyclers [37]. Another question concerning effective policy implementation is related with the unintended conflict amongst legislative instruments [38]. There is not yet, in fact, a consensus about the concept of circular economy [39], related strategies/options/alternatives [40], and methods for it to be properly assessed [41]. The policy dimension is one of the most important factors towards achieving levels of a circular economy [42], as well as, the governance dynamics and the respective adjustments [43]. Planned obsolescence is another question which legislation needs to address [44]. In general, the circular economy policies should address the following dimensions: Reuse, repair, and recycling; innovation; and promoting secondary material utilization [45]. The questions Sustainability 2020, 12, 7767 4 of 25 related with eco-design, fiscal policies, and public procurement should be addressed, and the obstacles should be explored for an effective policy implementation.

Product Life Cycle
The concept of circular economy has appeared these days from a perspective of increasing a product's life cycle through an approach of reuse, recirculation, and recycling [46], or reduce, reuse, and recycle [47]. This approach improves the efficiency of the resources used and promotes sustainable consumption models [48]. One of the greatest concerns related with product life cycles is related to plastic, due to the complexities associated with its composition [49], namely for the European Union [50]. A great part of plastic used is for packaging [51] and agro-food processes [52]. The production of plastic increased significantly in the last decades, and China is among the main polluters in this field [53]. The alternatives considered for packaging have, consequently, relationships with human health and sustainability [54]. Recovering aluminium is another concern with packaging [55]. The cascading use of waste, in some sectors, may be an interesting solution to mitigate the environmental impacts from the life cycle of some products [56]. Another example could be the use of plastic waste to be incorporated into transportation fuel production [57]. Another motive of concern is the electric and electronic waste [58], as a relevant challenge around the world [59] with a rapid increase in the European Union [60], or vehicles and tires [61], amongst the major sectors of the European economic activities [62], or lithium ion batteries [63,64], or the textile and clothing industry [65], or waste cooking oils [66], or baby diapers [67], or the forestry industry [68], or tablet, computer, and smartphone batteries [69]. A good end of life management mitigates the environmental impacts from the socioeconomic waste and residues [70].

Resources and Waste
The consideration of renewable resources for economic and social activities is determinant in order to decarbonise the planet [71], namely for energy inputs. In these cases, it is important, also, to minimize the environmental impacts from these alternatives [72]. The bio-based plastics may be an option for consideration in these contexts of renewable resources [73]. However, the increased stream of these products calls for further research into these alternatives, namely in terms of end of life [74]. The dependency of the European Union on raw materials from external markets is one further reason for an adjusted circular economy approach [75]. Only a small part of the waste materials produced are recycled around the world [76], and specifically in the Austrian context [77], sometimes caused by the use of waste and residues in bioenergy production [78]. This calls for adjusted measures, where waste reporting could provide its contribution [79]. In some contexts, the more efficient countries are, also, those with higher rates of recycling [80]. Recycling is, depending on the alternatives, always an interesting way to manage waste [81] from a sustainable perspective [82], as is reuse [83]. However, in these streams there are still some aspects that need more assessments [84] to make waste management and human health preservation compatible [85]. This is true across many dimensions of circular economy [86]. In these contexts, urban areas are those mainly responsible for solid waste generation [87], making solid municipal waste a real problem [88]. However, these are not the only sources [89] and the structure is diverse amongst different global regions [90], depending on their specific characteristics [91]. For example, Croatia recycled about 15% of its municipal solid waste [92]. In waste management, reuse and recycling contribute towards the circular economy, instead of incineration and landfills [93]. These authors highlighted the advantages of recycling and reuse towards economic circularity, due to the extension of a product's life cycle, and the disadvantages of traditional technologies such as landfills and incineration. These solid waste management techniques have their negative impacts on the environment, as have the liquid waste management technologies, such as sewage and chemical treatment. To avoid practices which are not compatible with the environment, other alternatives may be considered, such as the following: Detoxification; industry use; carbon sequestration; materials recovery [94]. Waste management may prove to be particularly Sustainability 2020, 12, 7767 5 of 25 problematic amongst the new European Union members [95]. The reality across the several European Union states is, in fact, extremely diverse [96].

Innovation and Opportunities
New technologies and innovative approaches are great opportunities to increase the sustainability of socioeconomic activities through a more circular economy [97], from a perspective of eco-innovation. In fact, the technological advances verified in the last few decades, such as autonomous robots, allow for the creation of new products and to redesign the productive processes. These evolutions may be great contributions in improving the circularity in socioeconomic activities, because they will help in the reduction of waste from raw materials. Circular economy is a broader concept that contains several dimensions [98]. However, there are also interesting opportunities in the development of new approaches and in the implementation of new ways of thinking about the several socioeconomic interrelationships [99], where recycling has its significance. The growing awareness of the several stakeholders about environmental problems and for the importance of a circular economy within current frameworks allow for these changes of socioeconomic paradigms. Considering the importance of the stakeholders' involvement and compliance with innovative strategies, these new ways of thinking are determinant for an effective eco-innovation implementation. For example, a deeper understanding of the several interconnections between energy, water, and food may bring additional insights [100], or new feed alternatives [101]. The applied scientific research brings about new opportunities to make the economic sectors more sustainable, namely those with more negative environmental impacts [102]. Research and innovation activities, as well as educational institutions, may bring forward relevant outcomes for the technological, governance, and social innovation that would provide an interesting support for the carbonization mitigation in cities [103]. Indeed, the research units and the institutions of higher education have a fundamental role to promote innovation and sustainable developments [104]. Reinforcing the network between business-higher education-research is an interesting pathway towards the circular economy [105]. The European Union promoted and created several initiatives, such as the Bio-based Industries Joint Undertaking, towards a more innovative and sustainable development in several member-states [106]. Sometimes changing old practices, with risks for sustainability, is not an easy task, which often requires adjusted approaches [107]. Some innovations in the commercialization chains, such as the agro-food short circuits, may promote a more circular economy in rural areas and improve the short profit margins of the farmers (for instance) [108]. In general, there is still a great need for significant steps to be taken in order to achieve the intended levels of sustainability [109], namely in waste management [110]. The 2030 Agenda for Sustainable Development, from the United Nations, and the European Union Action Plan for the Circular Economy, from the European Commission, are examples of these global concerns about sustainability [111], referred to in literature by several authors [112]. Recycling and innovation seem to be two determinant key words for a more circular economy [113].

Economic Sectors
The heterogeneity of the economic sectors across the European Union countries implies an existence of great heterogeneity in existing and applied circular economy strategies [114], including that for Electrical Waste and Electronic Equipment [115]. The industrial ecology (industrial networking to exchange resources and materials) and the related eco-industrial parks are adjusted approaches for a more sustainable planning [116], with interesting returns in some contexts [117], as shows an example from a Swedish region [118]. Nonetheless the exchange of data between industries may be a barrier for an effective industrial symbiosis [119]. Circular economy approaches may promote positive externalities [120] and economic growth [121]. The reverse is also true, where the economic and financial stabilities may create conditions for a more sustainable development [122]. These positive impacts are, for example, particularly relevant in agriculture, where the reuse of agro-waste [123] or waste from other sectors and activities [124] may improve the narrow margins of profit of the sector and bring alternatives for waste management [125]. Agricultural fertilizers appear to be an interesting alternative for several natural and anthropogenic wastes [126], having several applications [127] around the world [128], as well as the production of feed supplements [129] or in the construction industry [130], including end-of-life vehicle waste [131]. Circular economy activities in small and medium enterprises are interrelated and form a hierarchical structure where waste reduction is a priority [132], as well as product design [133].

Bioeconomy
The bioeconomy may contribute to a more sustainable and efficient development with positive externalities across several dimensions of society and the economy [134]. Buzzwords like bioeconomy, eco-innovation, or green economy, seem to have been replaced over recent years by the expression "circular economy" [135], which seems, in some circumstances (indeed), more comprehensive [136]. In any case, the concept of green (green houses or green buildings) seems to have its place [137], as well as the concept of bioeconomy [138] and green economy [1]. In some researches, the bioeconomy is viewed as a strategic approach for the European Union's development [139]. Other studies stress the need to interconnect these concepts in the debates about sustainability [140] and the importance of these approaches for the creation of new jobs, namely green [141], and economic growth [142]. Collaborative economy is another concept that appears in literature related with the circular economy [143], in amongst, for example, small and large companies [144], as well as the concept of ecodesign [145], where durability matters in the environmental tasks [146]. On the other hand, the circular economy has more than an economic and technological dimension, and should include social, behavioural [147], and cultural fields [148]. In fact, the behaviour and perceptions of the population about recycling, for instance, influence the effective implementation of circular economy strategies and plans [149]. The strategies adopted to promote the circular economy are different around the world. For example, China adopts more of a top-down strategy instead of the USA, European Union, and Japan [150]. In turn, China considers the circular economy as a response to the environmental problems from industrialization, and Europe has a perspective about this concept as an opportunity to make money and specifically to manage waste [151], focusing on innovation and business [152].

Bibliometric Analysis with Bibliographic Data
The bibliometric analysis allows us to highlight several pieces of interesting information available in the literature and may support an organized literature survey. For example, the studies developed by Martinho [6,7] produced relevant insights into the researches identified here. Following this, bibliometric dimensions related with the co-authorship, co-occurrence, citation, bibliographic coupling, and co-citation have been explored. Exploring these dimensions, in the above domains, contributes towards identifying gaps in the literature and to produce indicators which may support the several interested stakeholders, including the scientific researchers working on economic development compatible with the environmental and social dimensions, as referred by Mourao and Martinho [8]. The analysis performed in this section is based on the outputs obtained from the VOSviewer software through maps and tables. Figure 1 shows three network visualization maps for the co-authorship related with the number of documents of an author, organization, and country. In this bibliometric field, the dimension of the respective circle represents the number of documents [153] and the proximity between circles presents the relatedness for the respective items (in this case the relatedness is about the number of co-authored documents). In addition to this, Table 1

provides complementary information.
For the item country, Italy is the country with the highest number of documents (22), followed by England and Spain (with 21 and 20 studies, respectively). In addition, England and Spain have great relatedness, considering the proximity of the respective labels. Excluding residual exceptions, again in this item, it is observable that the average year of publication begins in 2011. Documents published by China have more average citations and are amongst those having more total citations. In this way, the authors Astrup, Thomas F. and Faraca, Giorgia are those having more documents (the first with 3 documents and the second with 2 studies). Figure 1 also reveals a significant relatedness, because these authors' names are significantly close and belong to the same cluster. In general, the authors presented in Figure 1 and Table 1 published their work related with topics of circular economy and European Union in the average years 2018-2019 (before the search did not consider any year range). This shows that these fields have recently aroused the curiosity of the scientific community, noting that the "average publication year" is the average publication year of the documents published. It is also relevant to observe that there are many works related to the topic "circular economy", but not so much when the topic "European Union" is considered simultaneously.
It is important to stress here that, if for the authors and organizations there is not a great difference between the number of documents published by the leaders and the remaining items, for the item country these differences are more visible. This seems to show that there do not yet exist specialised teams of researchers and organizations/Universities in these fields, having an international network. However, there are countries that are publishing more about these subjects, such as Italy, Spain, and England, with great networking between England and Spain. Finally, the international impact is higher for the documents published by the Chinese community. Figure 2 and Table 2 present the results for the co-occurrence links. Table 2 only exhibits the items with more occurrences. In Figure 2, the dimension of the circles/labels represents the number of occurrences of the keywords and the proximity (relatedness) is connected with the number of documents where these keywords appear together. Figure 2 and Table 2 present the results for the co-occurrence links. Table 2 only exhibits the items with more occurrences. In Figure 2, the dimension of the circles/labels represents the number of occurrences of the keywords and the proximity (relatedness) is connected with the number of documents where these keywords appear together.

Co-Occurrence
Considering all keywords, the items with more occurrences, beyond circular economy, are 'sustainability, recycling, China, management, efficiency, and waste'. The average citations are greater in documents with the following keywords: Waste management, recycling, resource efficiency, and China.
Considering only the author keywords, the documents with more average citations are those where the following items appear: Reuse, resource efficiency, industrial ecology, recycling, and sustainability. This framework stresses the interest for the scientific community related with circular economy in the European Union, in aspects particularly related with sustainability, efficiency, ecology, recycling, and waste management. This shows that the concepts of management, efficiency, and recycling are the main focus, and that waste seems to be the main concern. However, the circular economy concept is broader, as is shown, amongst others, in the work of Alhola et al. [154].   Considering all keywords, the items with more occurrences, beyond circular economy, are 'sustainability, recycling, China, management, efficiency, and waste'. The average citations are greater in documents with the following keywords: Waste management, recycling, resource efficiency, and China.
Considering only the author keywords, the documents with more average citations are those where the following items appear: Reuse, resource efficiency, industrial ecology, recycling, and sustainability. This framework stresses the interest for the scientific community related with circular economy in the European Union, in aspects particularly related with sustainability, efficiency, ecology, recycling, and waste management. This shows that the concepts of management, efficiency, and recycling are the main focus, and that waste seems to be the main concern. However, the circular economy concept is broader, as is shown, amongst others, in the work of Alhola et al. [154].  reuse  3  4  2018  141  478  transition  7  4  2018  14  36  bioenergy  6  3  2019  13  77  climate change  8  3  2017  5  228  indicators  10  3  1346  3  258  life cycle thinking  44  3  2018  4  334  policy  2  3  2018  4  370  recovery  4  3  2018  9  407  secondary raw materials  22  3  2018  4  490  waste  2  3  2019  1  507 waste-to-energy 5 3 2019 2
The authors Joanna Kulczycka and Marzena Smol are those with more documents also showing a significant relatedness, having worked together on the same documents. The authors with more total citations are the following: Willi Haas; Dominik Wiedenhofer; and Fridolin Krausmann. These authors also belong to the same cluster. In general, the authors with more documents and citations in this link also have more relatedness, having also worked together, showing that, when there are specialised teams for these topics, in general, they are small and come from the same organization, or at least, from the same country.
The Bucharest Univ Econ Studies is that which has more documents (8), but Univ Bologna is where the published documents received more total and average citations. As stressed before, the more productive organizations are not the same with greater international impact. Figure 4 shows the output for the links in bibliographic coupling where the relatedness is based on the number of references they share. This figure highlights that the document "ghisellini (2016)" is the most cited. Considering sources/journals, there is a relevant relatedness between the Journal of Cleaner Production and the following publications: Business Strategy and the Environment; Energies; and Marketing and Management of Innovations. The same happens for the Sustainability journal and the following publications: New Biotechnology; Autex Research Journal; or Journal of Food and Nutrition Research. However, there is a significant difference between the leading publication in these two clusters and other journals for several indicators (number of documents and citations). On the other hand, the Journal of Cleaner Production shares references with journals from the business, environment, energies, marketing, and innovation areas, and the Sustainability journal shares references with sources from the biotechnology, food, and nutrition issues. This reveals the relationships, for these topics, between sustainability and business aspects, namely those related with innovation. It also shows the interlinkages between sustainable development and new biotechnological approaches.

Bibliographic Coupling
The organization that has more documents (Bucharest Univ Econ Studies) also shares publications containing references with a relevant number of organizations around the world. However, the organization with more citations (Univ Bologna) shares references with a more limited number of organizations. Finally, Australia and Norway are clustered together (this means that the authors from these countries usually share references). Brazil, England, Austria, and Portugal are grouped in another cluster, and Croatia, Serbia, Switzerland, and Northern Ireland compose another cluster. Some countries from the Asian Continent and the USA form another group, and the remaining countries are clustered into two bigger groups. It seems that, in general, there are more references shared between authors from countries with some closer affinities. In any case, the fields related to circular economy in the European Union create curiosity amongst researchers around the world.

Co-Citation
In these filters the relatedness is based on the number of times the items are cited together ( Figure 5). For instance, the Journal of Cleaner Production is co-cited with the following publications (amongst others): J Ind Ecol; Ecol Econ; Nature; Clean Technol Envir; Res Policy; Technol Forecast Soc. For the item author, the European Commission is co-cited with the following authors: OECD; Bleischwitz, R; Howlett, M; Wilts, H; Eco-Innovation, Observatory; Winans, K; Zavadskas, Ek; Ekvall, T. In general, the most co-cited sources are from the same fields, and the authors who are more cited together have some affinity (in this case three organizations appear, the European Commission, OECD, and the Eco-Innovation Observatory).

Co-Citation
In these filters the relatedness is based on the number of times the items are cited together ( Figure 5). For instance, the Journal of Cleaner Production is co-cited with the following publications (amongst others): J Ind Ecol; Ecol Econ; Nature; Clean Technol Envir; Res Policy; Technol Forecast Soc. For the item author, the European Commission is co-cited with the following authors: OECD; Bleischwitz, R; Howlett, M; Wilts, H; Eco-Innovation, Observatory; Winans, K; Zavadskas, Ek; Ekvall, T. In general, the most co-cited sources are from the same fields, and the authors who are more cited together have some affinity (in this case three organizations appear, the European Commission, OECD, and the Eco-Innovation Observatory).

Discussion and Conclusions
This research was aimed to perform a literature review, complemented by a bibliometric analysis, about the topics "circular economy" and "European Union". We referred to VOSviewer software for the bibliometric analysis and to the platform Web of Science (as the major source of our observed references). From this scientific platform, 144 studies were identified.
The bibliometric effort identified that several issues related to the circular economy have attracted the attention amongst researchers [76,82,103,122]. This identification has shown the relevance of studies performed in these fields and the enormous potential to be explored in future work. On the other hand, it is also worth highlighting the great number of documents produced by international institutions such as the European Commission, revealing institutional concerns about circularity in the European economy [14,88,103]. In addition, within these frameworks another question is raised about the international impact from scientific production and, in this dimension, the studies published by Chinese authors have had a greater impact in the scientific community. Keywords like sustainability, recycling, reuse, management, efficiency, waste, and industrial ecology stress the concerns with waste management.
The bibliometric analysis has also shown that the more productive authors are those with more relatedness, since, in general, they had worked together. However, it seems that there are some specialised teams in these fields, usually involving a small number of members and from the same institution, or, at least, from the same country. This framework shows that it is important to promote further networking and more specialised teams around the world for these domains. These are interesting insights, presenting that the organizations with more impact seem to be more focused on positive returns across the scientific community. Finally, the authors from Australia and Norway tend to share references more likely, as well as those from Brazil, England, Austria, and Portugal.
In terms of practical implications, there is a great potential to be highlighted in the domains related with the circular economy in the European Union, because they are still emerging areas. In

Discussion and Conclusions
This research was aimed to perform a literature review, complemented by a bibliometric analysis, about the topics "circular economy" and "European Union". We referred to VOSviewer software for the bibliometric analysis and to the platform Web of Science (as the major source of our observed references). From this scientific platform, 144 studies were identified.
The bibliometric effort identified that several issues related to the circular economy have attracted the attention amongst researchers [76,82,103,122]. This identification has shown the relevance of studies performed in these fields and the enormous potential to be explored in future work. On the other hand, it is also worth highlighting the great number of documents produced by international institutions such as the European Commission, revealing institutional concerns about circularity in the European economy [14,88,103]. In addition, within these frameworks another question is raised about the international impact from scientific production and, in this dimension, the studies published by Chinese authors have had a greater impact in the scientific community. Keywords like sustainability, recycling, reuse, management, efficiency, waste, and industrial ecology stress the concerns with waste management.
The bibliometric analysis has also shown that the more productive authors are those with more relatedness, since, in general, they had worked together. However, it seems that there are some specialised teams in these fields, usually involving a small number of members and from the same institution, or, at least, from the same country. This framework shows that it is important to promote further networking and more specialised teams around the world for these domains. These are interesting insights, presenting that the organizations with more impact seem to be more focused on positive returns across the scientific community. Finally, the authors from Australia and Norway tend to share references more likely, as well as those from Brazil, England, Austria, and Portugal.
In terms of practical implications, there is a great potential to be highlighted in the domains related with the circular economy in the European Union, because they are still emerging areas. In general, the authors who publish on these topics have undergone very little networking. In turn, the findings obtained stress that the scientific community, related with these topics, focused their research, namely, on waste recycling and on business interrelationships. There are some fields' gaps here that may be addressed by the literature in future research.
In future studies, there are some topics, related with circular economy dimensions, that could be further addressed, as, for instance, the following: The design of companies' supply chains [155]; the indices, indicators, and assessment approaches [156]; the technological dimensions supporting the circular economy [157]; the circularity assessment in companies [158]; the relationships regarding human presence in organizations [159]; and implementation suggestions for recycling [160]. Funding: This work is funded by National Funds through the FCT-Foundation for Science and Technology, I.P., within the scope of the project Refª UIDB/00681/2020. Paulo Mourao acknowledges the following: This paper is financed by National Funds of the FCT-Portuguese Foundation for Science and Technology within the project «UIDB/03182/2020».