Keywords

1 Introduction

1.1 Circular Economy in Facility Management

Various environmental problems such as biodiversity loss, water, air and soil pollution, resource depletion and excessive land use are increasingly threatening the Earth’s life support systems. Especially in today’s linear economic models with the “take, make, dispose of” concept raw materials are extracted, processed, used and then disposed of as waste [1]. This approach leads to a high consumption of limited natural resources [2, 3].

Traditionally, the construction industry has also historically pursued an unsustainable, linear economic model based on the “take, make, dispose of” concept and seems to continue to do so (compare e.g. EMF, 2015) [4]. This linear approach does not allow for the targeted dismantling of buildings and the reuse of materials, components, or elements in order to conserve or conserve resources and reduce the need for new raw materials [5]. The built environment plays a significant role in terms of resource consumption due to its significant environmental impact, but at the same time it also offers great opportunities to reduce energy consumption, greenhouse gas emissions and waste emissions [6].

A look at the annual status reports of the United Nations Organizations (UN), the International Energy Agency (IEA) and the Global Alliance for Buildings and Construction (GABC) shows the importance of the construction and real estate industry in the global context of energy consumption – the industries in question are responsible for 36% of global energy consumption and 39% of CO2 emissions [7]. The figures from 2015 underline the importance of construction in energy and material consumption, also in Switzerland, where, for example, 40% of energy and 50% of material inputs were consumed, while at the same time 75% of waste was generated by this sector [8].

It is becoming clear that there is an urgent need for a transformation of the construction and real estate industry towards a circular approach. This is where the circular economy strives for better management of resources.

Guerra et al. (2021) research and a growing number of policy initiatives are increasingly focusing on implementing a circular economy in the real estate and construction sectors [9]. This trend is also a response to the increasing pressure due to dwindling natural resources, rising waste production and increasing building material costs. Çetin et al. (2021) argue that the industry is also generally considered to be highly fragmented and characterized by high material usage [10]. These authors advocate for the restructuring of existing structures and processes, along with the development of new holistic models to include the entire value chain from raw material extraction to production, construction, use and disposal [10]. Such approaches enable the closure of material cycles and facilitate more targeted control of resource consumption and waste. According to Wilts (2021) it is crucial to not only focus on optimizing energy consumption but also to address other methods for reducing CO2 emissions [11].

Despite various approaches in the literature on the implementation of the circular economy in the sector addressed, there seems to be a lack of a structured overview or a comprehensive model of possible strategies and a uniform understanding of the term (see also e.g. Adams et al., 2017) [12]. So far, the focus has mainly been on individual aspects of the circular economy, such as the planning, recovery, and reuse of building materials for new buildings. In the meantime, the circularity for existing buildings is also increasingly being investigated in various studies [13, 14]. However, an in-depth examination of the circular economy and its application is necessary, especially in practice and especially in the field of REFM, in order not only to reduce the ecological footprint of the industry, but also to focus on an optimized use of existing buildings or even completely new service-oriented circular economy models (compare also with e.g. Kyrö, 2020; Ness & Xing, 2017) [14, 15].

Ultimately, it can therefore be stated that existing models show rudimentary cycles and aspects of the circular economy – their location in the respective model is either incomplete or one-dimensional, for example by only showing activities at the end of the service life (compare also Antunes et al., 2021) [16], a specific resource flow or material component (compare with R. J. Geldermans, 2016) [17], or a single life cycle phase (compare with Eberhardt et al., 2022) [18] why there is a need for action for the development of a holistic circular economy overview mode [10, 19].

2 Purpose of This Study

This work aims to provide a structured and comprehensive overview of circular economy principles for buildings, acting as an overview model. It particularly considers a variety of circular economy models for resource areas such as waste, CO2, energy, materials, soil and water. However, this overview model is not confined to the individual resource areas alone; it focuses on buildings to capture the essential aspects of possible circular economy principles throughout their entire service life, though it does not claim completeness in terms of models and principles.

For this purpose, an overview of different circular economy models is presented. Ultimately, this overview serves as the basis for developing circular strategies for real estate and facility management (REFM) business processes for space and infrastructure.

The following research questions, are ultimately to be answered:

  • Research question 1: Which generic circular economy strategies exist for the building life cycle and in which life cycle phase can they be located?

  • Research question 2: Which circular strategies can be identified in terms of space and infrastructure?

3 Methodology

  • Step 1: Determine search terms. The following search terms, as well as variations and combinations thereof, were defined in German and English and used as an introduction to the research.

    • Circular Economy (Switzerland/EU)/Circular Economy (Switzerland/EU)

    • CEN/TC 350/SC 1 and ISO/WD 59004

    • Circular Economy in the construction industry (example/examples)

    • Green deal

    • Recycling construction industry/Recycling construction industry

    • Environmental Performance of Buildings (EPB)

  • Step 2: Carry out a literature search: The terms were researched on the Internet and in relevant online libraries.

  • Step 3: Evaluate search results and select literature: Based on the assignment, suitable sources and literature were searched for the individual topics, the sources were checked for content and accuracy and the best sources were used for the work.

  • Step 4: Identification which generic circular economy strategies exist for the building life cycle and localization of their life cycle phase.

  • Step 5: Identification of circular strategies in terms of space and infrastructure.

4 CE Definitions and Principles

Desing et al. (2020) highlight the lack of consensus and a uniform definition for “circular economy”, despite its widespread use (also see Kirchherr et al., 2017) [20, 21]. According to them, the Ellen Mac Arthur Foundation (EMF) definition, which emphasizes the regenerative economy and new business models, is the most cited and recognized. This definition has been widely adopted or modified by policymakers and institutions like the European Commission [4, 20, 22].

The Laboratory for Applied Circular Economy (LACE) proposes a resource-based definition of the circular economy, aimed at human well-being, but acknowledging biophysical and planetary boundaries [23, 24]. These limits are considered absolute and quantifiable for the resource base used for human activities [24]. Definition of the circular economy is:

The circular economy is a model that adopts a resource-based and systemic view and aims to take into account all the variables of the Earth system in order to maintain its viability for people.

The model serves society to achieve well-being within physical and planetary boundaries. This is achieved through technological innovations and new business models that provide the goods and services needed by society and lead to long-term economic welfare. These goods and services are produced with renewable energy and are made from materials that are either renewable through biological processes or can be safely kept in the technosphere, requiring minimal raw material extraction and ensuring safe disposal of the inevitable waste and distribution in the environment.

Circular economy builds on, manages, and optimizes the use of sustainably available resources by minimizing entropy production, slow cycles, and resource and energy efficiency [27, p. 6].

5 LACE Model

According to LACE (2020) a sustainable circular economy means that all economic and social decisions are based on the planetary boundary can be derived [24, 25]. It consists of a three-level hierarchy of environment, society, and economy, which are connected to each other in a cascading fashion. The environmental level forms guardrails for human activities or for society, which is part of this biosphere. Desing et al. (2020) argue in this regard that human activities should take into account the natural, non-negotiable, physical and environmental constraints of the environmental level in order to be sustainable in the long term [20]. Furthermore, according to Desing et al. (2020) also for third-level economic operators, who have to operate within these environmental constraints and therefore have to comply with these restrictions in accordance with LACE (2020, p. 3) as «… Absolute and quantifiable limits to the resource base” [20, p. 3]. To ensure an efficient use of available resources, the LACE (2020) focus on the three principles [20].

5.1 RESOLVE Model

The EMF’s RESOLVE Framework describes further circular principles [26]. According to Kyrö (2020), the EMF’s framework is probably one of the most widely used models in the field of circular economy [14]. EMF (2015) further points out that the principles can be used by both companies and governments to bring about a transition to a circular economy or to develop circular strategies [4].

5.2 “Butterfly” Model

Developed by the EMF (2015), the CE model – also known as the “butterfly diagram” – is basically based on three principles [4]. In the model of the EMF (2015) a distinction is also made between a biological and a technical cycle. The biological cycle refers mainly to products or materials that are biodegradable and can be safely returned to the biosphere. In the biological cycle, concepts are also described that return nutrients to the soil and contribute to the regeneration of nature (The biological cycle of the butterfly diagram, n.d.). The technical cycle provides different phases that help to keep products or materials in use and not become waste. In the phases, a distinction is made between inner and outer phases or loops. Internal phases such as sharing, maintenance or reuse should take precedence over external phases (e.g. recycling), as these preserve the value of a product or preserve the product as a whole and not dismantle it to make it again, as is the case with recycling. The outermost phase, recycling, thus represents the final stage of a circular economy. Products or materials should therefore be designed in such a way that they are designed for the individual phases (e.g. easily repairable products or a modular design with the possibility of replacing individual components, etc.) and thus the full potential of a circular economy can be exploited (The technical cycle of the butterfly diagram, n.d.).

5.3 FOEN Model

Like the butterfly model of the EMF, the circular economy model of the Federal Office for the Environment (FOEN) also shows a biological and a technical cycle, but these are not explicitly addressed in the model itself. In contrast to the butterfly model, on the other hand, the individual phases of products and materials are shown in the technical cycle, starting with the extraction of raw materials, followed by design & production, distribution, consumption & use and the final phase recycling & collection or incineration & landfill (FOEN, 2022) [26].

Comparable to the butterfly model, on the other hand, are individual cycles or loops within the technical cycle such as sharing, reusing, repairing and remanufacturing/overhaul. In this regard, the FOEN refers to these loops within the technical cycle mentioned above – i.e. sharing, reusing, repairing, and remanufacturing/overhauling – and should not only increase the service life and service life and lead to protection of the environment, but should also be preferred over recycling, the last resort of a circular economy, so to speak. This is justified in particular by the fact that recycling in turn requires energy, water and chemicals to recycle materials and thus has an environmentally harmful effect (FOEN, 2022) [26].

5.4 UNEP Model

Another notable circular economy model includes the United Nations Environment Programme (UNEP) [27]. As in the previous two models, the UNEP model is based on a linear economy but without distinction between a biological and technical cycle [27]. Apart from this, however, so-called “value preservation loops” are shown in the model and are referred to as “user to user” (purple), “user to business” (green) and “business to business” (blue) and are briefly explained in (Understanding Circularity, n.d.) [27].

5.5 European Commission Model

The European Commission’s Circular Economy model focuses on principles such as waste reduction, resource efficiency, and recycling. It advocates for eco-friendly construction materials, energy-efficient building designs, and the incorporation of reuse strategies throughout the building lifecycle [22]. This model, shifting away from the traditional ‘take-make-dispose’ approach, offers a practical framework also for the real estate development that minimizes environmental impact while potentially reducing costs and fostering new business opportunities.

6 Results

In the following, relevant circular economy models are compared, although there is no claim to exhaustiveness with regard to the coverage of all relevant models. Both definitions, principles and the models presented serve as an introduction to the topic of circular economy to familiarize the reader with various terms and aspects (Table 1).

Table 1. Summary of CE principles.
Full size table

Based on the analysis above, applying this model to real estate lifecycle management involves integrating the following principles (Table 2).

Table 2. Summary of CE principles.
Full size table

In addition, the “Material Circularity Indicator” developed by the Ellen MacArthur Foundation [4] was further elaborated to the Madaster CI. It is displayed for the entire building on a scale of 0 to 100% and refers to the data recorded in the “material passport” or in the Madaster database [28, 29].

The UNEP model maps circular processes or strategies (see, for example, reuse, refurbish or recycle), but is also assigned to the already mentioned value retention loops “user to user”, “user to business” and “business to business”. The overarching principle is “Reduce by design”, which exerts the greatest influence and the “business to business” value retention loop has the least influence on the circular economy [27].

The application of CE principles in real estate, building design and use (adaptability, durability, waste reduction and high-quality management according to the European Commission (EC 2020)) is mainly focused on new buildings where circularity can be embedded and facilitated since the early design stage and consequently throughout the whole life cycle of a building and its components and materials. Conversely, circularity in the context of existing buildings is not so far defined (compare Kyrö 2020) [14].

On the other hand, less has been said about the design aspect of circularity integration in buildings (e.g. design for disassembly (DfD), design for adaptability (DfA), design for change (DfC) etc.) and the role of building professionals and supply chain elements in embodying the CE principles into the building sector as also Kanters (2020) pointed out [30]. In other words, existing practices and concerns focus on the CE principle of “closing the loop” which assumes intensified reuse and upcycling of materials and components.

Meanwhile, the CE principle of “slowing the loop” that suggests increasing building and product longevity by preserving their value, quality, and efficiency to the highest possible extent has received less attention so far. This can be justified by the influence of the prevailing construction and design culture during the last decades of viewing buildings as temporal products of limited life service and predefined destiny – demolition. Another key principle of CE that is rarely addressed by existing frameworks is “narrowing the loop” which relies on using fewer resources per product. This principle is inspired from nature’s processes that mainly use a limited chemical palette often consisting of six elements: carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur, while industrial manufacturers follow a different approach, seeking out rare and toxic elements to reach the desired functional properties. Narrowing the loop delivers conditions for recycling by allowing efficient and facilitated material separation and recovery.

7 Conclusions

A collection of CE models is presented that helps to complete our understanding of the opportunities and limitations of CEM. This study analyses the existing CE models in a comprehensive manner. All important key strategies for the application of the circular economy over the entire life cycle of a building circular economy strategies in general were collected. Its applicability for the built environment was reviewed.

Research question 1 could be answered: The multitude of definitions of CE, and more specifically circularity in the built environment, does not contribute to a coherent, systematic approach. CE needs to be viewed as a business strategy, not only waste management or a design strategy. Optimising buildings’ use should also be spotlighted instead of only viewing those as potential material banks where components and materials can be recovered, reused or recycled for new constructions [12, 17]. Still, recovered materials from existing buildings face a critical barrier in their technical compatibility and quality appraisal, which put their direct reuse in question, leading to downcycling processes and engaging extra resources and energy flows.

Research question 2 could be answered: The circular economy is seen as a regenerative system in which resource use and waste as well as emissions and energy losses are minimized, waste is avoided and material and energy cycles are slowed down, closed and narrowed. This can generally be achieved through long-lasting design, maintenance, repair, reuse, remanufacturing or recycling. In the context of the real estate and construction sector mentioned, this means that no new resources are required in the production of materials and waste is also minimized. In addition, better resource management is sought by reducing consumption (or even avoiding unnecessary consumption) and striving for resource circulation through the reuse or recovery of materials, components or components.

The strategies could be assigned to the individual life cycle stages of a building, and differentiated between the design, construction and end-of-life phases. Some key strategies are explicitly focusing on specific life cycle stages, such as Material Banks, Design for adaptability, etc. On the other hand, most strategies include some sort of information and data management, like Adoption of Efficient Processes, Waste as a Resource, and Resources Data Management. By comparing the different origins it explains the opportunities and limitations of the different models. Providing the knowledge gaps is a valuable addition to of our current understanding of CE.