Ferney Osorio Bustamante
email: ferney.osorio-bustamante@univ-lorraine.fr

Laurent Dupont
email: l.dupont@univ-lorraine.fr

Mauricio Camargo
email: mauricio.camargo@univ-lorraine.fr

INNOVATION SPACES AS DRIVERS OF ECO-INNOVATIONS SUPPORTING THE CIRCULAR ECONOMY: A SYSTEMATIC LITERATURE REVIEW

Keywords: Circular Economy, Eco-Innovation, Innovation Spaces, Sustainability, Systematic Literature Review JEL codes : Q01, O30 Q56, B40

This paper explores the way in which academics address the role of innovation spaces in the development of circular economy. Considering their characteristics, objectives and functioning, we assume that innovation spaces can be favorable environments for eco-innovations facilitating the implementation of circular economy strategies. To examine this hypothesis, this paper mobilizes a mixed research method based on bibliometric analysis of keywords and content analysis. The results show that these collaborative environments can: foster sustainable experimental learning, provide methodologies and tools for the co-creation of circular solutions, drive the transition towards sustainable smart cities, foster the creation of new sustainable business models, promote sustainable urban entrepreneurship and facilitate knowledge exchange on circular solutions. However, most of the reviewed literature focuses mainly on their impacts on sustainability and less on the concept of circular economy per se. Consequently, this work provides insights on the potential of these spaces in the circular strategies' implementation.

Introduction

The circular economy (CE) principles contrast with the linear model of the current industrial systems based on the "take-make-use-dispose" logic. It represents a new economic model capable of achieving a sustainable development that is inspired by the natural ecosystem functioning [START_REF] Emf | Towards the Circular Economy Vol. 1 : An economic and business rationale for an accelerated transition | CIRCULAR IMPACTS[END_REF]. Indeed, the CE has been recognized by the scientific community as a transformation process of production and consumption modes requiring a series of changes and reconfiguration of the techno-economic systems [START_REF] Ghisellini | A review circular economy : The expected transition to a balanced interplay of environmental and economic systems[END_REF][START_REF] Kirchherr | Conceptualizing the circular economy : An analysis of 114 definitions[END_REF]. Eco-innovation as a means to operationalize these changes, can play a central role. It proves to be one of the relevant factors of resource productivity and efficiency intervening at the micro (product, company), meso (networks and cooperation) and macro (territories and policies) scales, responding thus to environmental and societal issues [START_REF] De | Eco-innovation pathways to a circular economy : Envisioning priorities through a Delphi approach[END_REF]De Jesus & Mendonça, 2018;[START_REF] Smol | Circular economy indicators in relation to ecoinnovation in European regions[END_REF][START_REF] Vence | Eco-innovation and Circular Business Models as drivers for a circular economy[END_REF]. Despite the growing scientific dynamic dealing with the importance of eco-innovation in the transition to a CE, the understanding of the mechanisms and conditions favoring their emergence remains limited. In fact, the systemic nature of the CE approaches requires a set of interacting actors exchanging material and/or informational flows that require collaborative physical environments with access to technology, knowledge and experimentation to them. This leads us to question the processes and environments conducive to the creation of these conditions. Moreover, in the field of innovation, a new phenomenon has attracted the attention of researchers and practitioners in recent years, that of innovation spaces (IS) like the Fab Labs, Makerspaces, Hackerspace, Living Labs coworking spaces…). These spaces play the role of innovation intermediaries, provided with devices, tools and new methodologies designed to strengthen innovation capacities [START_REF] Hossain | A systematic review of living lab literature[END_REF][START_REF] Morel | Espace d'innovation : De nouveaux lieux pour l'intelligence collective ? 13[END_REF][START_REF] Mortara | How do Fab-spaces enable entrepreneurship ? Case studies of[END_REF][START_REF] Osorio | Constellation of Innovation Laboratories : A Scientific Outlook[END_REF]. They have been designed to address societal and environmental issues and phenomena by making innovative tools and methods available to a wide public and by enabling different stakeholders (e.g.: companies, research centers, public actors, universities, and users) to form inter-organizational networks engaging processes of creating, prototyping, validating and testing new technologies, services, products and systems in reallife contexts [START_REF] Leminen | Living Labs as Open-Innovation Networks[END_REF]. The interest in these IS as new innovation enablers has been growing among academics. Several studies have focused on the emergence, design and management of these spaces [START_REF] Boutillier | Collaborative Spaces Promoting Creativity and Innovation[END_REF][START_REF] Kristensen | The Physical Context of Creativity[END_REF][START_REF] Lewis | The Organizational Innovation Laboratory[END_REF]. These research efforts seek to understand the nature of these spaces, how they are composed, who benefit from them, and how they 1. State of the art 1.1. The circular economy an umbrella concept: background The concept of CE has been gaining momentum since the 2000s, but its conceptual foundations date back to pioneering works highlighting the necessary transition to new production and consumption modes that consider the scarcity of the planet's resources [START_REF] Boulding | [END_REF][START_REF] Stahel | Jobs for tomorrow : The potential for substituting manpower for energy[END_REF]. The emergence of other concepts, such as "cradle to cradle" (Braungart, McDonough, 2002), industrial ecology and industrial metabolism (Frosch and Gallopoulos, 1989) has revealed the potential efficiency of natural ecosystems in recycling resources. The concept of CE grew out of these theories, thus became an umbrella concept with fuzzy boundaries [START_REF] Kirchherr | Conceptualizing the circular economy : An analysis of 114 definitions[END_REF]. Indeed, in the recent scientific literature, CE is represented as a synthetic concept bringing together different approaches mainly including: activities that extend the product's life span, waste and resource management [START_REF] Bakker | Understanding and managing product lifetimes in support of a circular economy[END_REF][START_REF] King | Reducing waste : Repair, recondition, remanufacture or recycle?[END_REF], reverse logistics and the integration of the CE in the production planning [START_REF] Suzanne | Towards circular economy in production planning : Challenges and opportunities[END_REF]; cleaner production [START_REF] Li | Reutilisation-extended material flows and circular economy in China[END_REF][START_REF] Su | A review of the circular economy in China : Moving from rhetoric to implementation[END_REF] with a growing interest in sustainable supply chain management [START_REF] Angelis | Supply chain management and the circular economy : Towards the circular supply chain[END_REF][START_REF] Elia | Evaluating the adoption of circular economy practices in industrial supply chains : An empirical analysis[END_REF][START_REF] Reh | Process engineering in circular economy[END_REF][START_REF] Safiullin | Increasing Stability of Economy through Supply Chain Management and the Circular Economy[END_REF]. The institutional literature has also made a significant contribution to the definition of the CE and the dissemination of its principles within the environmental policies, practitioners and companies by providing an operational framework allowing its deployment at different organizational scales. For example, the international Ellen MacArthur Foundation (EMF) defines the CE as "a new economic model that aims to decouple global economic development from the consumption of limited resources. The circular economy responds to the pressing resource-related challenges facing companies and countries, and has the potential to generate growth, create jobs, and reduce environmental impacts, including carbon emissions" (Ellen MacArthur Foundation, 2012, p. 2). The studies of the EMF underline the diversity of the CE practices including, use of renewable energies, renewables flow management, eco-design, economy of functionality, etc. Another example, that of the French ADEME (Agency for the Environment and Energy Management), often cited by francophone researchers, considers the CE as concrete strategy for sustainable economic development that brings together a set of measures, tools and instruments to address the depletion of natural resources. The ADEME proposes the implementation of three fields of the CE in order to "close the loop" and achieve a more sustainable economic system which are: the production and supply of goods and services ; consumption through consumer demand and behavior (economic or citizen); and the waste management (ADEME, 2013). Globally, when defining the CE, the focus is on the product and material flows and their management as well as the management of their supply chains, i.e. a technico-scientific approach. However, the implementation of the CE requires a systemic change [START_REF] Ghisellini | A review circular economy : The expected transition to a balanced interplay of environmental and economic systems[END_REF][START_REF] Kirchherr | Conceptualizing the circular economy : An analysis of 114 definitions[END_REF] and thus the inclusion of the socio-economic dimensions. Indeed, according to De Jesus & Mendonça (2018), the CE is "a multidimensional, dynamic, integrative approach, promoting a reformed socio-technical template for carrying out economic development, in an environmentally sustainable way" (p. 76). Based on an analysis of 114 definitions in the literature, [START_REF] Kirchherr | Conceptualizing the circular economy : An analysis of 114 definitions[END_REF] put forward the idea that "It operates at the micro level (products, companies, consumers), meso level (eco-industrial parks) and macro level (city, region, nation and beyond), with the aim to accomplish sustainable development, thus simultaneously creating environmental quality, economic prosperity and social equity, to the benefit of current and future generations. It is enabled by novel business models and responsible consumers. " (p. 229). Based on these scientific and institutional backgrounds, it is possible to identify four main CE strategies: (i) waste management and flow recovery strategies (including recycling and recovery practices); (ii) sustainable use and manufacturing strategies (focusing on sustainable supply and eco-design processes); (iii) sustainable use and consumption strategies (integrating responsible consumption and extend product lifespan practices); and (iv), sustainable organizational and territorial strategies (including economy of functionality and industrial ecology approaches). The transition towards a systemic circular functioning is based on the implementation of all these strategies at the micro, meso and macro scales.

Circular economy and eco-innovation: towards technological and non-technological change

The potential benefits of implementing the CE on the various micro, meso and macro scales are numerous on the environmental, social and economic levels. Its application within modern economic systems and industrial processes (micro scale) leads to multiple benefits resulting from reduced costs of resource-related inputs in production, supply chain optimization, reduced waste management costs, and the generation of additional revenues due to the higher value of by-products and material and energy flows [START_REF] Emf | Towards the Circular Economy Vol. 1 : An economic and business rationale for an accelerated transition | CIRCULAR IMPACTS[END_REF]. On a broader scale (business zone, agglomeration, city, territory, country, etc.), the CE can be a source of development and dynamism for the economy. The implementation of sustainable organizational and territorial strategies such as the economy of functionality and industrial ecology can lead to new forms of organization and management of industrial and urban activities and to the emergence of new innovation dynamics [START_REF] Gibbs | Industrial ecology and eco-industrial development : A potential paradigm for local and regional development[END_REF][START_REF] Gallaud | Circular economy, industrial ecology and short supply chains[END_REF][START_REF] Kasmi | Écologie industrielle, milieu innovateur et gouvernance territoriale : Le cas de Dunkerque (Nord-France)[END_REF][START_REF] Kasmi | Industrial Symbiosis and Territorial Development : The Cross-Fertilization of Proximity Dynamics and the Role of Information and Knowledge Flows[END_REF]. The literature thus shows that the CE holds promising opportunities in terms of in-depth structural changes in socio-economic systems. However, the implementation of its strategies comes up against many barriers. These may include all the technical and economic difficulties that hinder the optimization of resources, or organizational, relating to the regulatory/institutional context, to coordination and governance issues arising from the interdependencies between the involved actors, or to social aspects (table 2).

Regulatory/ institutional

Insufficient incentives and lack of a conducive legal system, overregulation, insufficient internalization of externalities through policy

Coordination

Lack of trust between actors, lack of communication, dissemination/confidentiality issues and secrecy culture

Social

Lack of employee involvement, shortfalls in consumer awareness, limited consumer acceptance, rigidity of business routines Sources: adapted from [START_REF] Boons | Types of industrial ecology : The problem of coordination[END_REF]De Jesus & Mendonça, 2018;[START_REF] Gibbs | Reflections on implementing industrial ecology through eco-industrial park development[END_REF][START_REF] Kasmi | Écologie industrielle, milieu innovateur et gouvernance territoriale : Le cas de Dunkerque (Nord-France)[END_REF] Transition is an innovation-intensive process of reconfiguration and adaptation (De Jesus & Mendonça, 2018). It requires profound changes anchored in a specific context over a long period of time. In this sense, recent literature emphasizes that the transition to a CE requires new forms of innovation to overcome the obstacles. The focus here is mainly on eco-innovation (De Jesus & Mendonça, 2018). Eco-innovations are generally defined as "the assimilation or exploitation of a product, production process, service, management or business method that is new to the firm or user and that results, throughout its life cycle, in the reduction of environmental risks, pollution and other negative effects of resource (including energy) use" (Kemp & Pearson, 2008, p. 3). They can be of different types: incremental, which consists of improving existing technology without changing uses and practices; radical, which then allows for radical technical changes while preserving existing practices; or transformative, corresponding to the implementation of new technological systems. The latter requires a complete reconfiguration of production processes and lifestyles [START_REF] Galiègue | Le regard de l'économiste : Portée et limites de l'innovation environnementale[END_REF]. According to [START_REF] Cainelli | Resource efficient eco-innovations for a circular economy : Evidence from EU firms[END_REF], "the dynamics of circular economy-related innovation imply a slow techno-economic transformative process. It is possibly more a 'reform' than a 'revolution', passing through the adoption of both incremental and radical innovations" (p. 10). Moreover, since the CE is a process based on multi-actors cooperation and systemic integration (De Jesus et al., 2018), transformative eco-innovations need to be technological to address technical issues (which relates to the product, process, or production systems), but also non-technological (organizational, institutional, commercial, financial changes, etc.) to facilitate and promote cooperation among stakeholders (De Jesus & Mendonça, 2018;OECD, 2009;[START_REF] Vence | Eco-innovation and Circular Business Models as drivers for a circular economy[END_REF]. Some studies show that eco-innovation can be a lever of this systemic transition (De Jesus et al., 2018, 2019). Indeed, at the macro level, eco-innovation accompanies global transition dynamics by strengthening cooperation between the public and private sectors and new public policies, it can thus contribute to the reduction of regulatory/institutional and governance limits; at the meso level, ecoinnovation allows new ways of sharing services, public services and by-products, thus promoting collaborations around sustainable products and services and reducing the coordination limits; at the micro level, eco-innovation can improve the eco-design processes of products, services and sustainable consumption enabling thus the technical, economic and social limitations (Figure 1). (OECD, 2009and De Jesus et al., 2018, 2019) In sum, a growing number of research studies presents eco-innovation as a major asset facilitating the development of the CE. Despite of this, the understanding of the links between these two concepts needs to be deepened. In particular to better understand the conditions and types of environments that support eco-innovation that comes with more radical circular changes. For this purpose, in this paper we explore a new field of analysis studying the role of IS in the transition from a traditional approach of ecoinnovation focused on technology at a micro scale (closed laboratory-based R&D and then industrialization), to a more collaborative approach combining both technological and non-technological solutions.

Overview on the concept of Innovation Spaces

Over the last few years, new structural and organizational entities facilitating the emergence of innovation have emerged. These are physical and/or virtual environments, playing the role of innovation intermediaries, provided with devices, tools and new methodologies designed to strengthen innovation capacities in a context of exchange, sharing and collaboration in order to achieve a goal of common interest [START_REF] Dupont | Innovative public-private partnership to support Smart City : The case of "Chaire REVES[END_REF][START_REF] Morel | Espace d'innovation : De nouveaux lieux pour l'intelligence collective ? 13[END_REF][START_REF] Osorio | Constellation of Innovation Laboratories : A Scientific Outlook[END_REF] in a trust climate [START_REF] Dupont | Living lab as a support to trust for co-creation of value : Application to the consumer energy market[END_REF]. These new forms of work organization address the need for organizations to open their boundaries to their external environment in order to capture new knowledge in a collaborative and open innovation process [START_REF] Boutillier | Collaborative Spaces Promoting Creativity and Innovation[END_REF][START_REF] Capdevila | Joining a collaborative space : Is it really a better place to work[END_REF]. Indeed, innovation processes must be open, as highlighted in the literature [START_REF] Chesbrough | Open Business Models : How To Thrive In The New Innovation Landscape[END_REF], in order to generate a real dynamic of innovation and capture positive externalities. The concept of IS refers to different types of co-creation environments such as fab labs, makerspaces, hackerspaces, tech shops, living labs, co-working places (see their definitions in appendix A). To refer to this type of spaces other terms like "third place" [START_REF] Oldenburg | Celebrating the third place : Inspiring stories about the « great good places » at the heart of our communities[END_REF] or "open labs" [START_REF] Merindol | Le livre blanc des open labs : Quelles pratiques ? Quels changements en France[END_REF] are used, in both the scientific literature and the public policy arena as a more generic term. In recent years a growing number of academics have been interested in these collaborative spaces. [START_REF] Kristensen | The Physical Context of Creativity[END_REF] has explored the importance of the space in enhancing creativity. According to this author, "creativity takes place in a physical context, i.e. in a confined space" (p. 89). He explains that such environments allow the creation of cognitive processes, facilitate information exchange and the availability of knowledge tools. But to achieve this result, Kristensen stresses the importance of designing and mobilizing spaces according to the nature of the stages of the creative processes (combination or separation of private and common spaces for example). [START_REF] Capdevila | Les différentes approches entrepreneuriales dans les espaces ouverts d'innovation[END_REF] also shows that IS are environments conducive to collective creativity by studying creative practices and approaches, the type of governance and modalities of collaboration between the members of these spaces as well as their motivations [START_REF] Capdevila | Joining a collaborative space : Is it really a better place to work[END_REF]. [START_REF] Lewis | The Organizational Innovation Laboratory[END_REF] focused their analysis on understanding the design, role and objectives of IS, which they call "innovation laboratories", in firms. They demonstrate their benefits in strengthening organizations' commitment to innovation and creativity by enhancing their learning capacity to improve their organizational routines. Recently, within a special issue of the Journal of Innovation Economics & Management on this theme [START_REF] Boutillier | Collaborative Spaces Promoting Creativity and Innovation[END_REF], the articles have contributed to the understanding of the functioning and mechanisms of the IS in particular through: the analysis of the role of the resources provided by these spaces (physical infrastructure, human and financial resources) in the strengthening of collaboration between companies and the actors of their ecosystem [START_REF] Tremblay | Coworking Spaces : New Places for Business Initiatives[END_REF]; the analysis of the evolution of the spaces, their design and the factors allowing their durability [START_REF] Osorio | Shaping a Public Innovation Laboratory in Bogota : Learning through Time, Space and Stakeholders[END_REF]; the identification of the processes and conditions allowing the development of collaborative learning through these spaces [START_REF] Delgado | Innovation Spaces in Universities : Support for Collaborative Learning[END_REF]; and their contribution in terms of evolution towards new modes of work organization [START_REF] Ballon | Re-Embedding Work in a Political and Social Project : The Case of Business and Employment Cooperatives in France[END_REF]. Thus, the study of the design and management of the spaces, the analysis of their functioning, their evolution and the conditions favoring their sustainability, their benefits in the strengthening of creativity and innovation are at the core of the academic research interests. However, these studies focus on a micro scale (the study of the space itself or the impact on the organization to which it is attached). Because of their specificities (innovative technologies, innovative collaborative methodologies, knowledge sharing, adaptable infrastructure, diversified skills, network creation…), these spaces can play a more systemic role by providing creative solutions that can respond to global challenges (economic, social and environmental) facing their local ecosystems. Their potential therefore seems to be an asset in supporting the transition to new development models such as the CE. Our questioning here aims to understand how and what kind of impact these spaces can bring to facilitate the implementation of the CE? Do they represent favorable environments for the emergence of different forms of eco-innovation? Based on a systematic literature review, we aim to explore this reasoning.

Methods and data

The choice to carry out a systematic literature review is justified by the relevance of this approach, which is becoming increasingly recognized by the scientific community. When guided by a specific research question, this approach makes it possible to analyze the evolution of knowledge on a given topic and to identify its related trends and changes [START_REF] Denyer | Producing a systematic review[END_REF]. This study draws on previous research that has focused on the constellation of innovation laboratories [START_REF] Osorio | Constellation of Innovation Laboratories : A Scientific Outlook[END_REF]. Based on a bibliometric analysis of 1307 scientific publications (published between 2000 and 2018), this study highlights the links between the most common concepts referring to IS (innovation labs, living labs, fab labs, makerspaces, third places, etc.). Furthermore, through content analysis it provides insights on the different impacts that these spaces can have on their community, environment, and partners. To reach this goal, we will build on from the path established in this previous work by updating and expanding its bibliographic database on IS while looking for intersections with the existent literature on CE. This review of the literature employs a mixed research methodology based on both bibliometric and systematic review [START_REF] Osorio | Constellation of Innovation Laboratories : A Scientific Outlook[END_REF] (Figure 2). The first consists in providing quantitative analyses based on the identification of the corpus of the literature through a set of statistical tools providing a bibliographic overview of scientific productions [START_REF] Ellegaard | The bibliometric analysis of scholarly production : How great is the impact?[END_REF]. It will allow to have a global vision on the trends of publications related to our two research equations (the first one focused on CE, and the second one on IS), in particular through the co-occurrence of keywords. The second allows for a qualitative study associated with a meta-analysis of a series of publications made in a more precise manner, facilitating the establishment of syntheses and overall conclusions [START_REF] Tranfield | Towards a Methodology for Developing Evidence-Informed Management Knowledge by Means of Systematic Review[END_REF]. To carry out this bibliographical analysis, several steps were followed: 1) Identification of the keywords that make up our two search equations: They are made up of all the keywords used in this search. These were defined according to the objective and scope of our study, as well as the relevant definitions on the CE and IS (Table 3).

2) Identification of research conditions: In order to have a large sample of publications related to our research question, we used the scientific databases Scopus and Web of Science. The search of keywords targeted titles, keywords, and abstracts of publications without defining a time limit neither a research discipline. To have a general vision of the publications, we chose to analyze journal articles, books, and book chapters (Table 3). By pooling Scopus and Web of science publications and removing duplicates, 863 publications were retained. 3) Bibliometric analysis of publications: At this step, the data extracted from Scopus and Web of Science were organized in a CSV file containing the title, abstract, keywords, name of the journal or publisher, DOI and document type. These data were then explored in the VOSviewer software, which mapped all the keywords of the 863 publications and provided an overview of their degree of kinship in the form of a network. This first step allowed the formulation of 5 main categories representing the major trends in the literature that were subsequently used in the next qualitative analysis to code the final selected articles. In parallel, a scan of the titles and keywords (and sometimes abstracts) of the 863 showed that not all the publications directly addressed the role of ISs in the development of the CE or more generally in sustainable development. Thus, a preliminary filter to the qualitative analysis was applied. This filter made it possible to select articles in which the keywords from our two search equations were found simultaneously in the title, the abstract and the keywords. A total of 107 publications were obtained. 4) Qualitative analysis of publications: After a manual inspection of the titles of the 107 publications in the CSV file, all the documents that did not correspond directly to our research question were excluded, 80 were thus retained for the qualitative analysis. A first step of scanning these articles was carried out by following a coding protocol using the Nvivo tool. The abstracts of each publication were first coded/screened according to five key dimensions: "context", "literature gap", "research questions and objectives", "methodology", "results"/"contributions" classified as "nodes" in Nvivo. This step allowed for a closer understanding of the topics of the articles. Subsequently, particular emphasis was placed on the content of the "nodes": "research questions and objectives" as well as the "results and contributions" of each article. The reading and analysis of these dimensions made it possible to classify each of the 80 articles into one of the categories identified through the bibliometric analysis (Appendix B), to be read afterwards and used in feeding the results. The 863 publications identified in the first step were transferred as bibliographic data to the VOSviewer software. This made it possible to build a network of keywords linked by co-occurrences (Figure 3). The distance between the different keywords represents the degree of closeness or distance between the selected publications. In our network, the keywords identified are mainly Living Labs, Sustainability, Makerspaces, Fab Labs, Smart Cities, Circular Economy, Urban Living Labs, Innovation, Education and Co-Creation, which we represent in a decreasing way according to the size of their nodes. The color of each node in the diagram (Figure 3) refers to its evolution over time. Between 2015 and the end of 2016, we observe a growing interest of researchers in the concept of the living lab and its link with the notion of sustainability (between dark blue and light green). An interesting trend linking living lab, sustainability and work on smart cities, innovation and co-creation can be noticed during this same period. More recently, researchers are increasingly focusing on the notions of makerspaces, circular economy, and urban living labs (between very light green and yellow). The main purpose of these observations is to describe the evolution of the interest in the different notions that make up our network of co-occurrences. In the next steps of our analysis, we take a closer look at their articulations.

Analysis of keywords co-occurrences network

From the analysis of the 863 publications, 15 clusters were identified (table 4: 1 st and 2 nd columns). Each cluster is composed of several keywords linked to each other but also to other clusters. This bibliometric analysis represented by the clusters provides a global view of the links between the different themes of the publications. At this stage, in the majority of clusters, keywords referring to sustainability and/or composing the search equation "circular economy" appear (see these keywords in bold in table 4, columns 2). However, the co-occurrence network is complex and does not facilitate a clear identification of the relations and boundaries between clusters. The complexity of our network can be explained by the use of two search equations (IS and CE) each with a group of keywords. The tool proves to be more effective when only one equation is used. We have thus chosen to mobilize the associated In parallel, the qualitative scanning of the titles and abstracts (consulted when the title did not clearly identify the research issue of the article) of the 863 showed that all the publications (863) that helped build the network did not directly address the link between the two research equations. This reading has also helped to reinforce the 5 categories identified from the cluster table.

The process of bibliometric analysis revealed in particular the limitation of the bibliometric tool/analysis to provide an in-depth answer to our research question. This analysis, based solely on co-occurrence, provides automated results that are insufficient to draw lessons concerning specifically the objective of this research, a qualitative analysis then seems necessary. However, this step played an important role in the understanding of the major themes addressed in the literature and the identification of categories that allowed for easy coding and qualitative analysis of the selected articles.

The qualitative content analysis was important for confirming the adequacy of the categories identified based on the bibliometric study with the content of the analyzed publications. But it also made it possible to: 1) change one of the 5 categories "Innovation spaces as accelerators of innovation and Sustainable Transition" to "living labs & knowledge transfer for circular solutions" which proved to be more adapted to certain publications; 2) highlight a new category that was not identified, which we formulated as follows: IS for sustainable entrepreneurship development. A large part of the literature considers that the living lab approach when developed at the university level, can play an important role in the transition towards more sustainable development. IS (in particular living labs) are defined here as university campuses adopting this approach [START_REF] Cianfrani | Center As A Living Laboratory : Connecting Campus Sustainability Goals With The Educational Mission At Hampshire College, Amherst, Ma[END_REF][START_REF] Cooper | A Holistic Approach to Embedding Social Responsibility and Sustainability in a University-Fostering Collaboration Between Researchers, Students and Operations[END_REF][START_REF] Favaloro | Mind the Gap ! Developing the Campus as a Living Lab for Student Experiential Learning in Sustainability[END_REF][START_REF] Filho | Universities as Living Labs for Sustainable Development : Supporting the Implementation of the Sustainable Development Goals[END_REF][START_REF] Hansen | The Campus as a Living Laboratory : Macalester College Case Study[END_REF][START_REF] Hua | Sustainable campus as a living laboratory for climate change mitigation and adaptation : The role of design thinking processes[END_REF][START_REF] Hugo | Delta Project : Towards a Sustainable Campus[END_REF][START_REF] Jernsand | Student living labs as innovation arenas for sustainable tourism[END_REF][START_REF] Kılkış | Comparative analyses of sustainable campuses as living laboratories for managing environmental quality[END_REF][START_REF] Lindstrom | Campus as a Living Laboratory for Sustainability: The Chemistry Connection[END_REF][START_REF] Pantaleão | Sustainable Campus in Brazilian Scenario : Case Study of the Federal University of Lavras[END_REF][START_REF] Sulkowski | University experiential learning partnerships as living laboratories for sustainability[END_REF]. When university campuses are transformed into living labs (which some authors call "student living labs") [START_REF] Cooper | A Holistic Approach to Embedding Social Responsibility and Sustainability in a University-Fostering Collaboration Between Researchers, Students and Operations[END_REF][START_REF] Jernsand | Student living labs as innovation arenas for sustainable tourism[END_REF], they become supportive environments for experimental learning in real-life situations. Experimentation would allow students to become experts in the technical and cognitive processes that are required in sustainability projects. These academic living labs allow students to exchange and reflect on complex and sensitive issues, but also to identify opportunities for action and solve real problems through collaborative projects that materially contribute to the sustainability. Students engage with experienced partners (faculty, staff, former students...) on sustainability issues in a transdisciplinary way. This, facilitate the collaboration between different stakeholders within the university (academics, operations and students), and strengthens the sense of commitment to sustainability goals within a learning community [START_REF] Buralli | MOVING TOWARDS THE SUSTAINABLE DEVELOPMENT GOALS : THE UNLEASH INNOVATION LAB EXPERIENCE[END_REF][START_REF] Cooper | A Holistic Approach to Embedding Social Responsibility and Sustainability in a University-Fostering Collaboration Between Researchers, Students and Operations[END_REF][START_REF] Sulkowski | University experiential learning partnerships as living laboratories for sustainability[END_REF]. Through the living labs, the university also open-up to the general public by integrating citizens into educational projects. But also, other territorial actors such as local authorities, business communities, companies, around urban projects focused on sustainability actions. This allows a wide dissemination of knowledge and innovation in the context of education for sustainable development [START_REF] Zen | University Living Learning Labs: an Integrative and Transformative Approach[END_REF]. Some authors emphasize the importance of pedagogy in supporting this type of experiential learning. It plays a key role in teaching sustainability concepts, practices and policies [START_REF] Lusk | From polyps to politics: Using a coral reef living laboratory in a politics of sustainability course[END_REF]. [START_REF] Bürgener | Sustainability competencies in teacher education : Making teacher education count in everyday school practice[END_REF] underline that this depends on the teachers 'commitment and competencies.

Category 2: co-creation, participatory design & real-life experimentations for circular solutions

The publication trends in this category focus on the approaches and practices developed in IS by involving the users. The potential for transformation of living labs in terms of sustainability is often linked to the user participation and their role in changing behavior towards environmental issues [START_REF] Liedtke | LIVING LAB: User-driven innovation for sustainability[END_REF][START_REF] Menny | Urban Living Labs and the Role of Users in Co-Creation[END_REF]. Some authors have notably studied the impact of these approaches in the transport sector. The design and implementation of a living lab allows the development, testing and demonstration of environmental innovations with the users [START_REF] Haider | Sustainable Transport in Upper Austria : Case Study for Setting up a Living Lab Concept to Accelerate Innovations[END_REF]. Another part of this literature focuses on sustainable domestic technologies and the adoption and appropriation of these solutions by users in their daily lives [START_REF] Keyson | Living Labs[END_REF][START_REF] Liedtke | LIVING LAB: User-driven innovation for sustainability[END_REF][START_REF] Romero Herrera | The Emergence of Living Lab Methods[END_REF]. The authors approach co-creation spaces as a socio-technical infrastructure to support user-centered innovation processes by fostering collaboration and exchange with professionals.

The authors also consider that users play an active role in the generation and application of contextualized practice-based knowledge in the innovation process. In this sense, the research and experimentations carried out in these co-creation environments can conduce to: market innovations by producing breakthroughs in sustainable household technologies that will be easy to install, user-friendly and meet real-life environmental performance standards, and to the practice of innovation by paving the way for new forms of contextual and user-centered research.

In this category the publications do not only deal with living lab approaches but also on physical cocreation spaces including Fab Labs and makerspaces [START_REF] Fleischmann | Making things in Fab Labs : A case study on sustainability and co-creation[END_REF][START_REF] Jurietti | How do virtual corporate social responsibility dialogs generate value? A case study of The Unilever Sustainable Living Lab: Virtual CSR dialogs: a case study of USLL[END_REF][START_REF] Kohtala | Making "Making" Critical : How Sustainability is Constituted in Fab Lab Ideology[END_REF][START_REF] Prendeville | Circular Makerspaces : The founder's view[END_REF][START_REF] Sugiyama | Elements to organize the third place that promotes sustainable relationships in service businesses[END_REF][START_REF] Thompson | Exploring the Nature of Third Places and Local Social Ties in High-Density Areas: The Case of a Large Mixed-Use Complex[END_REF][START_REF] Von Geibler | The SDG-Check: Guiding Open Innovation towards Sustainable Development Goals[END_REF]. They study their impact on changing user behavior and especially the opportunities offered by this type of space and the means they offer in the development of circular solutions, practices and technologies. These manufacturing spaces (open-access design and manufacturing workshops) provide new contexts notably for sustainable co-design. Digital Manufacturing Labs (such as fab labs) provide open access to technologies for producing objects from the initial idea to final production. Fab Labs encourage the open and free sharing of knowledge between "experts" and the general public. Their functioning is based on community-based digital fabrication workshops that transform design, innovation, production and consumption practices, while describing positive environmental impacts and social goals [START_REF] Crumpton | Fines, fees and funding : Makerspaces standing apart[END_REF][START_REF] Kallio-Tavin | If Fab Lab is the Answer, What is the Question? : Maker Culture as a Method for a Sustainable Future[END_REF]. They are also spaces that provide practical guidance for interweaving circular practices by fostering a supportive culture, creating local links, nurturing individuals/community capacity and stimulating practical know-how. In this framework, the role of the facilitators of these spaces is also explored.

Facilitators have the knowledge and skills that contribute to the development of circular economy practices. They are recognized as initiators of circular practices.

Category 3: Urban living labs & development of sustainable smart cities

For some authors, Urban Living Labs (ULL) are physical and virtual spaces aiming at the co-creation of eco-innovative solutions and strategies for urban areas. It is a new approach to open innovation linking technologies to people, urban territory, and cities [START_REF] Bulkeley | Urban living labs : Governing urban sustainability transitions[END_REF][START_REF] Bulkeley | Urban living laboratories : Conducting the experimental city?[END_REF][START_REF] Evans | Circulating experiments : Urban living labs and the politics of sustainability[END_REF][START_REF] Mai | Placing Sustainability in Communities: Emerging urban living labs in China[END_REF][START_REF] Paskaleva | The smart city : A nexus for open innovation? Intelligent Buildings International[END_REF][START_REF] Sharp | Direct Impacts of an Urban Living Lab from the Participants' Perspective : Livewell Yarra[END_REF][START_REF] Tremblay | Coworking Spaces : New Places for Business Initiatives[END_REF][START_REF] Van Geenhuizen | Applying an RRI Filter in Key Learning on Urban Living Labs' Performance[END_REF]. It is about using open innovation to share visions, knowledge, skills, experiences, and strategies to design the delivery of sustainable services, goods and policies in cities. [START_REF] Amenta | Managing the Transition towards Circular Metabolism : Living Labs as a Co-Creation Approach[END_REF] have identified five key characteristics of ULLs that explain their role in sustainable urban development: geographical anchoring, experimentation and learning, user involvement, leadership and ownership, evaluation, and improvement. According to this author, in ULLs, public-private-personnel partnerships are developed by applying an iterative methodology comprising five phases: co-exploration, co-design, co-production, co-decision, and co-governance. Urban Living Laboratories can thus be considered both as a physical space (geographically or institutionally delimited spaces) and as an approach for intentional collaborative experimentation between researchers, citizens, businesses, and local governments. This leads to questions of governance. A significant part of the literature addresses the issue of experimental governance that is facilitated and reinforced in ULLs. It promotes collaboration and innovative Public-Private Partnerships (PPPs) for more sustainable urban transformation [START_REF] Bulkeley | Urban living labs : Governing urban sustainability transitions[END_REF][START_REF] Dupont | Innovative public-private partnership to support Smart City : The case of "Chaire REVES[END_REF][START_REF] Evans | Living laboratories for sustainability : Exploring the politics and epistemology of urban transition[END_REF][START_REF] Sharp | Direct Impacts of an Urban Living Lab from the Participants' Perspective : Livewell Yarra[END_REF][START_REF] Voytenko | Urban living labs for sustainability and low carbon cities in Europe: Towards a research agenda[END_REF]. Through a user-centered design, collaborative processes, citizen workshops and new financial and organizational responses enabling collaboration between private companies and public institutions. In parallel, some authors highlight the role of public/institutional actors in this experimental governance process in terms of sustainability. They play the role of facilitators through a set of enabling policies and policy instruments aimed at overcoming the challenges of sustainability [START_REF] Buhr | Urban Living Labs for Sustainability in Suburbs in Need of Modernization and Social Uplift[END_REF][START_REF] Mukhtar-Landgren | Municipalities as enablers in urban experimentation[END_REF].

The living lab tools and methodologies promote urban experimentation, a practice that is becoming increasingly important in cities and territories. Experimentation allow to find new and more sustainable ways of planning and developing cities. The literature emphasizes the role of urban experimentation in integrating environmental concerns into development plans. It is a process by which city-based innovations are launched to test solutions that, if found to be effective, are intended to be scaled up with the ambition of leveraging a broader transition to urban sustainability [START_REF] Bulkeley | Urban living laboratories : Conducting the experimental city?[END_REF][START_REF] Evans | Circulating experiments : Urban living labs and the politics of sustainability[END_REF][START_REF] Mukhtar-Landgren | Municipalities as enablers in urban experimentation[END_REF][START_REF] Von Wirth | Impacts of urban living labs on sustainability transitions: Mechanisms and strategies for systemic change through experimentation[END_REF].

Cities become smart and sustainable when they provide intelligent services to citizens using information and communication technologies while considering environmental, economic and societal challenges [START_REF] Alam | and Designing Sustainable Smart City Services in a Living Lab Environment[END_REF]. Involving citizens in this process of transition to the smart sustainable city makes it possible to develop adapted smart services, disseminate them and put them into practice [START_REF] Palgan | Urban Living Labs : Catalysing Low Carbon and Sustainable Cities in Europe?[END_REF]. ULLs enable the demonstration of smart technologies, particularly in the information and communication technologies (ICT) and energy sectors. These technological demonstrators enable a real application of the smart city concept to the population and external actors while considering environmental aspects [START_REF] Alam | and Designing Sustainable Smart City Services in a Living Lab Environment[END_REF][START_REF] Bracco | Planning & Open-Air Demonstrating Smart City Sustainable Districts[END_REF]. The co-creation of innovative technologies in ULLs helps to reduce resource consumption and emissions from urban systems.

Category 4: IS for sustainable business model development

On the one hand, publications in this category study the impact of coworking practices on the development of innovation, in particular business model innovation for sustainable performance. Empirical analyses carried out on companies working within coworking spaces show a positive impact on their business model innovation due to the creativity capacities they can strengthen [START_REF] Cheah | Coworking and Sustainable Business Model Innovation in Young Firms[END_REF].

On the other hand, some authors address the issue of sustainable product and service systems (SPSS), the latter being an innovative form of business models. They highlight the importance of sustainable living labs for the implementation and dissemination of sustainable resource-efficient product and service systems in the context of a green economy [START_REF] Baedeker | Green Economy as a Framework for Product-Service Systems Development : The Role of Sustainable Living Labs[END_REF]. Indeed, these living labs contribute to the evolution of production-consumption systems towards sustainability by modifying processes and SPSS on a microeconomic scale. In the same vein, the Sustainable Living Lab (SLL) focuses on sustainability innovations and offers a number of new features reflecting the areas of intervention [START_REF] Burbridge | Business Models for Sustainability in Living Labs[END_REF]. For the authors, the SLL approach offers a basic research infrastructure for sustainability, in which the relevant actors are actively involved in the development, design and testing of new SPSSs aimed at the transition to circular and sustainable development.

Category 5: IS for sustainable entrepreneurship development

In this category, the authors study the contribution of living labs and coworking spaces to the promotion of urban entrepreneurship in cities and their sustainability [START_REF] Rodrigues | Importance of living labs in urban Entrepreneurship:A Portuguese case study[END_REF][START_REF] Seo | Priorities of Coworking Space Operation Based on Comparison of the Hosts and Users' Perspectives[END_REF]. Through qualitative analyses, they show that living labs are the "cradle" of this type of entrepreneurship allowing economic, social and environmental development. Three characteristics of these spaces have been detected as enabling the dynamism of sustainable urban entrepreneurship: the open network, the entrepreneurial spirit and the benefits/results of the living labs (creation of activities/jobs and generation of new local economic dynamics) [START_REF] Rodrigues | Importance of living labs in urban Entrepreneurship:A Portuguese case study[END_REF]. These findings are supported by the results of another publication showing that community and communication are the most important factors within the coworking spaces, followed by space and interior (infrastructure, technical and technological means), diversity of services and the facilitation of relationships and networking for the users [START_REF] Seo | Priorities of Coworking Space Operation Based on Comparison of the Hosts and Users' Perspectives[END_REF].

Category 6: Living labs & knowledge transfer for circular solutions

Living labs are represented in the publications identified in this category as open innovation systems that promote different knowledge transfers between the involved local actors, thus providing solutions for the development of innovation. However, beyond the knowledge created and disseminated by living labs at the local level, some authors focus on the transfer of knowledge at the regional level (between regions) via living labs (strengthening extraterritorial networks). Extraterritorial learning can be an asset for the development of knowledge, the emergence of innovation and diversification at the local level. It can strengthen and improve the sustainability strategies and policies implemented by regions and cities. Such a transfer can lead to sub-optimal solutions, especially when the imported practices concern complex phenomena, involving networks of multiple actors and relying on place-specific dynamics [START_REF] Schuurman | Living Labs as open innovation systems for knowledge exchange : Solutions for sustainable innovation development[END_REF]. In this context, some authors highlight the role of living labs in facilitating this transfer of knowledge, particularly in the field of the circular economy and environmental phenomena [START_REF] Amenta | Managing the Transition towards Circular Metabolism : Living Labs as a Co-Creation Approach[END_REF]. Based on the study of two metropolitan regions of (Amsterdam and Naples) the authors focus on the role of networks of peri-urban living labs in the emergence of ecoinnovative solutions supporting the valorization of wastes. They study how the process of co-creation of knowledge in the relational space of networked living labs takes place through the participation of stakeholders from the two regions and identify the barriers of this process.

Discussion: How IS enable the transition towards a CE? 4.1. The potential of IS for eco-innovation, sustainability and CE

Based on our literature review we were able to identify links between ISs, eco-innovation, sustainability and CE. From each category of publication trends, we have identified a categorization of these spaces and the features that allow them to generate certain types of eco-innovation, even though generally the term eco-innovation is replaced by "innovation", "environmental innovation" or "sustainable technology", etc. (see table 5). We were also able to point out that ISs can have an impact in: fostering the development of new forms of sustainable experiential learning (category 1); providing methodologies and tools for the co-creation of circular solutions while favoring users behavior change (category 2), driving the transition towards sustainable smart cities (category 3), fostering the creation of new sustainable business models (category 4), promoting sustainable entrepreneurship (category 5) and facilitating knowledge exchange on circular solutions (category 6).

IS for the CE strategies implementation

Despite the growing interest in the relationship between IS and CE, it has been observed that most of such literature has focused specifically on sustainability and circular solutions, rather than the concept of CE per se. Moreover, no publication brings a general view on the involvement of these different environments in the CE, but they are studied separately. Nevertheless, the mobilization of the results of this literature review provides several insights on the benefits of IS in the implementation of CE strategies. Thus, we will draw, on the one hand, on the characteristics and impacts of ISs highlighted in the results of this research and (table 5), the other hand, on the CE strategies identified in section 1 as well as the lessons drawn from the literature on technological and non-technological changes and eco-innovations necessary for the implementation of these strategies (figure 1). The objective is to discuss and propose a link between each type of IS and its potential impact on the development of new solutions or eco-innovations that can intervene in the implementation of the CE, enabling to overcome its limitations. Based on this discussion, we will propose a categorization of IS according to the needs and characteristics of each CE strategy, which we will summarize at the end in the Table 6.

Strategies of Waste Management and Flow Recovery

Some types of IS can facilitate the implementation of recovery and recycling strategies. Indeed, the reintegration of material and energy flows into production processes is not always simple, and obstacles, particularly technical ones, such as the complexity of the flows and their technical characteristics can hinder it. These are university campus living labs and fab labs. University campus living labs can offer technical learning and training in the field of waste management to train experts in technical processes (technicians, engineers, etc.) and specific skills relating to processes, residual materials and the different ways of recovering flows [START_REF] Laperche | Ecologie industrielle et développement territorial durable le rôle des services[END_REF]. These environments can thus be conducive to the development of innovative learning methodologies and know-how to reduce the problems related to the valorization of material flows. The fab labs are offering freely accessible means, machines and manufacturing technologies. They can foster the creation of new technologies, test new processes and manufacture new eco-innovative products from waste streams. we can mention the example of additive manufacturing of recycled plastics (3D plastic printers) (Santander et al., 2020). Fab labs can thus be enabling environments for technological eco-innovations that provide solutions to recycling problems.

Sustainable Use and Manufacturing Strategies

These strategies aim to increase the efficiency of manufacturing or product use by using fewer natural resources and materials. The sustainable purchasing practices and eco-design that are part of this strategy concern the product and its supply chain as well as the stakeholders involved in all stages of production from manufacturing, to transport, consumption and end of life of the products (ADEME, 2013). Based on the results of our literature review, it is possible to see that living labs and fab labs are environments that can be involved in these strategies. Indeed, living labs bring together different stakeholders in collaborative experimentation approaches by mobilizing co-exploration, co-design and co-production methodologies. These stakeholders can be members of a supply chain. These innovative methodologies can reduce the organizational and coordination problems linked to the production of an eco-product. But they can also encourage the development of sustainable purchasing practices, in particular by strengthening short supply chains at the local level [START_REF] Gallaud | Circular economy, industrial ecology and short supply chains[END_REF][START_REF] Torre | L'économie territoriale circulaire : Un pas vers la soutenabilité des territoires[END_REF].

For their part, the fab labs can serve as a space for demonstrating and testing new eco-design technological solutions. They act as facilitators in the exchange of knowledge and skills related to circular technologies. These technological innovations can thus respond to the technical problems of eco-design but also by offering alternative solutions to reduce the economic costs faced by companies and in particular smaller companies [START_REF] Gallaud | Circular economy, industrial ecology and short supply chains[END_REF].

Sustainable Use and Consumption Strategy

In the reviewed literature, urban living labs are defined as a means of transition to smart and sustainable cities. Citizens and users are at the center of their functioning. They are integrated in collaborative experiments bringing together different actors around intelligent and sustainable urban planning projects. This involvement of citizens allows, on the one hand, to raise their awareness and bring about changes in their behavior with regard to environmental issues by encouraging them to adopt circular practices such as sorting, recycling and responsible consumption. On the other hand, their integration in the transition processes towards the intelligent sustainable city makes it possible to successfully develop sustainable intelligent services, to disseminate them and to facilitate their use by citizens. The integration of citizens in university campus living labs in educational projects around sustainability issues, such as responsible consumption and reuse practices, can also influence their behavior through experimental learning and knowledge acquisition. Fab labs and makerspaces can also have positive impacts on the consumer/user behavior by encouraging them to promote practices that repair and extend the life of products. They give them access to workshops with open manufacturing tools and allow them to participate in the creation of new objects from recycled products or to repair their objects/products. This is for example the case of shared wood manufacturing workshops encourage users to make or repair products such as recovered wooden furniture. These spaces are not only limited to users and citizens but also to social and solidarity economy actors [START_REF] Torre | L'économie territoriale circulaire : Un pas vers la soutenabilité des territoires[END_REF]. These spaces are therefore sociotechnical infrastructure to support user-centered technological and social innovation processes by promoting collaboration and exchange with professionals. Such innovations help to reduce the environmental impact and social barriers associated with the implementation of the CE. Consequently, urban living labs, university campus living labs, fab labs and makerspaces can enable implementing sustainable use and consumption strategies mainly through the social innovations they generate. These innovations can respond to the social problems of the CE such as the rigidity of consumer behavior.

Sustainable organizational and territorial strategies

These strategies are based on the economy of functionality and industrial ecology approaches that operate on a larger organizational scale [START_REF] Maillefert | Écologie industrielle, économie de la fonctionnalité, entreprises et territoires : Vers de nouveaux modèles productifs et organisationnels ? Développement durable et territoires[END_REF]Merlin-Brogniart, 2017), even integrating other CE approaches or strategies such as waste recovery, recycling, and eco-design.

• Economy of functionality focuses on use rather than possession and tends to sell services related to products rather than the products themselves. The sale of a service replaces the sale of a good and where product-service systems are becoming more widespread. Its implementation requires major organizational transformations. Firms that choose to adopt the economy of functionality face the challenge of identifying the changes induced in their business model [START_REF] Meier | Life Cycle-Based Service Design for Innovative Business Models[END_REF]. They must thus overcome organizational (capacity constraints, inadequacy of available technologies) and economic (costs) limits. To face these limits, two types of IS can potentially intervene: coworking spaces and living labs. Indeed, the creative practices developed in the IS by companies contribute to the development of innovative business models. The same goes for living labs, which promote the implementation and dissemination of sustainable and resource-efficient product and service systems (SPS). These IS thus enabling the development of sustainable and profitable business models. • The industrial ecology strategy can be defined both by an operational dimension that focuses on the practices of the material and energy flow valorization, but also by the managerial, organizational and territorial dimensions linked to the exchanges of these flows (networks of actors forming industrial symbiosis) [START_REF] Kasmi | Écologie industrielle, milieu innovateur et gouvernance territoriale : Le cas de Dunkerque (Nord-France)[END_REF]. Accordingly, its implementation involves not only technical issues but also those related to the coordination of the actors involved and the governance of the related territorial projects. There are several obstacles to its implementation: technical, economic, organizational, regulatory and relational (coordination and governance). Several types of IS can facilitate the implementation of industrial ecology approaches. University campus living labs can offer experimental learning for students or even experimental training for employees (integration of the concept of industrial ecology in training programs). This can reduce the technical problems linked to the company's lack of expertise in the field of valorization. The same applies to the eco-technologies developed in the fab labs and makerspaces. The principle of urban living labs is based on the integration of a heterogeneous set of actors in local projects. This type of environment can be an important asset for the success of industrial ecology projects and the sustainability of industrial symbiosis. Their characteristics (geographical anchoring, experimentation and learning, user involvement, leadership and ownership, evaluation and improvement) and the innovative methodologies they offer can facilitate exchanges and strengthen relations between the actors involved. Experimental governance actions can provide new organizational, financial and regulatory responses/eco-innovations allowing collaboration between private companies and public institutions. These eco-innovations can reduce communication and trust problems that hinder cooperation. Extraterritorial living labs promote different knowledge transfers at regional level (between regions or territories). The exchange of good practices on territorial industrial ecology projects between different territories and extraterritorial actors through living labs can be an asset for its development.

Organizational eco-innovations can emerge, which can favor the creation of industrial networks and symbiosis, but also institutional ones that favor the adoption of new environmental policies that are favorable to the implementation of industrial ecology.

Conclusion

The objective of this research was to understand how the literature studies the contribution of IS in the CE with a particular focus on the eco-innovations that these spaces can generate. The literature review showed that the interest of scholars in this issue is continuously growing. However, compared to the existing number of publications in these two fields, this research dynamic remains insufficient. In addition, these studies are specifically focusing on sustainability rather than the concept of CE and addresses the impact of each space separately. As a consequence, this study introduces a categorization of IS conducive to the CE and identifies the eco-innovations they may induce. From a theoretical point of view other insights have been identified in this research that can be considered as a research agenda proposition to deepen the analysis of this topic:

• Great importance is given to the concept of the living lab in relation to sustainability and CE. However, its definition remains complex (a physical space, a virtual space, a methodology?) which can create confusion in the understanding of its contribution to the CE strategies. Consequently, the other types of IS and their impacts are less studied compared to the living labs.

• The contribution of IS in supporting territories and regions transition towards a systemic development of new sustainable models such as the CE is not directly and sufficiently developed in the publications. Especially the industrial territories that are strongly concerned by sustainability issues and circular strategies. • There is a need for further empirical studies to assess the real impacts of IS on the CE strategies.

From managerial perspective the identified roles and impacts could nourish the IS strategies leading to the exploration and further implementation of more clear strategies for those intending to insert their own lab in the CE dynamics. These potential roles could also help by shedding light on the possible interconnections and collaborations among IS, eventually leading and facilitating the establishing of shorter, more effective local circular cycles. From policy making perspective, the IS phenomenon continues to be spread all over the world, and more and more policy and decision-makers are favoring the implementation of these physical innovation environments. Therefore, the results from this work represent a valuable input for guiding new policies, investments but also clarifying expectations towards the real impact these kinds of initiatives may or may not have in overcoming CE barriers. However promising the IS are, it is important to stay aware of their limitations. The capacity of IS to deal with more systemic challenges is yet to be understood. Nevertheless, the answer to this may rely on the ability of IS to be not only the experimentation and learning arena of a local group of actors, but rather to serve as the interconnectors that enable favorable conditions for territories to work together and exploit complementarities towards more sustainable practices. To understand these limitations more closely and learn from them, this theoretical research will be the object of an empirical investigation. Thus, the next step will consist in analyzing a set of concrete IS cases. A particular interest will be focused on IS linked to universities and their contribution to fostering of CE in the territories while relying on sustainable development models such as the quintuple helix.

Figure 1 -

 1 Figure 1 -Eco-innovation as lever of systemic transition towards a CE

Figure

  Figure 2 -Adopted methodology

Figure 3 -

 3 Figure 3 -Evolution over time of scientific publications on the studied keywords

3. 3 .

 3 Qualitative analysis of publication trends: towards an understanding of the impact of innovation spaces in the development of the circular economyThe obtained results show that most of the reviewed literature integrates into the following categories: Research & Education for sustainable transitions, co-creation, participatory design & real-life experimentations for circular solutions and the Urban Living Labs & Development of Sustainable Smart Cities. These publications represent respectively 37.5%, 27.5% and 26.25% of the total of 80 publications. The remaining publications are included in the sustainable business models (3.75%), sustainable entrepreneurship (2.5%) and living labs & knowledge transfer for circular solutions (2.5%) categories (see Figure5and appendix C). A growing interest from scientific journals in these themes can be observed, 53 publications are articles against 25 book chapters and 2 books.

Figure

  Figure 5 -Trends of the scientific publications

Table 2 -Obstacles to the implementation of the circular economy Types of barriers Description Technical and technological Complexity

 2

of waste flows, insufficient waste separation at source, material degradation, sorting, storage space, unavailable or inappropriate technology, lack of technical support and training

Economic

Cost-benefit ratio, time scale, quantitative limits to cost-effectiveness, uncertain return and profit

Table 3 -Publications selection process Specifications Description Circular economy keywords (research equation 1) Circular

 3

	Innovation Spaces Keywords (Research Equation 2)	Innovation laboratory; innovation lab; innovation space; enabling space; living lab; fablab; fab lab; makerspace; hackerspace; coworking space; third place
	Source	Scopus and Web of Science
	Search fields	Title, Keywords & abstracts
	Data range	All years available to 2019
	Document type	Article, proceedings paper, book, book chapter, book review, review or early access
	Total des publications	863

economy; sustainable development; Refuse; Rethink; Reduce; Reuse; Repair; Refurbish; Remanufacture; Repurpose; Recycle; Recovery; industrial ecology; industrial symbiosis; sustainable/sustainability; ecoindustrial synergies; economy of functionality; closed loop; eco-innovation; environmental innovation; Green energy

  that have similarities in terms of relationships in the network but also in terms of their common themes and scientific domains, in the form of categories or major themes (for example city and smart city or education, open education, action research...). To support this keyword analysis, a few examples of publications have been consulted in order to understand the themes they address. The objective of this step was not to analyze qualitatively the 863 documents, but to support the construction of categories and their descriptions according to publication trends. A first proposal of 5 main categories has been established, which we have at this stage reformulated as follows: Urban Living Labs & Development of Sustainable Smart Cities, Co-creation, participatory design & real-life experimentations for circular solutions, Sustainable business models within innovation spaces, Innovation spaces as accelerators of innovation and Sustainable Transition, Research & Education for Sustainable Transitions (table 4, 3rd column). These categories have been considered at this point as hypotheses on how the literature brings our two concepts (IS and CE) closer together, which needs to be confirmed by qualitative analysis.

table generated by the software (table 4: 1st and 2nd columns). The qualitative scan of this table allowed us to make a comparison between clusters

Table 4 -Categories of publication trends

 4

	Clusters	Keywords

co-design; crowdsourcing; energy transition; older adults; rural development; social inclusion Business model boundary objects; co-production; collaborative innovation; community of practice; competencies; eco-innovation; social learning; sustainable; transdisciplinary

Table 5 -The IS features in favor of sustainability, eco-innovation and CE Publication trends categories IS types IS role from the literature review Types of eco- innovation

 5

	Examples	Synthesis of
	of	IS
	references	contributions

Table 6 -The role of IS in the implementation of the CE strategies

 6

	CE strategies	CE practices	Type of IS	Type of impact and potential eco-innovation	CE Limitations
	Strategies of waste	Recycle and	University labs campus living	creation Experimental learning and knowledge	Technical limitations
	management and flow recovery	recovery	Fab labs Makerspaces	3D printing of recycled plastic) Product and process innovations (e.g.	Technical limitations
	Sustainable use and manufacturing strategies	Sustainable supply and Eco-design	Living labs Fab labs Makerspaces	Organizational innovations favoring collaborative experimentation Co-creation, demonstration, and test of technological eco-design	Organizational limitations Technical and economic limitations
				innovations
			Urban living labs	Collaborative experiments and	Social limitations
	Sustainable use and consumption strategy	Sustainable/ responsible consumption and Extend lifespan of products	Campus living labs Fab labs Makerspaces	sustainable intelligent services inducing social innovations experiential learning and knowledge acquisition Technological tools for creation and reparation of products	(behavior change) Social limitations Technical and economic limitations
		Economy of functionality	Living lab and coworking spaces	Business model innovation (sustainable product-service systems)	Organizational and economic limitations
	Sustainable		Campus living labs	Experimental learning and knowledge creation	Technical and economic
	organizational and territorial strategies	Industrial ecology	Fab labs and makerspaces Urban living labs	Product and process innovations (e.g. 3D printing of recycled plastic) Organizational eco-innovtions (experimental governance actions)	Technical and economic Organizational/institut ional limitations
			Extraterritorial living labs	knowledge transfers at regional level	Organizational/institut ional limitations

Acknowledgments:

This study was supported by the INEDIT European Union's H2020 research program -Agreement N° 869952.


F Joud

F Laloë

M Atlan

J Hare

M Gross
email: gross@lkb.ens.fr

Imaging a vibrating object by Sideband Digital Holography

Keywords:

We obtain quantitative measurements of the oscillation amplitude of vibrating objects by using sideband digital holography. The frequency sidebands on the light scattered by the object, shifted by n times the vibration frequency, are selectively detected by heterodyne holography, and images of the object are calculated for different orders n. Orders up to n = 120 have been observed, allowing the measurement of amplitudes of oscillation that are significantly larger than the optical wavelength. Using the positions of the zeros of intensity for each value of n, we reconstruct the shape of vibration the object.

Holographic imaging is based on interferences between a signal optical field and a reference beam; it provides an accurate method to image the vibration of various objects. Powell and Stetson [START_REF] Powell | Interferometric vibration analysis by wavefront reconstruction[END_REF] have shown that the time-averaged hologram of an harmonically vibrating object involves the Bessel function J 0 (z), where z is the phase modulation amplitude. In the backscattering geometry, z = 4πA/λ where A is the mechanical amplitude of vibration and λ the optical wavelength. Image reconstruction then provides a direct mapping of the amplitude A at various points of the object, in the form of dark fringes appearing around points where J 0 (z) is zero.

Picard et al. [START_REF] Picart | Time-averaged digital holography[END_REF] have simplified the processing of the data by performing Time Averaged Digital Holography (TADH) with a CCD camera, leading to numerous recent developments [START_REF] Zhang | Vibration Analysis by Phase Shifting Digital Holography[END_REF][START_REF] Asundi | Time-averaged in-line digital holographic interferometry for vibration analysis[END_REF][START_REF] Singh | Dynamic characterization of MEMS diaphragm using time averaged in-line digital holography[END_REF][START_REF] Demoli | Detection of hidden stationary deformations of vibrating surfaces by use of time-averaged digital holographic interferometry[END_REF][START_REF] Demoli | Real-time monitoring of vibration fringe patterns by optical reconstruction of digital holograms: mode beating detection[END_REF]. Nevertheless, the quantitative measurement of vibration amplitudes remains limited to situations where fringes can be counted, which implies that the amplitudes of vibration must be relatively small; otherwise, it becomes difficult to count many narrow fringes, and even impossible when they are smaller than the optical resolution.

In this letter, we show how Sideband Digital Holography (SDH) can overcome the problem. Sideband holography was already demonstrated in 1971 by C.C. Aleksoff, in a pioneering experiment [START_REF] Aleksoff | Temporally modulated holography[END_REF] where the reference beam was frequency-shifted by an ultrasonic diffraction cell; selecting a given frequency resulted in a selection of a given sideband of the signal backscattered by the object. The experiment was done with holographic plates. Here, we use digital heterodyne holography [START_REF] Leclerc | Numerical Heterodyne Holography Using 2D Photo-Detector Arrays[END_REF]; both reference and illumination laser beams are frequency shifted, and the selection of one sideband is obtained by a proper detuning of one of the beams followed by heterodyne detection on a CCD camera; this technique provides much more flexibility and leads to accurate quantitative measurements. As a demonstration, inspired by the work described in [START_REF] Pinard | Musical quality assessment of clarinet reeds using optical holography[END_REF][START_REF] Facchinetti | Numerical and experimental modal analysis of the reed and pipe of a clarinet[END_REF] we perform an experiment where the vibrating object is the reed of a clarinet; in addition to the intrinsic interest of such an object, with its possible musical implications, a reed provides a test system that is particularly well adapted to our purposes, with typical vibration amplitudes of the order of 0.1 mm. We will see that, even with smaller amplitudes, there is no difficulty in obtaining holographic images corresponding to the n th sideband with n up to 100 or more. The experimental setup is schematically shown in Fig. 1. A laser beam, with wavelength λ ≃ 650 nm (angular frequency ω L ) is split into a local oscillator beam (E LO ) and an illumi- nation beam (E I ); their angular frequencies ω LO and ω I are tuned by using two acousto-optic modulators (Bragg cells with a selection of the first order diffraction beam) AOM1 and AOM2: ω LO = ω L + ω AOM1 and ω I = ω L + ω AOM2 where ω AOM1,2 /2π ≃ 80 MHz. The clarinet reed is attached to a clarinet mouthpiece and its vibration is driven by a sound wave propagating inside the mouthpiece, as in playing conditions, but in our experiment the sound wave is created by a loudspeaker excited at frequency ω A and has a lower intensity than inside a clarinet; no attempt has been made to reproduce the mechanical effect of the lip of the player. The excitation frequency is adjusted to be resonant with the first flexion mode (2143 Hz) of the reed. The phase of the field E backscattered by any element of the reed is then phase modulated at frequency ω A , so that E can be expanded into carrier (E 0 ) and sideband components (E n ) as:

E(t) = E e jω I t e jz sin(ω A t) = ∞ ∑ n=-∞ E n (t) (1)
E n (t) = E J n (z)e jω L t e j(ω AOM2 +nω A )t ( 2
)
where E is the complex field of the object in the absence of modulation, z = 4πA/λ is the phase modulation amplitude, A the amplitude of vibration of the particular element, and J n is the n-th order Bessel function of the first kind (with J -n (z) = (-1) n J n (z) for integer n and real z).

To selectively detect the n th sideband we use 4 phase shifting holography [START_REF] Yamaguchi | Phase-Shifting digital holography[END_REF] and adjust the frequency ω AOM1 to fulfil the condition:

ω AOM2 -ω AOM1 -n ω A = ω CCD /4 (3)
where ω CCD is the CCD camera frame frequency and n is a (positive or negative) integer; the phase of the modulated signal is then shifted by 90 • from one CCD image to the next [START_REF] Atlan | Accurate phase-shifting digital interferometry[END_REF]. The sideband complex hologram signal H n provided by each pixel of the camera, proportional to the local sideband complex field, is obtained by 4-phase demodulation:

H n = (I 0 -I 2 ) + j(I 1 -I 3 ) , (4)
where I 0 , • • • I 3 are 4 consecutive intensity images digitally recorded by the CCD camera (Pike: Allied vision Technology Inc, 12 bits, ω CCD /2π = 10 Hz, exposure time 100 ms, 1340 × 1024 pixels). The LO beam is slightly angularly shifted (∼ 1 • ) with respect to the beam originating from the reed; in this way, the zero order and twin-image aliases [START_REF] Cuche | spatial filtering for zero-order and twinimage elimination in digital off-axis holography[END_REF] can be suppressed and an ultimate detection sensitivity can be reached [START_REF] Gross | Digital holography with ultimate sensitivity[END_REF][START_REF] Gross | Noise and aliases in off-axis and phase-shifting holography[END_REF]. From the complex holograms, the images of the reed are reconstructed by the standard convolution method [START_REF] Schnars | Direct recording of holograms by a CCD target and numerical reconstruction[END_REF]. To simplify the Fourier transform calculation, the 1340 × 1024 pixels data are truncated to 1024 × 1024. Because of the angular shift, the image of the reed lies in the upper side of the reconstruction grid. In figure 2, for pixels ranging from 200 to 1023 along the x axis and 0 to 511 on the y axis, we show the reconstructed images for different sideband orders n; only the square modulus of the complex signal is retained (the phase coming from E is ignored), so that we obtain intensity images, proportional to |E n | 2 for each different sideband.

Figure 2(a) is obtained at the unshifted carrier frequency (n = 0). The left side of the reed is attached to the mouthpiece, and the amplitude of vibration is larger at the tip of the reed on the right side; in this region the fringes become closer and closer and difficult to count. The mouthpiece is also visible, but without fringes since it does not vibrate. Similar images of clarinet reeds have been obtained in [START_REF] Pinard | Musical quality assessment of clarinet reeds using optical holography[END_REF][START_REF] Facchinetti | Numerical and experimental modal analysis of the reed and pipe of a clarinet[END_REF], with more conventional techniques and lower image quality. Figures 2(b)-2(d) show images obtained for three sideband frequencies. As expected, the non-vibrating mouthpiece is no longer visible. Figure 2(b) shows the n = 1 sideband image, with J 1 fringes that are slightly shifted with respect to those of J 0 . Figure 2(c) shows the order n = 10 and (d) the order n = 100 (e). The left side region of the image remains dark because, in that region, the vibration amplitude is not sufficient to generate these sidebands, J n (z) being evanescent for z < n.

We have performed cuts of the reconstructed images signal |E n (x, y| 2 obtained for different sideband orders n along the horizontal line y = 174 (this value has been chosen because it corresponds to a region where the fringes are orthogonal to the y axis). To reduce the effect of speckle fluctuations, the intensity signal example of the normalized signals |E n | 2 /|E| 2 along the cut is shown for n = 5, in the lower part of Fig. 3, with a downwards intensity axis. In this case, and for many other values of n, we have checked that the normalized curves vary as the square of Bessel functions, with a first fringe that moves to higher values when n increases (it occurs when z ≃ n and the amplitude of vibrations increases with x). For instance, for n = 0, which corresponds to standard TADH, the variations of |J 0 (z)| 2 show a large number of nodes and anti-nodes, with decreasing visibility for increasing x; above x = 700, the fringes are no longer visible. For n = 20, the first fringe, which corresponds to z ≃ n = 20, is located near x ≃ 560. Going to n = 60 pushes the first fringe to x ≃ 755, where the counting of fringes with TADH would no longer be possible. In a more general way, the first fringe on the n th sideband image provides a convenient marker for the region z ≃ n.

For a more precise treatment of the data, we use the position of the antinodes, which is insensitive to inhomogeneities of illumination; no normalization is then required. To build the central part of Fig. 3, a similar linear cut at y = 174 is processed, for the values n = 0, 1, 5, 10, . . .100. The x locations of the successive minima of the signal |E n (x)| 2 are plotted against the zeros of the corresponding |J n (z)| 2 . To illustrate the way the points are obtained, we show in the left part of the Fig. 3 the expected signal |J 5 (z)| 2 , to be compared to the signal in the lower part. For all observed sideband order n ranging from 0 to 100, all the points displayed on Fig. 3 fall on a well defined curve, which provides the vibration amplitude z as function of the location x. The excellent consistency of the overlapping data sets demonstrates the validity of expansions Eq. 1 for any order n. Therefore the figure provides a direct and accurate visualization of the map of the maximal elongations of the reed, from the left part clamped on the mouthpiece to the tip on the right; here, the maximum amplitude is z ≃ 120 radians, corresponding to A ≃ 6.2 µm.

To conclude, recording separately different sideband Fourier components of the light backscattered by a vibrating object gives access to a large amount of information; this can be used to remove ambiguities and inaccuracies in measurements of large modulation amplitude. Using large sideband order n actually makes the calibration of the vibration amplitude z straightforward: the first fringe of a high order image can be used as a marker. This marker is easy to locate since it corresponds to a fast transition from zero signal, and moreover is brighter and broader. Performing sideband holography with many orders n gives a direct and accurate access to the shape of the vibration amplitude and its position dependence. Figure 3 shows only a representation of a slice of the data along one given axis, but more information is available if one changes the value of y or chooses another direction, for instance parallel to y to accurately map the transverse variations of the amplitude A. Sideband digital holography therefore opens up a variety of new possibilities in holography.

The authors acknowledge the support of French National Research Agency (ANR-05-NANO-031) and the "Centre de compétence NanoSciences Île de France" (C'nano IdF).

Fig. 1 .

 1 Fig. 1. Setup. L: main laser; AOM1, AOM2: acousto-optic modulators; M: mirror; BS: beam splitter; BE: beam expander; CCD: CCD camera; LS: loud-speaker exiting the clarinet reed at frequency ω A /2π.

Fig. 2 .

 2 Fig. 2. Reconstructed holographic images of a clarinet reed vibrating at frequency ω A /2π = 2143 Hz perpendicularly to the plane of the figure.Figure (a) shows the carrier image obtained for n = 0; Fig. (b)-(d) show the frequency sideband images respectively for n = 1, n = 10, and n = 100. A logarithmic grey scale has been used.

  Fig. 2. Reconstructed holographic images of a clarinet reed vibrating at frequency ω A /2π = 2143 Hz perpendicularly to the plane of the figure.Figure (a) shows the carrier image obtained for n = 0; Fig. (b)-(d) show the frequency sideband images respectively for n = 1, n = 10, and n = 100. A logarithmic grey scale has been used.

2 |E 5 2 Fig. 3 .

 2523 Fig. 3. A slice of the data along the y = 174 line is used in this figure; the x horizontal axis gives the pixel index (100 pixels correspond to 3.68 mm.), the vertical axis the phase modulation amplitude z. The lower part of the figure shows the normalized signal |E n (x)| 2 /|E(x)| 2 for a particular sideband order n = 5, with a downwards axis; the left part shows the corresponding square of the Bessel function |J 5 (z)| 2 with a leftward axis. The zeroes of the two curves are put in correspondence, which provides the points in the central figure; a different color is used for each harmonic order n = 0, 1, 5, 10...100; the crosses correspond to n = 5. The juxtaposition of the points for all values of n gives an accurate representation of the amplitude of vibration A as a function of x.