Strategies for Implementing the Circular Economy in the Built Environment

Abstract

In recent years, European cities have implemented numerous initiatives to reduce the use of resources and improve the resilience of climate change by promoting shifts toward the circular economy (CE). This comparative case study investigated the results of the applications of the CE model in the built environment from two different national approaches and perspectives of strategic planning in capitals that represent the “old” (Copenhagen) and “new” (Ljubljana) European Union (EU) member states. This paper introduces the original methodology to assess the implementation of the strategic approaches in the adaptation of the CE in architecture and urban design using a set of 10 selecting indicators. Although both cities have ambitious strategic goals and are undertaking actions aimed at shifting to the CE, they are driven by different motivations (climate crisis vs. urban revitalization and zero waste policy) and exhibit different implementation patterns (top-down systemic/institutional vs. gradual/sectoral). The results highlight the key role of a comprehensive approach to CE implementation, particularly the development of institutional frameworks and dedicated infrastructure and digital tools for transition management, the involvement of external stakeholders in the circular vision, wide-range educational activities, and the promotion of CE initiatives. However, limitations resulting from the lack of a comprehensive and standardized measurement framework pose a challenge to effectively accelerate progress in the shift toward a CE in the built environment. The main contributions of this study are: (1) to identify and verify the methods and strategies undertaken by European cities for the adaptation of a CE in the built environment and (2) demonstrate the different dimensions, levels, and the most relevant factors in the strategic management of the processes of transformation toward the CE. In addition, recommendations for future implementations based on CE systems are indicated.

1. Introduction

The current linear system that governs the circulation of materials increases the consumption of natural resources and causes rapid mass production. Globally, the consumption of raw materials has increased eightfold over the past century [1]. The rush to consume, which has mainly led to an ever-increasing scale of resource exploitation and contributes to climate crisis, raises legitimate concerns about the cumulative and global consequences of such actions [2]. They are felt most strongly in cities, which are most exposed to the effects of climate change [3]. At the same time, the buildings sector and the construction industry are already responsible for the largest material flows in the global economy [4], which generate both increased energy consumption and emissions. The construction sector accounts for 36% of final energy consumption and 39% of energy and process-related carbon emissions (2018), 11% of which resulted from the production of the most common building materials and products such as steel, cement, and glass [5]. One concept, which can contribute at the local and regional level to the minimalization of emissions, is the conversion of the linear economic model to a circular one. The circular economy (hereinafter: CE) implies reuse, maintaining the value of materials and components and the use of renewable energy sources [5,6]. In recent years, cities around the world have taken systemic action to mitigate the effects of climate change and the waste crisis by developing multi-faceted local strategies [7]. Due to the critical role of the buildings sector and the construction industry, strategies are focused particularly on the circular transformation of the built environment, which comprises all man-made or modified structures that provide people with living, working, and recreational spaces (buildings, roads, bridges, networks, etc.) [8,9]. Creating all of these spaces and systems requires enormous quantities of materials, which is why a main goal of these strategies is to transform the model of construction material cycle from linear to circular.

Despite the growing popularity of the CE, there is a notable lack of in-depth research on applications of the circular economy model in the built environment from the perspective of local strategic planning [10], the implementation process [11] as well as a comprehensive framework for measuring the benefits of CE implementation [12]. To address the gap, this research focused on the results of the applications of the CE model in the built environment from the perspective of strategic planning, the implementation process, and performance evaluation.

This study sought to answer the following research questions:

(A)

What are the main objectives of the local planning strategies that consider the implementation of the circular economy in the built environment?

(B)

What are the implementation patterns of the key strategic goals related to the built environment ?

(C)

What are the effects and benefits of CE implementation and what measures are used to evaluate them?

The study was structured with reference to previous studies of the circular economy and the most relevant threads recognized on this basis. Responses to the research questions were organized according to the current trends in approaches to adapting the circular economy to the built environment. First, the governance for sustainable cities was examined in order to determine the most significant strategic goals, measures, and actors involved in the implementation process. Second, the paper recognizes urban services and consumer practices adapted to the circular economy that enabled us to broaden the spectrum of undertaken actions. Then, cleaner production and construction—understood as a preventative strategy focused on resource efficiency and minimizing waste at the source—was investigated to identify good practices and the current impact of implemented circular strategies. As a foundational element of the CE, this concept addresses the efficiency of production processes before materials enter the use cycle, thus helping to outline the prospects for a fully circular built environment [13,14,15,16,17].

The rest of this paper is organized as follows. Section 2 presents the theoretical background of the CE concept, and practical aspects of its evaluation and implementation in EU policies; Section 3 addresses the methodology adopted to compare the case studies using a research design based on ten original criteria; Section 4 presents the results of CE conversion in the built environment in the selected case studies; Section 5 provides a discussion and recommendations for future implementations based on circularity; and Section 6 summarizes the paper.

2. Theoretical Background

2.1. The Circular Economy: A Conceptual Clarification

The circular economy is an alternative economic model that replaces the dominant ‘take-make-dispose’ economic system and instead promotes the renewal, regeneration, and recycling of high-value materials [10]. Depending on the context, various definitions of the circular economy can be distinguished [18,19,20,21]. One of its most frequently cited definitions in the literature [22,23] and has also been recognized by researchers was coined by the Ellen MacArthur Foundation [24]: “the CE is an industrial system that is restorative or regenerative in intent and design. It replaces the concept of ‘end of life’ with restoration, shifts toward the use of renewable energy, eliminates the use of toxic chemicals that impede reuse, and seeks to eliminate waste through better design of materials, products, and systems”.

Thus, the CE implies a critique of the way that the linear economy operates, which is seen in terms of the final consumption of finished products that are not recyclable and generate waste. Nowadays, the concept of the circular economy is trending among both researchers and practitioners [18], but it is not a new concept [25,26,27]. The idea was pioneered by Boulding [28] and was originally sketched by Stahel and Reday-Mulvey [29] but has received more attention since Pearce and Turner [5] developed the CE model in the late 1980s. The CE has its origins in industrial ecology [30] as well as biomimicry [31], natural capitalism [32], blue economy [33], and cradle to cradle (coined by Stahel [6], popularized by Braungart and McDonough [34]. Cradle to cradle encourages the use of patterns developed by nature and promotes taking action on the principle of “waste equals food” and focuses on the notion of doing “more with less”. Furthermore, a circular economy assumes that thanks to smart strategic planning, governments and the private sector can economically benefit from technological advances and support sustainable development at the same time [6]. Also noteworthy is the undertaking by the Ellen MacArthur Foundation to actively popularize the said concept; there is a series of reports that encourage the adaptation of the CE approach across many fields including architecture [3]. With the crucial role of building materials, urban stock, and infrastructure, the transition toward a CE is especially important in the built environment [35].

2.2. Shift Toward the Circular Economy in the Built Environment

The construction sector is critical for sustainable urban development and human health [36], therefore the principles of the circular economy are increasingly being applied to the built environment. A growing body of literature has explored this topic from various perspectives. Research covers the development of overarching CE frameworks with large-scale bibliometric analyses mapping the construction sector’s research landscape to identify key themes like energy efficiency and waste management [37]. Another key area is the creation of innovative CE business models such as product-as-a-service (PaaS) for building components [38]. The research also identified key barriers—such as the lack of specific regulations and high upfront costs—and corresponding enablers like policy incentives and technological innovation [39]. Other key areas include strategies for end-of-life management, particularly through product take-back systems designed for high-value recovery options like remanufacturing, and investigations into the factors affecting their financial performance [40]. Attention has also been given to energy-driven circular design, which integrates principles like the adaptive reuse of materials and renewable energy, often facilitated by digital tools such as BIM [41]. The literature also covers methods for assessing material and urban stock through urban mining concepts [42,43]. Furthermore, studies consistently link these circular strategies to positive environmental impacts and climate change mitigation [12,44].

The construction industry is consistently identified as a priority sector due to its high circularity potential. This potential stems not only from its immense scale of material consumption and waste generation, but from the opportunity to move beyond low-value recycling. A common misunderstanding, particularly in regions with high recycling rates, is that the sector is already circular. However, much of this involves downcycling demolition waste into low-grade aggregates. High-value circularity, in contrast, focuses on preserving the value embedded in buildings through strategies such as the direct reuse of components and designing new structures for future disassembly as “material banks” [45]. Therefore, an important issue is how urban strategies can actively promote such high-value circularity in practice.

While the core principles of CE are universal, the strategies and priorities adopted are highly dependent on the regional context. It should be noted that although many regions have been recognized as having a high level of circularity in the built environment, the methods and strategies for transformation and the evaluation criteria vary. In rapidly developing economies, the focus often lies on managing massive streams of construction and demolition waste (CDW), though the strategic approaches differ significantly. For instance, a study in Dubai, UAE [46], showed that while foundational policies and technologies like prefabrication are in place, the circular transition remains nascent, critically lacking advanced practices such as design for disassembly or deconstruction. Research in Suzhou, China [47] points to an innovation in governance, utilizing a flexible public–private partnership (PPP) model based on relational contracts to overcome traditional procurement delays and effectively manage CDW waste services. In the U.S., the perception that the construction industry is already circular because the majority of its waste is recycled acts as a significant barrier to implementing high-value circularity strategies, effectively stalling progress beyond low-grade aggregate production [48]. In turn, a more systemic and comprehensive approach is being implemented as part of the European Union’s circular policies.

2.3. European Union Policies

The implementation of CE principles is now one of the most prominent strategic objectives pursued at the internal policy level of countries belonging to the United Nations, which include the member states of the European Union and is a consequence of the urgent need to implement the Kyoto Protocol [49], Gothenburg Protocol [50], and their revisions, which have since been expanded upon by the Paris Agreement on Climate Change [51] as well as the UN Sustainable Development Goals (hereinafter: SDGs) under the 2030 Agenda [52] (namely, Goal 11: Make cities and human settlements safe, secure, sustainable and inclusive, Goal 12: Ensure patterns of sustainable consumption and production, and Goal 13: Take urgent action to combat climate change and its impacts).

In these circumstances, the EU has made the CE a priority agenda, obliging its Member States to implement the established guidelines. According to the European Commission, a circular economy is understood as an economy “where the value of products, materials and resources is maintained for as long as possible and the generation of waste is minimized” [53]. An EU action plan for the circular economy (the so-called First CEAP, FCEAP) [53] and relating legislation proposals [54] establishes new targets to be met by 2030 (e.g., a new Waste Framework Directive [55] mandates higher levels of waste recycling). These actions are part of the EU’s broader agenda to achieve the ambitious goal of moving toward zero carbon and climate neutrality by 2050, which was made official by the European Climate Law [56] approved in June of 2021. Prior to this, in 2020, the EU adopted a new circular economy action plan for a cleaner and more competitive Europe (the so-called new CEAP) [57] as a main building block of The European Green Deal [58]—a new flagship agenda for sustainable growth in Europe. The new CEAP [57] sets out to create “a climate-neutral, resource-efficient and competitive economy” through the implementation of 35 key actions necessary to change the economic model from linear to circular. These actions are aimed at sectors in which the most resources are consumed, along with those that have a “high circularity potential” such as the construction industry. An EU strategy for a sustainable built environment (SSBE) is a key part of the implementation of the new CEAP. Due to the hierarchical nature of the planning and programming system of the EU Member States’ development policies, the strategies and regulations of the European Union are transposed and implemented in the provisions of legal acts and lower-level documents (national, regional, and local) [59].

2.4. Implementation of the CE in Cities

The implementation of these CE strategies varies globally, adapted to the unique local political, economic, social, and technological conditions. One of the ways to apply the logic behind the EU and national approaches to managing the change from linear to circular consumption patterns is through the implementation of plans, programs, and strategies [60,61]. The CE is deployed at both the level of city strategies [47,62,63] and spatial planning (e.g., to organize material cycles, to activate stakeholders and to exchange experiences between actors) [64,65,66]. In the context of city governance and implementation, the scale of interest in the CE is evidenced by the adoption of circular economy strategies in places like Brussels [67], Coventry [68], Ghent, Amsterdam [69], Utrecht, The Hague [70], Rotterdam, Glasgow, Haarlemmermeer, The Hague, Barcelona [71], Melbourne, Malmo [10], London [72], or Odense [73]. Within the literature, three approaches are outlined for the adoption of CE in built environment governance for sustainable cities, urban services, and consumer practices for a circular economy and cleaner production and construction [13,35].

2.5. Performance Evaluation for the Circular Economy in Cities

When developing circular strategies for European cities, the results of their implementation need to be monitored in various aspects [25,74]. Monitoring the key trends and patterns is crucial to understand how various elements of the circular economy develop over time, identify success factors, and assess actions taken. The EC has adopted the Monitoring Framework for the Circular Economy [56], with indicators on resource efficiency that are being developed to track progress toward strategic objectives [75] including production and consumption, waste management, secondary raw materials, and competitiveness and innovation.

Another way to evaluate and measure the effectiveness of implemented CE strategies via the sets of dedicated indicators are enabled by initiatives such as the European Green Capital Award [76], which focuses on the assessment of EU cities in terms of “achieving high environmental standards, taking ambitious steps toward environmental improvement and sustainability, being able to act as a European leader and promoter of good practice in order to inspire green transformation in other cities”. It includes indicators such as climate change mitigation and adaptation or waste production and management, which directly relate to the CE principles.

International sustainability standards and models for cities are inconsistent [21,77,78,79] because cities formulate indicators according to their past experience rather than following strict top-down guidelines [25]. Although environmental indicators provide useful information, the literature and practical implementation lack a comprehensive framework for measuring the benefits of CE implementation in the built environment [12,25,80,81].

3. Materials and Methods

3.1. Research Design and Case Selection

This study identifies and describes different strategic approaches to the implementation of CE principles in the built environment of European cities. Due to the complexity and individual specifics of each EU city, a comparative case study method [82] was used. The method has been successfully used in research on topics related to the circular economy [10,65,71]. We decided to conduct a detailed study of cities that are leaders at implementing the closed-loop cycle, which makes it possible to obtain a more comprehensive answer to each of the research questions and identify good practices that are helpful in formulating recommendations.

Case studies were selected by applying the method of purposive sampling [83], which is typically used in pilot and comparative studies [10,84,85]. For the purpose of this research, four case selection criteria were identified: (1) winning the European Green Capital Award (hereinafter: EGCA); (2) signing the Circular Cities Declaration (hereinafter: CCD); (3) membership in the European Union, and (4) capital function. Two capitals were selected—the first from the so-called “old European Union” (Copenhagen, Denmark) and the second from the “new European Union” (Ljubljana, Slovenia). The countries of the so-called “old Union” are the founding countries of the Community (under the 1957 Treaty of Rome) and those that joined the EU between 1973 and 1995. The countries of the “new Union” are those from the former socialist bloc that joined the EU between 2004 and 2013 (Figure 1). This selection increases the comparative value of the study due to the possibility of demonstrating the relationship between the length of time since accession to the EU and the level of CE implementation. The appropriateness of the choice is confirmed by the fact that Ljubljana and Copenhagen are the only two EU capitals that have been invited by the Ellen MacArthur Foundation to become members of the Circular Cities Network.

3.2. Data Collection and Sources

This study was based on multiple sources of data to ensure a comprehensive understanding of CE implementation. The data collection process involved three main components: document analysis, questionnaires, and in-depth interview.

First, publicly available strategic documents were collected. To clarify terminology, a distinction between a strategy and a strategic plan should be identified. A strategy involves creating a unique position by making deliberate trade-offs—choosing what to do and what not to do. The strategic plan is the formal document that operationalizes this vision, outlining concrete actions, resources, and metrics [86]. In this analysis, ‘strategy’ refers to the overarching CE vision of the cities, while ‘strategic plans’ are the specific policy documents designed to execute it. The analyzed documents include national, regional, and local strategies that are presented in

Table 1. A compilation of the analyzed strategic documents.

Strategies	Copenhagen	Ljubljana
National	Strategy for Circular Economy [87]	Slovenian Development Strategy 2030 [88] Slovenia’s Spatial Development Strategy 2050 [89] Roadmap Toward the Circular Economy in Slovenia [90]
Regional	Regional Growth and Development Strategy—Greater Copenhagen 2020 [91]
Local	Copenhagen Climate Adaptation Plan/Copenhagen Carbon Neutral by 2025 [92] Circular Copenhagen—Resource and Waste Plan 2024 (hereinafter: RAP24) [93]	Environmental Protection Program for the City of Ljubljana 2007–2013 [94] Environmental Action Program for the City of Ljubljana 2014–2020 [95] Development Strategy for Waste Management Activities in the City of Ljubljana 2014–2035 [96] Sustainable Urban Strategy of the City of Ljubljana 2014–2030 [97]

. Based on these documents, we compiled data on strategic objectives and measures, planned activities, stakeholders involved, and expected outcomes.

Second, in order to refine and clarify the information obtained from the analyzed documents, a questionnaire survey was conducted with key practitioners from the municipal departments responsible for developing and coordinating the implementation of circular strategies. The survey featured a “circular transformation manager” from Copenhagen and a “circular economy manager” from Ljubljana. This survey was designed to verify which strategic documents are actively implemented by urban stakeholders and to gather granular insights into the operational aspects of CE transition. Specifically, it aimed to identify the key actors responsible for managing and realizing CE initiatives, define the primary beneficiaries of these strategies, and ascertain the specific methods and indicators employed for the performance evaluation of CE transition in the built environment. Additionally, an in-depth structured interview with the Ljubljana representative (R1) provided further data on the CE strategy beneficiaries, innovations, best practices, and implementation specifics.

The data collected through the surveys served as a crucial triangulation tool, corroborating and enriching the information extracted from official municipal and national documents by providing a practitioner’s perspective on the actual state of CE adoption and its challenges.

3.3. Data Analysis

To systematically answer the research questions, the data analysis was structured around three key thematic areas identified in the literature on CE adoption [13,35]: (1) governance for sustainable cities, which helps determine the most significant actors in the implementation process; (2) urban services and consumer practices, which enable a broader spectrum of beneficiaries; and (3) cleaner production and construction. The latter is understood as a preventative strategy focused on resource efficiency and minimizing waste at the source, and was investigated as a foundational element of the CE.

Within this thematic structure, a qualitative document analysis [98] was employed as the primary research method. To analyze the content of the strategic documents and the qualitative data from questionnaires and interviews, we used thematic analysis [99]. The aim was to identify recurring patterns and priorities in the cities’ policies. The analyses were carried out according to a deductive framework based on 10 original criteria corresponding to the three leading trends identified in the literature survey [12,13], which aligned with the three leading themes mentioned above. These criteria, presented in the

Table 2. A deductive framework used to analyze the selected case studies.

Problem	No.	Criteria	Detailed Description
(1) Governance of strategic transition toward CE	1	Governance model	Examination of how strategies are managed and implemented (top-down or bottom-up approach)
	2	Change dynamics	Analysis of the change of priority areas and directions of strategic measures in the dynamic system
	3	Priority areas and key measures	Determination of key priority areas and strategic actions for implementing CE in the built environment
	4	Stakeholders’ involvement and beneficiaries	Examination of the scope of social impact of the strategy, identification of groups directly and indirectly involved in the CE-related activities
	5	Indicators	Recognition of indicators to measure the performance of the implementation of the strategy
(2) City services and consumer practices	6	Circular city services	Identification of innovative urban services that support the implementation of the CE in the built environment
	7	Circular consumer practices	Determination of the extent of change in consumer practices in the city
	8	Main actions	Identification of action undertaken in order to fulfil the strategic aims
	9	Methods	Identification of the methods used to study the success of introduced urban services and changing consumer practices
(3) Cleaner production and building industry	10	Case studies and current effects	Identification of examples of successful implementation of the CE principles in the built environment in order to set recommendations

, provided the basis for summarizing each city’s activities that played a key role in transforming the built environment into the CE framework.

Finally, the identified good practices were categorized according to three key areas relevant to the transformation process: finance, planning, and urban policy. The research scheme is presented in Figure 2. The application of this research framework allowed for a holistic determination of the effects of strategic actions taken by the selected cities in terms of implementing the CE principles in the built environment.

4. Results

4.1. Copenhagen—Carbon Neutral City

The city has declared in its strategic documents to transition to a carbon neutral economy by 2025 and to recycle 70% of municipal waste by 2024. For the past 20 years, the recycling rate of municipal waste has increased by almost 20%. The city pays considerable attention to reducing building-related emissions, which are responsible for 75% of the city’s CO₂ emissions.

Rationale. Copenhagen points to the effects of the climate crisis as the leading reason for the strategic actions taken in its transition to the CE; it causes the need for more frequent repairs, a loss in value of buildings, and a reduction in its quality.

4.1.1. Governance of Strategic Transition Toward CE in Copenhagen

Governance model. The strategies incorporate diverse models of action that have a predominantly top-down approach, along with policies designed to support bottom-up activities.

Change dynamics. The Environmental Protection Act, passed in the 1970s, has provided Denmark with a legislative foundation to make incremental advancements in sustainability over the years. In 2009, Copenhagen made the decision to prioritize sustainable development, which has been reflected in strategic documents and initiatives related to waste management and climate change mitigation. Since 2019, it has been implementing the CE strategy, which aligns with the current EU policy on development and environmental protection. According to the Resource and Waste Plan [93], the city is involved in a collaborative effort to transform the material cycle in architecture.

Priority areas and key measures. In relation to the built environment, the strategy documents identify priority areas that include stimulating reuse and exchange, recycling construction materials, and renovating instead of demolition. Particular attention is given to recycling construction and demolition waste, which accounts for a 1/3 of all waste produced in the city. The RAP24 [93] presents innovative ways of waste processing including the selective demolition of civic buildings and city infrastructure. The core CE activities pertain to both the profitability of renovating infrastructure and buildings, which is linked to energy retrofits as well as the need to maintain material values. One of the key elements in Copenhagen’s implementation of the circular strategy is its education regarding waste processing.

Stakeholder involvement and beneficiaries. A variety of stakeholders have been involved in the CE transformation process. Supervision and coordination is provided by local authorities, the city’s specialized departments as well as municipal institutions (e.g., Sydhavn Recycling Center). Their activities are meant to engage public–private entities, private companies, NGOs, educational units (schools, universities), and resident associations. Top-down policies are designed to support individual grassroots activities.

Indicators. The city uses indicators for measuring the performance of the strategies regarding the amount of construction materials reused, the amount of construction waste recycled, and the reduction in a CO₂ emission. In addition, the indicators included in the Monitoring Framework for the Circular Economy [100] are being applied.

4.1.2. Urban Services and Consumer Practices in Copenhagen

Urban services. Dedicated and specialized urban services enable the change in consumer practices. For instance, employing a city-supported network of recycling centers where items through selective demolition, reuse, and recycling can be redistributed in a circular cycle (e.g., Sydhavn Recycling Center) or a network of recycling and reuse hubs and local centers. Additionally, the transition to the CE is supported by the Circular Copenhagen platform, which is designed and run by the city to raise awareness about the CE, identify environmentally friendly urban services, and provide up-to-date information about the process.

Consumer practices. One of the key outcomes of implementing CE strategies is a number of changes in consumer practices that have led to the sharing of goods and services among residents. The changes include: (1) leasing/rental instead of selling (e.g., office equipment, electronics, household appliances); (2) services instead of selling (e.g., specialized equipment or construction site amenities); (3) activities leading to the reuse of waste (e.g., recycling of plastics, insulation materials); (4) reusing instead of disposal (e.g., interior fittings); and (5) selective demolition instead of demolition (e.g., as part of the demolitions carried out by the city). The exchange of information and good practices is systemically supported by campaigns (launched by e.g., the Circular Copenhagen platform).

Main actions. Activities in line with the strategy and detailed program documents can be observed in: (1) the reuse and high-value recycling of components and materials by way of designing for disassembly; (2) sharing and multi-purposing of buildings to increase the utility of existing floor space; and(3) industrialized production along with the 3D printing of building modules to reduce time and material costs in construction and renovation. To reduce the environmental impact of the built environment, the city has initiated several policies and programs related to retrofitting the city’s aging building stock, which is largely energy inefficient; the actions support space reuse in buildings including the renovation of historic tenement houses for social housing.

Methods. The municipality investigates resident satisfaction and involvement in CE-related activities through community surveys including opinion polls, in-depth interviews, and meeting with residents.

4.1.3. Cleaner Production and Building Industry in Copenhagen

Effects. Environmental and financial savings are anticipated as a result of the implementation of these strategies [101]. The dynamics of change show a convergence between the objectives of local strategies and EU policies along with a gradual increase in new bottom-up, community-based initiatives. The aforementioned scenario not only requires the involvement of public finances and planning, but also the integration of said activities into urban policies. This is particularly noticeable when referring to changing consumption patterns (

Table 3. Schedule of undertaken activities, initiatives, and good practices as a part of the transition toward the CE in the built environment in Copenhagen in relation to the identified areas supporting the successful implementation process.

Type of Action	No.	Strategic Actions and Initiatives	Good Practices	Finance	Planning	Policies
(A) Change in consumption patterns	1	- Supporting the lending system - Supporting repair as part of the purchase agreement - Providing information on the whole life cycle of buildings	Sydhavn Recycling Center, - Recycling hubs for demolition materials	X	X	X
	2	Development of local centers for recycling and reuse of components (also with building materials, furniture, wood)	Resource lab at the Sydhavn Recycling Center	X	X	X
(B) Reduction in material consumption and value preservation	3	- Upcycling industrial waste into high quality materials - Partnerships between entities	- Recycling hubs for demolition materials, - Innovation Network under the Ministry of Higher Education and Science	X	X	X
	4	- Selective demolition to maximize recovery of materials from existing buildings - Removal of hazardous and contaminated materials			X
	5	Reuse building materials from existing properties	Sale of materials obtained from existing buildings belonging to the city at recycling centers	X	X	X
(C) Changes in existing policies	6	Compilation of the current technical and security status of the existing architecture and infrastructure, making this data public	- Circular Copenhagen platform, - ‘We Build Denmark’ national cluster		X	X
	7	Education of stakeholders	- Curriculum in public schools and universities, - Lifestyle and Design Cluster, - Innovation Network under the Ministry of Higher Education and Science, - Circular Copenhagen platform			X
	8	- Describing materials using the so-called sustainability class - Development of object classification via material passports	We Build Denmark national cluster		X	X
	9	Communicate the total cost of ownership throughout the building lifecycle process, not just the initial (purchase) cost	Circular Copenhagen platform			X
	10	Alignment of investment policies	Green procurement	X	X	X

Source—Own research based on: Strategy for Circular Economy (2018) [87], Copenhagen Climate Adaptation Plan/Copenhagen Carbon Neutral by 2025 (2012) [92], Circular Copenhagen—Resource and Waste Plan 2024 (RAP24) (2019) [93], and questionnaire survey.

, (A)). In instances of reducing the consumption of materials and raw materials, comprehensive actions mainly include upcycling (Table 3, (B). 3) and the reuse of building materials from existing properties (Table 3, (B). 5). Changes in existing urban CE policy are reflected in the adaptation of investment policies and in the growth of green procurement.

4.2. Ljubljana—Zero Waste City

One of Ljubljana’s leading problems, which is also characteristic of other post-socialist cities, is its urban sprawl and a degraded urban fabric [102,103]. Ljubljana has been gradually implementing the CE in cooperation with the Ellen MacArthur Foundation. The city proclaims that it is the first European capital to have carried out the conversion to zero waste. It aims to boost separate collection to 78% by 2025 and 80% by 2035, decrease the yearly total waste generation to 280 kg per inhabitant, and reduce residual waste to 60 kg by 2025 and 50 kg by 2035, showcasing a strong commitment to sustainable waste practices. Slovenia’s capital is the only post-socialist city to have been awarded the European Green Capital Award (2016). Between 2004 and 2018, Ljubljana experienced a tenfold surge in separate collection, resulting in a 95% reduction in the amount of waste sent for disposal, all while maintaining costs among the lowest in Europe.

Rationales. The main reason for Ljubljana embarking on its strategic transition to the CE is the set of problems that result from urban sprawl—among others, high costs, high CO₂ and pollutant emissions, and difficulties with urban management. The other reason is the city’s search for green alternatives as well as guidelines that it could carry out in order to revitalize its devalued urban space. As the city representative explained, this was a direct response to the negative trends of the post-socialist period, when “since 1995 Ljubljana lost over 20,000 inhabitants, mainly emigrated to the neighboring municipalities leading to uncontrolled suburbanization and significant infrastructural challenges” (R1).

4.2.1. Governance of Strategic Transition Toward CE in Ljubljana

Governance models. Drawing on the experience of other EU cities, Ljubljana’s strategies include various models of action in which the predominant approach is based on top-down processes that support bottom-up activities and public–private partnerships.

Change dynamics. The origins of the circular strategy in Ljubljana go back to 2007 when steps were taken to steer urban policy toward sustainable development, and from 2014 to implement zero waste principles.

Priority areas and key measures. The strategy documents identify priority areas such as the food system, forestry, the manufacturing industry, mobility, ecological design, industrial symbiosis (exchanging, recycling, reusing resulting from cooperation between public and private entities), reduction in material consumption, and reduction in plastic use. Strategic documents also stipulate closing the energy cycle, energy renovation (via e.g., thermal modernization) of buildings owned by the city, additive transformation, refurbishment, adaptive reuse of materials as well as changes in policy, financing, and public tenders toward green procurements. Sustainable development in Ljubljana is primarily based on the protection and maintenance of existing city infrastructure and the built environment. The most appropriate way for the city to successfully meet this objective is to promote development on land that is either vacant or occupied by abandoned buildings. As highlighted in the in-depth interview, Ljubljana’s approach to CE-focused revitalization is multifaceted, encompassing “urban renewal by preserving old city core, redevelopment of the city by modernization of existing built stock and restructuring of under-used built areas where more intensive use and denser development is justified, and rehabilitation as a strategy for reactivation of degraded areas, primarily for the construction of mixed-use residential neighborhoods along public transport lines” (R1).

Stakeholder involvement and beneficiaries. A variety of stakeholders are involved in strategic activities—public and private actors in different configurations of cooperation. For example, Energetika Ljubljana transfers excess energy that is not used by private entities to buildings in the city.

Indicators. The city does not use indicators to measure the success of the implementation of circular strategies, but does plan to do so in the future.

4.2.2. Urban Services and Consumer Practices in Ljubljana

Urban services. The city has a wide range of city services that support the CE, which include the JP Voka Snaga, a municipal institution that promotes rainwater retention and consumption, and RCERO deals with extending the lifetime of products and materials through their creative reuse. Energetika Ljubljana (a public energy company) collects waste ash from coal combustion as a raw material that is used as a construction composite, and the Repair Cafe is a network of municipal recycling sites. The information office of Ljubljana—Point For You, is a public entity providing education about the CE and sustainable consumption practices with the aim of not only increasing the level of involvement, but also expanding the group of beneficiaries.

Consumer practices. The city promotes changing consumer practices by implementing top-down initiatives and providing incentives to develop businesses in line with the CE model. The city encourages modular product design that emphasizes the ability to maintain, repair or refurbish, and recycle (as exemplified by Repair Cafe), and focuses on borrowing or renting a variety of items for use in homes or workplaces (via e.g., The Library of Things).

Main actions. Ljubljana is promoting selective demolition instead of demolition; however, there is no additional information about the subsequent circulation phases of neither the recovered materials nor the infrastructure, which would facilitate their remarketing. In order to foster the circular transition, the city has initiated programs related to the renovations of the public building stock and subsidy programs to support the refurbishments conducted by the city inhabitants. The city also seeks to stop the sprawl of its suburbs.

Methods. The survey revealed that Ljubljana currently does not employ methods to measure progress in follow-up actions related to introduced urban services and changing consumer practices. Appropriate methods and indicators are just now being developed.

4.2.3. Cleaner Production and Building Industry in Ljubljana

Effects. Nowadays, 69.5% percent of the city’s waste is collected through separation and sorting. This success is largely enabled by the strategies regarding the reduction in material consumption (

Table 4. Schedule of undertaken activities, initiatives, and good practices as a part of the transition toward the CE in the built environment in Ljubljana in relation to the identified areas supporting the successful implementation process.

Type of Action	No.	Strategic Actions and Initiatives	Good Practices	Finance	Planning	Policies
(A) Change in consumption patterns	1	Industrial symbiosis—exchange of products between entities in order to minimize waste	- Renovations conducted in public-private partnership with energy company - Reuse of the post-production waste	X	X	X
	2	Shift from products to services—product ownership displaced in favor of renting and sharing	- Reuse Center - Repair Cafe - A Library of Things	X	X	X
(B) Reduction in material consumption and value preservation	3	Ecological design: - modular design - promoting regular repair - reuse and refurbishment - maintaining the value of products - recycling of products and materials - designing items to have a longer life span	- Renovation of 48 public buildings: cultural, sports and health facilities, educational institutions, and city administration buildings - Park path paving made of the reused building materials	X	X	X
	4	- Closing the energy cycles - Minimizing environmental impact - Energy optimization of buildings		X	X	X
	5	- Changing tax and subsidy policies - Aligning investment policies	- “Ljubljana—My City” Subsidy Program supporting the refurbishment of private buildings - Green Procurement	X	X	X
(C) Changes in existing policies	6	Adaptive reuse	- Refurbishment and extension of the old Opera House - Additions to the former central barracks buildings for museums and new modern gallery - Conversion of former cinema to the municipal center of urban culture	X	X	X
	7	Building the appropriate infrastructure	- RCERO—recycling center - The Reuse center - Repair Cafe - Library of Things	X	X	X
	8	Directing science and research, fostering innovation	Coordination of activities and transfer of knowledge with the University of Ljubljana, Faculty of Architecture		X	X
	9	Education and awareness raising among stakeholders and beneficiaries	CE-dedicated curricula in kindergartens, schools, and public universities		X	X

Source: Own research based on: Roadmap Toward the Circular Economy in Slovenia [90], Environmental Action Program for the City of Ljubljana 2014–2020 [94], Development Strategy for Waste Management Activities in the City of Ljubljana 2014–2035 [96], questionary survey, and in-depth interview (R1).

, (B)) and changes in consumption patterns, particularly by industrial symbiosis (Table 4, (A). 1). According to the Zero Waste Declaration, Ljubljana [104] has committed to increase separate collection to 78% by 2025 and to 80% by 2035, and reduce the yearly total waste generation to 280 kg per inhabitant and yearly residual waste to 60 kg by 2025 and 50 kg by 2035 [105]. In 2020, 80% less rubbish went to landfill than in 2008, placing Ljubljana at the top of the recycling scoreboard of European capitals (according to in-depth interview). In fact, Ljubljana’s renovations will alone generate 968 tons fewer CO₂ emissions, which is an equivalent to the amount absorbed annually by 108 ha of forest. The dynamics of change show a convergence between the objectives of local strategies and EU policies along with a gradual increase in city-led initiatives.

The gradual change in local policy regarding the built environment is supported by the transfer of knowledge from the Faculty of Architecture at the University of Ljubljana (Table 4, (C). 8, 9) and by the growing experience gained by Ljubljana during the execution of recycling activities for various sectors. The expertise gained in the city’s transition toward zero waste is expected to soon be transferred to policy oriented toward recycling and reuse in the built environment. This will enable minimalization of the environmental impact and increase the energy efficiency of buildings (Table 4, (B). 4). As a core principle guiding its urban CE policy, Ljubljana emphasizes a fundamental preference for “renovation, refurbishment, and additive transformation of buildings over building new ones” (R1) while acknowledging that “the construction of new facilities is never completely excluded” (R1). This strategic orientation is reflected in the adaptation of investment policies and in the growth of green procurement.

5. Discussion and Recommendations

The comparative analysis of Copenhagen and Ljubljana revealed distinct pathways and shared challenges in the implementation of CE strategies. This section discusses the findings in relation to our key research questions, focusing on the objectives driving the transition, the dominant implementation trends, and the methods used to evaluate the shift toward the CE in the built environment.

Both cities—Ljubljana for more than two decades, Copenhagen since the 1970s—have been applying measures leading to sustainable development. The transformation level toward both sustainability and to the CE in cities varies due to their different geopolitical and socio-economic situations. The capital of Slovenia is a post-socialist city, which entered the period of political transformation in 1991; after joining the EU in 2004, it has focused on sustainable development; in 2014, it took the idea of zero waste as one of its strategic goals. Copenhagen, a city of the so-called “old union”, functioning in the structures of the EU since 1973, is a long-term leader in the accomplishment of sustainable strategies. Both cities use EU funds and expertise, and implement EU requirements in their legal systems and development policies at the regional and local levels. Since the adoption of the First Circular Economy Action Plan [53], strategic plans of both cities have focused on the implementation of the principles of CE convergent with the main objectives of the EU. This includes regulating the issue of recycled content requirements, promoting measures to improve the durability and adaptability of the built environment and infrastructure, developing digital construction logs, and revising recycling and recovery targets for construction and demolition waste.

Antecedents of these strategic actions demonstrate a certain heterogeneity. Ljubljana, through the CE, postulates an attempt to solve a wide spectrum of urban problems related to urban sprawl, the need for revitalization, and the renewal of degraded urban spaces. The CE capacity for effective urban regeneration has previously been demonstrated [106,107]. Copenhagen’s activities focus on urban management in the spirit of CE in the built environment and on changing the residents’ consumer practices. The two cities converge on a catalog of strategic actions and city initiatives that lead to close the material cycles and reduce waste generation. In both capitals, the approach to education at different levels (primary to higher) is parallel and constitutes a foundation for further effective changes.

In relation to the implementation patterns, Copenhagen demonstrates a high degree of systemic, top-down approaches to tasks such as maintaining the value of materials or closing the circulation cycles of building materials through selective demolition or the distribution of materials used in recycling centers. The city sets as an example of urban actions to be emulated by citizens and private actors at a later stage. Copenhagen’s example shows that, especially in the initial phases of the transition to the CE, it is crucial to consistently implement urban strategies that involve citizens and are supported by effective educational activities along with a variety of dedicated urban services and infrastructure, all of which ultimately facilitate changes in basic consumer practices. The effectiveness of such systemic approaches to circularity in the built environment has been consistently demonstrated in other pioneering “old” EU cities such as Amsterdam [65] or Brussels [108].

Ljubljana’s transition to a zero waste model is more gradual and sectoral, but with less attention to the built environment. Although the urban initiatives identified in this study provide a strong incentive for further action, they do not yet form a systemic solution for material circulation in architecture and construction. The city’s circular transition is currently driven by activities related to recycling materials from demolition and renovation, especially as part of the revitalization process. Nevertheless, there is not enough coordination and unification of strategies that relate to existing buildings and infrastructure. In contrast, education and community-based transition have yielded clear successes. These have effectively changed consumer habits, fostering business models that support rental and reuse, which could be replicated in architecture at some point in the future. This success in waste management stems from a broader, environmentally conscious cultural shift, which has been supported by educational programs starting from kindergarten. These findings align with broader academic discussions on urban CE transitions, which often highlight the critical role of public engagement and educational initiatives [109,110].

In both capitals, the top-down initiatives stimulate the development of bottom-up actions, a dynamic consistent with the logic of implementing smart governance [111,112] However, it is particularly noteworthy that in both cases, the local level strategy documents have given little consideration to areas related to the transition of the built environment toward the CE. It continues to be a side thread in the adopted strategies, which can be considered a factor impeding the progress of the circular transition [16]. Given the important role of revitalization [107], adaptive reuse, and sustainable urban development this issue should be thoroughly addressed in urban policies, finance, and planning [113].

The implementation of the circular model has brought tangible benefits to both cities such as a reduction in waste, increased cross-sectoral cooperation, accelerated urban renewal, and revitalization. Ljubljana’s gradual transition to a zero waste model and the CE translates to the city having reduced emissions as well as waste generation and production. In Copenhagen, the CE strategy delivers positive environmental outcomes by minimizing waste through city-wide recycling and reuse programs as well as social and economic benefits. A significant finding of our study is the disparity in formal evaluation approaches. Methods for measuring success and stakeholder interest are being developed and have taken the form of detailed indicators in Copenhagen and are under formulation in Ljubljana, which remain a key challenge in evaluating the evidence-based effects of implementing the CE in the built environment. This lack of a unified, systemic framework for tracking progress, even among leading cities, points to a broader gap in CE governance [114].

In relation to the analysis of strategic objectives, implementation trends, and the gap in evaluation methods, we propose the some recommendations for cities that aim to create a new socio-technical regime based on CE principles in relation to the three types of action analyzed (

Table 5. Recommendations for future CE implementation in the built environment.

Type of Action	Recommendation
(1) Governance of strategic transition toward the CE	Financial incentives and support for new, CE-related business models
	Organization of green public procurement (GPP)
	CE-related education for decision-makers
	Expanding building codes and creating a clear legal framework for reuse, adaptation, recycling within the built environment
(2) City services and consumer practices	Change of consumer practices support by education and promotion
	Entrenching sustainable standards
	Leasing instead of selling
	Services instead of selling
	Recycling instead of disposal
	Reuse instead of disposal
	Selective demolition instead of demolition
(3) Cleaner production and building industry	Inclusion of the measures related to the implementation of the CE in the built environment in city strategies and programming documents of urban policy
	Digitalization of the inventory process
	Digitalization of the as-built documentation
	Creation of material data banks (material depots)
	Establishing exchange and recycling centers

).

6. Conclusions

The paper presents the results of the application of the CE model in the built environment from the perspective of local strategic planning, the implementation process, and a comprehensive framework for measuring the CE performance.

Firstly, despite these different starting points, both cities have ambitious strategic goals that include shifting to zero waste (Ljubljana) and carbon neutrality (Copenhagen), altering consumer practices, and developing public–private partnerships that support the CE transition. The most significant objectives regarding the built environment are often shaped by the mandatory implementation of EU policy requirements and include the reduction in waste by decreasing the consumption of raw materials, the extension of the life cycle of buildings through responsible design, the development of material databases, and the preservation of the value of materials via renovation or adaptive reuse.

Secondly, we identified key patterns in the strategic management of the transition processes, where top-down initiatives undertaken by cities stimulate bottom-up actions. The fundamental changes in consumer practices and education demonstrated in this work enable the gradual implementation of sustainable models of material circulation and enhance the popularization and recognition of the CE concept among a wide range of beneficiaries. Accustoming residents and entities to a circular flow of materials, selective demolition, and the establishment of a network of recycling centers are the cornerstones of the transformation of the built environment toward the CE.

Thirdly, the implementation of the circular model brings tangible benefits in both cities such as a reduction in waste, increased cross-sectoral cooperation, accelerated urban renewal and revitalization, prevention of urban sprawl, or a reduction in carbon dioxide and harmful substance emissions. Our research indicates that the methods for measuring progress and stakeholder interest differ starkly. While Copenhagen is developing detailed indicators, Ljubljana is still working on their formulation. These approaches to performance evaluating are inconsistent and not yet systemic, which constitutes a significant barrier to the effective scaling and replication of good practices.

Beyond its academic contribution, this study offers several key lessons for cities undergoing a similar transition. The shift to a circular economy in the built environment requires a multi-actor approach with clearly defined roles and responsibilities. The key lessons learned indicate that governments are responsible for creating a stable legal framework for material reuse and providing financial incentives for circular business models through tools like green public procurement. Institutions, including universities and schools, play a crucial role in education, which proved fundamental in both case studies for changing consumer practices and fostering a culture of sustainability. Finally, the role of the residents and private sector is to actively adopt new practices such as shifting from ownership to leasing and prioritizing selective demolition over traditional methods. The primary challenge identified is the coordination of these multi-actor efforts and the full integration of the built environment into city-wide CE strategies.

By diagnosing this problem, our research lays the groundwork for future efforts to develop a coherent evaluation methodology to assess the results of the implementation of CE strategies in the built environment and suggest qualitative evaluation metrics. However, this study had its limitations, primarily its focus on two specific case studies and its reliance on official strategic documents supplemented by interviews with municipal experts. Future research should therefore not only broaden the empirical scope by including more cities and a wider range of stakeholders, but also complement our findings by developing and testing the unified set of quantitative indicators needed to create the comprehensive assessment framework that is currently missing.