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Open Bioeconomy—A Bibliometric Study on the Accessibility of Articles in the Field of Bioeconomy

Open access (OA) to scientific information is one of the major challenges and objectives of actual public research policy. The purpose of this paper is to assess the degree of openness of scientific articles on bioeconomy, as one of the emergent research fields at the crossroads of several disciplines and with high societal and industrial impact. Based on a Web of Science (WoS) corpus of 2489 articles published between 2015 and 2019, we calculated bibliometric indicators, explored the openness of each article and assessed the share of journals, countries and research areas of these articles. The results show a sharp increase and diversification of articles in the field of bioeconomy, with a beginning long tail distribution. 45.6% of the articles are freely available and the share of OA articles is steadily increasing, from 31% in 2015 to 52% in 2019. Gold is the most important variant of OA. Open access is low in the applied research areas of chemical, agricultural and environmental engineering but higher in the domains of energy and fuels, forestry and green and sustainable science and technology. The UK and the Netherlands have the highest rates of OA articles, followed by Spain and Germany. The funding rate of OA articles is higher than of non-OA articles. This is the first bibliometric study on open access to articles on bioeconomy. The results can be useful for the further development of OA editorial and funding criteria in the field of bioeconomy.


Introduction
The climatic context is forcing us to rethink our production and consumption methods to limit the damage to the environment. Not only the extensive use of non-renewable resources (with further depletion issues) but also irreversible impacts on life cycles are pointed out as the main causes [1]. The bioeconomy is part of this approach which aims to replace fossil resources-i.e., non-sustainable resources such as coal or oil-by "green" resources which are also called biomass, the process of which the rationalized processing would open more environmental-friendly perspectives to our Planet. Indeed, bioeconomy is more than a concept. It is a set of initiatives that reconciles both economic, environmental and social objectives [2].
Is it a new concept or not? Fifteen years ago, the European Commission observed that bioeconomy was one of the oldest economic sectors known to humanity but that the life sciences and biotechnology were transforming it into one of the newest [3]. Generally, bioeconomy is understood as an economy "where the basic building blocks for materials, chemicals and energy are derived from renewable biological resources, such as plant and animal sources," with a strong potential for environmental, • renewability, • carbon-friendliness, • inherent circularity,-particularly in closing cycles in waste processing, recycling and fostering bio-degradability, mostly in the format of cascades in biorefining activities • and, last but not least, offering new additional and better functions, such as higher stability, longer lifetime, less toxicity, less resources consumption, sustainability and so forth." [6].
Until recently, the concept of bioeconomy has been rapidly spreading in different spheres: institutional, scientific and entrepreneurial. The concept of bioeconomy is used in scientific publications and mobilizes on the one hand, experimental sciences and agronomic and environmental techniques and, on the other hand, human and social sciences. Moreover, this concept has been the subject of strong public policy attention. The Organization for Economic Co-operation and Development (OECD) is the first institution to underline the issues and the aims of bioeconomy through its pioneering work. According to Reference [1], "the transition to bioeconomy gains significant footing towards the end of the 20th century and is now a strategic element on a transnational, national and regional level" (p. 67). Most strategies "point to the need for strong collaborations between research institutions and industry in order to facilitate technological innovation" [5]. Companies are applying new technologies to meet the demands of pollution abatement, innovation and profitability. In the field of research and development, there is an innovation model based on sharing and collaboration between stakeholders. This model, called "Open Innovation," suggests calling on stakeholders outside the company to innovate [9]. In such an approach, a set of stakeholders can be profitably invested in the field of bioeconomy to achieve major advances both socioeconomic and environmental major advances.
Bioeconomy being a relatively recent and emergent field of research, a small but growing number of papers present results of bibliometric studies on this topic. A multilevel social network analysis has been applied by Reference [1] to construct a holistic and visual definition of bioeconomy and to describe its evolution, based on scientific literature from the European Union, the United States and China. Their data consists of 1369 articles from 2008 to 2018, retrieved from the Web of Science (WoS) database; the study includes a content analysis of strategic policy documents. In 2016, a study showed how in terms of publications, the importance of biotechnology had grown in South Africa following the country's launch of its Biotechnology Strategy in 2001, with accompanying government financial support for R&D [10].
A large study on about 7000 papers indexed in the Scopus database showed the decisive role of technology (industrial biotechnology, synthetic biology, metabolic engineering etc.) in the development of the bioeconomy and proposed a systemic model of 20 interacting factors influencing this development, such as research and innovation, energy consumption and policy [11]. Innovation is the main topic of a recent German study which aims to improve the measurement of innovation in bioeconomy, to discuss what kind of information may be needed to understand innovation patterns in bioeconomy and to assess the current data availability [12]. This study is particular insofar as it applies bibliometric methodology to patents, in order to highlight the innovation potential of bioeconomy and the public and private R&D funding activities and to contribute to the monitoring of the economic, social and ecologic developments of bioeconomy.
The relationship between bioeconomy and sustainability has been addressed by Reference [13], providing evidence how visions about this relationship differ across scientific publications, ranging from positive to negative: the assumption that sustainability is an inherent characteristic of bioeconomy; the expectation of benefits under certain conditions; tentative criticism; and the expectation of a negative impact.
Another bibliometric study on 453 articles published between 2005 and 2014 analyzed the meaning of the notion of bioeconomy by exploring the origins, uptake and contents of the term "bioeconomy" in the academic literature [14]. Main results are an increasing visibility of bioeconomy research, mainly by researchers affiliated to a higher education institution, much less from the corporate sector; a rather fragmented research community, with a core of European and American regional clusters most active and networked in the field and dispersed over many fields of science yet dominated by natural and engineering sciences. They also identified three different visions of bioeconomy (i.e., bio-technology, bio-resource, bio-ecology) and described their implications in terms of overall aims and objectives, value creation, drivers and mediators of innovation and spatial focus. Reference [2] conducted a complementary bibliometric study on temporal and geographical distribution of publications, most popular publication platforms, salient keywords and emerging topics in order to compare circular economy, green economy and bioeconomy as global sustainability concepts.
Reference [15] performed a bibliometric analysis on papers indexed by the Web of Science (WoS) for a number of South African authored publications and citations in bioeconomy and compared them with Brazil, Russia, India and China (BRICS) and selected countries for the period 2008 to 2018. Based on a large and inclusive query, they retrieved 19,040 publications in bioeconomy disciplines with at least one South African author for the period 2008-2018; about 55% were written in collaboration with researchers from other countries and the average percentage industry collaboration was at 1.3%. With a focus on biotechnology, Reference [16] evaluated the research output of ten Indian universities between 1997 and 2006, identifying prolific authors, most relevant journals and different document types.
Other bibliometric papers deal with specific aspects of bioeconomy, like biomass, biorefineries and forest bioeconomy [17][18][19]. Reference [20] performed a bibliometric analysis of a small corpus of 166 papers on bioeconomy retrieved through a systematic review of academic journals in social sciences. Their study confirms that most of the current analysis of the bioeconomy relates to genetics, chemistry, biotechnology, energy or biology issues and regrets that a proper interpretation of the significant implications of the bioeconomy from a social and economic perspective is still (too) scarce.
Most of these papers (9 out of 13) are based on WoS data; some are rather large and inclusive whereas others apply a more selective query approach. Half of them combine the bibliometric methodology with a conceptual analysis of the papers' content. However, so far none of the bibliometric papers investigated the accessibility of publications on bioeconomy on the Internet, to which degree the access to published research output is free, open and universal. Open access (OA) to academic papers and more generally, open science appears out of scope in this field of research. Now, open science is one of the major challenges of the European research and innovation framework program (Horizon 2020, Horizon Europe 1 ), along with bioeconomy. The objective is to accelerate the transition towards a sustainable European bioeconomy by reducing the gap between new technologies and their implementation. The position in favor of open science includes the obligation to ensure free access to publications resulting from funded projects. The European Commission defines open science as a way research is carried out, "disseminated, deployed and transformed by digital tools and networks. It relies on the combined effects of technological development and cultural change towards collaboration and openness in research" 2 . New technologies contribute to the improvement of scientific research and communication and "by providing unlimited, barrier free, open access to research outputs, open science makes scientific processes more efficient, transparent and responsive to societal challenges" (ibid.).
The scientific and technical information brings together all the information produced by professionals in research, teaching but also industry and economics. It covers all scientific and technical sectors and can be presented in several forms, such as articles, reviews, books, posters, technical documentation, patent notice, databases and gray literature [21]. The real challenge of research today is to democratize access to knowledge and to recognize that knowledge has a driving role for our society. The open access movement has focused on the communication and circulation of scientific publications while the open science movement values science and its evaluation by opening up research data and new measures to assess awareness, for example [22].
The aim of our paper is to assess the degree of openness of scientific articles on bioeconomy and related topics. Similar to Reference [14], we calculated bibliometric indicators on the development, impact (citations), journals, authors, institutions, countries and research areas; we also investigated the internationality [23] of the underlying research collaborations and the share and types of funding sources [24,25]. Based on this dataset, we explored the openness of each article, if it has been published in a gold or hybrid OA journal or if it is legally available on an institutional or a disciplinary repository or another, similar platform and we assessed the share of journals, countries and research areas of open access (OA) articles on bioeconomy.
After a short description of the applied methodology (Section 2), we present the results of the bibliometric analysis of scientific articles on bioeconomy published between 2015 and 2019, together with an assessment of their free and open availability on the Internet (Section 3). The results are discussed in Section 4, in particular regarding methodological limitations and downfalls, the differences with former studies and the impact of open science in this research field. We conclude our paper with some perspectives for further research.

Bibliometric Analysis
We used the multidisciplinary bibliometric database Web of Science (WoS) Core Collection in order to retrieve relevant articles in the field of bioeconomy. The choice of the WoS was conditioned by the purpose to provide results that could be compared with former research [14]. As the former corpus 1 EC Horizon Europe https://ec.europa.eu/info/horizon-europe_en. 2 EC Open Science https://ec.europa.eu/digital-single-market/en/open-science.  [14], we decided to cover the following five years, excluding 2020 because this year is not ended and because of lacking data on citations. The literature retrieval was therefore limited to articles published in scientific journals between 2015 and 2019.
The WoS Core Collection set we used consists of the following content, with coverage time spans: The WoS queries were performed on 24 June 2020. The retrieved references have been downloaded as a CSV-file and processed as Excel spreadsheets. Some variables needed curation and cleansing, in particular the data on publishers and affiliated organizations. Network maps were created with VosViewer 1.6.15 [26]. In case of missing data, articles were excluded from the analysis. Appendix A provides a list of the calculated indicators.

Evaluation of Openness
In a second step, we selected those articles with an DOI. For these articles, we performed a search in the open database Unpaywall 3 [27] in order to assess if the articles are freely available on the Internet (open access) or not, especially in gold or hybrid open access (OA) journals or in institutional or disciplinary repositories.
The queries via Unpaywall were performed on 24 August 2020. The retrieved references with all relevant information about open access have been downloaded as JSON and CSV files and the data were added to the WoS references. Appendix A provides a list of the calculated indicators.

Results
The search in the entire WoS Core Collection based on the selected keywords described above produced 6728 references. From these references, 5073 are identified as journal articles (75.4%). 2489 articles have been published from 2015 to 2019. These articles are the sample for the following bibliometric analysis. From this sample, 2329 articles have an DOI (93.6%) and serve as the subsample for the assessment of openness.    The annual increase in bioeconomy is well above the average global growth of published articles worldwide which is, for the given period, between 5% and 10% (WoS Core Collection).

Articles and Citations
At the time of the WoS query, the articles of our sample have been cited 18,431 times. As in Reference [14], the distribution of the citations is skewed but in a more long-tail way ( Figure 2).    20% of all articles received 66.9% of all citations while 80% of all citations are "produced" by 31% articles. This is not a classic 80/20 Pareto-like distribution but moves to the so-called "long-tail" distribution [29]. On the other extreme of the ranking, 332 articles (19.7%) received one citation only while 490 articles (13.3%) were not cited at all.
The median number of citations per article is low, with only 3 citations per article. For articles published in 2015, the median is 7 citations while for those published more recently in 2019, it is only 1 citation (Table 2).

Journals and Research Areas
The 2489 articles of our sample have been published in 932 different journals. From these journals, 607 (65.1%) have published only one article on bioeconomy in the given period 2015-2019. Again, the distribution is skewed. The five journals with the highest number of articles on bioeconomy and related subjects, together represent 332 articles (13.3% of all articles). Their articles received 3247 citations (17.6%). The journal which published the most articles in the field of bioeconomy in the given period 2015-2019, was the Journal of Cleaner Production, an international, transdisciplinary journal focusing on cleaner production, environmental and sustainability research and practice 4 , published by Elsevier, followed by the MDPI open access journal Sustainability, an international, cross-disciplinary, scholarly journal of environmental, cultural, economic and social sustainability of human beings 5 ( Table 3). 4 Journal of Cleaner Production https://www.journals.elsevier.com/journal-of-cleaner-production. 5 Sustainability https://www.mdpi.com/journal/sustainability.  The first twenty journals published together 703 articles on the topic (28.2%). These articles received 6362 citations (34.5%) (Appendix B). Applying the Bradford law on the distribution of articles and citations to our corpus, 29 journals (3.1%) (=1/3 articles) and 12 journals (1.3%) (=1/3 citations) can be identified as core journals in the field of bioeconomy (Appendix C).
The journals of our sample are published by 360 different publishers but some of them belong to the same publishing house. The most important publishers, in terms of articles and citations, are Elsevier, Springer Nature, Wiley, MDPI and Taylor & Francis (Table 4); except for the new open access publisher MDPI from Switzerland, these publishers belong to "big five" academic publishers. Together, the five publishers represent 1565 articles (62.9%) and 12,473 citations (67.7%), confirming in this particular, emerging field of research the global oligopoly of academic publishers [30]. Sage Publishing, the fifth of the "big five" academic publishers, produced only 27 articles over the given period, which received 274 citations. Clearly, Elsevier is in a significant, dominant position, as well in terms of production (articles) as in terms of impact (citations). The only surprise is the emergence of the newcomer MDPI, with a different publishing and business model based on 100% open access (see below).
Publications on bioeconomy are dispersed over many fields of science, yet dominated by natural and engineering science [14]. In our sample, we identified 161 WoS categories of research areas, most of them-the long tail-covered by few articles. Figure 3 shows the fifteen most important WoS research areas, representing the highest number of articles; one article can be indexed in more than one research area.
The most important research areas contributing to the growing corpus of journal articles on bioeconomy and related topics are, for the period 2015-2019, environmental sciences (19.5% of all articles), followed by biotechnology & applied microbiology (13.3%), green & sustainable science & technology (11.9%), environmental studies (11.7%) and economics (10.1%). A more detailed analysis of these figures provides complementary insight: • Ranking: the comparison of the annual ranking of the different research areas reveals that while over the whole period environmental sciences remain the first research area in terms of articles, four areas are gaining importance (green & sustainable science & technology; environmental engineering; forestry; multidisciplinary chemistry); three other areas become relatively less important (ecology; fisheries; agricultural engineering).  The most important research areas contributing to the growing corpus of journal articles on bioeconomy and related topics are, for the period 2015-2019, environmental sciences (19.5% of all articles), followed by biotechnology & applied microbiology (13.3%), green & sustainable science & technology (11.9%), environmental studies (11.7%) and economics (10.1%). A more detailed analysis of these figures provides complementary insight:

Authors, Organisations and Funding
The articles of our sample were written by 8566 authors. 8447 (98.6%) authors contributed only to one article on the topic of bioeconomy, which represents 2090 articles of the corpus. The ten most prolific researchers authored between 9 and 17 articles, together 125 articles which received 1153 citations, which is above the average number of citations per article ( Table 5). The most prominent author, S.Venkata Mohan, is working at the Council of Scientific and Industrial Research funded Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, India. The two following authors, Mario Pagliaro and Rosaria Cirminna, are both working at the Institute for the Study of Nanostructured Materials (ISMN) of the Italian National Research Council (CNR) at Palermo, Italy, while Qingling Zhang is working at the Northeastern University, Shenyang, China. The median number of authors per article is 4; the maximum number is 89, for an article on the emerging field of marine biotechnology in Brazil with 20 main authors and a network of 69 other researchers.
Among the references, the authors listed affiliations to 2471 organizations. The most performant institution, in terms of published articles in the field of bioeconomy but also in terms of impact (citations), is the Dutch University of Wageningen, followed by the French public National Institute of Agricultural Research (INRA) 6 , the US Department of Agriculture (USDA), the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO) and the Swedish University of Agricultural Sciences (Table 6). Except for USDA and CSIRO, all organizations are from the European Union member states.
These ten organizations together produced 415 articles (16.7%); their articles received 4198 citations (22.8%). In terms of impact, the most important organizations are the Dutch universities of Wageningen and Delft, followed by the German Helmholtz-Centre for Environmental Research (which is ranked #11 and not part of Table 6), the University of Helsinki and the Technical University of Denmark.
85% of these organizations could be clearly attributed to a specific type of academic or other structure. More than half of the organizations are Higher Education institutions (mainly universities) and they contributed to 86% of all articles (Table 7). They are followed by research institutes (like INRA, CNR or CSIRO) which represent 18.5% of all institutions but contributed to 32.4% articles. Corporate companies (5.2%) authored or co-authored 6.5% articles.
A total of 1677 articles (67.4%) acknowledge some kind of funding, from one (30.0%) or more funding bodies (37.4%). However, when this indicator-the funding rate-is broken up by the research areas, significant differences appear. Some research areas -especially (but not only) the most important in terms of published articles-show funding rates well above 70% or 75%, like green & sustainable science & technology, agricultural engineering but also marine & freshwater biology or fisheries, for instance ( Figure 4). In other research areas, the funding rate is lower, that is, the published results have less often received specific funding; this is the case for articles indexed in economics and management, similar to a long tail of articles covering less important or less central fields of bioeconomy. and they contributed to 86% of all articles (Table 7). They are followed by research institutes (like INRA, CNR or CSIRO) which represent 18.5% of all institutions but contributed to 32.4% articles. Corporate companies (5.2%) authored or co-authored 6.5% articles. A total of 1677 articles (67.4%) acknowledge some kind of funding, from one (30.0%) or more funding bodies (37.4%). However, when this indicator-the funding rate-is broken up by the research areas, significant differences appear. Some research areas -especially (but not only) the most important in terms of published articles-show funding rates well above 70% or 75%, like green & sustainable science & technology, agricultural engineering but also marine & freshwater biology or fisheries, for instance ( Figure 4). In other research areas, the funding rate is lower, that is, the published results have less often received specific funding; this is the case for articles indexed in economics and management, similar to a long tail of articles covering less important or less central fields of bioeconomy.

Affiliation Countries and International Collaboration
Based on the affiliations, the following table shows the cumulative number of articles and citations for the most "productive" countries in the field of bioeconomy research (

Affiliation Countries and International Collaboration
Based on the affiliations, the following table shows the cumulative number of articles and citations for the most "productive" countries in the field of bioeconomy research (Table 8). These ten leading research countries in the field of bioeconomy represent 1958 articles (78.7%) and 17,043 citations (92.5%). The researchers from US organizations, the best ranked country, have authored or co-authored 17.5% of all articles and received 19.0% of all citations. Articles from France, Spain, India and Australia are in average less well cited than from the other countries.
Two-third of the articles are domestic, that is, written by authors working in the same country (1685 articles, 67.7%). Most of the international articles have been published by authors from two or three countries (705 articles, 28.3%); yet, one article, a comparative property rights analysis on Europe's private forests, has authors from 29 different countries.
The topological map ( Figure 5) represents the affiliate network according to the share of international articles by country. Figure 5 highlights the international collaboration between different countries. The majority of countries that maintain international collaboration are developed countries: USA, Austria, Germany, England, France, Italy, Nordic countries and other countries from Europe. Interesting: the central role of Austrian research for partnerships with countries from Central and East Europe. Interesting, too, the strong partnerships of the US with the Commonwealth countries England, Canada and Australia but also with China and Brazil and, less, with Germany and France.
The word cloud represents the share of domestic articles per country, that is, highlights countries that have produced articles without international collaboration. Germany, the US and Italy are countries with a high amount of domestic research ( Figure 6, Appendix E); yet, all of them are also strongly invested in international collaborations (see Figure 5 above). More interesting is the case of India, with an important number of domestic research but less international partnerships.  Figure 5 highlights the international collaboration between different countries. The majority of countries that maintain international collaboration are developed countries: USA, Austria, Germany, England, France, Italy, Nordic countries and other countries from Europe. Interesting: the central role of Austrian research for partnerships with countries from Central and East Europe. Interesting, too, the strong partnerships of the US with the Commonwealth countries England, Canada and Australia but also with China and Brazil and, less, with Germany and France.
The word cloud represents the share of domestic articles per country, that is, highlights countries that have produced articles without international collaboration. Germany, the US and Italy are countries with a high amount of domestic research ( Figure 6, Appendix E); yet, all of them are also strongly invested in international collaborations (see Figure 5 above). More interesting is the case of India, with an important number of domestic research but less international partnerships.

Openness
1135 articles from the sample have been identified as freely available in open access (45.6%), nearly as much (1194 articles) are not open access but behind a paywall (48%); for the other 160 articles, because of lacking DOIs, Unpaywall could not identify the status (Figure 7).   n/a 6.4%  The share of OA articles is steadily increasing, from 31% in 2015 to 52% in 2019 ( Figure 8). The 1135 open access articles come from 505 journals (54.2% of all journals) but only 83 journals (8.9%) have 3 or more articles in open access, either on their own platform or on a green repository. Table 9 shows the five journals that published the highest number of open access articles. The first twenty journals cumulate 326 OA articles on the topic, which represent 46.4% of all OA articles but only 13.1% of all articles (Appendix B). Elsevier published the most articles in bioeconomy (791) and Elsevier is also the publisher with the highest number of OA articles (216, equal 19% of all OA articles). But as Table 10 shows, this represents only 27.3% of all articles published by Elsevier on bioeconomy, a share which is lower than the other "big five" publishers Springer Nature (37.7%), Taylor & Francis (39.2%) and Wiley Blackwell (44.2%).  The first twenty journals cumulate 326 OA articles on the topic, which represent 46.4% of all OA articles but only 13.1% of all articles (Appendix B). Elsevier published the most articles in bioeconomy (791) and Elsevier is also the publisher with the highest number of OA articles (216, equal 19% of all OA articles). But as Table 10 shows, this represents only 27.3% of all articles published by Elsevier on bioeconomy, a share which is lower than the other "big five" publishers Springer Nature (37.7%), Taylor & Francis (39.2%) and Wiley Blackwell (44.2%). The part of OA articles in the fifteen most important research areas (cf. Figure 3) range from 16.7% (Engineering, Chemical) to 78.6% (Multidisciplinary Studies) (Figure 9). Especially the applied domains of agricultural, chemical and environmental engineering have low rates of OA publishing while, except for the relatively small number of multidisciplinary studies, all other important research areas have average rates of OA publishing, between 40% and 50%. The full table with all WoS research areas in our sample is in Appendix D. The part of OA articles in the fifteen most important research areas (cf. Figure 3) range from 16.7% (Engineering, Chemical) to 78.6% (Multidisciplinary Studies) (Figure 9). Especially the applied domains of agricultural, chemical and environmental engineering have low rates of OA publishing while, except for the relatively small number of multidisciplinary studies, all other important research areas have average rates of OA publishing, between 40% and 50%. The full table with all WoS research areas in our sample is in Appendix D.    Table 8 (see above) ranks the ten most important countries, according to the total number of articles published in the field of bioeconomy. Table 11 shows the same countries, this time with the number and percentage of OA articles. The leading countries regarding the part of open access are the UK, the Netherlands, Spain, Germany and France; while Germany and the Netherlands appear preferring the gold variant of OA, the UK has a preference for OA hybrid and gold journals and France clearly prefers green.
Regarding the different types of organizations, the essential contribution to OA articles on bioeconomy comes from the universities which (co)authored 87.6% of all OA articles. However, the share of OA does not vary significantly between universities, research institutes, government organizations, companies and so forth.
A last result: 73.5% of the OA articles (834) present results from research that got funding from one or more funding bodies, a percentage which is slightly higher than the funding rate of the non-OA articles (66.2%).

Methodological Limitations
The WoS Core Collection is a representative but not exhaustive database. Also, as the transparency of the WoS Core Collection has been a matter of concern [31], we specified the customized sub-datasets we used for our study. In order to obtain a more complete picture, we could have included other databases, especially Scopus from Elsevier or used discovery tools like the BASE or Dimensions. We could also have considered other document types than journal articles, like books and book chapters, communications, dissertations, reports, preprints and other categories of grey literature. We made some comparative test queries in the field of bioeconomy; probably, Scopus would have produced 5-10% more articles while Dimension and BASE would have shown 50-80% more articles and two to three times more references, when other document types like reports, theses, preprints, books and book chapters, conference contributions and so forth were included. Clearly, this means that (much) more publications and other academic articles are available on bioeconomy and related topics than in our sample. For our study, however, we preferred consistency, representativity and reliability to exhaustivity. Journal articles are (still) the most relevant type of scientific information, especially in the fields of science and technology and they are the most important part of the Crossref DOI database, representing 72.9% of all content items 8 and of the Unpaywall search engine required for the OA assessment.
Another limitation is the preponderance of English articles in the WoS. Yet, searching through databases, catalogs and on the Internet reveals that at least for the moment, only few scientific articles have been published in French.
Our analysis of open access excluded all piracy platforms (e.g., Sci-Hub) and all academic social networks from the retrieval of OA articles, which probably contributes to an underestimation of the real open accessibility of bioeconomy articles.

Delineation, Growth and Diversification of the Field of Bioeconomy
The statistical delineation of bioeconomy remains a critical issue [12]. Setting boundaries, attributing some sectors to bioeconomy while excluding others depends on political and economic strategies and on academic definitions of what is or should be bioeconomy. However, so far there is no generally accepted and consensual definition, just more or less large and inclusive approaches.
Our empirical approach is based on the work of Reference [14] and replicates their search strategy, with an opening towards agriculture: the search terms we have added are "agrobased," "agro-based," "agrosourced," "agro-sourced" and "naturality." The term "naturality" was included experimentally as a central and highly-ranked attribute of renewable materials [32]. These keywords enabled us to include research in the field of agriculture and the natural environment. This means that our corpus of published articles is potentially larger and covers more domains than that from the 2016 study.
Our main purpose was to remain as similar and comparable as possible with [14]; prior to our study, we assessed different search strategies with different combinations of search terms and selected this one because it seemed to us as an acceptable compromise between former research (such as [14]) and the recent development of the field. On the other hand, we could have gone farther and include more keywords, as for example "bio-sourced," "biosourced," "sustainability" or "biomass"; but we did not because we preferred a reliable corpus of references to a larger sample with more "noise," that is, less or irrelevant articles. We are aware that this choice may reduce the visibility of certain topics, in particular the technology side of bioeconomy (biotechnology, chemistry).
Compared with other studies, our more inclusive approach probably explains one part of the increase of publications, authors, institutions and domains. Our assessment produced 2489 articles published between 2015 and 2019; for the period 2005-2014, Reference [14] identified only 453 articles, while [2] found 646 articles on bioeconomy for the period 1990-2017 and [1] 1369 articles published between 2008 and 2018. More or less inclusive views and queries and different data sources probably explain a large part of these differences, Scopus for instance having a broader coverage than the WoS. However, all these results, like figures from other recent papers [17,18], may also reveal a real and significant increase of publications in this field, from 2014 and 2015 on, which is well above the global increase of academic articles.
This growth of the number of articles is accompanied by an increasing number of authors, affiliated organizations and journals. For instance, Reference [14] counted 1487 authors; our corpus contains more than 8000 authors. They identified 459 organizations, in our study there were 2471 organizations. The articles of their corpus were published in 222 journals, while this number in our study is 932. Obviously, this is more than a numerical increase. Compared to former and other studies, our results reveal an increasing diversification and inter-or pluridisplinarity. Research on bioeconomy is conducted in an increasing number of scientific domains and the results are published in more and more journals covering a larger range of topics than before.
While the number of journals quadrupled, the number of articles per journal remained more or less stable, increasing slightly from 2 to 2.7. The analysis of citations shows the development of a long tail in 8 Figures from October 2019, cf. Crossref 2019 Annual Report https://doi.org/10.13003/y8ygwm5. the field of bioeconomy, with a less-skewed distribution of impact. In our study, 20% articles received 66.9% citations and 80% citations were "produced" by 31.1% articles. Compared to Reference [8], the most cited articles, that is, the "top of the charts" [28], become less important. In their sample, the three most cited articles received 18% citations, in our study the percentage is only 4%. Table 12 gives more evidence on this evolution. Table 12. Most cited articles and their part of citations (sources: [8]; own data).

Most Cited Articles
Citations On the other hand, the "far end" of the long tail becomes longer, with a higher percentage of articles that received only one or no citation at all-in our sample, this percentage is 32.8% while in the corpus of Reference [14] it is only 21.2%. In summary, the figures indicate the development of a larger, more diversified and less structured field of research, with less leading or "reference" articles and more and more studies with less or no impact.

Clusters of Bioeconomy
It was not the purpose of our research to provide a conceptual analysis of the field of bioeconomy, similar for instance to References [1,14,18]. Nevertheless, we conducted a co-occurrence analysis of the articles' keywords, for two reasons: we wanted to get a (visual) idea of the scope and the diversity of the research field, as a complement to the bibliometric assessment but also in order to control and adjust if necessary the underlying search strategy (WoS query); and we wanted to prepare a more detailed and differentiated evaluation of the development of open science in bioeconomy, based on the clustering of research articles, as a complement to the WoS indexing of research areas. Figure 10 presents the first results of this approach, a co-occurrence map based on 12,859 keywords. Reference [8], the most cited articles, that is, the "top of the charts" [28], become less important. In their sample, the three most cited articles received 18% citations, in our study the percentage is only 4%. Table 12 gives more evidence on this evolution. On the other hand, the "far end" of the long tail becomes longer, with a higher percentage of articles that received only one or no citation at all-in our sample, this percentage is 32.8% while in the corpus of Reference [14] it is only 21.2%. In summary, the figures indicate the development of a larger, more diversified and less structured field of research, with less leading or "reference" articles and more and more studies with less or no impact.

Clusters of Bioeconomy
It was not the purpose of our research to provide a conceptual analysis of the field of bioeconomy, similar for instance to References [1,14,18]. Nevertheless, we conducted a co-occurrence analysis of the articles' keywords, for two reasons: we wanted to get a (visual) idea of the scope and the diversity of the research field, as a complement to the bibliometric assessment but also in order to control and adjust if necessary the underlying search strategy (WoS query); and we wanted to prepare a more detailed and differentiated evaluation of the development of open science in bioeconomy, based on the clustering of research articles, as a complement to the WoS indexing of research areas. Figure 10 presents the first results of this approach, a co-occurrence map based on 12,859 keywords. For each article, all keyword occurrences have been counted. Yet, in order to keep the map intelligible, the visualization threshold was limited to those 861 keywords with at least five occurrences. The resulting map reveals three main clusters, among other, smaller clusters:  For each article, all keyword occurrences have been counted. Yet, in order to keep the map intelligible, the visualization threshold was limited to those 861 keywords with at least five occurrences. The resulting map reveals three main clusters, among other, smaller clusters: • General principles and challenges of bioeconomy (blue): bioeconomy, economy, policy, industry, sustainability, innovation. This cluster appears similar to Reference [1] cluster 1 on bioeconomy, biopolitics, political economy and so forth, except for the biodiversity which is missing in our blue cluster. The cluster seems to express at least partly the "bio-technology vision" described by References [14,18], with a focus on economic growth, innovation and investment. • Natural resource management (green): management, bioeconomic model, biodiversity. This cluster shifts the focus on management and modelling, especially in the field of fisheries and marine protected areas. It seems quite similar to a "bio-ecology vision" [14] which is held by France for instance, following [1].

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Transformation of bioresources (red): biomass, biofuels, biorefinery, transformation, extraction, fermentation, bio-based production/products. The cluster is similar to Reference [1] cluster 2 on biomass, biorefining and bioproducts and seems to express the "bio-resource vision" described by Reference [14] as focused on the processing and conversion of bio-resources into new products.
Other clusters are centered on bioenergy or on productivity, growth and a systemic approach while "naturality" appears (so far) out of scope and not related to bioeconomy; the analysis is still in progress. But for the purpose of this paper, two aspects are important: the similarities with other, recent studies on bioeconomy, which confirms the pertinence of our search strategy; and the reality of three large clusters of research that are interconnected, of course but can be clearly distinguished and described, which makes them interesting and relevant for further assessment of open science, beyond disciplinary boundaries.

Openness
The overall part of articles on bioeconomy that are freely accessible in open access is 45.6%. Compared to the metrics of the European Commission's Open Science Monitor 9 , this OA rate is above the average percentage of open access publications from 2015 to 2017 (Figure 8, in blue the EC Monitor's indicator, in green our own sample). Figure 11 shows that the open accessibility of our bioeconomy sample is well above the EC metrics based on a corpus of 1.7 m to 1. Bronze open access: fewer bronze articles in bioeconomy (3.7%) than in the EC sample (7-9%).
Taken together, the open access to articles in the field of bioeconomy is obviously more gold (including hybrid) than green. One reason may be that this is a young and emergent research area in need of quick communication and impact; perhaps bioeconomy is just some years ahead of the other research areas, regarding the preference of gold OA (journals) to green OA (repositories). OA journals 9 EC Open Science Monitor https://ec.europa.eu/info/research-and-innovation/strategy/goals-research-and-innovation-policy/ open-science/open-science-monitor_en. are the fastest way to disseminate peer-reviewed articles in a trustworthy environment; also, some major countries in bioeconomy (in particular, UK, Germany, The Netherlands) clearly prefer OA journals to open repository, for the publishing of their public research output. Another reason may be the high degree of funding in this new and challenging field with high societal and industrial impact. Especially funding from the EC (program Horizon 2020) but also from an increasing number of national research agencies or other funding bodies requires OA to results; more and more, research funds include the costs of OA publishing in gold and hybrid journals (article processing charges). This would explain why a relatively important part of bioeconomy articles is freely accessible on journal platforms and in repositories. An indicator may be the higher rate of funding in OA articles, compared to non-OA articles. Taken together, the open access to articles in the field of bioeconomy is obviously more gold (including hybrid) than green. One reason may be that this is a young and emergent research area in need of quick communication and impact; perhaps bioeconomy is just some years ahead of the other research areas, regarding the preference of gold OA (journals) to green OA (repositories). OA journals are the fastest way to disseminate peer-reviewed articles in a trustworthy environment; also, some major countries in bioeconomy (in particular, UK, Germany, The Netherlands) clearly prefer OA journals to open repository, for the publishing of their public research output. Another reason may be the high degree of funding in this new and challenging field with high societal and industrial impact. Especially funding from the EC (program Horizon 2020) but also from an increasing number of national research agencies or other funding bodies requires OA to results; more and more, research funds include the costs of OA publishing in gold and hybrid journals (article processing charges). This would explain why a relatively important part of bioeconomy articles is freely accessible on journal platforms and in repositories. An indicator may be the higher rate of funding in OA articles, compared to non-OA articles.
A recent study from Finland reports market shares of open access in eighteen Scopus-indexed disciplines ranging from 27% (agriculture) to 7% (business); it also provides percentages of OA articles that are published in gold OA journals, by discipline [33]. Figure 12 compares the overall OA share of our bioeconomy sample (45.6%, green) with the OA metrics of five disciplines from the Finish study (gold) and of five similar disciplines from the EC Open Science Monitor (blue). A recent study from Finland reports market shares of open access in eighteen Scopus-indexed disciplines ranging from 27% (agriculture) to 7% (business); it also provides percentages of OA articles that are published in gold OA journals, by discipline [33]. Figure 12 compares the overall OA share of our bioeconomy sample (45.6%, green) with the OA metrics of five disciplines from the Finish study (gold) and of five similar disciplines from the EC Open Science Monitor (blue).
The OA rate of the bioeconomy articles is similar to the OA rates in biological sciences and agriculture, forestry and fisheries in the EC Open Science Monitor; it is two times higher than in chemical engineering, chemical sciences and environmental engineering (blue). Following the EC Open Science Monitor, biological and agricultural sciences are leading disciplines regarding the implementation of OA strategies to scientific output. This disciplinary environment of good OA practice is probably the main reason for the relative high rate of OA articles in the field of bioeconomy.
When compared to the Finish study, which considers only gold OA articles, it is obvious that the bioeconomy gold OA rate is slightly higher than in engineering, chemistry and environmental science but quite similar to biochemistry, genetics and molecular biology and above all to agriculture and biological sciences. These similarities confirm the disciplinary dominance of agriculture, biology and, to a lesser degree, of environmental studies and engineering in the new research area of bioeconomy. Economics (not in Figure 9), on the other hand, has a much lower OA rate in the EC Monitor and the Finish study than our own sample and appears rather marginal, compared to the other disciplines. The OA rate of the bioeconomy articles is similar to the OA rates in biological sciences and agriculture, forestry and fisheries in the EC Open Science Monitor; it is two times higher than in chemical engineering, chemical sciences and environmental engineering (blue). Following the EC Open Science Monitor, biological and agricultural sciences are leading disciplines regarding the implementation of OA strategies to scientific output. This disciplinary environment of good OA practice is probably the main reason for the relative high rate of OA articles in the field of bioeconomy.
When compared to the Finish study, which considers only gold OA articles, it is obvious that the bioeconomy gold OA rate is slightly higher than in engineering, chemistry and environmental science but quite similar to biochemistry, genetics and molecular biology and above all to agriculture and biological sciences. These similarities confirm the disciplinary dominance of agriculture, biology and, to a lesser degree, of environmental studies and engineering in the new research area of bioeconomy. Economics (not in Figure 9), on the other hand, has a much lower OA rate in the EC Monitor and the Finish study than our own sample and appears rather marginal, compared to the other disciplines.

Conclusions
Our paper presents the results of a first comprehensive, scientometric study on the development of open science in the research area of bioeconomy, based on a corpus of 2489 articles from the WoS, published between 2015 and 2019. Among the main findings are the following: Bioeconomy (all) Figure 12. Percentage of OA articles (explication in text).

Conclusions
Our Elsevier published the highest number of OA articles but MDPI is the first gold OA publisher in the field of bioeconomy. • Open access is low in the applied research areas of chemical, agricultural and environmental engineering but higher in the domains of energy and fuels, forestry and green and sustainable science and technology.

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The UK and the Netherlands have the highest rates of OA articles, followed by Spain and Germany, while the lowest rates can be observed in India and China.

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The funding rate of OA articles is higher than of non-OA articles.

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The global OA share of articles on bioeconomy is above the average OA rate in the European Union and it is similar to the research areas of biological sciences, agriculture, forestry and fisheries.
Also, based on the study of keywords, other terms could and should be included in order to cope with the development of the research in the field of bioeconomy. Further, including the "bio-sourced" and "biosourced" keywords in the corpus would give a larger number of publications more centered on "technical" aspects of bioeconomy with technologies of transformation of bioresources to platform molecules, semi-finished and finished goods. This will be done in the future, along with a broader search for literature on bioeconomy from other sources, in particular Scopus and the French national open repository HAL.
The co-occurrence analysis of the articles' keywords is a first step to further research in this field, insofar it lays the foundations for a differential assessment of open access development in specific research fields, beyond the disciplinary boundaries. Other perspectives for further insight into open science in the field of bioeconomy: