A Prefatorial View of Solid Waste Management

Abstract

Solid waste management is the process of collecting, transporting, processing, and disposing of waste in a responsible and sustainable manner. Proper waste management is essential for public health, environmental protection, and the efficient use of resources. In many parts of the world, solid waste management remains a major challenge due to inadequate infrastructure, lack of funding, and limited awareness. The accumulation of solid waste in urban areas can lead to various health and environmental problems, including air and water pollution, disease transmission, and greenhouse gas emissions. Governments, organizations, and communities are implementing various waste management strategies to address these challenges, including waste reduction, recycling, composting, and waste-to-energy technologies. These strategies aim to reduce the amount of waste generated, recover valuable resources from waste, and minimize the negative impacts of waste on public health and the environment. Effective solid waste management requires a comprehensive and united approach that involves all stakeholders, including government, industry, civil society, and the public. Through collective action, we can create a more sustainable future by reducing waste, conserving resources, and protecting the environment.

1. Introduction

Waste management has a long and varied history, dating back to ancient times. The earliest forms of waste management were simple methods like collecting garbage and burying it in open pits on the outskirt of towns and villages and dumping it in water bodies. In ancient Rome, waste was collected from households by private contractors, and then dumped in designated sites outside the city walls. Another method was burning garbage in open-air pits, a practice that continued until the early twentieth century [1]. In the Middle Ages, waste products were often dumped into rivers or lakes, leading to severe pollution. During the Industrial Revolution, cities experienced a surge in population, which led to the growth of waste production. As a result, public health concerns emerged, and governments began to regulate waste disposal practices [2].

The modern era of waste management began in the late 1800s, with the creation of the first municipal waste disposal systems. These systems involved collecting and transporting waste to a central location, where it was sorted and recycled [3]. In the 1960s, the environmental movement led to increased awareness of the impact of waste on the environment, and recycling programs were introduced in some cities [4]. In the 1970s, the US Environmental Protection Agency (EPA) was established, and the Resource Conservation and Recovery Act (RCRA) was passed, which set standards for hazardous waste management [5]. In the 1980s and 1990s, waste-to-energy technologies were developed, which converted waste into energy through incineration or gasification [6].

Any material that is discarded after primary use is considered waste material. The increasing quantity and complexity of modern waste pose a serious risk to human health and the environment [7]. The increase in municipal solid waste in the modern world is a result of the world gearing toward urbanization. Waste generation is a burden that comes with development. Currently, municipal waste generated globally is estimated to be about two billion tons, and only 33% of that is managed properly [8]. The remaining 67% ends up in landfills, dumpsites, and the oceans then contributes to polluting our environment [7]. Reported that, by 2025, there will be about 4.5 billion urban residents generating 1.4 kg/capita/day of municipal waste.

Municipal solid wastes come from various sources, from households, offices, institutions, and other commercial organizations. The composition of solid waste from an area varies according to the lifestyle and living standards of the inhabitants of that area [3]. Lower to middle-income class generates more organic waste while high-income residents produce more metal, paper, and glass waste [9]. Solid wastes are made up of organic and inorganic materials, biodegradable and non-biodegradable materials. Because of the varying composition, strict and careful management practices are needed to control the flow of solid wastes from their source. Poorly managed waste pollutes the environment and oceans. It clogs drainage systems to cause flooding, increases the transmission of diseases, and air pollution from the burning of waste.

Safe handling of waste till final disposal is essential for any modern community or municipality. Proper handling of municipal waste could be an economic resource with great potential in the energy and manufacturing fields [9]. Effective waste management is a hands-on situation and requires participation from everyone, from the authorities to the individual waste generators [10]. In most developed countries, wastes are carefully regulated through well-established record-keeping systems. These countries have legislations in place to prevent improper disposal of waste that may cause pollution and outbreak of diseases. In developing countries, insufficient resources, and a lack of clear definitions, roles, responsibilities, and quality data have made waste management difficult [3]. Some of these developing countries have legislations to regulate solid waste management but have struggled to enforce these regulations.

As the realization that most of our resources are limited, it is necessary that we derive economic value from waste materials [11]. The process of finding value out of waste is known as recycling [12]. There are various ways in which waste materials can be recycled; the raw materials could be processed and used for another product or the waste material can be repurposed to generate energy. In order to extract value from waste, we must first start by properly managing solid waste right from the source.

Solid waste management includes; the generation, collection, treatment, disposal, and monitoring of waste. There are several factors such as environmental, political, economic, technical, and legislation that are taken into consideration during waste management. Sustainable waste management looks to promote reducing the amount of waste generated and recycling the majority of the waste. Minimizing waste produced heavily relies on the actions of the waste generator [12]. It is important that education and awareness in the area of waste management be prioritized. We shed light on the process of solid waste management, its importance, and its challenges.

2. Waste collection

The collection of waste is the first step to effective solid waste management. This includes collecting waste from the source and transporting it to be treated and/or disposed of. The waste collection process starts with generating, source segregation, storage, and transportation [13]. Collection and transporting of waste is the most critical and cost-effective part of solid waste management because it is laborious and requires the use of vehicles [11]. Factors ranging from the route to transport waste and the availability of storage for waste are all to be considered. It is a multipart process and requires intricate logistics management in order to operate well for a long time [14].

The collection system for waste depends on the source and type of waste. For instance, the collection system of waste from an urban area would not work in a rural area because of the difference in the amount of waste generated per a given time. Another scenario to look at is that waste from residential areas would be different from waste from commercial or industrial areas hence, cannot be collected the same way. Some areas generate more perishable waste products than others, hence the need for them to be collected and transported frequently. The type and quantity of waste produced will determine the scale and nature of the collection process. The collection of recyclable wastes has become very essential to most societies looking toward sustainable waste management.

In most urban areas the collection of waste is the responsibility of local authorities and in some areas, there are no formal methods of waste collection. Optimal locations for waste collection are a fundamental aspect of the cost-effectiveness and convenience of solid waste management [15].

3. Waste segregation

One modern system of waste collection is segregation at the source in order to minimize the complication of sorting through several heaps of waste before treatment. Waste segregation is considered to be an effective way for initiating the recycling process [16]. Source segregation is defined as separating ‘useful’ waste materials from the waste stream right after the waste has been generated. Waste is segregated either by recyclability or degradability. Ideally, waste should be segregated based on whether the material is paper, glass, organic, or plastic.

In doing this, the amount of waste that goes to landfills is reduced [16]. Source segregation of waste increases the amount of recycling, reuse, and recovery. When recyclable waste is not segregated at the source and is mixed with organic matter it makes sorting and recycling very difficult. In addition, the moisture content in waste is less when it is segregated at the source, this makes it easy for disposal by incinerating. Burning of recyclable wastes like plastics produces harmful gasses that harm the environment and its inhabitants [17].

Waste segregation begins at the basic source of waste like households, schools, offices, etc. The common method of segregating waste is to get different bins for the different waste types. These bins are labeled and placed conveniently so that after primary use, waste materials are stored in their appropriate bin. When the time comes for the waste to be transported, recyclable wastes are taken to the recycling sites while non-recyclable waste is taken to be disposed of. This helps to achieve a better recirculating rate for waste management systems [18]. The quality of raw materials for recycling is much higher in source-segregated waste than it is in materials sorted from a mixed waste stream.

It is important that all solid wastes generated must be stored properly while waiting to be transported. Plastic dustbins are the most commonly used waste storage devices in this part of the world. The bin must have a tight lid to prevent fumes from polluting the environment and also diseases from breeding from it. These bins should also be conveniently placed and accessible to waste generators and collectors.

4. Waste transportation

Transporting waste is the next step in solid waste management after storage. Waste materials are either transported to a treatment facility or a landfill to be disposed of. Transporting waste is a very complex and cost-inducive process. It requires a collection crew, vehicles, pick-up points, and intricate logistics [19]. In most urban and residential homes, the storage of waste is done by individuals and residents whereas the transportation is outsourced to private collectors by municipal authorities. In some instances, the waste is collected from bins placed in front of the respective residence for collection. Other situations require that the waste be sent to designated pick-up spots for collection. After waste is collected, they are transported to treatment sites to be sorted and treated before disposal. The main thing that must be looked at when analyzing waste transportation is economics [20]. It ranges from the cost of fuel for transporting to the cost of crew members collecting waste materials. The distance of transportation routes and the size of the axle of waste trucks contribute to the total cost of collecting and transporting waste [13]. If the distance between the collection sites and the treatment site is too far, the vehicles use up more fuel to make the trip. The capacity of the axle of the waste truck also contributes to the cost of transportation [20]. If the waste truck has a smaller axle then it must make multiple trips within a given week or month. A model adopted by some developed countries is that waste is moved by smaller vehicles to a temporary dumpsite, then large garbage trucks collect the solid waste from the temporary site to their preferred destination [21].

5. Waste treatment

Treatment of waste is the next essential part of solid waste management. In an ideal system where waste is segregated at the source, after collection, recyclable materials are sent to the appropriate recycling plants, and the remaining waste materials are sent to a landfill for treatment and disposal. However, in most cases, the segregation of waste is done after it has been transported to landfills. After recyclable materials are sorted from the waste stream the remaining waste materials have to be treated to either facilitate easy disposal or to be used as a resource material. Waste treatment varies according to the type of waste material and it includes, biotreatment, incineration, energy recovery, and pyrolysis, among others [22].

5.1 Biotreatment

Biotreatment is the preferred method for treating biodegradable waste materials. Biotreatment of solid waste materials is mainly by anaerobic degradation; this is a process where bacteria are used to break down components of organic matter. The process of anaerobic degradation is in four stages namely: hydrolysis, acidogenesis, acetogenesis, and methanogenesis [23]. The goal of this process is to generate renewable energy in the form of methane gas from organic solid waste [24]. Aerobic degradation is the preferred method for the treatment of large volumes of wastewater and sludge with rich organic matter because the process requires oxygen [22]. The difference between this and the former is that, anaerobic digestion happens in the absence of oxygen. Anaerobic degradation is the most extensively used form of biodegradation because of its versatility. It can be used to digest a large variety of biomaterials (sewage sludge, municipal solid wastes, industrial wastes, manure, etc.); the system can be used to produce energy generation and soil fertilization [25].

5.2 Incineration

The thermal treatment process is mostly reserved for combustible and dry waste materials. It involves burning the waste materials in a controlled environment. Most incineration facilities are known as waste-energy facilities; the generated heat and electricity can be supplied to small towns and other urban areas [26]. Incineration is the best treatment method for eliminating infectious components of waste [22]. It can reduce about 90% of the volume of municipal solid wastes and minimize dependency on fossil fuels [27]. Relative to other waste treatment methods such as composting and landfilling, incineration with air emission management systems is seen to be the best option [28].

Traditional incineration is known to emit greenhouse gasses and poses a health risk to the nearest inhabitants [29]. Traditional incineration is where by there are no air emission management systems hence, the smoke from the incinerator goes into the atmosphere. Incineration plants require high operation costs and are more expensive than controlled landfilling [30]. Because of this, waste generators may find alternatives to disposal than incinerating.

Other thermal treatment processes for solid wastes are gasification and pyrolysis. Biomass gasification is a thermochemical process whereby waste is heated at high temperatures with low oxygen to break it down for the production of syngas and char [31]. Syngas can be used as fuel and raw materials for the production of solid and liquid fuels [32]. Pyrolysis is a thermal degradation process whereby waste is heated at high temperatures in the absence of air to produce valuable materials such as char, wax, and fuel gasses [33]. Both gasification and pyrolysis are waste-to-energy methods of processing solid wastes and are sustainable way to foster a circular economy. However, both processes require a high amount of energy for processing and so have high operation costs [34].

5.3 Recycling

Recycling of waste material has become a necessity in modern-day waste management. With the continued increase in the volume of municipal solid wastes, it is important that most waste materials are redirected from landfilling. Recycling is any means by which waste material is converted into useful products either for their original or other purposes [35]. The recycling process begins with the waste generator; as stated already, sorting solid waste from the source is the best way to initiate the recycling process. The municipal solid waste stream is not homogenous hence recycling is difficult. Some recyclable waste materials are plastics, paper, glass, and metal. Recycling is the most practiced reduction technique for solid waste management. Some ways of recycling solid waste materials are described in the subsections.

5.3.1 Recycling of plastics

Plastic recycling is a globally recognized process of managing plastic waste. The versatility of polymer has made plastics integral in today’s society, from packaging materials to medical and electronic equipment [36]. The most common kind of plastic waste is plastic packaging because it is mostly single-use [37]. Ref. [36] reported that plastics are recycled chemically or mechanically. Mechanical recycling is where plastic wastes are cleaned, melted, and extruded to form various products. These products usually have low quality and molecular weight than the primary products [37]. For chemical recycling, the plastics wastes go through several steps to break the long chain bonds in order to form new plastics or use them for fuel/other chemical products [38]. Not all plastics can be recycled both mechanically and chemically the recycling techniques are dependent on the type of plastic [36].

5.3.2 Recycling of metals

Recycling metals from solid waste streams is another huge step toward sustainable waste management and a circular economy. Light metals used for machine parts and food packaging are the most common in municipal waste streams [39]. Metal parts, aluminum, and steel cans and sheets pose a danger to the environment when they are dumped in landfills. While modern society looks at green environment and waste reduction, waste metals are better managed by recycling. There are a variety of methods in metal recycling including mechanical, hydrometallurgical, and pyrometallurgical processes [40]. Mechanical recycling of metals includes sorting the metals from the waste stream, processing them through mechanical processes such as shredding, and then melting the metal down in order to produce new products. This is a common recycling method for aluminum cans, steel sheets, and other scrap metals [41]. For pyrometallurgical recycling, the metal is heated at elevated temperatures to remove any impurities and other materials, then the resulting molten metal is cast into a new product. This process is mostly used to recycle lead, copper, and zinc [42]. The other widely used process for metal recycling is hydrometallurgy. This involves dissolving the metal in a chemical solution to recover/extract metals then the metal is processed into a new product. This technique is mostly used for precious metals like gold, silver, and platinum [43]. Other methods for recycling metals like electrochemical and bio metallurgical methods are being developed [44, 45]. The choice of recycling method is reliant on the kind type and quantity of waste metal as well as the environmental and economic impact [43].

5.3.3 Recycling of glass

Glass recycling involves melting down glass into molten form then it is refined to remove impurities before a new product is formed with the molten glass [46]. This process usually requires about 1500°C which is less energy than what is required to make new glass from raw materials [47]. There are two main ways by which glass is recycled. They are either by the closed-loop system where the recycled glass is used to make new products of the same type and color. With this method, there is very little loss in the quality of the glass [48]. The other method by which glass is recycled is the open-loop system whereby glass is recycled into new products that are not necessarily the same type or color as the original material [49]. An example is when glass is recycled to make fiberglass insulation or decorative tiles. The closed-loop system of recycling is considered the most sustainable because it conserves energy and releases minimal greenhouse gasses; open-loop recycling allows for a variety of materials to be made from recycled glass [48].

5.3.4 Recycling of paper

Paper is also one of the most common waste materials. It is used everywhere from offices to schools, for packaging to decorating [50]. After the waste paper is collected and taken to a recycling facility, the papers are sorted according to their types i.e., office paper, cardboard, etc. Then, the papers are shredded into smaller pieces and mixed with water to form a pulp. The pulp is screened thoroughly and refined to remove any impurities and/or non-fibrous materials. Chemicals like surfactants, caustic soda, and peroxides are then used to de-ink the paper [51]. The pulp is now bleached to get the desired brightness before it is repulped to make new materials like cardboard, tissue paper, or printing paper [52]. Paper recycling preserves natural resources and reduces the amount of waste sent to landfills.

Upcycling is another sustainable way to manage waste. It is when waste products are given a second life as it is upgraded and reused for another purpose [53]. Upcycling is about creating a new design and meaning to a material that has already served its purpose. The creation of art from plastic waste and making flower beds out of car tires and other waste containers can be considered upcycling. Waste materials are also recycled in the construction industry as building aggregates/materials [54]. Researchers have studied the effects of waste glass and plastics as aggregates and binders in concrete and cement materials. Studies show that if managed carefully, solid wastes can be effectively recycled into concrete and other cement materials without destroying the integrity of said materials [55].

5.4 Landfilling

Landfills are sites designed to store garbage; they are mostly used to store non-hazardous waste [56]. Waste in landfills undergo biological, physical, and chemical transformations [9]. Hence, extra steps must be put in place to prevent pollution and contamination of the environment. Sustainable landfilling is a concept to minimize the environmental impact of landfills while allowing for solid waste disposal [57]. Sustainable landfilling can be achieved by the use of landfill liners, energy recovery, gas and leachate collection, and frequent maintenance [9]. Gas emissions from municipal landfills can be collected to generate waste. Methane gas from composting waste can be captured and used to generate fuel or electricity either by steam turbines or oxide fuel cells [58]. Organic food waste can be secluded from other waste in landfills for composting to produce nutrient-rich soil [59]. By implementing the necessary practices, sustainable landfilling can minimize the environmental impact of solid waste disposal and offer economic breakthroughs.

6. Advantages of solid waste management

Solid waste management is an essential part of the development of any town, city, or urban area. Some of the key benefits of an effective solid waste management practice are: Improved public health, environmental protection, resource conservation, economic benefits, reduced greenhouse gas emissions, and improved esthetics.

Proper waste management practices help prevent the spread of diseases, reduce the risk of contamination, and minimize exposure to harmful toxins and pollutants. Poor solid waste management is linked with poor public health and affects the sustainable development of most cities [60].

Proper disposal of waste reduces the risk of soil, air, and water pollution, preserving the environment and protecting wildlife [9].

Solid waste management involves the recovery and recycling of valuable resources, such as metals, plastics, and paper. This reduces the amount of waste sent to landfills and deductively conserve natural resources [61].

Proper waste management practices can create jobs and generate income by collecting, transporting, and processing waste materials [62].

Landfills are a significant source of greenhouse gas emissions, particularly methane. Proper solid waste management, including waste reduction, recycling, and composting, can help lower these emissions and mitigate the effects of climate change [48].

Properly managed solid waste helps maintain a clean and tidy appearance in public spaces, reducing litter and improving the overall quality of life in a community.

7. Challenges with municipal solid waste management

Some challenges faced by most municipalities when enforcing solid waste management are: Increased waste generation, inadequate infrastructure, financial constraints, public attitudes and behavior, recycling and composting, and hazardous waste management.

The sheer volume of waste generated by urban areas is steadily increasing each year, and finding suitable locations for landfills and waste disposal facilities can be difficult due to limited space and environmental regulations [9].

On the infrastructure, many cities lack the necessary systems and resources to effectively manage waste, including collection and transportation channels, sorting and processing facilities, and trained personnel [13].

Economically, implementing effective waste management systems can be costly, and many municipalities may lack the necessary funding to invest in these systems [63].

The public behavioral limitations originates from the poor waste management practices learnt from less informed individuals who illegally dump or litter the environment and create long term challenges for municipalities with consequential undermine of their efforts at managing the waste [64].

Recycling and composting can help reduce the volume of waste sent to landfills, however, these activities can be challenging to implement effectively due to logistical and economic barriers, such as inadequate recycling infrastructure and limited markets for recycled materials [63].

Managing hazardous wastes, such as chemicals, batteries, and electronic waste, present unique challenges and requires specialized facilities and processes to ensure proper disposal and harmless to the environment and public health [65].

8. Conclusion

For the sustainable development of our cities and urban areas, solid waste management must be practiced effectively. Best solid waste management programs improve the health and environmental conditions of residents and animals. This creates an opportunity for waste materials to be used as a resource which in turn, generates significant economic benefits. Recycling provides job opportunities for several people and enhances the economic quota of a particular region and/or country.

The extraction of energy from waste material is an important addition to the solutions for the global depletion of non-renewable resources. Proper management of waste reduces the volume of waste on landfills and subsequently minimizes the emissions of greenhouse gasses. A significant reduction in waste generation from successful solid waste management practices is a huge step toward achieving sustainable development goals.

Despite the many challenges that are faced with the implementation of solid waste management, it is necessary that municipalities and governments provide the right infrastructure and systems that will minimize waste, channel generated waste to recycling, and minimize landfilling to protect the people and the environment.