The Circular Economy Concept in the Outdoor Sporting Goods Industry: Challenges and Enablers of Current Practices among Brands and Retailers

: Based on an analysis of challenges and enablers of circular economy (CE) practices for outdoor brands and retailers, we aim to identify which of these CE practices are best suited for the outdoor sporting goods industry. To develop the study, we used a qualitative methodology through a content analysis of 21 expert interviews. From these interviews, we derived challenges and enablers for different CE elements in the categories reduce, circulate products, circulate materials, and shift towards renewable resources. Our ﬁndings indicate trade-offs related to the high complexity and functionality of many products, the juxtaposition of extremely technical and less technical products, and the low product return rate as challenges, while design for durability, design for repairability, and linking the degree of circularity to product types were identiﬁed as enablers. Based on our data, we argue that among circular practices reduce should form a basis upon which other aspects can build, with durability and repairability best suited for technical outdoor gear. As our study adds an industry-speciﬁc perspective, it contributes new knowledge to the CE literature. It also helps managers with the practical implications, as we argue they should be aware of potential downsides of CE elements and thus consider carefully which of those elements can help support their overall business and sustainability strategies.


Introduction
Resource depletion and biodiversity loss are undoubtedly urgent issues today, with the result that sustainability is a topic now widely discussed in both the business world and more theoretical literature [1]. Accompanying this discussion is the concept of a circular economy (CE), which has drawn attention for its supposed economic and environmental benefits [2,3]. However, along with these positive views, research has also highlighted potential implementation problems [4]; for example, Masi et al. [5] have stated their doubts regarding the realisation of several CE aspects. This tension shows the importance for practitioners to be aware of both the benefits and downsides of the concept if they want to promote CE practices in their organisations.
One sector where the CE concept is discussed intensively is textiles [6]. Within this sector, actors from the outdoor sporting goods industry (OSGI) have often been identified as forerunners when it comes to single elements of a CE [7][8][9]. However, it was only recently that a structured analysis of CE implementation in this industry was conducted, with our findings recently published in this journal [10]. Although that research focused on current practices of outdoor brands and retailers, challenges and enablers for such CE practices in the OSGI have not yet been examined. Hence, to expand this discussion and to address the literature gap, we intend for this paper to supplement the first by offering an analysis of challenges and enablers for CE practices. Furthermore, we will evaluate which of CE practices are industry-specific and cannot be commonly observed in other textile sectors. Based on this, we also aim to obtain insights into which CE practices are most suited for the OSGI.
In our study, we focus on actors from the European outdoor market. This is because Europe (besides China) is the region where the CE concept is most promoted on the political level and thus most present [11]. It has also been selected as it is a key market for the outdoor industry in terms of sales numbers [12].
As our study adds an industry-specific perspective, it contributes new knowledge to the CE literature. In doing so it looks to provide clarity around the competing claims for positive benefits and implementation challenges. Moreover, it allows managers to understand the practical implications and supports them with the implementation of CE elements. This paper begins by offering an explanation of the CE concept in more detail (Section 1.1), before continuing with a review of the literature related to the challenges and enablers of CE practices in textile industries (Section 1.2), from which we subsequently derive our research questions (Section 1.3). Next, we present our methodological approach (Section 2) before we describe (Section 3) and discuss (Section 4) the findings. Finally, we state the theoretical contribution, practical implications, limitations, and future research possibilities (Section 5).

The Circular Economy
After its political uptake in China (Circular Economy Promotion Law in 2009) [11] and the EU (Closing the Loop: An EU Action Plan for the Circular Economy in 2015, renewed in 2020 within the European Green Deal) [13], the concept of a CE has also seen increased popularity in the private business sector as well as in the literature since 2015 [2,3]. By delineating it from the so-called linear production model, which is based on a "takemake-consume-throw away" [14] philosophy, the European Parliament defined a CE as "a production and consumption model which involves reusing, repairing, refurbishing, and recycling existing materials and products to keep materials within the economy wherever possible. A circular economy implies that waste will itself become a resource, consequently minimising the actual amount of waste" [14]. Accordingly, a CE involves narrowing resource flows (more efficient production processes), slowing resource loops (durable products, repair, re-commerce, and rental), and closing resource loops (recycling and using recycled materials) [7].
While there are several suggested environmental, economic, and social benefits of a CE, as for example less costs for waste disposal, less emissions, and better health through less-polluted closed loops, the downsides of the concept-as higher fixed costs for reverse logistics-are often understudied [15]. Accordingly, some research argued that it is difficult for CE approaches to economically outperform the linear model [16]. However, Geissdoerfer et al. [1] concluded that a CE is a beneficial tool to achieve better sustainability performances. At the same time, the study highlighted that there are other concepts that also lead towards more sustainability.
Due to the complexity of transformations towards, as well as the knowledge gap about innovation processes in a CE, literature often stressed the need for collaboration, both along the supply chain and cross-sectoral [17,18]. Consequently, concepts such as circular ecosystems [17,19] or open innovation [20][21][22] have recently become more popular in the CE literature. Parida et al. [17] proposed a two-step procedure to develop circular ecosystems where firms first assess their and their partners' preparedness and subsequently start shaping their collaboration together. Similar to the notion of circular ecosystems, the open innovation approach encompasses intentionally managing "knowledge flows across organisational boundaries" [23] (p. 6) to further innovative processes in a firm. The predominant outside-in approach asks organisations to open their innovation processes to external (cross-sectoral) influences (e.g., from suppliers, customers, users, and research centres) [20].
For an extensive review of the CE concept in literature, see our article recently published in this journal [10].

Challenges
A number of broader challenges have been identified, many of which also break down into smaller sub-problems. First, within firms, internal challenges are little management support, non-strategic or short-term management approaches [24,25], lack of performance measures [6], and a lack of staff qualifications (for example, designers lacking design for circularity know-how) [26,27].
Addressing a second challenge related to product, Franco [28] stressed that the complexity of many textiles is a problem. Often, it is barely possible to adapt all required inputs (such as zippers, dyes, glues, etc.) to circular requirements. For textiles that consist of many different parts, this problem is usually greater than for relatively simple textiles. For instance, recycling is complicated for non-mono-material products, like those made from a combination of natural and synthetic fibres [6]. In addition, using only circularity-proof components can hamper functionality of products and thus consumer demand [29,30]. Franco [28] underlined that performance loss is a no-go for functional textiles.
A third challenge is supply chain related, with Jia et al. [6] finding that some companies fear that the use of recycled material could mean a compromise in quality and thus refrain from it. Linked to that, the availability of recycled material is often limited, which poses another challenge. Furthermore, resource-intensive reverse logistics are often not yet effective and pose challenges to firms [26,31]. For example, firms engaged in the collection of pre-owned products often receive items from several brands and subsequently face difficulties in identifying their material mix-information which is crucial for the entity that executes the recycling process [6]. Similarly, it is difficult to predict at what time, in which quantity, and of which quality products will be returned by consumers [28]. Jia et al. [6] found that many textile firms are increasingly challenged by the growing amount of product returns due to fast fashion tendencies. In contrast, Kant Hvass [32] concluded that firms fear not having enough return flow for a re-commerce model. Regarding stakeholder collaboration, manufacturers find it difficult to convince their suppliers to rearrange their material supply to be more circular if they are not in a strong market position and able to demonstrate a clear business case to suppliers [6].
A fourth challenge relates to policy: Ki et al. [26] stressed an absence of political and legal guidelines regarding CE implementation for companies. Furthermore, policy currently seems not to sufficiently inform and educate consumers about more sustainable purchase behaviour [9]. This is needed and relates to the fifth challenge of consumer demand, which is moderate, with consumers often not yet aware of the CE concept or having reservations about circular products (e.g., used, rented, or recycled) [9,32]. According to Franco [28], low consumer demand did not prevent firms from embarking on a path towards more circularity but might prevent them from staying on it.
An additional sixth challenge arises because current recycling technology is still causing a loss in quality during the recycling process [26,33]. Tracing technologies could play an important role to facilitate CE practices (e.g., identification of material mixes) but are not yet sufficiently developed to provide the support needed [28]. Lastly, required financial investments are one of the main challenges [34]. There is still a high level of uncertainty about the success of scaling up circular businesses in the future and whether this would render them economically profitable [35].

Enablers
As with the challenges, there are also several enablers, many of which also break down into smaller enabling elements. First, among internal enablers, the commitment of organisations and in particular their upper management is crucial for CE implementation [9,26]. Furthermore, long-term strategic approaches that focus on the business case around circular products increase the chances of success [9,28]. Piloting different circular business models can also be a way to overcome the high uncertainty related to scalability and profitability around circularity [24]. Training designers is also important [26,36], as shown by the example of designing for durability, which facilitates several circular services such as rental or reuse [9].
A second enabler is that the development of infrastructure related to reverse supply chains (i.e., collection, sorting, and recycling) can strongly support CE practices [8,26,28]. Henceforth, increased transparency along the supply chain is needed [8,26]. Moreover, horizontal, vertical, or cross-sectional stakeholder collaboration can be a major enabler to facilitate CE implementation [8,9,36]. Such collaborations can be reinforced by a common vision and mutual trust [28] as well as through industry associations taking a coordinating role [8]. Similarly, and third, tracing technologies can play a crucial role within this context as it can render care, repair, return, or recycling approaches more effective [24,33].
Fourth, consumer demand and awareness can be raised through marketing efforts [8,9]. This can include incentivising users to bring back no-longer-wanted products or animating them to value circular products by providing information [37]. Finally, policy can help by providing a clear legal framework including standard transparency requirements, recycling provisions, or intellectual property regulations to reduce firms' moderate uptake of tracing technology and collaboration [6,8]. Stahel [38] further mentioned taxes as a financial means to accelerate CE implementation.

Research Questions
As shown by this overview, there has been significant research on challenges and enablers for CE practices in the textile sector. Nevertheless, an OSGI perspective is still missing. Thus, we aim to answer the following research questions:

1.
What are the challenges complicating the Circular Economy practices of brands and retailers in the Outdoor Sporting Goods Industry? 2.
What are the enablers facilitating the Circular Economy practices of brands and retailers in the Outdoor Sporting Goods Industry? 3.
What Circular Economy practices are best suited for brands and retailers in the Outdoor Sporting Goods Industry?

Materials and Methods
As few studies in the CE literature focus on the OSGI, little is known about sectorspecific CE challenges and enablers. As recommended when confronted with such significant knowledge gaps or the need to identify new and unique perspectives [39,40], we thus used a qualitative exploratory research approach. Hence, our main goal was not to test hypotheses regarding challenges and enablers from other industries but rather to add the perspective of a new industry to the CE literature.
Therefore, we decided to conduct semi-structured expert interviews with brands and retailers. To supplement this with an external and more critical perspective, we also elected to include different stakeholders from the OSGI supply chain. Based on the circular supply chain structuring (for fashion) of previous research [41], we looked at the following stakeholder groups: suppliers, brands, retailers, service providers, and consumers. Since we explicitly wanted to gain an external view on brands and retailers, we added researchers, journalists, as well as independent industry experts to our groups. We identified relevant organisations within these stakeholder groups from the literature, analysis of OSGI firms' homepages and sustainability reports, and via snowball sampling [42,43]. During the interviews, it was recommended by experts to also add an industry association perspective.
We recruited individual experts via mail request to their organisations and, in total, 21 agreed to participate in our investigation (Table 1). Interviews were conducted between April and September 2021. It is important to state that the interview guideline was not exclusively focused on the research questions of this study but also aimed at further questions related to the field of CE and OSGI. We chose this procedure to reduce the transaction costs of initiating several interviews. As noted above, because the CE concept is mostly promoted in China and Europe, and many important outdoor markets are located in Europe, we decided to look at European (or the European branches of) brands and retailers. Consequently, all stakeholder interviewees were also based in Europe; however, the entities represented by these experts often operate globally.  1 At the time of the interview, not employed by but with experience in the industry. 2 Representing the consumer perspective. 3 Research focus: sustainability in textiles.
The key questions of the interview guideline were mainly formulated to be relatively open to allow for new aspects to arise. Subsequently, these initial questions were followed by more detailed ones to clarify or deepen insights related to the research questions. The guideline was slightly different for each stakeholder group. Moreover, as is common in the qualitative research process, we made minor changes to the guideline after each conducted interview when appropriate. We forwarded key questions to the experts before the interviews, which lasted 30 to 100 min with an average of 80 min and were held via video conferencing. The interview language was English or German. We determined the number of interviews based on the degree of information received; that is, when no more new information was being generated, no further interviews were conducted. Our overall interview goal was to have informants describe the current challenges and enablers that complicate or facilitate CE implementation efforts of brands and retailers.
Interviews were pseudonymised and transcribed via MAXQDA (version 20.4.2). Subsequently, the transcribed interviews were coded to extract key aspects from the data. Coding was also facilitated via MAXQDA and was done deductively based on the framework of our previous research [10] and adapted inductively within an iterative process when indicated by the content of the interviews [44]. As recommended [44], a definition, standard example, and-when needed-coding rules were created. As a result, we identified challenges and enablers for each of the principles of reduce, circulate products (durability, repair, reuse, rental), circulate materials (use of recycled materials, recycling products, remanufacturing, industrial symbiosis), and the shift towards renewable materials and energy practices. These are outlined in turn in our findings below.

Reduce
Mainly, firms try to reduce the use of energy, water, chemicals, waste, and emissions while there are often interdependencies among these categories. As concerns chemicals, the main challenge is the trade-off between the reduction of certain substances (fluorocarbons [PFC] are mainly highlighted) and functionality, as some products don't equally perform without them. While stakeholders do not seem to agree on this topic, enablers could be accepting compromises for less technical products and informing users about the topic as illustrated by the following statement: Yes, the quality did go down. And up to now there are no PFC-free technologies that achieve the same level of water repellence as fluorocarbon technologies. And we must live with that. And so must the consumers [ . . . ] Therefore, the consumers will be complaining more often-they are already complaining: why is my jacket no longer water-repellent? We must live with that, that's how it is.
Regarding waste, a major issue is the reduction of plastic waste resulting from packaging and microfibers, for which the industry has created two multi-stakeholder initiatives: the Single Use Plastics Initiative and the Microfibre Consortium. Furthermore, stakeholders mentioned overstock as an environmental problem which is at the same time economically troublesome for companies. Both researchers suggested that a more demand-oriented production could be a solution to this problem, albeit one that comes with many challenges.
On the topic of energy, it was mainly the use of renewables that was mentioned (see Section 3.4), with stakeholders underlining that it is comparatively easy to convince suppliers to save energy as that also saves them money. In contrast, water scarcity was highlighted as an upcoming problem that must be considered more intensively in the future while water processing, organic materials, solution dyeing, and industry-spanning multi-stakeholder collaboration were the most frequently cited enablers.
To foster and steer emission reduction, industry associations such as EOG or OIA have started climate action initiatives. Moreover, LCAs or LCA-based tools (e.g., sciencebased reduction targets or the SAC HIGG-Index) can serve as major enablers. A challenge seems to be emissions reduction outside one's own company: in other words, to convince suppliers (Scope 3). While many mentioned offsetting to achieve carbon neutrality, it is seen as greenwashing by some stakeholders.
In addition, a fundamental challenge is the decoupling of growth and emissions since any consequent emissions reduction would also mean selling less. However, this would contradict the basic success metric of companies in society (sales and profits) and would mean that many players cease to exist. Most stakeholders are aware of the problem but do not have an answer, as illustrated by the statement that "If we really think it through, it will hurt us if people would only buy what they truly need" (Retailer_1). Challenges and enablers related to reduce are summarised in Table 2.

Durability
The durability model seems to be very well suited for outdoor products as low hurdles and several enablers were identified. The only major challenge is consumers' low willingness to pay for high quality and thus very durable products. The main enablers are design for durability (i.e., high quality) and repairability, as well as informing consumers. Challenges and enablers related to durability are summarised in Table 3.   From a product point of view, just as for durability, there is a fit between repair models and outdoor products. Moreover, repair and durability are mutually dependent and supportive. Notwithstanding, a main challenge for repair seems to be the differences in price levels between production costs in low-wage countries and repair costs in high-wage outdoor markets that lead to repair prices out of proportion to the original price. As a consequence, users' acceptance is rather low and rendering this practice profitable is hardly possible for firms. Challenges and enablers related to repair are summarised in Table 4. From an economic viewpoint, reuse models for outdoor products seem to make more sense than rental models as stakeholders mention good growth numbers. Additionally, there seem to be fewer questions about environmental impact compared to rentals. The biggest challenge is the low return rate (and thus the limited supply) of outdoor products since they are very durable, and people grow emotionally attached to gear worn during outdoor adventures. This was underlined by one interviewee as follows: "In particular, customers don't quickly return their products, but rather use our products for a very long time. Thus, we didn't get a significant return flow" (Brand_3).
The end-of-life service provider mentioned the importance of incentives to motivate customers to bring products back while the form of this incentive is not decisive. Another major enabler is to partner with an experienced service provider who can strongly facilitate (the initiating phase of) re-commerce models. This was acknowledged by one interviewee, who explained that "We partner with The Renewal Workshop [ . . . ] they do both the front end and the back end of re-commerce" (Brand_1). Challenges and enablers related to reuse are summarised in Table 5.

Rental
Since rental models involve many hurdles, their implementation is more challenging than, for example, reuse. First and foremost, it is difficult to render the model profitable as it is very resource intensive and consumer uptake is quite slow. The following statement demonstrates existing doubts: "Is it economically viable? That is a really interesting question. I mean, honestly, we are still looking" (Industry Association_1). As enablers, stakeholders highlighted rental hubs where products meet users, pilot projects, as well as an existing re-commerce business to sell products at the end of rental-life. Challenges and enablers related to rental are summarised in Table 6.  Table 4) -Tracing technologies (to track product history) -Automation of rental processes

Using Recycled Materials
The high number of outdoor firms engaging in the use of recycled materials despite several challenges seems surprising. Mainly, this can be attributed to the marketing narrative of recycled material contributing to sustainability being very plausible for consumers. One challenge is the trade-off related to functionality and the subsequent limit to the share of recycled material in a product. Accordingly, brands are careful, as demonstrated by the following observation: I must honestly say that we have some problems sometimes with textiles not being strong enough. So, we have a quality process where we need to take several steps before we approve any material and that is normally even if it is recycled or not of course. But it has to be a little bit more conscious when we are using recycled materials.

(Brand_5)
However, most stakeholders also stated that the quality of recycled materials has constantly increased over recent years. Moreover, the applicability strongly depends on the type of product.
Another challenge is the difficulty of knowing where the materials come from and what exactly they contain. While many firms use GRS certification, a very fundamental criticism was issued by one researcher, who suggested that many of the claims regarding the content of recycled material are misleading (but not necessarily illegal) since there is, for example, not enough recycled polyester available to entirely satisfy firms' claims.
In addition, stakeholders do not agree how much recycled materials can contribute to reducing the environmental impact. Some stated that it is not a perfect solution, but rather a bridge and the most scalable solution on their journey towards their science-based targets. At the same time, some stakeholders claimed that the emission benefits of using recycled materials are overstated, explaining that "You don't replace the manufacturing processes [ . . . ]. You don't replace the spinning of the yarn. You don't replace knitting or weaving. Thus, with recycled input you only replace a relatively small amount of the LCA" (Supplier_2). Challenges and enablers related to using recycled materials are summarised in Table 7.

Recycling of Products
Recycling of outdoor products comes with a high number of challenges. This could explain why fewer firms try to implement it rather than the use of recycled material. Fundamentally, outdoor products such as hiking shoes or functional rain jackets often have high functionality requirements and thus consist of many different materials (e.g., polyurethane or polytetrafluoroethylene membranes between outer fabric and inner lining from polyamide and polyester, adhesives, dyes, or coatings such as fluorocarbons) and many small parts (e.g., buttons, zippers). This prevents (economically and environmentally) efficient recycling since materials would have to be separated and small parts detached. The dilemma is illustrated by the following statement: We want to have garments which are super durable, last a long time and are able to withstand extreme conditions. But then we are going to think about designing it in such a way that they have these characteristics, but they are still able to be recycled at the end of their lives. That is not always an easy compromise.

(Brand_1)
Furthermore, such complex outdoor products with many components stem from many different supplier factories, which renders it difficult for brands to know exactly what is in their products. However, precise data is important for the recycling process. One interviewee explained that "from the perspective of the recycler it is quite important to know whether it is 100 or 99.98 or 97%. After all, the recycling plant is at stake and could be damaged" (Service Provider_end-of-life). Table 7. Using recycled materials: challenges and enablers.  Table 4) -Tracing technology (to prove origin of the materials)

Consumer
One often-mentioned approach to overcome this issue is monomateriality. Notwithstanding, monomateriality can mean a functionality trade-off. For example, elastane can hamper recyclability but adds a lot of functionality to many products. While new approaches (stretch parts from polyester only, freedom of movement via cut) exist, it is not simple to replace elastane. Another example is zippers from polyester which are inferior to polyamide or steel. Building on that, one researcher argues that complex outdoor products are not particularity suited for recycling-such as, for example, leased linen or public procurement textiles where one can find high quantities of homogenous products. Challenges and enablers related to recycling of products are summarised in Table 8.

Challenges Enablers
Technology -Challenges related to tracing technology (see Table 4) -Tracing technology (to increase supply chain transparency) -Designers do not know what future recycling technologies (e.g., in 10 years) they are designing for today -Tracking devices must be easy to detach before recycling or easy to recycle themselves -Recycling technology Mechanical recycling reduces the material quality and cannot cope with blends Chemical recycling technology is in its infancy

Remanufacturing
The main challenge for remanufacturing is that firms must deal with unique pieces that cause low scalability and thus profitability. Moreover, this is enhanced as the supply of material for these pieces-which is stemming from returned products-is also limited. For that reason, remanufacturing is mainly seen as a tool to generate interest in other models (e.g., repair or reuse). This being said, the training of designers and tailors as well as collaboration with specialised service providers (e.g., The Renewal Workshop) can function as enablers.

Industrial Symbiosis
Industrial symbiosis is mainly limited by an unsteady stream as well as heterogenous composition of waste, which complicates the establishment of long-term collaboration. On the other hand, geographic proximity of partners as well as matching platforms linking waste-demanding and waste-offering actors can strongly facilitate industrial symbiosis approaches.

Shift towards Renewable Materials and Energy
Some stakeholders see a huge potential in certain renewable materials (namely biobased synthetics) as the following quote showcases: "For synthetics the next evolution beyond recycled content is going to be bio-based synthetics" (Brand_1). Yet, there are a multitude of hurdles that must be overcome before implementation, including the fact that stakeholders may have to limit the share of bio-based synthetics in their products if they are not to reduce functionality. For example, one supplier mentions that they did not yet manage to increase the bio-based share to over 25% without losing performance. While stakeholders agree that it does not make sense to sacrifice quality for a higher share of biobased synthetics, some also demanded a certain willingness to compromise. Accordingly, one researcher states that the use of such solutions might be better suited for more casual than for very functional products.
Some brands mentioned they are refraining from using bio-based synthetics for now as they are not yet sure about the overall environmental impact. According to LCA data, biobased synthetics sometimes do poorly compared to fossil-based synthetics, as emphasised by the following statement: If you just do an LCA-based on numbers, then probably a jacket from 100% polyester or also a shirt from 100% polyester would always have a lower environmental impact over a certain time. It is durable, you can theoretically wear it for 100 years, you can wash it with cold water, it does not need a tumble dryer, it does not require ironing, you can theoretically recycle it forever, you can burn it and recover energy, you do not need to grow it, you need no farmland, no irrigation.

(Researcher_2)
Notwithstanding, one brand explained that this also comes with risks, such as leakages, which are not being considered for fossil-based synthetics. Challenges and enablers related to shift towards renewable materials and energy are summarised in Table 9.

Discussion
Among internal challenges, our results confirm the literature that stresses a certain lack of know-how [26,27] and the subsequent need for training [26,27,36]. Stakeholders mainly underlined the absence of design for circularity skills as well as firms not knowing how to start their approach towards the CE. While non-strategic approaches were mentioned by some interviewees, they also referred to the fact that many firms are currently increasing strategic anchorage. Notwithstanding, limited management support [24,25] was not mentioned as a challenge since experts agreed on a high intrinsic motivation among the responsible persons in the OSGI to foster sustainability processes. As suggested in the literature [24], outdoor stakeholders cited pilots as a way to find out about potential scalability and thus profitability potentials. This is important, as rendering CE practices economically profitable [35] was confirmed as a major challenge for outdoor firms.
For product-related issues, the problem of adapting complex items for CE-related practices [6,28] is present to a very high degree in the outdoor sector. Outdoor gear often has high functional requirements (e.g., climbing harnesses or gear for very cold environments) which complicate the implementation of several elements of a CE (e.g., recycled materials, recyclability, bio-based materials, reduced use of certain chemicals). At the same time, there is a wide range of different products with different characteristics in the OSGI (footwear, apparel, equipment) that all have different preconditions for CE practices and therefore require differentiated approaches. For example, lifestyle and thus less technical products can nowadays be seen more often in outdoor stores. Accordingly, stakeholders propose to engage in circular practices depending on product types. Thus, for some less technical products, compromises in favour of circularity and to the detriment of functionality could be conceivable. To some degree, this conflicts with Franco [28], who claims that performance loss is a no-go for functional textiles. While design for durability as well as repairability are major enablers for circularity for outdoor products, this is hardly stressed in literature about other textile areas.
Similar to the literature related to supply chain challenges [26,31], reverse logistics also pose a major problem for many outdoor actors, which find it difficult to obtain enough supply for re-commerce models. This confirms the view of Kant Hvass [32] and contradicts the findings of Jia et al. [6], who mentioned the problem of too many returned items. The latter can be an indicator that the OSGI has different preconditions for a CE than other textile industries-such as, for example, fashion, where product returns are more common. Moreover, the low availability of recycled material [6] as well as problems regarding certainty about the exact inputs of a product (e.g., for later recycling) [6] were confirmed by outdoor stakeholders. Accordingly, the need for more supply chain transparency [9,26] was echoed in the interviews. Moreover, industry(-spanning) collaboration coordinated by industry associations [8,9,28,36] is mentioned as a tool to increase knowledge and to strengthen the network infrastructure that is needed for a functioning and worthwhile CE.
As the challenge of low consumer demand [9,28,32] was confirmed during the interviews, interviewees demanded more marketing activities as well as incentives by firms to raise awareness as well as acceptance for circular products or services [37]. However, the often-used term "education" [9] was rejected several times as patronising. As different forms of collaboration were one of the most frequently mentioned enablers, the concept of outside-in open innovation [23] could be a pathway towards stronger consumer engagement.
At the same time, the responsibility of policy to better inform users [9] was not mentioned by the outdoor stakeholders. Yet, the literature as well as outdoor actors stress that currently, there is a lack of political guidelines [26] and the need to come up with a more aligned legal framework for CE practices to provide firms with a uniform situation and thereby increase effectiveness [6,8]. Moreover, stakeholders do not seem to agree regarding Stahel's [38] call for a stick (taxes), as some prefer a focus on carrots (incentives).
Lastly, the problems related to current technology solutions are also reflected in the outdoor industry as stakeholders mention processes such as chemical recycling [26] and tracing technologies [8,24]. These are seen as truly promising but not yet developed sufficiently and are still far from being implemented.
In summary, challenges specific to the OSGI are trade-offs related to the high complexity and the high functionality requirements of products, the juxtaposition of extremely technical and less technical products, as well as the low product return rate. At the same time, design for durability, design for repairability, as well as linking the degree of circularity to product types are outdoor-specific enablers. In addition, more common challenges also found in the OSGI are missing or uncertain consumer demand, complexity of topics for consumers, low supply chain transparency, overproduction, decoupling problems, and rendering circular practices profitable. In contrast, (industry spanning) collaboration, pilot projects, design processes that are aware of circular requirements, informing and animating users, and tracing technologies are more common enablers also found in the OSGI. Based on our findings, we argue that among circular practices, reduce should form a basis upon which other aspects can build. For this, durability and repairability are best suited for technical outdoor gear. However, this can vary by case or product specificity as, for example, for less technical outdoor gear.

Conclusions
The aim of this paper was to establish a structured overview of challenges and enablers that complicate and facilitate CE practices of outdoor brands and retailers and to answer the question which CE practices seem best suited for the OSGI. Our findings are important since they add an OSGI-specific perspective to the CE discussion in the literature and contribute new knowledge to the field of sport(ing goods) management. Moreover, they can help practitioners in the decision-making process.
Accordingly, the main recommendations for practitioners are: First, outdoor brands and retailers should choose a strategic approach to the CE concept. This includes carefully thinking about how CE, or rather which CE elements, can help support the overall business as well as sustainability strategy. Since some CE practices include major challenges, firms should be clear about why it makes sense to implement them into their products or processes. In particular, brands should adapt product circularity to product requirements (less vs. more technical products). Second, firms should increase visibility of circular products and services and intensify information provision for potential customers. Third, they should prioritise reduce, durability, and repairability approaches. Fourth, collaboration within the industry as well as between industries is essential and should ideally be coordinated by industry associations.
Based on these findings, future research might investigate how consumers are best informed about circular outdoor products and services. Moreover, it could be worthwhile to quantify users' willingness to accept a performance trade-off for less technical outdoor products. Lastly, the suggested low consumer demand for circular products or services should be quantitatively tested with a representative sample.
Besides consumer-related research, it seems obvious to ask what pressures make firms still engage in certain CE practices, despite the many challenges they bring. Thus, it could be rewarding to use an institutional theory [45] perspective to analyse the pressures behind firms' CE practices, clarifying to what degree they originate from efficiency or legitimacy imperatives. Beyond institutional theory, as interviewees mentioned their high willingness to collaborate in the field, an open innovation [23] view could be used to look at the CE implementation processes in the OSGI and to identify ideal knowledge flows. Additionally, such an open innovation approach could also prove interesting in the light of the suggested low consumer acceptance as a potential pathway towards stronger consumer engagement. Further, since experts describe a high intrinsic motivation to engage in sustainability (and thus circularity) efforts in the OSGI, it might be worthwhile to compare the transition processes to a more circular model as employed by other industries. Moreover, a validation of all identified challenges and enablers via a quantitative questionnaire among different industry stakeholders seems evident and necessary. Lastly, the focus on European brands and retailers (or their European branches) and their customers and clients could be extended to other relevant outdoor markets.
This study has some limitations. Namely, the brands and retailers selected for interviews were mainly forerunners in the field of CE-related practices and were not likely to emphasise CE challenges as compared to enablers. While this indicates a certain sample selection bias, we deliberately chose a stakeholder approach to cover different perspectives. Moreover, while we strove to be neutral, our interview questions might have biased the mentioned challenges and enablers. Finally, brands and subsequently their point of view are overrepresented when compared with, for example, suppliers or consumers; the latter are only advocated by the product tester. Therefore, while the aim of this work was to identify challenges and barriers for brands and retailers, our sample could have led us to neglect the outside-in perspective offered on brands and retailers by other actors.  Data Availability Statement: Data presented in this manuscript are available upon request from the corresponding author. This comprises the codebook of the expert interviews (including category definitions, standard examples, and coding rules), and exemplary key questions of the expert interviews. Transcribed expert interviews, though pseudonymised, cannot be provided as this was agreed with the interviewees.

Conflicts of Interest:
The authors declare no conflict of interest.