A Study on the Types of the Circular Economy

doi:10.21203/rs.3.rs-2000438/v1

As an alternative for sustainable development, the circular economy is currently attracting great attention from many countries and regions, and is supported by various theories and practices. This paper aims to classify circular economy forms according to various markers. To this end, the authors explain the theoretical and practical background, and based on this, distinguish the circular economy form according to various signs. The research clarified that the types of circular economy can be classified according to the realization way and level, the realization target and method from the perspective of circular economy practice and theory implemented and discussed around the world. This classification is meaningful in that it systemizes the circular economy type realized by various circular economy-related theories and practices from a new angle scientifically and theoretically, and helps regions and countries to realize the circular economy form suitable for the actual situation.

Circular Economy (CE)

Type of Circular Economy

Classification of Circular Economy

Economic development on a global scale along with the Industrial Revolution that began in the 18th century brought great material benefits to people's lives, accompanied by the creation of enormous amounts of material wealth that could not have been imagined in the past. Countries and companies have preferred the mass production method of material wealth based on the mass consumption of natural resources as the main economic development method while pursuing high economic growth and maximum economic profit. However, these days, this economic development method faces various limitations. Serious economic, environmental, and social problems that were unthinkable in the past, such as mass generation of wastes exceeding the natural purification capacity, enormous damage to human health and environment, deepening of natural disasters and global warming, various social and geopolitical disputes surrounding natural resources, deepening of inequality and the like were raised. This required a shift from the traditional economic development method based on the extraction-manufacturing-use-disposal to a new economic development method that guarantees sustainable development.

The circular economy (CE) is emerging as an alternative to solve various serious problems inherent in traditional economy, because the CE is an economy that guarantees economic development, environmental protection, and social development by satisfying people's demands while maintaining the value and use value of products or parts for as long as possible through various activities including reuse and recycling. In this regard, research on the CE has been deepened in recent years, and in this process, various examples of the CE have been created in various countries, regions, and companies, and various views related to the CE have been raised by various scholars and institutions. However, research on types of CE has limited aspects, and this remains an empty space in theoretical research on CE. Classifying the types of the CE can help to fill the theoretical gap and explain the theoretical basis for realizing the CE type according to the situation of the country, region, and company. From the significance of this study, this paper is organized as follows. The second section of the paper discusses the theoretical and practical backgrounds that can classify the types of CE. In the theoretical background, representative views on the definition of the CE are outlined, and the limitations of the study on classification of CE are discussed. In the practical background, the principles of the CE, the business model, and various practical cases which are the basis for classifying the CE type are discussed. In the third section, based on this background, types of the CE are classified according to various classification markers and its characteristics are explained. The remaining sections deal with the results, the argument, and the conclusion.

2.1. Theoretical background

In order to classify the types of CE, it is important to first explain the theoretical background for classification. In this theoretical background, representative views on the definition and types of CE and discussions on their limitations are included.

Above all, the CE has been defined by various scholars and experts, government agencies and international organizations from various viewpoints and standpoints. This is because the definitions reflect their own needs to cope with various environmental problems, and laws, development strategies, and policies are developed and implemented based on them.

Internationally, various organizations have proposed different definitions of the CE. Among them, the representative ones are summarized as follows.

The representative focus in the definition of the CE by various organizations internationally can be summarized as follows (see Table 1).

Table 1

Focus in definition of CE by organizations
Focus	Organization
The benefits resulting from the realization of the CE	EU Commission (2015), EU parliament, EU parliamentary research service
The ways to realize the CE	U.S. Chamber of Commerce Foundation (2015), Ellen MacArthur Foundation (2013)
The sustainable development	Circular Economy European Summit (2016), Sitra (2015)
An economy that can replace the traditional linear economy	WRAP (Waste and Resources Action Program)
Source: Own elaboration

As such, institutional definitions of the CE have been mainly centered on the role of the CE from a practical point of view.

The representative focus in the definition of the CE by various scholars and experts can be summarized as follows (see Table 2).

Table 2

Focus in definition of CE by scholars and experts
Focus	Scholars or experts
The contribution and role of the CE to sustainable development	Korhonen et al. (2018), Buren et al. (2016), Murray et al. (2017)
Closed loop realization	Geissdoerfer et al.(2017)
Complex and systematic concept	Korhonen et al.(2018)
Source: Own elaboration

These are only a few of the definitions of the CE proposed by academia and the industry. However, the various efforts contained in the above definitions reflect the intention to establish a CE academically.

In relation to the various perspectives and definitions of the CE, many studies focused on analyzing and evaluating various definitions of the CE have been conducted in recent years. These research efforts are aimed at analyzing how the concept of the CE is perceived by reviewing the proposals or definitions proposed by several authors.

Representatively, the innovation research group at Utrecht University in the Netherlands collected a comprehensive group of 114 CE definitions proposed in various publications and systematized it by applying coding means in terms of goals, means, and scope, and defined the CE in a relatively comprehensive sense. They define the CE as an economic system based on business models operating at the micro level (products, companies, consumers), meso level (eco-industrial zone) and macro level (city, region, country and higher) while replacing the concept of 'end of life' with saving of materials in processes of production or distribution and consumption, alternatively reuse, recycling and recovery with the aim of achieving sustainable development that brings benefits to present and future generations, while achieving environmental quality, economic prosperity and social equality (Kirchherr et al. 2017).

On the other hand, researchers from the University of Navarro, Spain, after conducting an extensive literature search, came to the conclusion that it is necessary to systematically include the four components in the definition of the CE in order to reach a consensus on the CE (Prieto-Sandoval et al. 2017). Such components are:

Recycling of resources and energy, minimizing demand for resources, recovering value from waste,
Multi-step approach,
Its importance as a pathway for sustainable development,
Close relation with the way society innovates.

As seen above, defining the CE requires a wide-ranging research on the CE as a multi-disciplinary concept that encompasses various aspects such as its goals, means, methods, and scope. Analyzing the various definitions proposed so far, it can be seen that these reflect ideas or goals from various scientific and industrial fields.

This definition of the CE can serve as the theoretical basis for classifying the types of the CE. However, these views are merely unilateral views in the classification of the CE. Therefore, the type of CE must be based on various practical cases to have more realistic significance.

2.2. Practical background

In practice, the CE is realized through various principles, and valuable examples that can classify the types of CE have been created in this process.

As a practical background for classifying the types of the CE, the principles and business models of the CE and various examples through them are included.

Above all, various R principles were outlined as principles of the CE. The 12 R principles presented so far can be the basis for classifying types of CE.

The 12 Principles of the CE and their contribution can be depicted in the following figure (see Fig. 1).

The economic content and examples of each principle of the CE can be explained as follows (see Table 3).

Table 3

The economic content and examples of principles of the CE.
R Principle	Meaning	Case
Refuse	In essence, people live within the range of meeting basic needs and do not consume more than necessary.	The “No Straws Attached” campaign started in Delhi (India) in 2018 (Kanti, 2018)
Reduce	Reducing consumption, and in the case of a product, it means reducing the size, quantity, toxicity or intensity of the use of materials and energy of the product.	“Sustainable detergent” called Tide Eco-Box released by Tide (Tide, 2020), Reusable and durable spray bottle produced by Replenish (Replenish, 2020)
Re-design	Making changes to the structure and functions of an artifact, building or system so as to better serve the purpose of the original design, or to serve purposes different from those set forth in the original design.	Packaging and building materials using mycelium as a natural binding agent (Ecovative Design, 2020), Kitchen fronts which is made from recycled plastic bottles and reclaimed industrial wood (Material District, 2017)
Reuse	Reusing an object to its original state	Sustainable packaging service for e-commerce (RePack, 2020), Library of Things in England (Library of Things, 2020)
Repair	Putting something damaged, broken, or not working correctly back into good condition or make it work again	Repair café in Amsterdam (Coggins, 2017), Modular phone that made repairing possible at the users end (Fairphone, 2020)
Refurbish	Improving older or damaged equipment to bring it to a workable or better-looking condition	Provisions to custom build and remanufacture its own servers so that those can be refurbished at the end of their life (Google, 2018), Microsoft-Uganda partnership for to addressing the challenge of shortage of high-quality, affordable hardware and software (UNIDO, 2008)
Renovate	Restoring something to a newer or better state	Online hub for homeowners and businesses to access information, rebates, and support to reduce energy use and greenhouse gas emissions in homes and buildings (Better Homes BC, 2020).
Recycle	Turning an item into raw materials which can be used once again, usually for a completely new process or product	Toys made from recycled plastic milk jugs along with other forms of recycled plastic (Green Toys, 2020), Footwear from 100% recycled materials, including sheep’s wool, recycled cardboard and plastic, and castor bean oil (Allbirds, 2020).
Recover	Converting waste into resources (such as electricity, heat, compost, and fuel) through thermal, mechanical, chemical, and biological means	Service to divert compostable waste from the landfill (Compost Now, 2020), Biogas recovery at household level (LONO, 2020), Facebook data centre supported by 100% of renewable energy (Edelman, 2020)
Return	Taking back products and packaging after use as a responsible manufacturer.	Indonesia’s refill delivery network that offers everyday cleaning products in reusable bottles (Hepi Circle, 2020), Reusable beverage mug (Cupable, 2020)
Remanufacture	Rebuilding a product to specifications of the original manufactured product using a combination of reused, repaired, and new components	Cat Certified Rebuild service (Caterpillar, 2020), Xerox’s takeback program that includes taking back “end of life” photocopiers, printers, scanners from customers, creating a remanufacture and parts reuse programme that forms the foundation of waste free Initiatives (Gray & Charter, 2020)
Rethink	Thinking out of the box to innovate	An edible cutlery manufacturing (Oriqa Edible, 2020), Plastic-like bags using cassava, an edible root – also known as yucca, arrowroot, or tapioca (Avani Middle East, 2020) and the like
Source: Authors’ elaboration from Modak (2021b) p. 87–107

As shown in Table 3, in accordance with the CE principles, many companies on a global scale have created various practices that are the basis of the CE classification.

Next, the business model for realizing the CE can be the basis for classifying the CE. Various business models have been proposed by various scholars in the process of practicing the CE so far, and they are broadly summarized into four categories; net-zero innovation, servitization, product life extension, and product residual value recovery (for example, Lüdeke-Freund et al. 2019; Tonelli & Cristoni, 2019; Lacy et al. 2020; Itkin, 2021; Modak, 2021c).

The business models for realizing the CE and their application cases can be summarized as follows (see Table 4).

Table 4

The business models for realizing the CE and their application cases
Business model	Meaning	Cases
Net-zero innovation	A business model based on the use of raw materials (inputs) with negligible negative impacts on the environment and no ecological footprint or production of such final products and the operation of related production processes	A process to convert a pineapple by-product into a unique material – Pinatex used as an alternative to leather, plastic, and technical textiles in a variety of products patented by Ananas Anam, An ecologically harmless synthetic fabric – Climatex developed by Rohner, A chemical-free recyclable packaging solution for its sportswear by Nike, and the like
Servitization	A business model in which ownership of a product (primarily machinery or equipment) is not transferred to the purchaser	Interface’s program that provides customers with services for sale, installation, cleaning, and replacement of carpet, while the customer lease such services instead of ownership of carpet, Car sharing service, Lighting service by Philips, and the like
Product life extension	A business model focused on making products that last longer and are more economically useful	All reverse cycle activities aimed at prolonging the life cycle of a product or its functioning parts (reuse, repair, refurbishment, and remanufacturing) (for example, Patagonia, Miele, and Rolls Royce)
Product residual value recovery	A business model that utilizes the value remaining in a product when it cannot be remarketed through further processing (recycle) of the product or when it has reached the end of its life cycle	Activities in Interface and Aquafil that collect and reprocess discarded fishing nets from the bottom of the seas, and transform into nylon yarn to make carpet tiles, Reverse cycling operations in Dell and HP whereby plastic from discarded computers and toner cartridges get recovered and turned into input material for new products, and the like
Source: Authors’ elaboration from Tonelli & Cristoni (2019) pp. 90–105.

The business models for realizing the CE and their application cases show the theoretical basis for classifying the core activities in the current CE. As such, the theoretical and practical backgrounds for classifying the CE type make it possible to judge the core activities, principles, and opportunities in the CE, and furthermore, to set the mark for classifying the CE type.

3.1. Classification according to realization way

Classifying the CE type according to the realization way is meaningful in understanding the levels of minimization of waste and resource conservation due to development of science and technology, and selecting an appropriate CE type according to the situation based on it.

The linear economy consisting of take-manufacturing-use-disposal could solve the problem of meeting human demand following mass production, but it could not solve the problem of enormous resource consumption and environmental degradation caused by production. Therefore, people started to study and apply the CE to reality as an alternative that can solve both resource consumption and environmental problems while ensuring continuous economic growth. These activities were initially shown to create an industrial ecosystem that mimics the circular principle of the natural ecosystem. At the same time, as resource recovery, life extension, and recycling technologies are gradually developed for the purpose of reducing resource consumption and waste, this CE came to include the activities that consist of repair, refurbishment, and remanufacturing to preserve the value of products and materials in use for as long as possible. From this, it can be said that the first economic type according to the CE realization way is a value-preserving CE. With the development of science and technology, especially material engineering technology and the development of digital technology, a methodology that can completely eliminate waste after use has been pursued by separating useful materials from waste and using them for production. This is because a product or material must be discarded after multiple uses. The CE type that has emerged by realizing this demand is a resource-recovering CE that separates materials or molecular substances with high value and use value from waste. Since then, people have implemented a methodology to extend the lifespan of a product or material and maximize its use value in economic practice as a strategy to reduce resource consumption and reduce waste. In other words, the economy of having to go through multiple uses in the stage of use after production has emerged. This is widely known today as the performance economy or the sharing economy. Therefore, it can be said that the third type of CE according to realization way is a product-functional CE. Today, these types of CE are applied in combination with each other because the level of economic development differs according to region, sector and country. However, these types have different characteristics in various aspects.

3.1.1. Value-preserving CE

The value-preserving CE is a type of CE that maximizes the value of products and parts through reuse, repair, remanufacturing, and technological renewal, and optimizes the use of products by extending their lifespan. The value-preserving CE has several characteristics. First of all, the value-preserving CE has different characteristics from the traditional linear economy in terms of value and profitability creation. First, the profitability of the linear economy is large and comprehensive, whereas the profitability of the value-preserving CE is small and local. Also, the smaller the loops, the more profitable and resource-efficient the loops are. Next, the value-preserving CE guarantees sustainable development. Such sustainable development can be guaranteed in terms of economic growth, environment, and social development. First, value-preserving activities for mass-produced products are economically profitable because they are less expensive than the newly manufactured identical products that compete with them. Second, value-preserving activities are ecologically desirable because they conserve most of the embodied resources (energy, materials and water). Third, value-preserving activities are socially feasible because they are labor-intensive services that are best carried out in the areas where customers are. Next, the value-preserving CE includes very diverse activities to preserve the value of goods and extend their lifespan such as reuse, repair, remanufacturing, recycling, reprogramming, and type renewal. As such, the value-preserving CE is leading the transition from a linear economy to a CE in the early stages of CE development.

3.1.2. Resource-recovering CE

The resource-recovering CE is a CE type that manages the inventory by separating atoms and molecules, which are chemical elements, from waste in order to maintain the highest value and purity of materials. The resource-recovering CE refers to the non-destructive collection of used goods and the unmixed collection of used materials that increase the profitability of resource-waste managers along with the change from volume reduction to value acquisition in waste management. Therefore, this CE requires innovative separation technologies for materials. The resource-recovering CE has several characteristics. First of all, for any resource-recovering activity to be effective, three conditions must be met; safe transition from product use to end-of-life, separation of clean material parts, and continuing ownership and responsibility for objects and embodied materials. Next, the resource-recovering CE guarantees sustainable development due to following features. First, resource-recovering CE guarantees economic profitability by allowing economically recovered molecules to be advantageous in price competition with natural resources. Second, in the resource-recovering CE, the recovery of spent molecular materials reduces a significant amount of mining waste, reduces water and energy consumption, and reduces the negative impact on the environment in the mining and beneficiation of natural resources compared to the production of natural resources. Third, the resource-recovering provides commercial opportunities for socially skilled workers and creates new markets for trading second-hand goods and their parts between buyers of the value-preserving CE and those of the resource recovery CE. In addition, R&D activities to develop innovative small-scale process technology for recovering pure molecules and atoms will be actively carried out.

3.1.3. Product-functional CE

Product-functional CE is also called “the function or performance economy” (Stahel, 1982) by not selling the product itself, but its function or performance to customers through shared or leased space, thereby maximizing the use value of the product. A performance economy that sells products and molecular substances as a service, guarantees of function or results has become the most sustainable business model of the CE because it provides manufacturers or managers of products with a strong fiscal stimulus to prevent losses and waste by bearing the costs of product liability, risks and waste. The product-functional CE has several characteristics. First of all, performance economic activities take various management methods according to the characteristics and functions of products and the characteristics of users. First, performance economic activities take different management methods according to the characteristics and functions of products. The fabric-leasing enterprises are operated through regional franchisees rather than through a centralized method because their operations are geographically limited by transportation costs and knowledge of consumer demand is vital. Real estate owners are often insurance companies interested in stable income streams, long-term value preservation and low operating and maintenance costs. Performance economy in these objects can be achieved at the highest level by providing a high initial quality of materials and objects and a high familiarity with local customs and conditions. Second, performance economic activities take different management methods according to the characteristics of users. In case the users are individual persons, on the one hand, a product or service sold as a dedicated service includes rental apartments, tools and vehicles for rental, books in public libraries, public sanitation rooms, shipping boxes and rental installations and recyclable packaging. On the other hand, products or systems that are sold as a service for shared use include all forms of public transport (buses, trains, passenger ships, airplanes), as well as public swimming pools, concert halls and laundries. If the user is an enterprise, performance economic activity applies to individual products or chemical or metallic materials. For example, the United Nations Industrial Development Organization is promoting chemical leasing as a strategy for Africa to minimize pollution and toxic packaging waste in less industrially developed countries (Grineva, 2018). Metal leasing has recently been proposed as a strategy for mining companies and governments with mining areas. In other words, in this model, the purpose of lending effective substances contained in minerals, not minerals, is to ensure continuous long-term income. Next, the performance economy is the most sustainable form of the CE because performance sales improve sustainability through higher profits or lower costs, less resource consumption, and more skilled labor. First, a performance economy is profitable because it develops sufficiency (getting the required output with minimal input), efficiency, and systemic solutions, has lower transaction and compliance costs than linear and other CE types, and is not subject to import duties on resources. Second, a performance economy is ecologically beneficial because it minimizes the need for consumables, transport and packaging by fully exploiting the local reuse and life extension of goods. Third, a performance economy is socially viable because it is labor intensive, producers and managers bear producer and user responsibilities, as well as risks and waste costs (in a linear economy, borne by society). The different types of CE according to the realization way and the principles of the CE unique to them can be described in the following figure (see Fig. 2).

3.2. Classification according to realization level

Classifying the CE type according to its realization level has important significance in promoting the realization of the CE. This is because there are differences in technological and economic measures for the realization of the CE according to realization level.

From the historical point of view of the development of the CE, it can be said that his early stages began with CE activities related to individual products, materials, processes, and consumers. It is because people's attention was mainly focused on products or materials that significantly affect resource consumption and environmental degradation and at that time, the level of technological development related to recovery, separation, and recycling of waste was limited to individual products or processes. After that, the rapid economic development and consequent increase in consumption made resource consumption and environmental degradation problems more broadly, namely, global problems. From this, the realization of the CE was promoted in a wider scope beyond the narrow scope of the initial stage. It is related to this situation that at present, many countries around the world are building eco-industrial zones and circular cities, and that various initiatives to promote the CE on an international scale are becoming active. Therefore, the CE can be divided into types of enterprise level, regional level, and national level according to its realization level.

3.2.1. Enterprise-wide CE

When the CE is realized by expanding the entire enterprise beyond the scope of individual product processes or facilities, such a enterprise is said to be a CE enterprise. Enterprise-wide CE is the most important link in the realization of CE. This is because the CE at the regional and national level is realized based on the construction of a CE enterprise, and CE activities limited to product processes or facilities cannot be considered outside the enterprise. CE enterprise is characterized by the closed loop flow circulation of materials, and the principles are reduction, reuse, and recycling. In other words, it is an enterprise in which materials and energy are used rationally and continuously in all economic activities by organizing business activities in a semi-combination process of resources-products-renewable resources in accordance with the principle of ecology. CE enterprises have their own unique characteristics compared to linear economy enterprises. First, the characteristic of CE enterprise is that the theory of sustainable development is the theoretical basis of business strategy. The theory of sustainable development has the basic core of sustainably developing the economy by grasping both economic development and environmental protection. Second, the characteristic of CE enterprise is that achieving economic and ecological effects is the enterprise’s dual strategic goal. In the past, business strategy was based on achieving economic effect, and achieving ecological effect was considered as secondary or not at all, and did not become a strategic goal. However, in CE enterprises, not only economic effect but also ecological effect is a strategic goal at the same time. Third, the characteristic of a CE enterprise is that reduction, reuse, and recycling are the environmental management principles of an enterprise. It realizes the minimization of resource input by implementing the principle of reduction, realizes the maximization of waste by implementing the principle of recycling, and realizes the minimization of pollutant discharge by implementing the principle of harmlessness.

3.2.2. Region-wide CE

A representative type of region-wide CE in the regional scope is an eco-industrial park. Eco-industrial zone refers to a business community of manufacturing and service enterprises that pursue improved environmental and economic performance through collaboration in the management of environmental and resource issues such as energy, water, and materials (for example, Boix et al. 2015; Winans et al. 2017). Enterprises in the eco-industrial zone realize the optimal use of resources and energy through the exchange of materials, energy and information, and minimize the negative impact on the environment of the industrial zone. In the eco-industrial zone, each enterprise is not isolated from each other, but is related to each other through material flow and energy flow and information. In the eco-industrial zone, unification of common resources, unification of water resources, unification of energy resources, and unification of public utilities are realized. At the same time, by jointly establishing a common infrastructure and treating sewage, waste, etc., it reduces the cost required for individual enterprises to achieve ecological effects. From this, the ecological industrial zone has different characteristics from the traditional industrial zone. First, eco-industrial zones implement the principles of industrial ecology based on industrial symbiosis. Eco-industrial zones are generally interconnected with the principle of industrial symbiosis, in which enterprises work on a collaborative basis, and the waste of one enterprise becomes part of the process of another. From this, in many cases, eco-industrial zone and industrial symbiosis are regarded as synonymous. However, the eco-industrial zone can be considered more accurately as a practical realization of the concept of industrial symbiosis. Therefore, while industrial symbiosis is a concept that is less limited by space, eco-industrial zones give more importance to the physical environment in terms of regional basis. According to some views, at least three different entities must be involved in the exchange of at least two different resources to be considered a basic type of industrial symbiosis (Chertow, 2000). Second, the realization of the eco-industrial zone is represented by the exchange of materials at different levels between enterprises. In general, the following five types of material exchange are carried out between enterprises in the eco-industrial zone. The first type of material exchange is waste exchange. In this format, waste is traded and the person in charge of managing these transactions is a third-party intermediary or trader. However, these forms are one-way exchanges and are concentrated in the end-of-life stage, so they are not generally regarded as industrial symbiosis. The second type of material exchange is the form realized within an enterprise or business unit. Business units, especially large enterprises such as large complex, can take advantage of industrial symbiosis by considering the entire life cycle of products and processes. As a result, enterprises can profit from secondary material flows and find new ways to eliminate waste. The third type of material exchange is between enterprises co-located in a limited eco-industrial zone. Here, enterprises and other business units exchange materials, energy, water, information and services in a limited area or site. The fourth type is a type that is formed between enterprises that are not together in a specific area, but are located in a geographically close area. With the beginning of this new exchange, enterprises can connect themselves to each other and create something new. The fifth type of material exchange takes place between enterprises organized “virtually” over an area by distant business units or networks. Third, there are various starting points and methods for developing eco-industrial zones. First of all, unlike traditional industrial zones, the development of eco-industrial zones starts by renovating traditional industrial zones or developing new industrial zones. Next, eco-industrial zone development proceeds in two ways: voluntary (bottom-up) or planned (top-down). Currently, eco-industrial zones of various levels have been formed and operated around the world. A representative example of an eco-industrial zone with a regional scope is the Kalundborg eco-industrial zone in Denmark. In the 1970s, this industrial zone started with the establishment of a network of resource exchange between companies due to the limited availability of groundwater and the necessity of a surface water supply source. This triggered the voluntary development path of the cooperative effect and gradually developed into an example of industrial symbiosis in the early 1990s. There are four basic industries around Kalunborg: coal power plants, refineries, pharmaceutical and enzyme producers, and gypsum board manufacturers. It also provides public facilities and services (Jacobsen, 2006).

3.2.3. Country-wide CE

The country-wide CE is a type that CE is realized in a certain region including cities and country. A representative example of a CE on a national scale is a CE on a city scale. The CE in the urban area has developed in various forms. Eco-city or eco-friendly city is important among representative types of urban circulation economy. Eco-city means a city with a system where people, nature, and the environment can harmonize and coexist.

Another representative form of the urban CE is the Zero-Waste City. The Zero Waste International Alliance adopted the first internationally recognized definition of zero-waste on November 29, 2004. According to it, zero-waste is the conservation of all resources through the responsible production, consumption, reuse and recovery of products, packaging materials and materials without burning or releasing to land, water or air so as not to endanger the environment or health (Ellen MacArthur Foundation, 2020). Today, the concept of the zero-waste was implemented in the city, which gave birth to the concept of the construction of the zero-waste city. Theoretically, a zero-waste city is a very encouraging concept that aims to recycle all municipal solid waste and recover all resources in the waste. Several studies have been conducted to analyze the challenges, threats, and opportunities for converting the traditional waste management system into the zero waste management system. In this process, it is recognized that the following strategies including short-term strategy (for example, expansion of producer and consumer responsibility, zero-landfilling and incineration related laws, and innovative business design) and long-term strategy (for example, behavior change and sustainable consumption, 100% recycling of urban solid waste, awareness, education and system thinking) are necessary in order to transform the city into a zero waste city (Hoornweg, 2013; Zaman & Lehmann, 2011; Zaman, 2015).

In general, the country-wide CE has the following characteristics. First of all, the country-wide CE is implemented through a top-down approach. In the implementation of the CE at the enterprise or regional level, a bottom-up approach (voluntary) is mainly used, but the CE at the national level is implemented by a top-down (planned, intentional) approach. Next, a CE at the national level necessarily requires cooperative relationships among various participants. In the realization of the enterprise- or region-wide CE, participants who mainly carry out the same mission participate, but in the realization of the country-wide CE, several participants or institutions with different missions are required to cooperate. For example, in order to implement a CE in an urban area, cooperation of various organizations and enterprises such as production enterprises, service enterprises, city administration organizations, and research institutes in the city is essential. Even on an international scale, cooperation between international organizations and countries and between countries is essential. As described above, the CE is divided into the enterprise-, region-, and country-wide CE according to the level of its realization. Therefore, it is necessary to set the scale differently and implement it according to its mission and characteristics. The types of CE according to the level of realization and concrete realization objects can be described as follows (see Fig. 3).

3.3. Classification according to realization target

The CE can be classified according to the target of economic activity that it is realized. Economic activities can be broadly divided into production and consumption activities. To classify the CE according to the realization target means to classify it into production-oriented and consumption-oriented types. A production-oriented CE is a type that embodies the principle of a CE in production activities, and a consumption-oriented CE is a type that embodies the principle of a CE in consumption activities. Production and consumption activities can be carried out in various forms in many aspects, but in a broad sense, production activities are conducted in the manufacturing industry and consumption activities are conducted in cities.

3.3.1. Production-oriented CE

The production-oriented CE is a CE that identifies and utilizes CE opportunities in production activities. Production activities are mainly carried out in the manufacturing industry sector, so the production-oriented CE is specifically represented as a circular industry. Circular industry is an industry in which CE principles are implemented in all processes from raw material input to processing, finished product production, and industrial waste treatment (Shi, 2021). Industry is becoming a driving force for the establishment and development of modern society by creating material and energy flows to convert resources into products or provide services. An industry is a sector in economic activity that provides certain products or related services. These industries have brought enormous amounts of material wealth to mankind. But it also left a serious negative mark on nature. The first half of the 20th century witnessed the emergence of environmental problems in industrialized countries. As more and more new industrial sectors are created, more and more unpredictable environmental problems, including resource scarcity and environmental degradation, are occurring. More seriously, the scope of the impact of these problems has expanded from a local to a regional and ultimately global scale. From this, the demand for realizing a CE in the industrial sector came to the fore. In industry, the CE principle is implemented in a number of ways due to the complexity of the industry. In other words, the industry has a complex hierarchical structure and various processes and elements, so many CE opportunities exist, and various CE principles and methods are implemented.

First of all, various CE opportunities exist in industrial activities. These opportunities include, first, opportunities through product circle, ie, on-site and off-site reuse, and cascading reuse. Second, through replacement or repair of components or parts, the lifespan of products can be extended, which generates a part cycle. Third, material recycling takes many forms in all industrial sectors, which gives the CE opportunities. Fourth, there is a chemical circle which requires a chemical reaction. As a result, recycled material can replace certain fossil resources for chemical products.

Next, circular industry develops with the following trends. First, it is the ecological design of the product. By adopting various measures to improve circularity in products, industries can achieve the objective of a CE. For example, an industry can design and manufacture products that can be recycled more than once, products that have a longer service life, and products that are easier to recycle or biodegrade. From a CE point of view, ecological design can maximize the conservation and recycling of natural resources over the entire life cycle of a product by considering multiple criteria in sequential steps: raw material extraction, manufacturing, product use and end-of-life management (recovery and recycling). Second, clean production at enterprise scale is promoting. Enterprises are the basic units of production. Therefore, there are many opportunities for the CE in enterprises. According to the United Nations Environment Program, clean production is the continual application of an integrated environmental strategy to processes, products and services to reduce risks to humans and the environment and increase efficiency. Third, there is a circular transformation at industrial parks’ scale. From an industrial ecology point of view, industrial zones create opportunities for inter-enterprise industrial symbiosis, which is described as encompassing traditional individual industries as a collective approach to competitive advantage, involving the in-kind exchange of materials, energy, water and by-products. So far, following the model of Kalunborg Eco-Industrial Zone in Denmark, many countries around the world have started planning eco-industrial zones or renovating existing industrial zones. Fourth, there is a sustainable industrial transition at regional scale. Today's industrial production is expanding on a global scale. Products have been globalized and connected by trade networks all over the world along with production factors including raw materials, labor and capital, forming a global production network. It offers the opportunities such as the change of business models, the emergence of sharing economy, green supply chain, green trading, and green logistics for cyclical transformation at a regional scale implemented in global production chains.

3.3.2. Consumption-oriented CE

People's consumption activities are mainly carried out in the city as the main base. From this, the consumption-oriented CE also refers to circular economic activities surrounding urban consumption. A consumption-oriented CE is realized in the form of a circular city in practice. A circular city is a city that reduces waste and regenerates natural systems by maintaining products, materials and resources in use (Bolger & Doyon, 2019; Kisser & Wirth, 2021). Cities are centers of human and economic activity, as well as resource utilization and waste discharge. Currently, major streams of materials, energy and water are taken from the environment, which are then processed into products and transported to cities, where their value is consumed and finally lost or disposed of. Cities are also centers of direct and indirect consumption of water and energy. In other words, it means consuming water and energy embodied in food and ingredients. The increase in population, urbanization, and living standards are causing environmental problems such as huge resource consumption and urban waste discharge today, and have made cities into resource sink dependent on the consistent inflow of original resources. And the traditional waste management in cities causes huge waste management costs and harms people's health. This situation in people's consumption life requires cities to implement the closed loop principle of material and build a CE. The type of CE that has emerged by realizing these demands in consumer life is a consumption-oriented CE, specifically, the construction of a circular city. In the city where people live, there are various CE opportunities and methods in relation to various consumption lives. First of all, there are various CE opportunities in the city. In cities, people consume a variety of consumer goods, resulting in a variety of wastes. In this regard, various CE opportunities exist for these consumer goods. First, there are sharing and reuse of commodities. Short distances between tool users, repair shops, and recovery and redistribution centers in cities make new CE models based on the sharing, repair and reuse of goods much more practical, manageable and user-friendly. In addition, traffic congestion not only makes passenger cars a burden to citizens, but also enables efficient operation of public transport. Second, there are recycling and reuse of building materials. Cities have high potential for recycling and reuse with economically appropriate separation technologies for construction and demolition waste. Construction and demolition waste can be prevented through local management measures and reuse strategies. As such countermeasures and strategies, appropriate purchasing and handling of materials on site, as well as the use of standardized parts and reuse of existing construction structures, are included. Third, biological nutrients are used. Nutrients are obtained from the topsoil of agricultural land, enter cities as food, and are then removed as waste. It is said that 2.8 billion tons of organic waste is generated in cities every year, and less than 2% of the nutrients contained in this organic waste are recycled back to food production (Ellen MacArthur Foundation, 2018). So far, the economy has lost US$23.3 billion of agricultural nutrients from human excrement alone (Jenkins, 2011), and an additional 100 million tons of biological waste from organic waste disposal each year (European Compost Network, 2019). These nutrients are largely lost to the atmosphere (through nitrification and incineration), landfill treatment and the environment (residual impact loads of effluents). At the same time, Europe imports 30% of nitrogen, 71% of phosphorus, and 73% of total potassium fertilizer used (Fertilizers Europe, 2017). Organic residues are converted to safe for reuse as fertilizer or nutrient-rich irrigation water so that “spent” nutrients are returned to the soil and from there they enter a new life cycle for food production. By applying currently available technologies, cities can capture nutrients from wastewater and realize their metabolism to produce fertilizers or land amendments. In this way, secondary nutrients can replace imported synthetic fertilizers produced from primary mineral deposits, avoiding their high carbon footprint and reducing dependence on external resources.

Next, in the construction of a circular city, the following ideas are being studied.

First, there are several ideas in the design and use of materials. Materials are locally sourced, risk-free and made from renewable energy sources. Some objects or parts thereof may be disposed of after final use, but their chemical composition allows for separation and recycling with minimal energy input. Also, most of the materials are made of biomass. It can be composted as fertilizer to produce new biomass after final use or directly processed into secondary biocomposites and industrial chemicals. Second, urban infrastructure will be designed for decentralized production and service. Residents have access to nearby repair shops, recovery points and decentralized manufacturing with 3D printing centers and resource recovery centers. Because of the city's living hubs nearby, people live, work, and exercise in increasingly close links, accessible on foot or by bicycle and public transport. Third, nature is integrated with cities to perform ecosystem functions for resource recovery and to improve energy balance, air quality and well-being in cities. Fourth, the buildings are used as stockpiling warehouses or “material banks”. These building materials are modular, repairable, degradable, and reusable, extend their lifespan as long as possible, and are recycled only as a last resort. Buildings may incorporate complementary functions and these functions should be taken into account during the construction or refurbishment of the building. Fifth, in a circular city, goods are no longer used only once. Goods are repaired and refurbished. Disposable items, including packaging materials, disappear from the circular city. If things are destroyed, there are suppliers for parts. Circular product design minimizes the complexity of material composition for more effective recycling. Commodities will be managed under the return system and producer responsibility extension system, and will mostly be supplied by bio-based natural materials. People approach their needs in new ways. Instead of owning the goods, they are used through sharing or leasing or through product as a service contracts. Sixth, the circular urban food system can function in infinite loops of nutrients while gaining a sense of inspiration from nature. Some residuals of nature always become food for others. These natural methods already allow nutrients to be recovered from municipal wastewater and can be safely reused locally for urban agriculture, while providing benefits such as converting carbon dioxide into edible or combustible biomass and improving air, water and soil quality. The city's greens, parks and underutilized infrastructure can be used for urban agriculture and money can be distributed through flexible urban infrastructures such as regular markets with local food suppliers. The surplus nutrients can be returned to the green areas of cities and surrounding rural areas. In this way, there are various opportunities and methods in developing a city in a circular type, and in constructing a circular city using these opportunities and methods, it is important to cooperate with each other for different parties living in the city and to take the necessary financial, technological and economic measures.

3.4. Classification according to realization method

Classifying the CE type according to the realization method means classifying the CE type into a bottom-up type and a top-down type. This is related to the fact that there are certain differences in the way of implementation depending on the social and institutional characteristics of the country and the actual situation. In general, the process of emergence and development of the CE has been mainly based on a bottom-up approach. Under the condition that the importance of the CE has been increasingly emphasized and the sustainable development goal has become an important national strategic goal, the process of realization of the CE has come to accept a top-down approach by the state or the central government rather than the spontaneous approach of the past. From this, depending on the realization method of the CE, the CE can be divided into a top-down type and a bottom-up type.

3.4.1. Top-down CE

The top-down CE is a CE in which central and local government agencies present CE-related action plans, initiatives, laws, and regulations, and make the following units to implement them. In countries where the current economy is centralized and planned, the CE-related plans, laws, and regulations are presented, and the following units are obliged to enforce them (for example, Democratic People’s Republic of Korea and China). It can be said that this CE has a planned and obligatory character. Of course, some countries and regions are using a set of legal tools to establish and implement comprehensive CE strategies and goals. In this case, the CE can be said to have an intentional character. The downside of top-down methods is that they run the risk of being too vague, impractical, and difficult to convey throughout the units below. In fact, the distance between central government and lower-level governments or enterprises represents the difference between managerial intentions and corporate behavior, and if not controlled, it can lead to a mismatch between “intended” and “implemented” strategies. Mainly, it can be widely used when realizing a CE at the sectoral, regional, and national scales.

3.4.2. Bottom-up CE

The bottom-up CE is a CE that is voluntarily realized by individual companies or local governments starting from their own interest in economic and environmental benefits through collaboration. In particular, in countries where the economy has a market economic character, this type is becoming dominant. One problem with this approach is that the CE implemented by enterprises or local governments is not consistent with the overall strategy of the country, as it usually does not have a national perspective. Although this approach has the potential to bring more innovation than the top-down approach, it is often not easy to integrate disparate perspectives into a single action plan. Since the CE is a multifaceted and innovative concept to a certain extent, the bottom-up process is not the best approach for strategic planning, especially when business operations are complex and in-depth expertise to understand the meaning and opportunities of the CE is required.

3.4.3. Hybrid CE

To overcome the limitations of the previous two approaches, some enterprises choose a hybrid solution that collects ideas for a CE from the bottom up, but the final implementation plan is drawn up only by the central government. For example, when drafting a CE strategic plan, the central government can provide guidelines for strategic planning for small and relatively new enterprises, and the planning process should be led by a group of people representing various fields. In other words, companies can participate in the early stages of planning, communicate, and collectively discuss ideas for future products. It is then arranged by the Steering Committee prior to final approval by the central government. In other words, the central staff department becomes a source of information and insight related to the CE. From the merits and demerits of the realization methods of the CE, CE type according to the realization method of the CE must be reasonably selected depending on the degree of preparation of management staff with knowledge and experience related to the CE, the degree of complexity of the enterprise's process, and the degree of enterprise and central government's awareness of the environment and the like.

The types of CE according to different classification markers can be summarized as follows (see Fig. 4).

The aim of this paper is to classify CE forms according to various markers. To this end, the authors explain the theoretical and practical background, and based on this, distinguish the CE form according to various markers. The research clarified that the types of CE can be classified according to the realization way and level, the realization target and method from the perspective of CE practice and theory implemented and discussed in a global scope. The study results are summarized in Section 3 and Fig. 4. The following can be discussed from the study results. First, in the classification by realization level, there is a phenomenon that the principles implemented among the different CE types are overlapping (see Fig. 2). In this regard, the problem of distinguishing types may arise. For example, the principles of reuse and repair are implemented in the product-functional CE and the value-preserving CE. Although these principles have the same linguistic meaning, they are different in the economic sense. Reuse and repair in the product-functional CE are principles that are supplementary to the sale of product performance or functions, whereas those in the value-preserving CE are principles implemented in order to reuse or sell products or parts. Second, there may be a problem of classifying the types of CE enterprises in the classification by level. A CE enterprise as a enterprise-wide CE in classification by level means an enterprise that realizes a CE by applying the closed loop principle within the scope of the enterprise. However, in reality, there are many cases where the closed loop principle is not only realized within the scope of an enterprise, but also a CE is realized through mutual relationships with other sectors or enterprises. Even in this case, these enterprises can be said to be CE enterprises. For example, the closed loop principle of materials can be implemented between enterprises in an ecological industrial zone or between enterprises in a certain area, including a city. At this time, these enterprises can also be called CE enterprises. However, these enterprises should be viewed as elements of the region-wide CE. Third, the CE types according to various classification markers are interconnected. It is related to the situation that various markers proposed in this study can be used in mutual combination according to the research purpose. For example, the classification type according to the realization method can also be classified by the realization level, the realization target, and the realization method. In other words, the value-preserving CE can be divided into enterprise-wide, production-oriented and bottom-up. However, it is not practically meaningful to apply all the different classification marks to each type. For example, the product-functional CE at a national scale is difficult in reality, and the top-down method is meaningful in realizing the CE at a national scale. In addition, the consumption-oriented CE has greater significance at the national or regional scale, and can be applied to the realization of a resource-recovering or value-preserving CE.

The following conclusions can be drawn from the research results and discussion. First, the form of the CE can be classified according to various markers. The classification methodology proposed in this paper is classified according to the basic research purpose, and as research deepens and various theories and practices are created, detailed classification can proceed. Second, the type of the CE has its significance only when it is realized according to the circumstances and characteristics of a given region and country. This is because the various CE forms have their own unique characteristics, and each country, region, and enterprise has differences in the level of development. Of course, this study has limitations that are biased toward theoretical research in terms of methodology. However, this study is meaningful in that it makes it possible to fill the theoretical void for classification in the CE theory by systemizing theories and practices on the definition and type of the CE. In addition, this study can help to provide a certain reference in making CE-related policies and setting goals in practice.

Acknowledgements:

We would like to thank the reviewers and scholars of Faculty of Economics at Kim Il Sung University for insightful comments and materials related to circular economy.

Declarations of interest: None

Funding: Not Applicable

Data availability: Data sharing not applicable to this article as no datasets were generated or analyzed during the current study

Competing Interests: The authors have no conflict of interest.

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A Study on the Types of the Circular Economy

Status:

Version 1

Abstract

Figures

1. Introduction

2. Background For Classifying The Types Of Ce