Identification of barriers to reverse logistics of organic waste: a literature review considering the stakeholder Public EntitiesAbstract
This research aimed to identify the barriers to reverse logistics (RL) of organic solid waste for the stakeholder Public Entities in the literature. We adopted a systematic literature review strategy using the Scopus and Web of Science databases, employing the PRISMA method. In total, 34 articles were identified, including 14 barriers related to Public Entities. The results of this study contribute originally to the field as this is the first research to identify and discuss in-depth the barriers to RL of organic waste related to Public Entities, paving the way for empirical research and the development of this field of study. Additionally, it provides practical contributions for public policies and private sector actions to be addressed in an integrated manner to overcome these barriers.
Keywords: organic waste; reverse logistics; barriers; Public Entities; urban solid waste
RESUMO
Esta pesquisa objetivou identificar na literatura as barreiras para a Logística Reversa (LR) de Resíduos Sólidos Orgânicos (RSO) para o stakeholder Entidades Públicas. A estratégia de pesquisa adotada foi a revisão sistemática da literatura utilizando as bases de dados Scopus e Web of Science, usando o método PRISMA. Foram identificados 34 artigos, e nestes, 14 barreiras relacionadas às Entidades Públicas. Os resultados deste estudo contribuem de forma original para a área de estudo, pois esta é a primeira pesquisa que identifica e discute de forma aprofundada as barreiras à LR de resíduos orgânicos relacionadas às Entidades Públicas, abrindo caminho para pesquisas empíricas e para o desenvolvimento desse campo de estudo. Também contribuem de forma prática para que políticas públicas e ações da iniciativa privada possam ser endereçadas de forma integrada para contornar tais barreiras.
Palavras-chave: resíduos orgânicos; logística reversa; barreiras; Entidades Públicas; resíduos sólidos urbanos
INTRODUCTION
Reverse logistics (RL) has emerged as a crucial component in the sustainable management of organic solid waste (OSW), helping to mitigate the environmental impacts associated with the improper disposal of waste. Large generators and those involved in RL assume responsibilities within the scope of ensuring environmentally appropriate waste disposal (Brasil, 2019). Organic waste presents a complex challenge for the implementation of composting units in Brazilian municipalities (Conceição et al., 2024), making it a critical issue that deserves due attention. Organic waste primarily includes biodegradable materials from plants or animals, food waste, yard waste, wood, and paper products (Kazuva; Zhang, 2019), among others. It is estimated that Brazilians generated an average of 1.04 kg of urban solid waste per day in 2022, totaling approximately 77.1 million tons of urban solid waste generated in the country that year (Abrema, 2023). This corresponds to over 211,000 tons of waste generated per day. Improper management of this waste can result in greenhouse gas emissions, with the decomposition of organic waste accounting for 4% of Brazil's greenhouse gas pollution, equivalent to 96 million tons of CO2 emitted (Conceição et al., 2024), as well as soil and water contamination and public health issues. In this sense, RL constitutes a strategy and a necessity for the disposal of organic waste.
However, there are associated barriers to implementing an RL chain for organic waste. These include the lack of adequate infrastructure (Gebreegziabher et al., 2014), the lack of public policies related to this end (Menyuka; Sibanda; Bob, 2020; Teixeira et al., 2024), and the absence of economic incentives (Ludlow et al., 2021; Faro et al., 2024). Thus, the role of stakeholders, especially Public Entities such as municipal governments, is to formulate and implement policies that promote RL, as well as to raise awareness and educate the population on this topic.
Therefore, this article seeks to answer the following question: What barriers to the implementation of RL for organic waste relate to the stakeholder Public Entities? To explore this question, this study aims to identify the barriers associated with the RL of organic waste through a literature review, considering the stakeholder Public Entities. The relevance of this study lies in the urgent need for sustainable solutions for the management of organic waste, highlighting the essential role of public policies and collaboration among different stakeholders to achieve an efficient and sustainable circular economy. Understanding the barriers and strategies to overcome them, focusing on Public Entities, can provide valuable insights for the formulation of effective policies and the promotion of sustainable practices in organic waste management.
METHOD
A systematic literature review was conducted to answer the research question: What are the barriers to the implementation of RL for organic waste for stakeholder Public Entities? Thus, the research was carried out following the stages of the PRISMA method (Galvão; Pluye; Ricarte, 2017): identification and selection of articles, coding of articles, analysis of the coded database, and discussion of the results.
Consultations were made to the Web of Science (WOS) and Scopus databases for the first stage. For the searches, the terms "municipal solid waste," "urban solid waste," "barrier," "limitation," "challenge," "wet waste," and "organic waste" were used. The search returned 181 and 162 articles from the WOS and Scopus databases, respectively. Inclusion and exclusion criteria were applied to these results: works must be in English or Portuguese (BR), excluding conference papers, book chapters, and duplicates. As a result, 220 articles were obtained from these databases.
In the second stage, the titles and abstracts of the 220 articles were read, classifying them as irrelevant (articles that did not address the topic of barriers to RL for organic waste) to highly relevant (articles related to organic waste, RL, and barriers). After this stage, 123 articles remained.
Next, the third stage of coding began, in which the articles were read in full to identify the specific barriers to the stakeholder Public Entities. In this stage, 55 articles were excluded for being inaccessible or not meeting the research objective, leaving 68 articles in the database. Finally, 31 out of 68 articles were directly related to the barriers to RL for organic waste for stakeholder Public Entities. These steps are demonstrated in Figure 1.
RESULTS AND DISCUSSION
Descriptive analysis of the database
To form the database, 31 articles published between 2014 and 2023 were selected, identifying 14 barriers in the literature related to Public Entities that hinder the implementation of RL for organic waste. These barriers are summarized in Table 1.
The articles that make up the database were published between 2014 and 2023 (first semester only). The years with the highest incidence of publications on the topic were 2015, 2018, and 2020–2022, corresponding to 23/31 articles. The publication timeline is shown in Figure 2.
In order to show the impact of the set of articles that make up the database, we present in Table 2 the H-index (www.scimagojr.com) of each journal that was published, as well as the number of articles in the database published in each journal. For 24/31 articles, the H-index was above 100, with the Renewable and Sustainable Energy Reviews Journal having the highest H-index (421) and the Waste Disposal & Sustainable Energy Journal (8) having the lowest index. The journals with the highest number of published articles are Sustainability with 4 articles and Renewable and Sustainable Energy Reviews, International Journal of Environmental Research and Public Health, and Resources, Conservation and Recycling with 3 articles each.
Table 3 lists the 14 barriers and their locations. The barriers are concentrated in developing countries in the Americas, such as Brazil, Chile, and Mexico; Africa, such as South Africa, Ethiopia, and sub-Saharan Africa; and Asia, such as China and Malaysia. Barriers also occur in Europe (Italy), Australia, Canada, and the United States.
Barriers to RL of OSW for Public Entities
Barrier 1—Lack of urban planning and adequate infrastructure for waste treatment facilities
Gebreegziabher et al. (2014), in a study conducted in sub-Saharan Africa, identified urban planning and adequate infrastructure for the construction and modernization of treatment facilities as the main barriers. Given that urban facilities require basic infrastructure to build and operate a biogas unit, as well as to treat digester effluents and technological alternatives for their application, governments and municipalities need to explicitly address the issues surrounding the problem through policies and regulations to realize this potential.
Regarding municipal solid waste (MSW) treatment in Dar es Salaam, Tanzania, Kazuva and Zhang (2019) pointed to the lack of necessary infrastructure for waste treatment as a major barrier. The authors advocate for composting, with its economic competitiveness and moderate environmental cost, as the best option, as it will not only improve the MSW problem in the city and other parts of the country but also enhance soil nutrients, adding value to urban agriculture.
Bong et al. (2017), in their review of renewable energy policies and solid waste management for biogas development in Malaysia, also identified the lack of infrastructure due to the high costs of equipment and research as one of the main barriers. The authors predicted that with appropriate SWM policies, more financial initiatives and technical support within RE policies could complement each other, allowing biogas development in Malaysia to progress more efficiently.
Daskal et al. (2022), in their analysis model of decentralized composting through a cost/benefit decision-making methodology, allowed the examination of project viability in different scenarios, helping to indicate the most feasible alternative. They identified, among other things, odor management, animal/rodent hazards, flies and insects, raw material, and compost storage areas as major barriers. Therefore, they suggest implementation by municipal statutes and related charges, proper facilities, a fully enclosed composting system, and external rodent and animal-proofing as measures to overcome these barriers.
Zhang, Wen and Chen (2016) emphasized that many developing cities face challenges with insufficient infrastructure to handle the amount of solid waste generated, corroborated by Mascarenhas et al. (2021), who assert that inadequate infrastructure is a common challenge in Kisumu, Kenya, when it comes to solid waste management, including the absence of adequate facilities for collection, transportation, and treatment to deal with the increasing amount of waste generated.
Mushtaq, Dar and Ahsan (2020), in a study conducted in the western Himalayas, identified the lack of urban planning and adequate infrastructure for the construction and modernization of facilities as barriers, given that waste management is underdeveloped, and they propose treatment methods such as composting, biomethane plants, recycling plants, and converting dumping sites into sanitary landfills.
Barrier 2—Difficulty in expansion due to composting areas requiring large tracts of land
The discussion on the limited capacity for waste treatment in Shanghai highlights the specific issue of land use for composting areas. Xiao et al. (2020) indirectly addressed the difficulty of expanding such composting facilities in urban areas with limited and valuable land availability. To address the limited capacity for organic waste treatment, the authors propose policies aimed at strengthening the recycling processes of MSW. However, the lack of land remains a critical factor.
According to Menyuka, Sibanda and Bob (2020), not having land ownership rights is a challenge related to the use of organic waste in urban agriculture, which can restrict the expansion of composting areas. They also highlight the importance of land availability to encourage participation in composting activities, as the lack of access to land and the need to obtain permission from municipal authorities or landowners to use land may discourage farmers and residents interested in employing organic waste in urban agriculture.
Zhang, Wen and Chen (2016) said that the government is essential in providing land and funding for the recovery of organic waste. The authors emphasize that the Green House program can help reduce waste through sorting and separation, but it requires its facilities, and due to the unavailability of land and government support, it creates a barrier to waste treatment. Gonçalves et al. (2018) stated that in BRICS countries, the lack of available land for composting is a limiting factor in implementing programs for urban solid waste management based on composting.
Barrier 3—Lack of policies supporting the useof organic waste
A significant proportion of respondents in a survey conducted in Durban, South Africa, perceived the lack of a policy supporting the use of organic waste in urban agriculture (Menyuka; Sibanda; Bob, 2020). This indicates the need for clear guidelines and frameworks to facilitate and regulate such practices. Although there is recognition of the potential benefits of using organic waste in urban agriculture, challenges and risks also need to be addressed through informed policy-making and planning initiatives.
Ludlow et al. (2021), in research conducted in Chile, pointed out that the absence of supportive policies, market interventions, or regulations for waste management and energy recovery can create institutional barriers to the widespread adoption of organic waste-to-energy solutions. Carmen-Niño et al. (2023) in turn, in research carried out in a city in southern Mexico, stated that the lack of accurate and up-to-date information on the volume of waste generated, along with limited financial, technical, and logistical resources to effectively manage MSW, poses a significant obstacle to the implementation of effective waste management strategies.
The lack of knowledge, planning, financial resources, and infrastructure to implement efficient composting systems is a significant challenge, according to Gonçalves et al. (2018), in a study conducted in the BRICS countries (Brazil, Russia, India, China, and South Africa). Pan et al. (2015) highlighted the importance of governance, policy-making, and stakeholder involvement in waste management and circular economy systems, emphasizing that establishing policies, promoting government responsibility, and ensuring stakeholder awareness are essential for successful implementation.
Barrier 4—Lack of funding and investment
Zhang, Wen and Chen (2016), in their study conducted in Beijing, identified the lack of government involvement as the main barrier, emphasizing that the government should be extensively involved in the Green initiative to provide initial funding and operational subsidy resources.
Similarly, in their study on the potential use of MSW as a resource for bioenergy with carbon capture and storage (BECCS), Pour, Webley and Cook (2018) identified the lack of economic support schemes, such as those typically applied to solar and wind energy, as one of the main barriers. The authors emphasized the limited understanding and aversion to MSW recovery as an alternative bioenergy source among stakeholders and the lack of policies to incentivize energy generation from waste.
Ludlow et al. (2021), in a research on the potential for transforming organic waste into energy in the Chilean context, concluded that financial, technical, and institutional barriers hinder waste utilization, highlighting the need to address the high investment costs and heavy reliance on landfill disposal practices, which, along with public policies, could enable full exploitation of these resources to ensure energy security and efficiency.
Moreover, Pandyaswargo et al. (2019), in their research on the use of biogas technology in emerging Asian countries, identified financial challenges as one of the main barriers, considering that biogas plant projects of various scales depend on external support in the form of government subsidies and favorable loans. Additionally, they point to the need for financial assistance from private investments with a public–private alliance mechanism or public–private partnership. For larger biogas plants, project technology transfer mechanisms can make the private sector more confident in investing.
In Brazil, Santos et al. (2018), in his research on the evaluation of the potential for biogas production from multiple organic waste sources, considering the impact on energy generation, use, and emissions reduction, identified economic viability, the absence of incentive policies, and the weak development of business models as major barriers. These limitations are highlighted as factors hindering the successful implementation of biogas, considering the lack of urban planning and adequate infrastructure for the construction and modernization of treatment facilities.
Barrier 5—Excessive bureaucracy due to weak legislative coordination across different institutional levels
According to Morone, Yilan and Imbert (2021), the Italian bioeconomy sector, by using the organic fraction of MSW to produce value-added sustainable products, faced significant barriers such as excessive bureaucracy, lack of social acceptance, barriers to circular planning, operational limits in project implementation, and the national economic crisis. For Lohri et al. (2016), current policies that prioritize fuel switching are considered unrealistic and incomplete, failing to recognize the realities of actual energy costs, future consumption trends, and the significant potential offered by biomass energy in Ssub-Saharan Africa.
Barrier 6—Inadequate management of organic waste (limited transportation and collection, costs, inadequate handling, and treatment)
A major concern highlighted by Xiao et al. (2020) is the insufficiency of OSW treatment. The authors provided valuable insights into innovative strategies and challenges in MSW management related to transportation, costs, inadequate handling, and treatment of organic waste as factors hindering the reuse of some waste. Addressing these challenges requires better collection networks, enhanced treatment capacities, and the optimization of incentive schemes such as the Green House program to promote the efficient management of organic waste in Shanghai.
According to Siqueira and Assad (2015), including better transportation conditions, cost reduction, proper handling, and adequate treatment methods would greatly support diverting organic waste from landfills and promoting composting, which is a more environmentally beneficial form of reusing OSW. The authors confirmed that public support, institutional commitment, and decentralized approaches are essential to addressing the inadequacies in current waste management practices.
Carmen-Niño et al. (2023) highlighted that budget constraints faced by municipal authorities regarding solid waste management lead to technical deficiencies and inadequate operational planning. According to the authors, these limitations result in inefficient waste collection practices, such as irregular visits, making organic waste management challenging. Moreover, poor use of municipal collection routes and the lack of timely replacement of the vehicle fleet contribute to operational inefficiencies, especially in organic waste treatment. The authors further highlight the need for technological solutions and qualified human resources to enhance organic waste management, emphasizing the importance of geographic information systems (GIS) to optimize routes and improve services provided. They also emphasized the high operational costs that hinder the efficient provision of waste collection services in all communities. Therefore, this situation leads to inadequate waste disposal practices, such as burning, burying, or dumping in water bodies, which contributes to the proliferation of open dumps.
According to Mushtaq, Dar and Ahsan (2020), the underdeveloped infrastructure for MSW management is a determining factor in perpetuating inadequate disposal practices. The absence of efficient systems for waste collection, transportation, and treatment results in inadequate disposal, such as dumping in open dumps, which are environmentally unsustainable and harmful to public health. According to Fereja and Chemeda (2022), solid waste management in Dilla, Ethiopia, faced significant challenges, such as waste collection and transportation carried out by inadequate and outdated trucks, resulting in mixed waste dumping in unsanitary locations, exacerbating environmental and public health problems.
Barrier 7—Technical challenges of MSW separation planning
In research on the potential use of MSW as a resource for BECCS, Pour, Webley and Cook (2018) identified the dispersed nature of MSW as one of the main barriers. They highlighted the technical challenges related to MSW, such as the lack of extensive adaptive planning (separation) and the insufficient availability of MSW for energy use.
In a case study on the feasibility of central MSW sorting conducted in Beijing, Zhang, Wen and Chen (2016) identified technical/managerial deficiencies as one of the main barriers. They highlighted that the main reasons for work stoppages are technical deficiencies, such as machine malfunctions and water supply system failures. The authors pointed out that the design of machines and systems for the Green House project was not carried out by professionals experienced in this field of study, and there was a shortage of equipment and technologies for controlling secondary pollutants.
Gonçalves et al. (2018), discussing BRICS countries, identified that the main barriers to MSWM faced by these countries are directly related to the lack of adequate local infrastructure, planning, quantitative data on the types of waste generated, and the definition of responsibilities of the agents involved in the process. Thus, the implementation of long-term planning measures that encourage reduction at the source, source separation, recycling, composting, and landfill volume reduction are some actions that can be taken by these countries to improve the MSWM system.
In their study in southern Mexico, Carmen-Niño et al. (2023) identified the lack of information from responsible authorities on the volume of waste generated in the study area and limited technical resources and knowledge as major barriers. They emphasized that GIS are a current trend for modeling and optimizing service routes, proposing a better scenario.
Barrier 8—Availability of MSW for energy use is insufficient to meet urban demands
According to Pour, Webley and Cook (2018), the availability of MSW depends on parameters such as human population, economic development, degree of industrialization, public habits, and waste management regimes. Moreover, waste management policies that promote reduction, reuse, and recycling can further decrease the availability of waste for energy use.
According to Espinoza Pérez et al. (2022), the main challenges for the industrial-scale implementation of hydrothermal carbonization are the variability in the composition of untreated biomass and the seasonal and geographical availability.
Barrier 9—Low technical knowledge and aversionto MSW recovery as an alternative energy sourceamong stakeholders
In Brazil, there is an evident reluctance to use organic waste as an alternative energy source. Santos et al. (2018) stated that there is an aversion to this use, which extends to the Brazilian legislature, implying barriers to incentives due to a lack of resources. Moreover, the lack of interest from representatives causes delays in how this material is treated, resulting in a missed opportunity for a new alternative energy source. The authors also say that this hesitation is reflected in the slow incorporation of, for example, biogas into the national energy matrix, which has great potential.
Thus, there is a need to raise awareness and educate stakeholders about energy recovery technologies from organic MSW. The lack of technical understanding can lead to biases and resistance to implementing innovative solutions. Pour, Webley and Cook (2018) discussed the combustion of MSW-derived coal, highlighting the importance of understanding the behavior of elements during the incineration process. Resistance to organic MSW recovery as an energy source can be attributed to environmental, social, and technical concerns. The authors say that carbon capture and storage in biomass have environmental impacts that must be considered. Therefore, the lack of technical knowledge and aversion to organic MSW recovery as an alternative energy source should be combated with education, awareness, and comprehensive impact assessment to promote the adoption of BECCS technologies based on MSW.
Dhanya et al. (2020) addressed problems related to recycling, emphasizing the growing dependence on fossil fuels and the need for a sustainable approach to bioenergy production. The authors also comment that the successful implementation of a zero-waste discharge policy is a way to achieve sustainable bioenergy development, emphasizing the conversion of organic waste into bioenergy as essential.
Corroborating this debate, Sousa et al. (2022) discussed how biodiesel and biogas production at UFPE's biorefinery have the potential to generate significant financial savings for the university. The technical knowledge and acceptance of stakeholders represent challenges for organic MSW recovery, as both are essential for these projects to occur. The authors also state that for energy generation, the implementation of integrated biorefinery structures offers a practical and sustainable solution, and although it is a good solution for using organic waste, technical knowledge is necessary for the production of these compounds.
Logistical costs (transportation, maintenance, and retraining in new technologies)
Perteghella et al. (2020), in a study in low- and middle-income countries, found that waste was only collected in the city's urban center, which had approximately 16,000 inhabitants. People living in rural contexts were hardly reached by collection trucks due to narrow and unpaved roads, as well as high costs that the public concessionaire and the municipality could not bear due to the location's logistics. According to Menyuka, Sibanda and Bob (2020), there are obstacles associated with organic waste management in urban agriculture, especially regarding restricted transportation and high costs. Important challenges in urban agriculture also pointed to problems with access to inputs due to high costs, which hinder the effective use of organic waste. Additionally, the authors revealed difficulties with organic waste transportation, resulting in increased costs and challenges for the municipality in proper treatment.
Carmen-Niño et al. (2023) mentioned that the formal waste collection service in Xaltianguis has areas of opportunity for improvement, including service coverage. However, technical and logistical complications are common, such as the obsolescence of the collection vehicle fleet, which was not replaced promptly. The authors also highlighted the insufficiency of the vehicle fleet in their locality, resulting in dependence on informal collections.
Perteghella et al. (2020) considered that the expenses required for maintenance operations to ensure the functionality and longevity of equipment, structures, and buildings become essential to generate a more comprehensive holistic vision to find waste management solutions. According to the authors, this assessment should consider various cost factors, including direct costs, overheads, indirect costs, maintenance costs, and fixed costs.
Sealey and Smith (2014), in a study conducted in the Bahamas, identified logistical and labor costs, as well as awareness and education requirements, as barriers, as successful integrated waste management, require essential components of government regulation, producer responsibility, and consumer awareness. They also highlight that one of the main barriers to recycling is the economy, considering short-term costs and the recycling required to change old habits and adopt new technologies.
Barrier 11—Limited technical knowledge for identifying and separating waste
The limited technical knowledge in waste identification and segregation presents significant challenges in waste management, particularly in maximizing resource recovery and minimizing environmental impacts. Shen et al. (2015) asserted that the lack of technology in waste sorting can lead to inefficient recovery. Addressing this lack of technical knowledge would require investment in education and training for those managing this waste.
Zhang, Wen and Chen (2016) pointed out that there is a need for waste sorting programs and technologies to assist in the proper separation of material to improve the effectiveness of its management. They also state that technical knowledge is essential to ensure the success and sustainability of waste management programs. Kazuva and Zhang (2019) emphasized the critical role of technical proficiency in waste management processes. Low knowledge in identifying and separating various wastes can hinder effective initiatives for their treatment and recycling and lead to insufficient environmental outcomes.
Improved technical knowledge can significantly contribute to enhancing waste management practices and mitigating the environmental impacts associated with inadequate handling. Lunag Jr., Elauria and Burguillos (2021) focused on the importance of community involvement, especially in the design of household composting systems. The authors highlight the need for practical and sustainable approaches to waste management, such as composting at the household and community levels. These practices eliminate the need for technical knowledge for waste separation, constituting an action to overcome such a barrier.
The informal sector plays an important role in waste collection, despite the need to formalize these systems. Thus, Gonçalves et al. (2018) emphasized that the waste management system in BRICS countries lacks well-developed structures, leading to inefficiencies in waste collection and inadequate storage. Moreover, the authors stated that due to the high organic fraction present, composting is suggested as a method for using and reducing this waste, implying the need for greater technical knowledge to improve waste management practices.
Barrier 12—Lack of government cooperation inproviding accessible financial and environmental values for MSW investment
Kazuva and Zhang (2019) analyzed waste management scenarios, emphasizing it as a very profitable option due to its cost–benefit ratio and environmental benefits. The authors commented that the discrepancy arises when considering the lack of government cooperation to provide accessible financial resources and environmental values for investment in organic waste management. Without adequate government support and incentives, implementing sustainable organic waste management practices becomes a challenge. The authors also reinforce that the implications of this inadequacy in government cooperation are reflected in the limited adoption of economically and environmentally correct waste management solutions. Greater financial and political support would be essential to encourage investment in organic waste management.
According to Carmen-Niño et al. (2023), the presence of informal waste collection systems operating outside legal frameworks demonstrated the vital role played by informal sectors in supporting formal collection services. Therefore, there is a need for government support for these collection practices to continue and for those performing this service to have adequate equipment, a good fleet, and safety when collecting waste. According to the authors, the lack of government cooperation for MSW investments can hinder the development of sustainable supply chains.
Barrier 13—Lack of supervision and monitoring of indicators in obtaining results/reports
Inadequate data collection practices can lead to insufficient evaluation of this waste. Carmen-Niño et al. (2023) stated that to minimize these impacts, more efficient collection processes should be created with regular monitoring indicators and mechanisms. Perteghella et al. (2020) corroborated this, stating that solid waste management evaluation in developing countries faces a lack of available data and difficulties in its interpretation.
Inconsistent monitoring is also a critical obstacle. Hettiarachchi, Meegoda and Ryu (2018) addressed the concept of organic waste buyback programs, delving into the challenges of unimplemented regulations and insufficient monitoring, highlighting that developing nations struggle with inadequate waste management practices due to a lack of governance in the effective enforcement and supervision of regulations.
Barrier 14—Lack of measures to encourage waste recovery by stakeholders
Behrooznia, Sharifi and Hosseinzadeh-Bandbafha (2020) emphasized the lack of awareness and understanding among municipal authorities regarding the technologies in question, partly attributable to their technical complexity and the high initial cost associated with building and operating large-scale anaerobic digestion facilities. Furthermore, the absence of a clear regulatory and policy framework that encourages and facilitates investment from both the public and private sectors in these technologies is a significant limitation.
Siqueira and Assad (2015) emphasized that while municipal governments in the state of São Paulo have been the main promoters of urban composting, with the installation of composting sites in public spaces such as parks and municipal gardens, participation from other sectors, such as companies and nongovernmental organizations (NGOs), has been limited. This restriction is attributed to municipal regulations that may restrict the practice of composting in urban environments.
According to Bong et al. (2017), despite the Malaysian government's efforts to implement national policies to promote biogas development, barriers such as the lack of comprehensive support measures, especially related to the availability of financial resources and the addressing of technical issues and guarantee requirements, persist.
According to Delley and Brunner (2018), residents in municipalities without taxation tend to divert a significantly higher amount of biogenic waste to unsorted trash bags compared to those subject to taxation. On the contrary, citizens in rural municipalities tend to divert fewer biogenic resources and generate less food waste in unsorted trash bags. The reasons for this difference may be related to the prevalence of household composting in rural areas.
According to Hettiarachchi, Meegoda and Ryu (2018), the lack of source separation of organic waste is a challenge in developing countries, while in nations with more developed infrastructure, implementing regulations and education programs has successfully reduced the diversion of organic products to incinerators or landfills. Developing countries face obstacles due to the lack of infrastructure to implement such systemic measures effectively.
Khamkeo et al. (2021) indicated the lack of an efficient waste separation system, emphasizing that the success of sustainable solid waste management depends on the participation of communities, local authorities, and the private sector. Besides participation, community knowledge and understanding of the solid waste problem are crucial. Daskal et al. (2022) stated that there is a need to overcome the public perception that waste should simply be disposed of as quickly as possible, rather than seen as a resource.
The barriers are summarized in Table 4.
DISCUSSION
According to the literature review, the Public Entities stakeholder plays a central role in the reverse RSO channel, as they range from more operational barriers such as limited technical knowledge for waste identification and separation (B11), through more tactical barriers such as lack of urban planning and adequate infrastructure for waste treatment facilities (B1) to more strategic barriers such as excessive bureaucracy due to weak legislative coordination of different institutional levels (B5).
When these barriers exist at a certain level, strategic for example, they cause chain barriers, at the tactical and/or operational levels. When a territory (city or metropolitan region) adopts waste management policies that promote the reduction or reuse of organic waste for composting purposes, it may compromise the availability of this waste for energy use (B8) (Pour; Webley; Cook, 2018). In this situation, waste management strategies (composting and energy production) are competing for the same resource, which can compromise the availability of waste for both strategies, promoting an operational barrier of unavailability or insufficient waste. Likewise, the lack of planning and adequate infrastructure for the installation of organic waste treatment (B1), related to the tactical level, such as biogas production units (Gebreegziabher et al., 2014; Bong et al., 2017) or composting (Daskal et al., 2022; Kazuva; Zhang, 2019; Mushtaq; Dar; Ahsan, 2020), cause the barrier, at the operational level, of a lack of extensive adaptive planning for the separation of waste at the generating source (B7) (Pour; Webley; Cook, 2018), because if there are no waste recovery units, there is no reason to separate them, much less commit the generators to this task.
When waste management is inadequate (B6), meaning there are no proper collection and transportation systems, which are limited and do not meet the needs of the generation system, and there are no facilities for the recovery of MSW, this waste tends to be disposed of in open dumps (Mushtaq; Dar; Ahsan, 2020; Carmen-Niño et al., 2023). In the worst-case scenario, when waste is not collected, it can attract urban pests, contaminate soil and rivers, and cause harm to living species’ health. Inadequate waste management (B6) does not consider MSW as a resource that can be recovered and revalued, thus wasting these resources. When this barrier exists, it inevitably relates to the (un)availability of MSW for recovery (Pour; Webley; Cook, 2018), whether through composting or for energy purposes (B8), since if the management system does not consider waste for recovery, it will be insufficient to meet this demand. Therefore, in addition to addressing the aspects of inadequate waste collection, transportation, handling, and treatment (B6), it is necessary to consider planning in waste treatment so that there is no competition for waste by more than one type of treatment (B8) (energy and composting).
The lack of knowledge regarding the waste generated in a given territory, such as quantitative data, types of waste generated (Gonçalves et al., 2018), and technical knowledge (Carmen-Niño et al., 2023) to interpret such data, presents itself as technical challenges (B7) in long-term planning for waste recovery, relating to the insufficient availability of MSW for energy use (B8). Since there is no technical knowledge about the waste generated and that can be directed for recovery with an energy purpose, as well as the quantity generated of this waste, including generation and demand projections, it is difficult to design an efficient system where generation and demand are balanced, as well as to analyze the cost–benefit relationships of this recovery system.
Limited technical knowledge to identify and separate waste (B11) hinders the maximization of resource recovery, potentially exacerbating the insufficient availability of waste for energy purposes (B8). The lack of technology in waste sorting and the lack of education and training for people involved in the process (Shen et al., 2015; Zhang; Wen; Chen, 2016; Kazuva; Zhang, 2019) compromise the maximum recovery of waste to supply recovery and treatment systems. When associated with technical challenges such as the lack of data and interpretation skills regarding the generated waste (B7), it will certainly aggravate the insufficient availability of resources for energy purposes (B8).
The review of the literature revealed that the focus of research is concentrated on developing countries and that, despite their geographic and political differences, they share common barriers. For example, the barrier Lack of measures to encourage waste recovery by stakeholders (B14), where both in Brazil (Siqueira; Assad, 2015) and Malaysia (Bong et al., 2017), other stakeholders in the reverse channel are penalized by the lack of incentives and support from local governments for the development of recovery facilities (B1 and B4). Additionally, the lack of government cooperation in providing financial values for MSW investments (B12) can hinder the development of sustainable supply chains in Tanzania concerning composting (Kazuva; Zhang, 2019) and in Mexico concerning informal waste collection systems (Carmen-Niño et al., 2023) or even the failure to provide land for the expansion of composting areas in China (B2) (Zhang; Wen; Chen, 2016). Logistical costs (B10) are also common barriers in South Africa, which faces high costs for access to inputs and transportation of organic waste for urban agriculture (Menyuka; Sibanda; Bob, 2020), as well as in Bosnia-Herzegovina and Mozambique, which face high transportation costs for waste collection due to narrow and unpaved roads (Perteghella et al., 2020).
The lack of policies supporting the use of MSW (B3) is a common barrier in South Africa when considered for use in urban agriculture (Menyuka; Sibanda; Bob, 2020) and in Chile for the widespread adoption of organic waste-to-energy solutions (Ludlow et al., 2021). Inadequate collection, transportation, and disposal of MSW (B6) in both Ethiopia and Mexico occur due to the use of improper and outdated transportation equipment (Fereja; Chemeda, 2022; Carmen-Niño et al., 2023). Barrier B9, related to low technical knowledge and aversion to MSW recovery for energy purposes, has been observed only in Brazil, both due to the disinterest of the Brazilian Legislature, resulting in disincentives for resource allocation (Santos et al., 2018), and for the implementation of biogas and biodiesel biorefineries on a university campus (Sousa et al., 2022). Additionally, the lack of oversight and monitoring of indicators in obtaining results/reports (B13) leads to insufficient evaluation of these wastes in Mexico (Carmen-Niño et al., 2023), compromises solid waste management assessment in Bosnia and Mozambique (Perteghella et al., 2020), and inconsistent monitoring of indicators in Africa and Colombia hinders waste repurchase (Hettiarachchi; Meegoda; Ryu, 2018).
The orchestrating role of Public Entities in the reverse channel ranges from regulating, executing, and/or enabling LR activities to monitoring and supervising the evaluation of policies and programs. The regulation function is the primary function, intended to order activities in the reverse channel and can manifest as a barrier when there is excessive bureaucracy due to weak legislative coordination, hindering organic waste recovery (Morone; Yilan; Imbert, 2021) or the absence of clear guidelines and frameworks to facilitate and regulate the use of organic waste in urban agriculture (Menyuka; Sibanda; Bob, 2020). Second, as an executor, it may not use efficient management for organic waste treatment concerning inadequate transportation, costs, handling, and treatment practices (Xiao et al., 2020; Fereja; Chemeda, 2022) and as an enabler of LR activities, not providing permits for land use for composting expansion (Menyuka; Sibanda; Bob, 2020) or for sorting and separation facilities (Zhang; Wen; Chen, 2016). Third, as a supervisory and control entity for evaluating adopted LR activities, if regulations are not enforced due to a lack of governance and monitoring is insufficient (Hettiarachchi; Meegoda; Ryu, 2018), it will become a barrier to RL objectives for waste. Finally, Public Entities as orchestrators extend the educational role they play over the other stakeholders in the reverse channel, as, in addition to participation, community knowledge and understanding of the solid waste problem are crucial (Khamkeo et al., 2021), as is the understanding that as generators, they have responsibility for the waste. These educational actions need to be orchestrated by municipal authorities and are also welcomed by nonprofit organizations.
Due to the possibility of barriers being correlated, meaning that when they occur at one level, they trigger barriers at other levels (strategic, tactical, or operational), and due to the functions related to the role of orchestrator in the reverse channel, the actions taken by Public Entities need to be integrated so that the objectives of organic waste management are achieved, and the results of RL are maximized.
CONCLUSIONS
This study aimed to identify the barriers to RL for MSW, considering the stakeholder Public Entities in the literature. A total of 31 articles were identified, relating 14 barriers to the mentioned stakeholder, ranging from more strategic barriers such as "Excessive bureaucracy due to weak legislative coordination," to more tactical barriers such as "Lack of government cooperation in financial values," to more operational barriers such as "Lack of supervision and monitoring of indicators." The possible correlation between barriers due to the functions of Public Entities (regulation; execution/enabling of RL activities; supervision and monitoring) and the occurrence of barriers across levels (strategic, tactical, and operational) was also discussed.
This research contributes to the theoretical field as few studies address the barriers in the MSW management scenario in the regions (Huang; Liu; Dhar, 2022) and because it is the first study to thoroughly discuss the barriers to MSW RL for the stakeholder Public Entities. Identifying and understanding these barriers is essential for advancing theoretical knowledge in the field of urban solid waste management, providing a solid foundation for future research and developments in this area. It also contributes to practice by compiling barriers that, if identified for a given territory, can help managers address public policies and private sector actions in an integrated manner to overcome these barriers and achieve the objectives of the MSW reverse channel.
As this is the first study to survey the barriers to MSW RL for Public Entities, we acknowledge that being a theoretical survey, it requires a practical application to confirm these barriers. For future research, it is suggested to conduct an empirical survey with statistical analyses to identify the significance of these barriers among experts in the field and/or with technicians from municipal bodies responsible for MSW management. It is also recommended to conduct statistical tests (multivariate analysis) to validate the correlation between the barriers. Finally, we suggest conducting research that explores the barriers related to the other stakeholders as generators of waste (large and small) to elucidate whether the barrier to waste segregation is the same regardless of the source and whether for large producers, this barrier is lower or higher compared to organic waste generated in households.
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