Analyzing Municipal Solid Waste Treatment Scenarios in Rapidly Urbanizing Cities in Developing Countries: The Case of Dar es Salaam, Tanzania

Global perspective of municipal solid waste and landfill leachate: generation, composition, eco-toxicity, and sustainable management strategies

Globally, more than 2 billion tonnes of municipal solid waste (MSW) are generated each year, with that amount anticipated to reach around 3.5 billion tonnes by 2050. On a worldwide scale, food and green waste contribute the major proportion of MSW, which accounts for 44% of global waste, followed by recycling waste (38%), which includes plastic, glass, cardboard, and paper, and 18% of other materials. Population growth, urbanization, and industrial expansion are the principal drivers of the ever-increasing production of MSW across the world. Among the different practices employed for the management of waste, landfill disposal has been the most popular and easiest method across the world. Waste management practices differ significantly depending on the income level. In high-income nations, only 2% of waste is dumped, whereas in low-income nations, approximately 93% of waste is burned or dumped. However, the unscientific disposal of waste in landfills causes the generation of gases, heat, and leachate and results in a variety of ecotoxicological problems, including global warming, water pollution, fire hazards, and health effects that are hazardous to both the environment and public health. Therefore, sustainable management of MSW and landfill leachate is critical, necessitating the use of more advanced techniques to lessen waste production and maximize recycling to assure environmental sustainability. The present review provides an updated overview of the global perspective of municipal waste generation, composition, landfill heat and leachate formation, and ecotoxicological effects, and also discusses integrated-waste management approaches for the sustainable management of municipal waste and landfill leachate.

Sanitary municipal landfill site selection by integration of GIS and multi-criteria techniques for environmental sustainability in Safita area, Tartous governorate, Syria

Urban waste disposal is a problem that poses a major challenge to city planners as a result of rapid population growth and urbanization. Finding suitable sites for solid waste is one of the most important solutions developed globally to manage this problem. In this regard, a set of physical, socio-economic and technological criteria must be considered to tackle the problem. Safita area (Tartous governorate) witnessed a rapid population growth during the decade of the war in Syria due to the onrush of internal refugees, which resulted in several environmental problems, including random waste dumps. After perusing the previous literature and considering expert opinions, a map of the spatial suitability of sustainable waste sites in the Safita area was developed by integrating the multi-criteria decision- making methodology (analytic hierarchy process) with the geographic information system. Thirteen criteria, including elevation, slope, permeability, distance to faults, distance to settlement, land use/land cover, distance to drainage, distance to water supplies, distance to lakes, distance to road, distance from tourist centers, distance from archaeological centers, and distance from religious centers, were used to achieve the goal of this study. The layer maps for these criteria were developed based on various data sources, including conventional and remote sensing data. Potential landfill sites were identified and divided into five categories: unsuitable (83.28%), less suitable (8.49%), moderately suitable (4.49%), highly suitable (2.57%), and very highly suitable (0.72%). The results of this study provide reliable spatial outputs that will help in suggesting new landfill sites that maintain environmental and socio-economic sustainability in the post-war phase. Moreover, the application of the methodology of this study can be generalized to the rest of the regions in Syria within the framework of the integrated management of the problem of random landfills.

Food industry waste - An opportunity for black soldier fly larvae protein production in Tanzania

Black soldier fly larvae composting is an emerging treatment option with potential to improve biowaste valorization in cities of low-income countries. This study surveyed the current generation and management status of food industry biowaste and their availability and suitability as potential feedstock for black soldier fly larvae (BSFL) composting treatment in three Tanzania cities, Dar es Salaam, Mwanza, and Dodoma. Biowaste-generating food industry companies (n = 29) in the three cities were found to produce banana peels, mango seeds, sunflower press cake, brewery waste, and coffee husks in large quantities (~100,000-1,000,000 kg y^-1). Around 50 % of these companies (16/29), primarily vegetable oil companies (10/11), either sold or gave away their waste as animal feed, while most companies (9/11) with unutilized food industry waste landfilled the generated biowaste. Multi-criteria analysis based on substrate availability criteria identified banana peels, mango seeds, and coffee husks with total score points of ≥10/12 as the most suitable feedstock for BSFL composting. However, multi-criteria analysis based on physical-chemical criteria identified brewery waste and sunflower press cake with total score points of ≥11/15 as the most suitable feedstock. Combined availability and physical-chemical properties of individual biowastes showed that all identified types of food industry biowaste can be suitable feedstock for producing BSFL biomass for protein production, but certain waste streams needed to be mixed with other waste streams prior to BSFL-composting to ensure sufficient availability and provide a balanced nutritional profile compared with the single-source biowastes. This study concluded that large volumes of food industry waste are being generated from food industry companies in Tanzania and there is need to establish new biowaste management interventions for resource recovery. Furthermore, for interested stakeholders in the waste management business, multi-stream BSFL-composting can be a suitable solution for managing and closing nutrient loops of the unutilized food industry biowaste in Tanzania and in other similar settings globally.

Barriers in biogas production from the organic fraction of municipal solid waste: A circular bioeconomy perspective

Biogas-based circular bioeconomy can provide a long-term way out of the organic fraction of municipal solid waste. The barriers to biogas production are obstructing the growth of the biogas-based circular bioeconomy. This study provides a comprehensive analysis of the barriers to biogas in developing countries for the wider implementation of biogastechnology. Twenty barriers are identified and categorized into technical, logistical, institutional, and social dimensions. The analytical hierarchy process is applied to rank the barriers. The result of barrier ranking shows that the lack of appropriate segregation facilities is the most crucial barrier, followed by waste characteristics variation, and inconsistent supply. This study will provide an outline for rational decision-making in the sustainable organic fraction of municipal waste management.

Solid waste dumping site analysis using GIS and remote sensing: Bonga Town, Southwestern Ethiopia

The main objective of this study was to select potential solid waste landfill areas suitable for Bonga Town that are environmentally sound. The key data were LANDSAT 8 and SPOT-6 satellite images with a spatial resolution of 15 and 1.5 m, respectively; a digital elevation model with a spatial resolution of 30 m; and a ground control point, which was collected through a ground point survey and a topographic map of the study area. Each parameter was subjected to a peer review according to the analytical hierarchy process. Once the weights were established, the weighted overlap analysis was determined, which combined these criteria and classified them into high, medium, less suitable and inappropriate regions of the study area. The results show that 75.65% of the study area is not suitable for the solid waste landfill, 18.86% less suitable, 5.17% moderately adequate and 0.3% very adequate. Therefore, the ability to use inaccessible geological information framework and detection innovations for mandatory discrimination evidence for a reasonably robust waste dump will minimise opportunities and natural human well-being problems.

Optimal Process Network for Integrated Solid Waste Management in Davao City, Philippines

Municipal solid waste management (MSWM) systems in developing countries adopt practices from developed countries to reduce their environmental burdens. However, several complex issues specific to developing countries hinder the full implementation of these practices. The future of MSWM in Davao City, Philippines, is envisaged as a notable example of the combination of new infrastructure and local MSWM practices. A linear programming model was developed, following material flow analysis and life cycle assessment, to design an optimal system for Davao City. The performance of the system was evaluated in terms of greenhouse gas emissions, energy and revenue generated, and the amount of landfill waste. The results show that the proposed system positively affects the environment compared to the current system, due to additional treatment options. However, the main allocation concern transitions from organic waste in the current system to plastic waste in future scenarios. Furthermore, the mitigation of greenhouse gas emissions and the extension of landfill life will be heavily influenced by trade-offs between sorting operations and the management of incinerated wastes with high calorific values. Therefore, plastic-waste-specific treatment options will be critical for future MSWM systems. The results herein underscore the need for sustainable MSWM in the study area, considering the region-specific conditions.

GIS- and MCD-based suitability assessment for optimized location of solid waste landfills in Dar es Salaam, Tanzania

Despite recent advancements in waste management technologies, landfills remain the dominant approach for the final disposal of solid waste (SW) around the world. However, landfills are associated with adverse environmental and health-related impacts. This study is primarily applied to Dar es Salaam, a city in the East African region that has failed to follow appropriate approaches for site selection and that the methods used to select the current sites are manually operated. The study used a geographical information system (GIS) combined with multicriteria decision analysis (MCDA) to objectively determine the optimal landfill sites. A comprehensive list of assessment criteria was examined through a computerized site selection procedure based on GIS to analyze the ground that was surveyed and to remotely obtain data. Analytical hierarchy process (AHP)-one of the best MCDA approaches-was used to assign relative weight and evaluate each criterion. Finally, the study computed site suitability indices (SSIs), which aids in the identification of site suitability levels (SSLs) for the entire region. The final suitability map produced by overlaying the criteria map layers showed that a large part of the study area (60.92%) was completely unsuitable for landfill siting. The remaining areas consisted of land with varying suitability level, which were grouped into four classes: very low (30.92%), low (2.05%), moderate (5.65%), and high (0.46). To this end, only the high suitability class (0.46%) was of acceptable suitability levels (ASLs) (SSI ≥ 2.0). From the numerous identified sites with ASL, only three sites were suggested. Due to concerns regarding the lifespan and environment-related risks associated with these suggested sites, there is a need to further study new environmentally friendly techniques, considering the importance of circular economy agenda of waste to resource/energy for sustainable solid waste management.

Utilizing an integrated assessment scheme for sustainable waste management in low and middle-income countries: Case studies from Bosnia-Herzegovina and Mozambique

Solid waste management assessment methods that simultaneously analyze the economic, social and environmental dimensions are limited. Tools are rarely applied in developing countries because of several constraints encountered during their implementation (e.g. lack of data availability and difficulties concerning data interpretation), consequently hampering the development of sustainable solid waste management practices. In addition, the incorporation of stakeholders in most decision-making tools and processes, as well as the availability of credible data in developing countries is often limited. To address these issues, this paper presents one of the first large scale studies, utilizing a tool, named Integrated Assessment Scheme (IAS). Use of IAS provides a holistic, integrated approach evaluating the economic, environmental and social dimensions in order to support the decision making process and to facilitate more sustainable waste management in low and middle-income countries. The use of IAS in the two case studies from Bosnia-Herzegovina and Mozambique suggests its suitability to communities in similar contexts. However, its limitations are also discussed.

Assessment of Used Baby Diapers Composting in Bolivia

Solid waste open dumping in developing countries is a global concern. To move towards sustainable development, mixed waste should be reduced, and recyclable waste recovered. The aim of the current research was to find appropriate solutions to disposable used baby-diapers recycling in Bolivia since it is a waste fraction widely produced and commonly disposed of in open dumps. Composting of the organic diaper hydrogel was assessed in five trials, adding components available locally: cow dung, activated bacteria, and Californian red earthworms (Eisenia fetida). It was observed that about 60 days were globally required for biomass decomposition with cow dung, activated bacteria, and earthworms, and more than 70 days for the treatment of the substrate mixed only with manure, while the diaper hydrogel did not degrade without cow dung. This research is the first that attempted to treat disposable used baby diapers with the vermicomposting process. In general, the outcomes of the research are promising: vermicomposting with cow manure can be a recycling option for disposable used baby diapers, introducing appropriate practices toward a circular economy in developing regions.

Life cycle and End-of-Life management options in the footwear industry: A review

It is well recognized globally that the footwear industry contributes to a large waste stream throughout its life cycle. This article reviews the literature pertaining to the life cycle of footwear products and their End-of-Life (EoL) management strategies. The review discusses critical aspects of the footwear industry, commencing with a background on the growth and consumption of footwear products across the globe. The review provides an overview of the environmental impacts of different footwear materials across their life cycles. In this regard, leather materials are given intense focus due to their poor environmental performance. The review further examines proactive and reactive approaches to footwear waste management, whilst additionally exploring the challenges facing EoL footwear recovery. Finally, pyrolysis is examined as a thermochemical treatment process with value due to its potential to recover materials from post-consumer footwear. The significant findings in this review paper are as follows: (a) leather footwear materials have the most detrimental environmental impacts across their life cycle; (b) there is limited scientific literature on thermochemical processes (particularly pyrolysis) as waste recovery options for post-consumer footwear; and (c) several challenges face the recovery of post-consumer footwear products, including inefficient reverse logistics, mixed product recycling and difficulties establishing a value recovery chain. This review paper recommends further research on pyrolysis as a potential post-consumer footwear recovery option. Exploring the viability of new avenues for footwear waste recovery is significant due to its potential to divert this waste stream from landfills and allow a progression toward a more circular economy.

A product-service-system proposal for municipalities in developing countries with tight budget to convert the organic waste in energy to eliminate dumps

In developing countries, organic waste is commonly dumped in untreated landfills. Brazil has around 3,000 landfills distributed in 1,600 cities. The Brazilian government instituted the National Solid Waste Policy (PNRS), which set the goal of ending the dumping grounds in 2014. However, it was not accomplished. Municipal governments do not have the resources to fund the existing treatment technologies. Thus, there is an urgent need to propose low-cost alternatives to solve this problem. This work proposes a low-cost Product-Service System (PSS) solution that enables the proper treatment of organic waste using the current municipal budget, based on the renting of household biodigesters. It was outlined from a model built on various proposals for the PSS design, published between 2011 and 2018. A feasibility simulation of the proposal conducted for the scenario of the Brazilian city of Porto Amazonas has demonstrated that, by adopting the proposal, the administration could comply with the PNRS and save part of its actual budget. It also showed 75% of probability of financial viability for the PSS provider, in a scenario of reduction of up to 20% in the current municipal costs for organic waste collection and transportation, and up to 40% off in cooking gas costs for the equipment-hosting households. The proposal is a potential solution for the Brazilian municipalities with more favorable scenarios to comply with the PNRS, as well as other countries' municipalities with budget constraints to eliminate their dumps.