Abstract
This review provides the history and current paradigms of waste management (WM) practices in developing nations during the last five decades. It explores the evolution of the challenges, complexities, and trends during this period. This paper, for the first time, presents an estimation of the amount of municipal solid waste (MSW) generated in developing nations in the last five decades based on the material flow analysis approach. Overall, the amount of MSW in developing countries has increased from about 0.64 billion Mt in 1970 to 2 billion Mt in 2019. This review demonstrates the importance of finding new WM approaches in developing nations in the context of formulating policies, strategies, and highlights the major trends that re-define WM in developing countries. It also aims to present the holistic changes in technology, economic and environmental feasibility aspects to attain an integrated sustainable WM system in developing countries. Specific focus on open-burning, open-dumping, informal recycling, food waste, plastic pollution, and waste collection with reference to Sustainable Development Goals are explained. Drivers for the way forward including circular economy are investigated.
Keywords
Introduction
Waste management (WM) is a local problem with global consequences. As the world’s population expands, so does the amount of waste generated. According to the World Bank’s What a Waste 2.0 report, the world produces 2.01 billion metric tonnes (Mt) of municipal solid waste (MSW) per year, with at least 33% not being managed in an environmentally sound manner (Kaza et al., 2018). Rapid urbanization, population growth and economic development, according to this report, will cause worldwide waste to increase by 70% in the next 30 years, reaching by 2050, a startling 3.40 billion Mt of waste produced annually (World Bank, 2018). By 2050, the amount of waste in low-income nations is predicted to increase by more than three times (Kaza et al., 2018). As the amount of waste produced grows, so does the need for having a proper WM system in place. However, when it comes to appropriately managing solid waste, cities and local governments confront several challenges. As a result, at least 2 billion people are predicted to live in areas without waste collection and rely on unmanaged dumpsites or open burning of waste (United Nations Environment Programme and International Solid Waste Association (ISWA), 2015). In many cities, especially of developing countries, inadequate solid WM systems pose major risks on the human health, environment, livelihoods and the conservation of natural resources (United States Environmental Protection Agency and Office of Resource Conservation and Recovery, 2020). The unmanaged and improperly managed waste generated during decades of economic progress necessitate immediate action at all levels of society (Mahmudul et al., 2022). In the context of developing nations, waste operations, which are costly and complex, must compete for funding with other priorities such as clean water and other utilities, education and health care. Local governments are frequently in charge of WM, despite having limited resources and capacity for planning, contract administration and operational monitoring. Moreover, international development agencies and funding organizations support national efforts since WM is crucial for sustainable development as well as to meet the challenges in emerging and developing nations. Nevertheless, allocating funds effectively is difficult due to the complexity of the system and the necessity of a multi-criteria decision-making problem for optimizing the system (Campitelli and Schebek, 2020). The complexity of WM in developing countries involves different aspects such as poor governance, lack of financial resources and infrastructure, serious environmental and health problems as well as other technical, social (poverty and population growth), legal, organizational and political factors. These reasons make sustainable WM a difficult prospect on the way to economic development, and most low- and middle-income countries, as well as their cities, struggle to meet different targeted measures for improvement (Campitelli and Schebek, 2020). Poor WM has catastrophic consequences that disproportionately affects the poor, who are frequently unserved or have little influence over the waste disposed of formally or informally near their homes (Agamuthu et al., 2020; World Bank, 2022a). Waste-related greenhouse gas (GHG) emissions are also a significant contributor to climate change (Maalouf and El-Fadel, 2019, 2020), it accounted for 5% of worldwide emissions (excluding transportation) in 2016 (World Bank, 2022a).
Over the past years, many review studies (summarized in Table 1) were published considering a comparative analysis of WM in developed versus developing contexts. For example, Wilson (2007) investigates six broad categories of WM drivers in developed and developing countries, focusing on WM practices and policies. Marshall and Farahbakhsh (2013) extend the work of the latter paper to consider developing countries more explicitly by evaluating these drivers as part of the historical framework that shapes contemporary WM practises and challenges in developing nations. Mmereki et al. (2016) provided a comparative analysis of WM practices in lesser developed, and developing countries, using existing data from 2005 to 2015. Other review studies have focused on specific waste streams, WM technologies/methods and/or waste governance aspects and drivers, especially in developing nations. In particular, these studies considered food WM (Thi et al., 2015), medical WM (Ali et al., 2017; Windfeld and Brooks, 2015), informal sector (Ezeah et al., 2013; Wilson et al., 2006) as well as the risks that such practice pose to vulnerable informal workers (Maalouf et al., 2021), specific WM technologies (Tun and Juchelková, 2018), environmental contamination and social issues (Ferronato and Torretta, 2019), impact on human health (Giusti, 2009), among others. Review studies on WM in developing countries’ context considered different levels such as regions, continents, nations, cities and communities to individuals. For instance, some studies covered WM in Asian developing countries (Ali and Sion, 2014; Dhokhikah and Trihadiningrum, 2012), in South Africa (Godfrey and Oelofse, 2017), in Latin America and the Caribbean (Ulloa-Murillo et al., 2022) and cities in developing countries (Guerrero et al., 2013; Wilson et al., 2013). Other studies have focused in their reviews on the assessment methods (i.e. life cycle assessment, benchmarking, sustainability assessment, etc.) that can be used to support WM in developing countries (Campitelli and Schebek, 2020; Zurbrügg et al., 2014). Additionally, some reviews have identified indicators for comparing different technologies and WM systems (Cervantes et al., 2018; Wilson et al., 2012, 2015a).
Summary of the main elements considered in review studies of waste management in developing countries.
WM: waste management.
While these studies continue to provide information regarding WM in developing nations, their scope and comprehensiveness vary, restricting a clear representation of the emergent issues in the global south. Moreover, these studies lack a comprehensive evaluation of the evolution of WM in developing countries. As can be seen in Table 1 different elements were used in the literature to assess WM in developing countries. However, given the complexity of WM systems, different aspects need to be considered such as economic, social, technical, health, environmental and/or governance to provide a comprehensive overview. Another problem is the requirement for WM-related data, where data availability is far more difficult in developing than in developed nations. According to Wilson et al. (2012, 2015b), a systemic description of the Integrated Sustainable Waste Management Framework requires the discussion of the ‘Hardware’ and ‘Software’ of WM. The ‘Hardware’ comprises all the ‘physical components’ (i.e. collection, prevention, recycling, recovery, treatment and disposal) and the ‘Software’ comprises all the ‘governance components’ (i.e. strategies, policies, waste market and regulation). In conclusion, a much more thorough review of WM in developing countries is required than what is currently available in the literature.
Research aims and scope of the review
This study provides a comprehensive analysis of published literature for the last five decades (1970–2020s). The main purpose of this review paper is to analyse and demonstrate the main changes in WM in developing countries during this period to draw experiences and improvements towards an integrated sustainable WM.
Several definitions of waste and developing countries exist. In this review, waste is considered as solid waste, which is neither water (wastewater) nor airborne. In addition, ‘developing countries’ is used to refer to emerging, under-developed, lesser developed and global south countries or nations, as well as low-income and lower-middle income countries (according to World Bank country categorization by income group). Only literature reported in English was included in the review scope. Literature data was collected from scientific research articles, books and reports, using available quantitative and qualitative data. The identification of studies in scientific journals was selected based on the authors’ knowledge in the field of WM in developing countries using google scholar search engine, and other databases such as Scopus and Web of Science. For simplicity, the review’s findings are typically presented and discussed in aggregated form, which means that studies are rarely singled out unless they are crucial to supporting the arguments and suggestions that have been made.
The novelty of this study in comparison to existing reviews is that it provides a coverage of the ‘physical’ and ‘governance’ components described by Wilson et al. (2012, 2015b) as following: (1) for the physical aspects, this study for the first time provides an estimation of MSW generated in developing nations in the last five decades and demonstrates the main WM trends during this period (see ‘Evolution of WM in developing countries’ section); and (2) for the governance components, this study analyses the main challenges in WM in developing nations (see ‘Challenges of WM in developing countries’ section), and highlights the main drivers towards the success of WM changes (see ‘Drivers towards the success of WM changes’ section). Finally, some recommendations are provided based on the literature study. This review lay the ground for future WM research to develop effective solutions for tackling WM difficulties and mitigating the effects of uncontrolled solid WM.
WM in developing countries
History of WM (1970–present)
Historically, WM systems were driven by public health concerns, security, scarcity of resources and aesthetics (Louis, 2004; Marshall and Farahbakhsh, 2013; Melosi, 1981; Wilson, 2007). The history of WM was also always connected with the history of the largest cities. Even though largest cities had more advanced waste treatment methods, burial of waste or disposal in nearby rivers or water bodies, was relatively easier in small communities and rural areas since the earliest civilizations. With increasing population density, waste production per unit area is also increasing, but land accessible for disposal is decreasing. Simultaneously, disposal issues and waste accumulation grow more complex. Significant development in WM was witnessed since the ancient times. Solid wastes in the city of Knossos were placed in vast holes with layers of earth at intervals, recording the first landfill developed during the flourishing of the Minoan civilization on Crete from 3000 to 1000 BC. To preserve the city’s beauty and avoid illness, by 500 BC, Athens, Greece, enacted a legislation mandating waste to be thrown at least one mile away from the city, and by 200 BC, Chinese cities had ‘disposal police’ enforcing disposal laws (Wilson, 1976). The Romans, on the other hand, had no structured waste removal system: waste piled in the streets and around towns and villages. This tradition is claimed to have continued until the nineteenth century (Wilson, 1976). As described by (Worrell and Vesilind, 2012) ‘people in cities lived among waste and squalor for the most part’. Waste was only removed outside city boundaries in Athens and Rome when defences were endangered by opponents who could scale up the waste piles and over the city walls (Worrell and Vesilind, 2012). In the Middle Ages, city streets were covered by an odourous sludge made up of soil, stagnant water, domestic waste and animal and human faeces, resulting in good conditions for creating vectors of diseases (Louis, 2004). Indeed, the early 1300s Black Death in Europe might have been exacerbated by the dumping of organic wastes in the streets (Louis, 2004; Tchobanoglous et al., 1977; Worrell and Vesilind, 2012). Many projects to clean up the streets were launched, but they all failed since the poor were preoccupied with feeding themselves, and the wealthy were averse to paying to clean up for the poor (Wilson, 2007). Due to a lack of resources, many objects were repaired and reused, and the waste stream was scavenged carefully.
According to Wilson (2007), since 1970 Waste disposal has finally made its way into the political agenda in the developed nations, with environmental protection emerging as a crucial driver. When development in WM finally began, it was driven by five major factors: public health, the environment, resource scarcity and the value of waste, climate change and public knowledge and engagement (Marshall and Farahbakhsh, 2013). In the 21st century, WM is a critical public service, especially in heavily populated places. Despite this, WM has a low public and political profile, and regulations and related statistics are underdeveloped in many nations (United Nations Economic Commission for Europe, 2022).
Waste generation trends
Globally, assessing and reporting on MSW generation remains a challenge. Five major reports assessed MSW generation at a global level between 2006 and 2018, using different datasets and approaches and responding to diverse stakeholders’ interests in a variety of institutional landscapes. The amount of MSW estimated by these reports is demonstrated in Table 2.
Amount of MSW estimated by five major global reports.
MSW: municipal solid waste.
Data extracted from: Maalouf and Mavropoulos (2022).
A comparison of these reported data conducted by Maalouf and Mavropoulos (2022) revealed that the MSW created during this time period was in the order of 2 billion Mt per year. The stated amount is questionable because the global population rose by about 1 billion people (equal to a 15% rise) yet gross domestic product (GDP) per capita rose by 30% between 2006 and 2018 (Maalouf and Mavropoulos, 2022). The findings of this study revealed a continuing inconsistency in predicting worldwide MSW arisings across different reporting schemes, necessitating uniform accounting techniques to achieve accurate waste quantification. In the context of developing economies, there are some issues to consider in estimating the amount of waste generated: these studies do not take into account unregistered waste amounts, which are not frequently included in reporting systems, such as the open burning of waste in rural areas; there is a considerable variation in waste definitions, which renders the reported figures incomparable; and finally these studies do not consider waste associated with commerce and exports/imports. In terms of waste definitions, for example, in developing nations, MSW is commonly characterized as waste produced in municipalities. Moreover, many developing nations are lacking waste separation at source of MSW (Karak et al., 2012) as well as the separation of hazardous waste from non-hazardous waste (Maalouf and Maalouf, 2021). Other difficulties in estimating waste created include the exclusion of waste that is not managed/collected by the municipality or is produced in rural regions. For instance, the World Bank’s report (Hoornweg and Bhada-Tata, 2012), simply recorded the amount of waste generated in urban areas despite that waste generated in rural regions is projected to be half that of the aggregate urban rate (Karak et al., 2012). As a result, ignoring waste produced in rural regions may result in an underestimating of overall waste generated at the national (developing or developed nations) or global level. As a result, there is no worldwide evaluation of solid waste produced at the global level and particularly in developing nations (Tisserant et al., 2017). Attempting to tackle this is a governance problem that is critical if appropriate measurement of waste created is to be ensured in Sustainable Development Goals (SDGs) reporting.
A vast number of research studies have been conducted in recent years to determine relevant elements impacting WM systems in cities in developing-nations. Guerrero et al. (2013) conducted a review of publications from key scientific journals linked to WM from 2005 to 2011. The review revealed information on system-influencing factors and showed that few studies provided quantifiable data.
In this context, analysing global MSW arisings has received a lot of interest in recent research. The material flow analysis (MFA) has become one of the most extensively used approaches for providing a system-oriented perspective of interrelated processes and flows to assist strategic and priority-oriented choices and for devising management solutions (Allesch and Brunner, 2017). The yearly worldwide MSW generation rate was determined using a MFA technique by some studies (Maalouf and Mavropoulos, 2022; Tisserant et al., 2017). The MFA concept is gaining attention as an alternate method to quantifying total waste generated, rather than officially published numbers or literature statistics. Most data on waste produced are extrapolated from several sources, such as macroeconomic data, statistical data, and/or other surveys (e.g. websites, reports, etc.). This is especially essential given the prevalence of unregistered waste volumes that are typically not included in waste reporting systems, especially for developing countries, and the variable usage of waste definitions, which renders reported numbers and waste data incompatible. As a result, MFA is gaining traction as an alternate way to increasing the efficacy and usefulness of knowledge construction from massive data sources and surveys. Furthermore, the main reason for calculating waste using the MFA approach is that input data on natural resources, products and emissions are generally of higher quality than data on reported waste generation provided by national institutions using various waste definitions, classifications and accounting schemes. The MFA approach links the amount of resources extracted worldwide to the amount of waste. Figure 1(a) demonstrates the global resources extracted since 1900, including a forecasting until 2050. This data was compiled by Krausmann research team (Krausmann et al., 2018) and is in consistence with International Resource Panel updated by United Nations Environment Programme (UNEP). In 2050, it is forecasted that globally more than 200 billion Mt of resources will be extracted and transformed into water vapour, emissions, solid and liquid waste and a big part will be added to stocks as shown in the Sankey diagram in Figure 1(b) (extracted from Krausmann et al., 2018). This system needs to change if we need to remain in the boundary of our ecosystem. Therefore, we need to take good ideas from the WM sector, despite its small contribution in comparison to other sectors such as the industrial sector. The WM sector, circular economy (CE), and recycling activities will allow us to change the whole economy. Therefore, WM can be a great catalyst to achieve this change. As defined by the European Parliament (2022), waste circularity, referred to as CE, is a model of increasing efficiency and waste reduction. It aims to reduce waste through better materials management throughout the product lifecycle. This goal can be achieved by sharing, leasing, reusing, repairing, refurbishing and recycling existing materials for as long as possible.
Global resource extraction to outflows of wastes and emissions (figures extracted from Krausmann et al., 2018). (a) Global material extraction in billion Mt/year by main material groups, 1900–2015 (historic data) and 2016–2050 (scenario results). (b) Sankey diagram showing the cumulative flow of materials through the global economy from extraction to use and output of wastes as well as emission.
This study provides an estimation of the amount of MSW generated in developing nations in the last five decades based on the MFA approach. According to the OECD (2013) and other research (Haas et al., 2016; Krausmann et al., 2018), between 20 and 22.5% of all materials extracted globally end up as total waste. Note that ‘total waste’ in this article refers to waste arising globally from all economic activities and sectors (including MSW).
In an attempt to correlate global material extraction (known as domestic extraction (DE)) with total MSWs, this study used an average of 21% of resources extracted globally to estimate total global waste arisings. The amount of DE in the last decades (1970–2019) was extracted from UNEP, International Resource Panel (2022). Following that, it was assumed that MSW accounts for about 15% when mining industries are lacking compared to a lower value of 11% of total waste generated in developed countries (e.g. EU and OECD). Given that the World Bank What a Waste 2.0 (Kaza et al., 2018) report has estimated that approximately, high-income countries generated about 34% of the world’s MSW. Therefore, it can be assumed that developing countries generate about 66% of the world’s MSW. Figure 2 demonstrates the total amount of MSW generation in developing countries between 1970 and 2019, estimated in this study. Overall, the amount of MSW has increased from about 0.64 billion Mt in 1970 to 2 billion Mt in 2019, equivalent to more than 200% increase. During the last decade (2010–2019), the total MSW generated has increased by around 20% in developing countries.
Estimated total MSW generation in developing countries between 1970 and 2019.
Looking to the future, worldwide waste is anticipated to reach 3.40 billion Mt by 2050, more than doubling population growth during the same time. Overall, there is a link between waste production and income level. High-income nations’ daily per capita waste production is forecast to rise by 19% by 2050, while low- and middle-income countries’ waste generation is likely to rise by 40% or more. Waste generation reduces initially at the lowest income levels and subsequently grows at a quicker pace for incremental income changes at the lowest income levels than at the highest income levels (World Bank, 2018).
The entire amount of waste produced in low-income nations is predicted to more than triple by 2050. The East Asia and Pacific area accounts for 23% of global waste generation, whereas the Middle East and North Africa region accounts for 6% in absolute terms. However, Sub-Saharan Africa, South Asia and the Middle East and North Africa are the fastest increasing areas, with total waste generation anticipated to more than quadruple, double and double by 2050, respectively (World Bank, 2018). Given these predictions, many low-income nations will probably be entering the middle-income group by 2050, thus predictions for waste generation for the low-income group will alter. Currently, more than half of waste is dumped publicly in these areas, and waste growth trends will have far-reaching consequences for the environment, health and prosperity, necessitating immediate action (World Bank, 2018).
Waste composition and material consumption pattern
Waste production is rising at an alarming rate, even though this is an issue that people are aware of. Without proper procedures in place to handle the changing composition of citizen waste, countries are fast evolving. Cities, which hold more than half of the world’s population and produce more than 80% of the global GDP, are leading the way against the world’s waste problem (World Bank, 2022a).
Depending on economic level, waste composition varies, indicating various consumption patterns. High-income nations produce 51% more dry waste, which includes recyclable materials like plastic, paper, cardboard, metal and glass, while producing relatively less food and green waste (32% of total waste). Middle- and low-income nations contribute 53 and 57% of food and green waste, respectively. Materials that might be recycled account for just 20% of the waste stream in low-income nations (World Bank, 2018).
Evolution in WM technologies
Recently, Maalouf et al. (2020b) assessed the newly delivered capacity of waste infrastructure projects worldwide between 2014 and 2019. The study revealed that during this period, the new delivered capacity amounted to 243 million Mt, out of which only 9% of the new delivered capacity was delivered to developing nations. The highest share of total new MSW infrastructure delivered capacity was attributed to upper-middle-income countries (46%), followed by high income countries (45%) (Figure 3(a)). The largest share in terms of capacity of new implemented projects is related to thermal technologies (about 57%), particularly new incineration plants, followed by recycling facilities (about 13%) and landfills (only about 8%) (Figure 3(b)). In terms of new capacity, China and the United States contributed around 37 and 12% of total new MSW capacity, respectively, from 2014 to 2019. Overall, China and high-income countries contributed around 82% of new infrastructure, while the rest of the world contributed only around 17%. In terms of budget, the study revealed that the total investment of new implemented MSW projects during 2014–2019 was about US$67.7 billion out of which, only 4.42% was reported for lower middle-income countries and 1.5% low-income countries.
Distribution of new implemented MSW projects with a total new capacity of 243.1 million Mt (data extracted from Maalouf et al., 2020b). (a) Distribution of new implemented MSW projects in terms of capacity in countries by income level during 2014–2019. (b) Distribution of new implemented MSW projects in terms of technology during 2014–2019.
This emphasizes the developing nations’ lack of investment in new waste infrastructure, which will lead to continuing waste disposal in uncontrolled or controlled dumpsites. As a result, in developing countries, dumping to land remains the primary technology solution. The study by (Maalouf et al., 2020b) also reveals that the considerable differences in MSW generation and real MSW infrastructure delivery contribute to an ongoing increase in uncontrolled waste disposal. Furthermore, developing countries, lacking enough financial capability, rely heavily on donors’ funds to sustain the development of new waste infrastructure projects. Despite securing financial funding, developing countries were unable to maintain the operation of waste development projects (post-donation), owing primarily to social and political interventions that prevent regulatory compliance, monitoring and enforcement, exacerbating WM challenges and resulting in project failure and return to a poor state. In this context, it is critical to assist developing countries in self-implementing advanced WM technologies while continuing to operate them in a compliant manner, as well as developing strategies to encourage the reintroduction of waste resources into our global economy rather than just encouraging waste disposal (Maalouf et al., 2020b).
It is a common misconception that technology would solve the problem of mismanaged and growing waste. When it comes to solid WM, technology is not a panacea and is generally only one issue to consider. Countries that move away from open dumping and other primitive WM systems are more likely to succeed if they use locally relevant alternatives. Most waste is presently dumped or disposed of in some type of landfill across the world. According to the World Bank (2018) report, about 37% of waste is disposed of in some type of landfill, with 8% disposed of in sanitary landfills equipped with landfill gas collecting systems. About 31% of waste is sent to open dumping, 19% is recovered through recycling and composting and 11% is incinerated. Proper waste disposal or treatment, such as controlled landfills or maintained facilities, is almost entirely reserved for developed nations (high and upper-middle-income group). Developing nations (low-income group) often rely on open dumping: 93% of waste is dumped, whereas just 2% is dumped in developed ones (World Bank, 2018). Uncontrolled disposal is predicted to increase until 2028 (reaching 730 million Mt of MSW per year), whereas new infrastructure deployed is expected to increase by 2% per year under an optimistic scenario (Maalouf et al., 2020b).
Challenges of WM in developing countries
Indeed, increasing urbanization and socioeconomic disparities, inadequate provision of sanitary and environmental amenities, social exclusion and inequalities related to existing WM systems and high levels of morbidity and mortality linked to inadequate sanitation, waste disposal and water supply provision were all common then, as they are now, particularly in poorer urban neighborhoods in low-income countries (Marshall and Farahbakhsh, 2013). The following sections describe the key factors challenging WM with key figures highlighted in Figure 4.
Key figures highlighting waste management challenges in developing countries.
Open burning and open dumping with its associated potential health risks
With over 90% of waste openly dumped or burnt in developing nations, the poor and most vulnerable suffer disproportionately. According to the ISWA and D-Waste (D-Waste, 2014; ISWA, 2016) estimates, dumpsites receive roughly over 40% of the world’s waste and provide service for approximately 3.5–4 billion people. The world’s 50 largest active dumpsites influence the lives of 64 million people, a population the size of France. However, hundreds of more dangerous sites exist across the world. Fifteen million people earn a living by scavenging waste and are disproportionately affected when inadequately or unmanaged disposal sites fail to function in the face of ever-increasing refuse and bad weather. Those who live on or near trash disposal sites are the most exposed to dump landslides. They are frequently the ones who fuel their communities’ recycling systems (Kaza and Yao, 2018).
Landslides caused by waste dumps have buried homes and individuals in recent years. And it is generally the poorest who live near garbage dumps and fuel their city’s recycling system by rubbish picking, exposing them to major health consequences. Landslides at waste dumps happened with startling frequency in 2017, killing over 150 people and displacing hundreds more in Colombo, Sri Lanka; Addis Ababa, Ethiopia; Conakry, Guinea; and Delhi, India (Kaza and Yao, 2018).
Maalouf et al. (2020a) show the unreasonable potential for damage to human health and safety in a systematic review of over 3000 papers from 22 countries. It provides strong evidence for health effects caused by uncontrolled land disposal, thus, alerting us to the urgent need to shut down and mitigate danger at dumpsites as well as avoiding harm to some of the world’s poorest inhabitants. This study identified common hazard-pathway-receptor combinations and then rated, compared and ranked the relative risk of damage suffered by diverse actors in land disposal locations. The evaluation suggests that contact with medical waste, pollutants from waste burning, and, most importantly, the lethal danger of waste slope failure have resulted in the deaths of at least (on average) 34 persons each year since 1992. Despite significant anecdotal evidence of the general nature of the health and safety concerns at hand, many of the sources lack key information with which to evaluate and correlate the causality of health impacts with the existence, or even exposure to, emissions or other risks. Nonetheless, the rigorous analysis clearly reveals an unacceptable danger to human health and safety, alerting us to the necessity to close and control concerns at dumpsites quickly, averting harm to some of the world’s poorest populations.
Waste pickers/informal sector
A review of informal WM system as well as challenges to an inclusive proper WM system by Oguntoyinbo (2012) showed that the majority of the research reviewed acknowledged the important environmental and socioeconomic contributions that informal waste collectors and scavengers play in developing nations. According to the studies, the following are challenges to a proper WM system: oppressive policies, unsanitary waste collecting techniques, a lack of proof to substantiate action and a lack of secondary materials of sufficient quality and quantity. Another study by Ezeah et al. (2013) critically reviewing trends in informal recycling sector activities in selected developing and transition nations showed that this sector is critical to the recycling process. This is due to a mix of governance deficits, economic opportunity, industrial symbiosis and the sociological realities that prevail in such areas. Overall, their influence on the urban system’s economic, social and environmental fabric is favourable. In addition, ignoring the critical role played by the informal sector in the design of new services, as is now the situation in several countries, is likely to result in delays and controversy. It has been demonstrated that incorporating existing informal recycling structures into formal WM systems makes WM sense since there is a clear opportunity to build formal–informal partnerships. It may also provide jobs, defend the lives of some of society’s most marginalized members, supply secondary raw resources, and improve environmental protection. The organization’s structure should not be built on a ‘universal’ model, but rather on local settings and situations.
Therefore, informal recycling, when properly encouraged and coordinated, has the potential to create jobs, boost local industry competitiveness, alleviate poverty and decrease municipal spending. However, the reality for the world’s more than 15 million informal waste pickers – mainly women, children, the elderly, the jobless or migrants – is one of poor health, a lack of social security or health insurance and social stigma. According to the World Bank (2022b), effective interventions to improve waste pickers’ livelihoods include formalizing and integrating waste pickers into the economy, strengthening the recycling value chain, considering alternative employment opportunities and enabling dumpsite closure, developing sustainable livelihood programmes for waste pickers and linking payments to better service delivery through results-based financing.
Many thousands of people in developing countries rely on recycling and material recovery from waste for their livelihoods. With the emphasis of the Millennium Development Goals on poverty drop, and of waste strategies on increasing recycling rates, one of the major challenges in solid WM in developing countries is how best to work with this informal sector to improve their livelihoods, working conditions and efficiency in recycling (Song et al., 2015).
The general characteristics of informal recycling were reviewed, highlighting both positive and negative aspects. Despite the health and social problems associated with informal recycling, it provides significant economic benefits that need to be retained. According to Awasthi et al. (2021), experience shows that it can be highly counterproductive to establish new formal waste recycling systems without considering informal systems that already exist. In addition, the latter study recommends to integrate the informal sector into WM planning, building on their practices and experience, while working to improve efficiency and the living and working conditions of those involved.
Food waste
Food waste is a global issue that is often tackled by focusing on important behaviours foremost to overall food waste. According to FAO (2011), nearly one-third of all food produced for human consumption in the world is lost or wasted each year, amounting to approximately 1.3 billion Mt. In the SDG target 12.3, the United Nations (UN) has set a target of halving per capita global food waste at the retail and consumer levels, as well as decreasing food losses along production and supply chains, by 2030. Globally, much more food is wasted in developed countries than in developing (FAO, 2011).
The variance in waste food generation trends among developed and developing countries was evaluated in several work, which indicated that the effects of population growth, income level and local public participation in waste food management are significantly important. Kaza et al. (2018) indicated that as income levels increase, the percentage of organic content in waste decreases. In this context, developing countries are characterized by a high food waste fraction (around 55% of total waste) in comparison to a lower fraction of biodegradable waste (32% of total waste) in developed countries (Kaza et al., 2018). The food waste generated causes many issues. The deposition of biodegradable waste in landfills causes an increase in methane output due to its decomposition. In 2009, bio-waste degradation in landfills accounted for 2.6% of total GHG emissions in the EU-28 (European Environment Agency, 2009). In particular, the cost of food waste in the EU-28 was estimated to be over €143 billion. In addition to the negative economic impact of food loss and waste, there are environmental and social consequences (Corrado and Sala, 2018; De Laurentiis et al., 2020). When coming to food waste-associated issues in developing countries, it is currently considered to be a major threatening factor for sustainable development and waste-food management systems. Owing to incomplete waste-food management approach, several developing nations are facing serious challenges, such as environmental and public health issues that are caused by food waste. Food waste regardless of the production site is either disposed of in landfill sites or is treated biologically or chemically for minimizing environmental problems. For example, India and China, generate most waste food in the world. While landfill and composting are traditional approaches for waste food management and disposal in developing countries, however, are not considered feasible owing to toxic gases released, bad odour and environmental pollution linked with it. Due to tightened rules and regulation and need for renewable energy fuels led to research in areas of waste food valorization. For example, biodiesel, bioethanol production for green fuel and generation of other industrially important and valuable chemicals through green synthesis are new research sectors. Therefore, the regular shifting of food WM from a linear to a CE has been shown through case studies. Waste food is being treated as a valuable resource by using novel and advanced environment-friendly system technologies such as greener fuel production through anaerobic digestion (AD) and potential future routes have also been evaluated (Sinha and Tripathi, 2021). In this context, Thi et al. (2015) present an overview of recycling activities, in the context of relevant rules and regulations, and current waste-food recycling technologies in developing nations. The study also proposed a sustainable WM for developing countries based on CE system as an appropriate model for waste-food management.
Furthermore, a very important input is to formulate proper interventions to recognize food category as well as social context to food waste. For example, vegetable and fruits waste is by far the major waste food types in the context of food waste quantity. The information and data are valuable when prioritizing and planning food types according to behavioural intervention strategies to minimize household waste food (Ananda et al., 2022). Minimization of food waste in developing nations can offer multiple advantages for their sustainable growth and development, by enhanced food security, income as well as the creation of eco-friendly secondary markets. Food WM schemes, however, are often categorized by means of a complex network of players across the value chain, where a narrow involvement at a local level does not always reach a global need. Rolker et al. (2022) systematically reviewed over 8000 studies for assessing necessary interventions for the reduction of food waste in developing countries. The food waste, at first, classified involvements through the goal stage within the value chain as well as by the instrument of action, and according to whether they are primarily designed to prevent or mitigate (recycle, reuse, remanufacture, re-purpose and recover) food wastage. The analysis demonstrates that existing studies lack information on preventive and mitigative interventions, as well as considering food waste material-focused interventions in developing countries.
Plastic pollution
Plastic has become a critical material in the modern world due to its low cost and easy production. However, inadequate management and open disposal make plastic a major obstacle to achieving the UN SDG (Awasthi et al., 2020). As a major economic actor, the plastic industry corresponds to about 3% of the global economy, with estimated revenue of about 1722 billion Euros in 2015 (UNEP and UNDP, 2020). The current linear economic model of ‘take, make, use, and dispose’ has significant impacts on natural resource depletion, environmental degradation, human health as well as climate change. Producing plastics using fossil fuels is a significant source of GHG emissions, as is the open burning and incineration of plastic wastes. GHG emissions from plastics were estimated to be 390 million Mt of CO2-eq in 2012. In 2015, about 388 million Mt of plastics were produced with 99.5% being from petro-based non-renewable sources (UNEP and UNDP, 2020). Approximately, 60% of produced plastic has ended up in landfills or disposed in the natural environment. If current trends continue, by 2050 the plastic industry could account for 20% of the world’s total oil consumption (UNEP, 2018). Accordingly, the International Resource Panel has identified the plastics value chain as one of the key sectors or value chains to trigger the most significant enhancement of national determined contributions through CE and resource efficiency.
The single-use plastics being progressively produced as well as used worldwide, furthermost particularly items such as consumables or packaging, shopping bags and disposable tableware. In 2016, the globe produced 242 million Mt of plastic waste (World Bank, 2022b). Most single-use plastics are incinerated or landfilled, which are sources of pollution, and also occupy valued land area and consume much important natural resources. Only comparatively insignificant quantities are at present properly treated and recycled, a burden to the idea of a CE. Besides, single-use plastic litter accumulation in the natural environment is a serious and key concern (Chen et al., 2021). In the aspect of rising evidence about the risk posed to soil invertebrates, plant growth as well as marine ecosystems, there is an increasing push to reduce the single-use plastics. Therefore, voluntary actions and regulatory tools to minimize single-use plastic consumption must be put forward more, with more specific recommendation for controlling single-use plastic waste (Chen et al., 2021). At a global level, many nations that were importing recyclables from the United States, EU and Australia strengthened quality regulations to prevent contamination brought on by the importation of ‘dirty recyclables’, starting with China. These actions, which are encouraged by a recent Basel Convention decision, alter the global plastic recycling environment and force exporting nations to come up with new local remedies. Governments, local authorities and the recycling sector must thus confront the end of recycling as we know it and develop creative business plans for long-term recycling initiatives (Mavropoulos and Nilsen, 2020).
Waste collection
According to optimistic estimates, about 30–70% of waste produced in developing-country cities is collected (Ezeah and Roberts, 2012). As a result of documented shortcomings in waste collection and disposal, waste is frequently deposited in open dumps, on roadways, in rivers or on vacant lots. This can result in soil deterioration, extensive floods, water/air pollution and serious sanitary and hygiene issues (Matter et al., 2013).
Waste collection is a critical step in managing waste, yet rates vary largely by income levels, with upper-middle- and high-income countries providing nearly universal waste collection. Waste collection is a crucial phase in WM, although rates vary greatly according to economic level, with upper-middle- and high-income nations offering practically universal waste collection. According to the World Bank (2018), low-income nations collect around 48% of waste in cities, but this figure drops dramatically to 26% outside of cities.
Drivers towards the success of WM changes
Five major trends (Figure 5) identified by Mavropoulos and Nilsen (2020) had their highest impact between 2015 and 2020, and their combined effect promotes a systemic shift in WM theory, practises, business and regulatory instruments. The proper WM through these trends will help address the main challenges identified in the previous section (see grey boxes).
Interconnections of the five major trends (and their combination) is redefining waste management (adapted from Mavropoulos and Nilsen, 2020).
For more than 40 years, official waste statistics have been produced. Initially, they were designed to monitor and manage risks to human health and the environment. Recently, information requirements have changed towards determining the economic value of waste, particularly in the context of the ‘circular economy’. This shift in perspective has resulted in increased need for greater information on specific waste streams (such as food waste), as well as the economic value of waste as a resource (Maalouf and El-Fadel, 2017). Greater understanding is also sought into waste flows that are difficult to quantify but critical for effective WM (such as the informal waste sector) (United Nations Economic Commission for Europe, 2022). While the lack of agreement among academics, policymakers and practitioners on a common use of the CE definition is well documented (Kirchherr et al., 2017), the need for quantitative indicators for assessing the ‘circularity’ of national economies, material cycles, supply chains and product life cycles is critical to its implementation (Ellen MacArthur Foundation, 2015). Most of existing initiatives identifies CE as a way of advancement in recycling and thus ignore the complexity of the sustainability context speaking about environmental, economic and social dimensions. Despite the lack of a particular definition or theory underpinning it, the CE drives WM towards better integration with resource management and incorporates WM practises into every supply chain (Mavropoulos and Nilsen, 2020).
In 2016, it was estimated that the WM sector has contributed to about 5% of worldwide GHG emissions, depending on the volume of waste generated, its composition and how it is managed. The total amount of emissions generated from this sector is 1.6 billion Mt of CO2-eq. This is mostly due to waste disposal in open dumps and landfills without landfill gas collecting systems. Food waste accounts for roughly half of all emissions. If no changes are made in the sector, solid waste-related emissions are expected to rise to 2.38 billion Mt of CO2-eq. per year by 2050 (World Bank, 2018).
Despite that the waste sector is a small contributor to total GHG emissions, it is considered as a major contributor to potentially reduce emissions through proper WM systems, particularly in developing countries (characterized by a high share of organic fraction in its waste composition) (Maalouf and El-Fadel, 2018). The sector may reduce direct emissions by properly operating landfills, AD and composting plants, using methane capture technologies, and using green energy to power collecting, sorting and treatment systems. In addition, waste reduction and recycling activities help by reducing the demand for virgin raw materials and, as a result, the GHG emissions associated with their extraction and refinement. According to ISWA (2021), overall, the impacts of waste avoidance, recycling, and substitution of fossil fuels and virgin raw materials with secondary raw materials from waste streams have the potential to reduce world GHG emissions by up to 20%.
At the global level, the International Bank for Reconstruction and Development/The World Bank (2020) report ‘Minerals for Climate Action: The Mineral Intensity of the Clean Energy Transition’ anticipated that approximately 3 billion Mt of minerals and metals will be required by 2050 to deploy wind, solar, and geothermal power, as well as energy storage, in order to keep the increase in global average temperature to well below 2°C. This 3 billion will not be available unless we are able to recycle a lot of the existing infrastructure and stocks. Most of the time the focus is on the management of MSW and some other streams. Therefore, we clearly underestimate CE when we reduce the focus to MSW and recycling. A comprehensive approach combining new data and modelling of economy-wide material stocks and flows, GHG emissions and industrial value chains across interlinked sectors is necessary towards achieving CE. Future research work and initiatives should consider the development of new simulation modelling approaches for analysing circularity from a system’s perspective, limiting material stock growth; lifetime extensions of material stocks through repair, maintenance, reuse; material recycling and WM.
In recent years, there has been a growing interest in the concepts of sustainability and sustainable development, as well as the strategies and activities that must be implemented to achieve such goals (Di Maria et al., 2022). Starting with this first definition, the UN introduced the well-known 17 SDGs in the 2030 Agenda (United Nations, 2015). Several of the United Nations’ SDG targets and indicators reflect the importance of waste and its management at municipal and national levels. The different targets include: Access to basic services (Target 1.4); eliminate dumping to improve water quality (Target 6.3.); municipal solid waste management (Target 11.6); food waste (Target 12.3); chemicals and hazardous waste, including e-waste (Target 12.4); recycling (Target 12.5); and marine litter (Target 14.1).
Moreover, two other associated targets consider material footprint and domestic material consumption (targets 8.4 and 12.2). As a result, sustainable WM can help to achieve several SDGs. There are several indicators available to track progress against each SDG target. These indicators include indicator 11.6.1 – proportion of MSW collected and managed in controlled facilities out of total municipal waste generated by cities; indicator 12.3.1 – food loss index and food waste index; indicator 12.4.2 – hazardous waste generated per capita; and proportion of hazardous waste treated, by type of treatment; indicator 12.5.1 – national recycling rate, tons of material recycled; indicator 14.1.1 – index of coastal eutrophication; and plastic debris density (United Nations Economic Commission for Europe, 2022). The absence of internationally agreed definitions, concepts and procedures adds to data non-comparability and concept overlap. The key environmental statistics guideline manuals, such as the Framework for the Development of Environmental Statistics (United Nations and Statistical Division, 2017) and the System of Environmental-Economic Accounting, provide only general guidelines and leave a lot of room for different methods and interpretations. Recently, the SDG 11.6.1 (United Nations, 2019) tries to close the gap of internationally agreed definitions/concepts/approaches by standardizing terminology and making data points comparable.
Conclusions and way forward
Changes in WM in the last five decades are evident. Waste generation and waste composition has evolved while the complexity of WM technology has also changed positively. Parallel developments in technology have somewhat reduced the impacts to environment. However, all these have escalated the cost of WM several fold.
With the focus of the Millennium Development Goals on poverty reduction and of waste strategies on improving recycling rates, one of the major challenges in WM in developing countries is how best to work with informal sector to improve their livelihoods, working conditions and efficiency in recycling. However, WM in developing nations has been hampered by urbanization, inequality and economic growth; cultural and socioeconomic factors; policy, governance and institutional challenges; and foreign effects.
Most developing nations have the dilemma of accepting some modern technologies which are too costly, such as incineration and pyrolysis. However, others are exploring these changes positively. Several economic powerhouses are among the developing nations and these countries are seriously exploring newer technologies. Overall, the outlook for developing nations looks very promising in changes for the betterment in WM in the future.
To go forward, developing nations need to establish waste-related statistical database and standardize the waste definition. Compliance must be improved while the inaction impacts must be highlighted. Developing nations should use economic instruments to enhance the current scenario and finally sustainable consumption should be practised to reduce waste generation.
Footnotes
Acknowledgements
The authors are grateful to the University of Oxford, Oxford, UK, and Jeffrey Sachs Center on Sustainable Development, Sunway University, Sunway, Malaysia, for supporting international collaboration. Special thanks are extended to Prof. Visvanathan from AIT, Bangkok, Thailand, and Prof. Abhishek Kumar Awasthi, School of the Environment, Nanjing University, Xianlin Campus, Nanjing, China, for reviewing this paper.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
