Advancing Plastic Waste Management for a Circular Economy: Comparative Insights from Plovdiv (Bulgaria) and Kostanay (Kazakhstan)

Abstract

Plastic waste management is a critical challenge worldwide, influenced by the socio–economic conditions and policy frameworks of individual countries. This study evaluates the plastic waste management practices in two cities, Kostanay, Kazakhstan, and Plovdiv, Bulgaria, through a comparative analysis of household waste data, recycling systems, and legislative frameworks. The cities are similar in their main features, but the practice of plastic waste management is developed to varying degrees. In the period from 2017 to 2023, the population of Plovdiv decreased by 6.77% and the amount of municipal waste decreased by 3.55%. In Kostanay during 2021–2023, the population of the city increased by about 5%, and the amount of waste generated by more than 25%. Using morphological analysis and municipal records, this research identifies gaps in current practices and explores actionable strategies for enhancing plastic waste recycling. The qualitative analysis of the practice of urban plastic waste management shows that, compared to Plovdiv, the Kazakh city has underused the managerial and technological capabilities in the process of developing the plastic waste management industry and the transition to a circular economy. This study highlights the potential for implementing circular economy principles in both cities, with targeted recommendations to address existing challenges and maximize waste treatment and recycling. In Plovdiv, thermochemical processes for recycling plastic waste into new products are promising, while in Kostanay, mechanical methods for optimizing waste collection and transportation are promising.

1. Introduction

Plastic, as a light, convenient, flexible, and durable material, occupies an increasingly important place in the production of widespread waste, and its quantity in the market continues to grow. The global production of plastic was estimated at 400.3 million tons in 2022. Also called the “material with 1000 uses”, plastic finds application throughout human life with its versatile properties. Since a large amount of plastic products become waste within just a few months or years, they are also one of the priority sectors for implementing a circular economy. The sustainable management of plastic waste is a critical component of the broader waste management strategies aimed at achieving a circular economy. This requires not only an understanding of the sources and collection methods for plastic waste, but also the integration of legislative, technological, and socio–economic factors that influence its effective recycling and recovery. Despite global efforts, a significant portion of plastic waste continues to be discarded in mixed municipal waste, complicating the subsequent recycling and recovery processes [1,2]. Previous studies of urban solid waste management systems focused on the analysis and assessment of sustainable management of both the system as a whole, using individual cities as examples, and individual influencing external and internal factors. Modern factors that ensure the growth of plastic waste generation include such socio–economic factors as an increase in the standard of living [3], GDP [4], population density [4,5], urbanization [6], and urban population growth [3]. At the same time, a decrease in the volume of plastic waste occurs if investments in waste management infrastructure grow [7] and waste collection routes and schedules are optimized [8].

Factors influencing the formation rate of municipal solid waste have been classified into seven types [9,10]. Most often, studies show that the composition and quantity of municipal waste are most strongly influenced by the number and level of income [10].

Analysis of waste management systems in the literature is usually carried out within a specific country or city [11,12,13,14]. A significant part of the studies is devoted to the analysis of practices in one region: the Global South [15], developing countries [16], EU countries [17,18,19], etc. Authors of country-wide and regional studies critically rethink the experience of municipal solid waste management and specialize in their needs. As a result, driving factors are persistently identified; a search is underway for those relationships that improve the practices in municipalities, preferred recycling methods that increase the efficiency of waste management systems, and methodologies that allow a full assessment of the work of waste management systems using an optimal set of indicators.

Papers on Kazakhstan in the English-language sector of scientific research in waste management are few. They examine various aspects of plastic waste management in Kazakhstan. The sustainability of household waste management in Kazakhstan, including plastic waste, is limited by the fact that the infrastructure for waste processing and disposal is not developed, insufficient investment, and weak coordination between government agencies and businesses [20]. It is also noted that, although there is a Green Economy Transition Plan, a plan for the transition to a circular economy is needed [21]. More complex strategies for the sustainable operation of waste management systems, Zero Waste, Integrated Waste Systems, and Industrial Symbiosis, are useful, but will not be applied in Kazakhstan until later.

Since 2007, the European Union and Central Asia (CA) have been developing a partnership in five areas, including environmental protection [22]. At the same time, there are no cross-sectoral studies in these regions in the area of waste management, which reduces the potential for transferring European experiences. Such studies will help countries at the early stages of waste management system development to highlight gaps in this activity and contribute to the formation of a more effective waste management system, and on this basis, to achieve progress in a shorter period of time.

This study aims to evaluate and compare the plastic waste management practices in two cities—Kostanay in Kazakhstan and Plovdiv in Bulgaria—by analyzing the household waste data, recycling policies, and the readiness for transition to a circular economy. This study considers the integration of circular economy principles, paying specific attention to the differences in separate collection systems. The research objectives are to: (1) identify gaps in current waste management systems, (2) evaluate the economic and legislative frameworks influencing plastic waste recycling, and (3) propose strategies for enhancing the sustainable management of plastic waste in both cities.

2. Materials and Methods

For the purposes of this study, a comparative analysis was conducted between the cities of Kostanay in Kazakhstan and Plovdiv in Bulgaria to evaluate their plastic waste management practices and readiness for a circular economy.

Study Area

In order to turn waste into a resource, the goals of waste management must be aligned with the goals of the transition to a circular economy. Sustainable solid waste management (SWM) contributes to achieving 11 United Nations Sustainable Development Goals (SDGs) [23,24]. The Republic of Kazakhstan and the Republic of Bulgaria have implemented their waste management targets for achieving recycling levels that are relatively similar and aimed at the transition to a circular economy. For Kazakhstan, the goal is for the share of recycled waste to reach 50% by 2050 [25]. Although the country has not yet set specific targets for plastic waste collection and recycling, its recent policy initiatives such as the 2019 ban on the disposal of dry fractions of waste (plastic waste, waste paper, cardboard and paper waste, glass) into solid waste landfills indicate a growing commitment to improving waste management. Kazakhstan was chosen for comparison because it represents an example of a country in the early stages of implementing circular economy principles. This comparison allows for an analysis of how different levels of policy maturity influence the effectiveness of plastic waste management, Figure 1.

In contrast, Bulgaria fulfills the ambitious pan-European goals for waste recycling and reuse, with the aim that by 2035, 65% of household waste in the country must be prepared for reuse or recycling, and only up to 10% of household waste will be landfilled [26]. Special attention in the regulatory framework of Bulgaria is paid to waste from packaging, which is one of the common mass-distributed household wastes. In packaging waste regulations, recycling targets have been set at 55% of plastic packaging in the market by 2030 [27].

In the Republic of Kazakhstan, no specific goals have been set for the collection and recycling of individual waste streams and their fractions. One of the shortcomings of the waste management policy in the country is the lack of clear and accurate information regarding the quantities of individual types of waste in the mixed household waste. Clarity about the type and quantity of recyclable and recoverable waste is key to sustainable waste management and the selection of appropriate waste treatment methods within the context of the circular economy.

Bulgaria is a member of the EU and Kazakhstan belongs to the Central Asian region (CA). In 2023, Bulgaria’s GDP was $37,410 per person, while Kazakhstan’s GDP was $38,515 per person [28]. There is no informal waste collection sector in either country.

Plovdiv is located in the south of Bulgaria. The city is the administrative center of the region of the same name, the second most populous city, the second industrial center of the country, and the center of an agricultural region; tourism is developed here, including global tourism. The area of the city is 102 km².

Kostanay is located in the north of Kazakhstan. The city is the administrative center of the Kostanay region and one of the three largest agricultural regions in Kazakhstan. Industry and tourism are developed in the city. The area of the city is 240 km².

The cities of Plovdiv and Kostanay were chosen due to their similar population sizes, economic profiles, and university presence, which ensures a comparable socio–economic context. Additionally, both cities represent diverse regulatory frameworks for waste management, offering valuable insights into the influence of policy maturity on circular economy implementation.

This analysis focused specifically on household waste, with particular attention on plastic waste as a key component. The research methodology includes an analysis of the most important quantitative parameters for a waste management system’s performance, as well as a comparison of the qualitative parameters for plastic waste management in the cities under consideration. The quantitative parameters in this study were the total amount of household waste generated and the population number. The qualitative parameters were the components of the organizational and institutional structure, economic measures, and legislative initiatives (

Table 1. Aspects of waste management systems in the studied cities.

Aspects of Waste Management Systems	Plovdiv City	Kostanay City
Legislation	2008—EU Waste Directive [29] 2018—European Strategy for Plastics in a Circular Economy (recycle 50% of plastic packaging waste by 2025 and 55% by 2030) [30,31] 2019—Directive on reducing the environmental impact of certain plastic products [32]	2007—Environmental Code of the Republic of Kazakhstan (RK), on waste—chapters 42–44 2010—Comprehensive Waste Management Plan in the RK, now no longer in effect 2012—Concept of the transition of the RK to a green economy. The main indicators of the Comprehensive Waste Management Plan of the RK were included in the Action Plan for the implementation of the Concept of the transition of the RK to a green economy. 2021—Environmental Code new edition on waste, chapters 23–31
	The EPR principle is applied to plastic packaging	The EPR principle has been applied in a limited scope (2016, cars and their components; 2017, packaging at a “zero rate”, manufacturers and importers do not pay a recycling fee; 2020, agricultural machinery)
	2020—Ban on eight single-use plastic products in the EU Requirements for PET bottles—from 1 January 2025 at least 25% by weight must be made of recycled plastic, from 1 January 2030 at least 30% EU introduces mandatory transition to 100% recyclable packaging by 2030	2019—Landfilling of plastic waste banned
Plastic waste management	2015 EU Circular Economy Action Plan Targets by 2035: 65% recycling or recycling, only 10% of plastic waste will be landfilled	Green Economy Concept for the Republic of Kazakhstan The goal of the Republic of Kazakhstan by 2040 is to recycle 40% of solid waste, in 2050—to recycle 50% of solid waste 100% coverage of solid waste collection in large cities 2024—3.5% of plastic recycled in Kazakhstan
	Plastic packaging targets: by 2030, 55% of plastic packaging, 90% of single-use plastic will be recycled 2018 Bulgaria—59.2% recycling of plastic packaging, 3rd place in the EU	There are no targets in the Republic of Kazakhstan for the plastic waste cycle
	Plovdiv Municipality Waste Management Program for 2021–2028	Development plan for the territory of Kostanay region for 2021–2026 2024 Development of the Program for handling solid municipal waste in the territory of Kostanay Plastic bags—packaging in stores to choose from, at the request of buyers Recycling of plastic in Kostanay region—into 9 types of new products
	Financial incentives for municipalities to meet established targets Deposit system for types of plastic packaging	No deposit-collateral packaging system—planned, not implemented
	Separate collection of plastic (plastic packaging, household plastic)	Separate collection of plastic waste in mesh containers, at the same time mixed solid waste is collected, which also contains plastic waste Sorting—separation of commercial types of plastic (PET bottles, HDPE, LDPE) Collection of solid waste in Kostanay region: 2007—0.7%, 2023—18.2%
	The infrastructure includes containers for separate collection, garbage trucks, sorting (transfer) stations in the form of reception points, solid waste landfills	The infrastructure includes containers for separate collection, garbage trucks, solid waste landfills Sorting (transfer) stations—no
Organizational structure	Municipality—executive authority, waste flow management Collection of packaging in containers Organization for the recycling of packaging—collection, sorting, transportation Separately, there are centers for the purchase of plastic bottles from the population	Government agencies authorized in the field of waste management at the regional/provincial level: Department of Ecology (legislative functions), Department of Natural Resources and Nature Management (executive authority) Local level: city akimats (executive authority), waste flow management Collection and sorting of plastic waste is performed by waste collection and/or waste removal organizations Recycling is performed by recycling organizations Landfills—for the disposal of mixed solid municipal waste and plastic waste in their composition

).

3. Results and Discussion

3.1. Identification of the Amount of Household Waste Generated

Data for the city of Plovdiv show that there has been a trend of decreasing the generated mixed municipal waste in recent years. According to the Waste Management Program for the Municipality of Plovdiv 2021–2028, mixed municipal waste collected by municipal systems decreased by 3.55% for the period 2017–2020. The trend is expected to continue, with the quantities of mixed waste collected decreasing while preventing waste generation and expanding the separate collection system in the municipality, with the aim of permanently remaining below 125 thousand tons per year. This trend is also associated with a gradual decrease in the population of the city of Plovdiv (Figure 2). According to Eurostat data, in most countries households generate an average of up to 90% of municipal waste, with the rest generated by commercial sources and the administration. For the period from 2017 to 2023, the city’s population decreased by 6.77% and this is also reflected in the amount of waste generated [33].

The amount of household waste generated directly depends on the population of the locality.

In Plovdiv, a well-developed infrastructure supports the collection of household plastic waste through designated bins and recycling companies. In this regard, a more accurate reflection of the amount of mixed household waste generated is given by the accumulation rate per inhabitant. The reported accumulation rate for mixed household waste in the municipality of Plovdiv in 2020 was 369.58 kg/inhabitant/year or 126,413.38 tons of waste generated by the 342,048 inhabitants of the municipality per year.

In Kostanay (Figure 2), there is also an increasing trend in the city’s population, which is associated with the larger amounts of household waste generated.

For the period 2021–2023, the city’s population increased by about 5% and the generated waste by over 25%, which can be attributed to the increasing standard of living in the city. The rate of accumulation of mixed household waste calculated for the city of Kostanay is significantly higher than that determined for the city of Plovdiv, and amounts to 736 kg/h/y [36,37].

A review of the generated mixed household waste for the city of Kostanay (Figure 3) shows an increasing trend, both for mixed household waste and for solid household waste. In contrast, in Plovdiv (Figure 4) we see a downward trend.

Municipal waste is the waste generated in populated areas, including as a result of human activity as well as industrial waste, that is similar in its composition and nature of formation. Solid municipal waste includes only the municipal waste in solid form [37].

In 2024 in Kostanay, public hearings were held regarding the adopted city Solid Waste Management Program. The current coverage of 80% to 100% of the population with solid waste collection and removal is calculated for the period 2024–2031. Separately collected waste will be additionally sorted with the allocation of the most economically valuable fractions. The existing system of separate collection will be expanded by collecting food waste and textiles. Research will be conducted on the morphological composition of the solid waste to select a technology for deep processing, the use of an automated geoinformation system “Waste Management”. Assessing the current state of the solid waste system in Kostanay, experts say that the waste recycling market in the city is characterized by low competitiveness [39].

3.2. Amount of Plastic in Household Waste

Of the mixed municipal waste generated in the city of Plovdiv, according to a morphological analysis of the waste (Figure 5), 16.81% is plastic, or about 21,250 tons per year.

In the two cities under consideration, different systems for the separate collection of plastic waste operate. An organized system for the separate collection of packaging waste has been introduced in Bulgaria. The system for the separate collection of packaging waste, organized by recovery organizations and based on joint activity contracts with the mayors of the municipalities, includes at least green and yellow (and blue) containers for the collection of packaging waste from households. This is in addition to those for household waste, ensuring a minimum total container volume for settlements of over 100,000 inhabitants: for every 750 inhabitants—containers with a minimum total volume of 3300 L [27]. The system is based on the principle of “Extended Producer Responsibility”—an environmental principle applied as a set of measures to reduce the overall environmental impact of a product after the use of which widespread waste is formed. In addition to the commitments related to packaging waste, which is considered widespread waste, the mayors of the municipalities are obliged to organize the separate collection of household waste in the territory of the municipality, at least for the following waste materials: paper and cardboard, metals, plastics, and glass, and to provide sites for the free transfer of separately collected household waste in all settlements with a population greater than 10,000 inhabitants [26]. A system for the separate collection of packaging waste has been established in the territory of the municipality of Plovdiv, which is operated by packaging recovery organizations, and six sites have been designated for the free delivery of separately collected waste from households in different parts of the city. Various types of waste are collected at the designated sites, including plastic packaging (150,102) and household plastics (200,139) [33]. These requirements for waste management in the municipality of Plovdiv are legally established; in addition to them, there are over 30 waste collection sites and six plastic waste recycling companies in the territory of the municipality, established as private initiatives of legal entities, to which plastic waste can also be transferred [6]. Based on all the established separate collection systems in the municipalities in Bulgaria, including the private initiatives, municipalities receive financial incentives for meeting the set targets which aim to increase the recycled and recovered municipal waste.

Morphological analysis of waste in the city of Plovdiv (Bulgaria) was carried out in accordance with the current methodology used in Bulgaria [33,40]. In the territory of the municipality of Plovdiv, the generated plastic waste, calculated based on the morphological analysis, is about 21,250 tons per year. The coverage of the population of Plovdiv by the household waste collection system is approximately 99%. Plastic occupies a significant part of the generated municipal waste, ranking second after the fine fraction in the composition of mixed municipal waste.

The collection of household waste in Kostanay is carried out in two ways: in containers located on container sites, and in a container-less way by travelling around the territory and collecting waste in bags placed in certain places, according to a schedule. Collection in bags (roadside collection) is carried out mainly in the private sector. Then, the waste is transported by garbage trucks to the site of the sorting organization. The coverage of the population of Kostanay by the household waste collection system is 80%. For the collection of plastic waste from the population, mesh containers are installed [41]. Despite the established separate plastic collection system, large quantities of plastic are also found in containers intended for mixed solid waste. The data are similar to the results from Plovdiv, where large quantities of plastic waste are found in the mixed household waste. This shows that people in both Plovdiv and Kostanay still do not have sufficiently well-established habits for the separate collection of plastic waste; as it is contaminated with food waste, part of the plastic waste ends up in landfills.

Plastic accounts for 13% of the total waste volume (Figure 6).

According to the sorting company, it separates about 3–4 tons of recyclable waste daily, of which about 70% is plastic; about 2.1–2.8 tons of plastic is separated from mixed household waste daily. With 246 working days a year, this amounts to about 520 tons of plastic waste per year that could be transferred for further processing or recovery. However, a large portion of the plastic waste from mixed waste is heavily contaminated and unsuitable for subsequent recycling [41]. This leads to the loss of valuable materials suitable for use in the country’s industry.

In the city of Kostanay, there are six enterprises that carry out the separate collection and sorting of plastic waste, and three that recycle the plastic waste. As a result of recycling the plastic waste, nine types of finished products are produced from plastic waste: hatches for inspection wells, geogrid, geotextile, geocomposite, geoframes, polyethylene gas and water pipes, cable pipes, and polymer sand pavers [41].

Although in both cities—Plovdiv and Kostanay—there are currently separate collections and some of the plastics have found their application in new products, there is still significant potential for the implementation of a circular economy for plastics, which remains unrealized. For the city of Plovdiv, this amounts to over 21 thousand tons per year. For the city of Kostanay, assessing the potential for a circular economy is more difficult, since there is no practice of regularly conducting a morphological analysis of the composition of household waste in this country. For the purposes of this article, we calculated the amount of plastic waste in the mixed flow of household waste in the city of Kostanay, based on a percentage content of 13%. Therefore, if the 196,168 tons of annually generated mixed household waste has a plastic content of 13%, 25,502 tons of plastic waste will go to landfills. Thus, in the mixed municipal waste of each of the two cities in Bulgaria and Kazakhstan, there is a hidden potential for the introduction of a circular economy for approximately 20 thousand tons of plastic waste. Since the average price of plastics is about 100 euros per ton, the waste from these two cities contains a potential 2 million euros worth of lost value buried in landfills.

3.3. Green Solutions for a Circular Economy of Household Plastic Waste

In recent years, sustainable waste management has been largely associated with achieving compliance with the waste hierarchy. The waste hierarchy is implemented as a priority order in legislation and in waste prevention and management policy. It is the final corner of the European Union (EU) policy and legislation in the field of waste and is set out in the EU Waste Framework Directive [29]. Its objectives are to minimize the adverse impacts of production and waste management and to improve resource efficiency. In the field of plastic waste, the EU has set targets for achieving the waste hierarchy. The targets set are also applied in Bulgaria through the country’s regulatory documents (Figure 7).

In accordance with the waste management hierarchy, for already generated plastic waste it is advisable to seek methods for its recycling or recovery—raw material or energy recovery—and to direct that part of the plastic waste that is not suitable for recovery to a landfill. Part of the plastic waste is often contaminated and not suitable for recycling. In order to meet the requirements of the waste management hierarchy, various options for waste recovery are sought.

Options for recovery of MSW, including plastics, through which primary and secondary products can be obtained are given in Figure 8 [43].

The capacity of the installation can hold from 10,000 t/year to 100,000 t/year of pro-cessed waste. The main facility is a thermocatalytic reactor in which triboactivated waste is converted into “synthetic oil” in the presence of a catalyst, an inert or low-oxygen gas environment, a temperature of 400–500 °C, gaseous and liquid hydrocarbons, intensive mixing with gaseous, liquid, and solid products for 30–40 min. Physicochemical processes, cracking, “thermolysis”, and Fischer–Tropsch synthesis take place in the reactor, which converts the waste into a mixture of liquid hydrocarbons or “synthetic oil”. There are two outlet streams from the reactor:

• Primary—consisting of a mixture of gaseous hydrocarbons (C9–C20) which, after passing through a catalyst, are converted into “synthetic oil” with impurities of aromatic and cyclic hydrocarbons.
• Secondary—consisting of solid particles of graphite (carbon), spent catalyst, and inert (inorganic) waste. These are separated and used in commercial products.

The demonstrated technological possibilities for treating solid municipal waste, including plastics, through thermochemical and thermocatalytic treatments are applicable in practice and convincingly show that waste can also be an alternative raw material resource for obtaining organic and inorganic compounds with wide applications.

In the cities of Plovdiv and Kostanay, as shown in the previous sections, the plastic waste management systems are at different levels of development, although they are evolving in one direction—a circular economy. In Kostanay, further development is associated with increased efficiency at the stage of collecting and transporting plastic waste to processors. In Plovdiv, the stage of processing plastic waste into new products requires development. Therefore, the proposed scheme of thermal technological changes (Figure 6) for the production of primary and secondary products is promising for Plovdiv. In Kostanay, technological changes in the city’s plastic waste management system will be more associated with mechanical processing technologies.

In general, the results of the comparison of the urban management systems in the cities of Plovdiv (Bulgaria) and Kostanay (Kazakhstan) can be presented in the form of Table 1, which demonstrates the similarities and differences in the studied aspects of the waste management systems.

3.4. Discussion

The results of this study allow us to consider the urban plastic waste management systems in Kostanay and Plovdiv from the perspective of a circular economy, revealing both similarities and differences that determine their development trajectory towards sustainability. Despite significant territorial distance, both cities demonstrate similar characteristics, namely lower GDP and higher levels of waste generation [17]. This allows us to classify them into the same category of city, which is confirmed by the comparable quantitative indicators for the performance of the waste management systems. Both cities have the necessary technical infrastructure; however, the potential of this requires further development. In particular, for Kostanay, a key step towards increasing the degree of circularity will be the creation of collection points/transfer stations, which will optimize the collection and sorting of waste. The presence of plastic recycling plants in both cities, as well as attempts to economically assess the potential of plastic waste, indicate the recognition of plastic as a valuable resource, and not just as garbage. Separating the plastic waste stream into a separate category and creating a dedicated infrastructure will help to maximize the value of these materials through reuse, recycling, and other strategies, which is a key principle in the circular economy.

Studies in Africa [44], South Asia [45], and the EU [Swedish and Bulgarian] have shown intra-regional differences in the maturity of the waste management regulations. A comparison of waste management in Kostanay and Plovdiv (Table 1) demonstrates this trend at the inter-regional level, in particular for the EU and Central Asian regions.

The comparison with Plovdiv, which has significant experience in the circular economy, serves as a valuable source of knowledge and best practice for Kostanay. Implementing proven tools and approaches, such as developing targets for plastic waste, identifying hidden waste volumes, and implementing effective information strategies, will help accelerate the transition to a circular model. It is important to highlight that the circular economy and the Sustainable Development Goals (SDGs) are closely interrelated and complementary. The circular economy is a powerful tool for achieving many of the SDGs, while the SDGs create favorable conditions for its development. The circular economy is based on the principles of responsible consumption and production, which include waste reduction, efficient use of resources, and reuse and recycling of materials. Systematic consideration of these principles when improving waste management systems, as shown in [24], will allow the economic potential of plastic waste to be translated into reality for both cities.

Similar studies in Eastern Europe [46,47] highlight the importance of regulating packaging waste to achieve higher recycling rates, which is also true for Plovdiv. Studies in Central Asia, including Bishkek and Almaty [48], reveal gaps in data availability and public awareness, which is also true for Kostanay.

These studies highlight the need to develop tailor-made strategies for urban waste management systems that take into account local socio–economic and legislative conditions. Kazakhstan’s lag in this area is explained by the later development of waste management compared to EU countries, which determines legislative, technological, and organizational features. Thus, both cities have already moved away from the linear model of waste management and are taking active steps towards circularity.

4. Conclusions

As a result of this study, the following conclusions can be drawn:

• The compared cities of Kostanay in Kazakhstan and Plovdiv in Bulgaria have a similar population, a well-developed economy and tourism, and are university cities. Nevertheless, the rate of MSW accumulation for Kostanay is 736 kg/person/year, and for Plovdiv it is 369.58 kg/person. One of the factors in this difference is probably the need to purchase drinking water in Kostanay, which is available in plastic packaging.
• The methodology used is applicable for comparing settlements close in population, especially when no morphological analysis has been done for one of them.
• An information strategy is needed to explain to the population in both the city of Plovdiv and the city of Kostanay the good practices for the separate collection of plastic waste so that it is not contaminated with other waste, including food waste, so it is not recycled but landfilled.
• The analysis shows that in the mixed household waste of only two cities in Bulgaria and Kazakhstan, there is a hidden potential for the implementation of a circular economy for over 50 thousand tons of plastic waste; with the average price of plastic at about 100 euros per ton, the waste in these two cities has a potential value of over 5.4 million euros.
• In both cities, in the context of green solutions for a circular economy, the collected plastic waste is recycled into products, but this does not exhaust all possibilities.
• A comparative analysis of the practices in the two cities showed differences in the level of circularity and in the methods of recycling plastic waste. If the system of solid waste management, including plastic waste, is developing according to the 3R scheme, then in Plovdiv the current level corresponds to the 5R scheme. Improving the collection of municipal solid waste, especially plastics, can also lead to the implementation of thermochemical and thermocatalytic technologies for the production of organic and inorganic compounds for subsequent use as basic raw materials or reagents. This is another green solution for a circular economy in Plovdiv. In Kostanay, the acceleration of progress in plastic waste management is linked to the development of infrastructure and mechanical recycling methods.
• Future studies on the development of plastic waste management systems towards a circular economy in the cities under consideration should include other areas of technological change for plastic waste recycling, and characterize the development efficiency with indicators acceptable at different levels of system development for their comparability and evaluation.