Solid Waste Management

Abstract

In many countries of the world, especially underdeveloped countries, the practice of solid waste management is inefficient. Solid waste management has become a difficult environmental issue. Due to poor waste handling practices, many environmental and health issues arise. In this regard, many countries are trying to find ways to deal with the problem of solid waste. This chapter is an overview of solid waste management practices knocking the waste minimization techniques that play an important role in eliminating environmental problems. In developing countries, the practice of waste handling for infectious and non-infectious waste is of mixed type. Such mismanagement of solid waste paves the way for environmental pollution, leading to adverse effects on human health. Various factors such as poor policies, inefficient organizations, lack of financial support and poor governance, are the major constrains in safe waste management. Therefore, it is considered difficult to manage the recovery and safe disposal of solid waste. This study shows that there should be an appropriate organizational configuration for the separate treatment of different types of solid waste. For this, the authorities concerned must be strengthened financially and in skilled manpower for a good management of solid waste with a good recovery of resources.

1. Introduction

Majority countries of the world are facing the issue of solid waste management. Initially it was thought that all the waste coming from household and animal wastes are solid waste. Later on it was proved that all the waste generated as a result of catastrophic events as well as construction and demolition sites are considered to be solid waste [1]. But solid waste are any materials that are being generated as a result of our daily activities, such as packages, bottles, leftovers, newspapers, equipment, gadgets, batteries, and colors [2]. Solid Waste Management (SWM) is becoming a global challenge throughout the world because of overpopulation and change in consumption patterns [3]. Improper disposal of solid waste causes variouse environmental problems like soil, water and air pollution as well as surface and ground water contamination. Decomposition of organic waste causes greenhouse gases into atmosphere [4]. While many health issues are also related to improper disposal of solid waste. The management of solid waste requires interdisciplinary links between politics, planning, geography, economics, public health, sociology, engineering, and materials science [2]. Integrated solid waste management is a process which is completely based on 3Rs (Reduce, Reuse, Recycle), with the goal of reducing the amount of waste that must be disposed of while maximizing material and energy recovery from waste, Figure 1 [1].

Figure 1.

Integrated SWM system [5]. The poor policies of transportation, energy, and waste management causes one in eight deaths worldwide in 2012, being related to air pollution [6].

Growing economies and populations in emerging nations like China, India, and Brazil have produced enormous amounts of solid waste that need to be managed [7, 8]. A number of these nations desire an advanced sustainable solid waste management system that supports better source material sorting and high recycling rates, but they do not have the necessary SWM capabilities to balance their sustainable development objectives [9]. Among the developed countries, the amount of waste generated in the United States was 88.1 million tons in 1960, later on it was increased up to 250 million tons in 2008 [10]. While in developing countries, the practice of solid waste management is inefficient. In Pakistan, there is no adequate waste collection and disposal system. All types of waste (industrial, municipal, hospital, etc.) are treated in the same way. The solid waste generation rate in Pakistan is calculated at 70,715 tonnes per day. In total, about 51–69% of solid waste is collected daily in Pakistan, while the rest of the waste is burnt or illegally dumped [11].

Urbanization and overpopulation is the root cause of increasing waste. By 2025 there will be 8 billion of world’s population reach, out of which 5 billion will be living in cities [12]. Similarly, the rapid population growth, ongoing urbanization, and the expansion of commercial, industrial, and service activities in Iran have increased waste production, which has caused a significant issues including environmental contamination [13]. Most MSWs in many nations are landfilled, while facilities for waste treatment including composting and incineration of wastes are rarely employed [14]. Solid waste management is important with the goals to plan strategies to address the health, environmental, esthetic, land-use, resource, and economic issues that arise from improper waste disposal [3]. The responsible team is municipal authority working at local level. Due to lacking of resources, the majority of municipalities do not collect the increasing level of waste. SWM is essential for conserving urban landscapes, people’s health, and cities’ reputations. It is important to support the waste colleting authority and all issues associated with the collection and disposal of solid waste because the situation will get worse over time due to the high rate of urbanization [15].

1.1 Types of solid waste

Solid waste is of different type, depending upon the sources from which it is generated, Table 1 [4, 5]. These wastes carry two main types including hazardous and non-hazardous waste. Hazardous waste includes metals (Cd, Cr, Cu, Ni, Pb, etc.), chemicals, sharp objects, paints and is difficult to reuse or recycle. While non-hazardous waste includes food waste, paper, plastic, tin metals, glass, wood, etc. that can be recovered in a conventional solid waste management system [11]. The majority of waste generated by industries, hospitals and laboratories is considered hazardous while waste from commercial areas and municipal waste is not hazardous to health. Depending on the nature of the type of waste, treatments or appropriate disposal are required as a management strategy [5].

Sources	Industrial Area	Commercial Area	Residential Area	Institutional Area	Hospital Services
Types of Wastes	Hazardous and nonhazardous wastes, e-waste, metallic and non-metallic waste, paper, plastics etc.	Glass, metal, plastic,; e-waste,; hazardous waste etc.	Kitchen waste, textile, construction and demolition, batteries and hazardous waste etc.	Ashes, infectious and toxic waste, hazardous and e-waste, plastic and paper waste, glass waste etc.	Hazardous (sharps, medical waste), non-hazardous waste (food waste, paper, metal, plastic) Construction and demolition waste etc.

Table 1.

Sources and types of solid waste.

1.2 Adverse health impacts

The effects of solid waste on health may vary based on a number of factors, including the type of waste management practices, the traits and behaviors of the population exposed, the period of Interventions for exposure, prevention, and mitigation. The health consequences included mortality, neonatal outcomes, cancer, respiratory illnesses, gastroenteritis, vector-borne infections, cardiovascular disorders, and mental health issues [16]. Vegetable peels, common household waste, medical waste, e-waste, etc. are all thrown away. Decomposition of the waste results in the release of numerous noxious gases, which draw numerous mice and other pests to the area and create major health dangers. Due to the unscientific and unsanitary way of life of the people of Garia, Kolkata, individuals frequently suffer from diseases like diarrhea, malaria, and dengue. While certain health effects may be rapid, clear to see, and directly related to the exposure to solid waste, others may be occult, long-lasting, and difficult to identify to a specific type of trash. The four groups-model represents the health implications easier to understand, Figure 2 [17]. The model shows the mechanism of improper waste disposal and its health impacts on human health. Such diseases are infections and chronic effects. The responsible sources for health diseases are improper disposal of hazardous type of waste such as sharps etc.

Figure 2.

Poor SWM and adverse health impacts [17].

2. Waste management practices

The adoption of integrated sustainable waste management techniques that are based on a comprehensive, multifaceted, and multi-stakeholder approach to the design and operation of MSW management systems. The 3Rs principles, prioritizing actions in accordance with the waste pyramid hierarchy, and embracing life-cycle thinking are all crucial components of this, Figure 3. This practice of waste management is quite easy and cheap. While being encouraged by contemporary waste management strategies, reuse, and recycling, composting, and safe disposal through landfills are usually not carried out. A significant fraction of waste generated in underdeveloped nations is not recycled. The only problem is the improper and unsafe disposal of unwanted items. It is challenging to recycle or compost due to the lack of waste recycling. Due to this, a large amount of solid waste in developing nations is dumped in open areas and frequently burned [17].

Figure 3.

Safe disposal to minimized residual waste [18].

The existence of laws and policies controlling waste management and the extent to which they are enforced, the amount of funds sources, and the type and amount of waste generated all have an impact on the differences in waste management methods. The final disposal is frequently at an open dumping site on the outskirts of the city, with collection frequently occurring near the source or temporary dumping site. Truckloads of wastes are usually dumped at dump sites, which are typically large open spaces or water channel. Dumped waste is searched for usable and recyclables items by the scavengers or it is frequently burned to minimize the bulk [17]. Solid waste composition is complex due to inadequate solid waste sorting at any level and may contain industrial, medical, electronic, and human waste deposited on the same open grounds where all the other municipal waste is dumped [19].

2.1 Landfill technology

The process of properly disposing of biodegradable and non-biodegradable wastes in a landfill (set apart and away from locality) is known as landfilling. In many nations, landfilling has been the traditional and most profitable method of waste disposal [20]. Due to its low cost and labor-intensiveness, landfilling is preferable to incineration and recycling of municipal solid waste. Additionally, by using its landfill gas and leachate for energy production, a consolidated landfilling can also generate income [20]. However, due to improvements in recycling, composting, incineration, and energy recovery technologies, landfilling of municipal solid waste decreased from 89% in 1980 to less than 53% in 2014 in the USA [20]. According to the type of waste, such as household waste, toxic chemicals, biohazards, biomedical wastes, radioactive wastes, as well as building, demolition, and restoration wastes, different landfills and remediation facilities are located in different areas. There is no proper landfill system for the safe disposal of solid waste in underdeveloped countries such as Pakistan. The practice of solid waste disposal is in open land areas or in the nearby areas of water channels. This not only opens a pathway for soil and water contamination but also lead to severe health issue to the scavengers (birds, animals, human). There are the following categories according to the type of solid waste which is to be refused, Table 2. These types of waste area generated from different sources as mentioned in the table.

Category	Type of Solid Waste Disposal
Class 01	Soil disposal.
Class 02	Disposal of construction and demolition, renovation waste and minerals.
Class 03	Disposal of municipal solid waste.
Class 04	Disposal of wastes coming from industries and commercial sectors.
Class 05	Disposal of hazardous waste.
Class 06	Underground disposal of wastes.

Table 2.

Categories of solid waste disposal.

2.2 Bioreactor landfills

A bioreactor landfill is a specially designed contemporary landfill that transforms waste disposal from storage to treatment. In comparison to conventional landfills, bioreactor landfills have different advantages, i.e. (i) improved leachate quality, (ii) storage and partial in situ treatment of leachate, (iii) high landfill gas production rates and yields, (iv) effective gas recovery for on-site flaring, (v) early waste stabilization, (vi) improved biodegradation of biodegradable components in municipal solid waste leading to faster settlement, and (vii) cost- and time-effective (ix) increased waste into energy conversion. Temperature inside bioreactor ranges from 45 to 60°C. While the preferable temperature for the optimal activity of methanogenic bacteria range between 35 and 45°C. At a bioreactor landfill with pH levels between 6 and 8, and alkalinity levels about 2000 mg/L, the methanogenic bacterial population also thrives in alkaline conditions [20]. Bioreactor landfills can be divided into anaerobic, aerobic and semi-aerobic landfills.

1. Anaerobic bioreactor landfills, an anaerobic bacteria transform biodegradable wastes into volatile fatty acids, which are subsequently converted into landfill gases like CH₄ and CO₂. Organic wastes are degraded anaerobically to produce leachate and landfill gases by a number of sequential processes, including hydrolysis, acidogenesis, acetogenesis, methanogenesis, anaerobic oxidation, and fermentation [20].

2. Aerobic bioreactor landfills speed up the breakdown of waste by supplying aerobic bacteria with excess oxygen. The aerobic bacteria generate energy by oxidizing organic molecules, which primarily produces CO₂ and water. Aerobic degradation happens more quickly than anaerobic degradation because aerobic bacteria reproduce more quickly as a result of aerobic respiration, which is more efficient at generating energy than anaerobic respiration. By adding air to the soil layers and waste matter, aerobic bioreactor landfills promote aeration. Methanogenesis and CH₄ synthesis in landfills are lowered from starting levels of 60 to 10% within 7–10 days while anaerobic bacteria development is slowed [20].

3. Landfills with semi-aerobic bioreactors provide partially oxygen-deficient environments that promote the growth of both aerobic and anaerobic bacteria. According to this, methanation, hydrolysis, and fermentation likely occur simultaneously, albeit depending on the oxygen level, aerobic and anaerobic reactions may compete. The corresponding aerobic and anaerobic microbes may also locate in the landfill’s most advantageous microbiome niches. In semi-aerobic bioreactor landfills, air is transmitted through the waste layer from the bottom of the landfill, whereas air is injected into the aerial space of aerobic bioreactor landfills. Air can naturally circulate through the leachate collecting pipes in some designs [20].

3. Thermal chemical conversion

This is a process of conversion solid waste into energy by thermal decomposition of waste material [18]. There are various ways for treating solid waste, and choosing the best one relies on the kind of waste, the amount of land that is available, and the cost of disposal, Figure 4 [4]. These are as follows.

Figure 4.

Treatment techniques of solid waste.

3.1 Incineration

It is a controlled combustion process for producing gases and residue including non-combustible material by burning solid wastes at high temperatures of around 1000°C and above in the presence of excess air (oxygen) [4, 18]. The ability to employ the incine ration process to reduce the original amount of combustible MSW by 80–90% is one of its most alluring aspects [4]. Solid waste incineration typically produces 65 to 80 percent thermal energy. Stoker and fluidized bed furnaces are the two types that are most frequently used. Advantages: they are energy efficient, odorless as well as noiseless; disadvantages: Dioxin formation, SOx and NOx emissions, and particle creation; expensive; requires skills during its handling [18]. In undeveloped countries, majority of incineration plants are non-functional and hazardous waste is discarded and handled like non-hazardous type of waste.

3.2 Compaction

All the collected wastes are compressed and break into small pieces for further operations [4].

3.3 Pyrolysis

This is an endothermic process. Solid wastes are burned at the temperature range between 400 and 1000°C. Syngas, char and oil are produced as a result of pyrolysis [4] and a mixture of combustible gases CO, CH₄ and H₂ [18]. The feedstock for high-quality pyrolysis products should consist of a certain type of waste (plastic, rubber, electronics, electrical waste, wood waste, etc.). Several earlier research that focused more on the pyrolysis process itself than on the potential economic applications of the pyrolysis products reported on the pyrolysis of specific types of waste. Recently, pyrolysis has drawn interest in especially for recycling discarded tyres in order to recover oil, wire, carbon black, and gas.

3.4 Gasification

The temperature ranges between 1000 and 1400°C and less amount of oxygen of required [21]. Pyrolysis and gasification is more preferable and favorable process of treating MSW than incineration. Due to its lower impacts on environment. These processes use less energy for the reduction of waste up to 95% than incineration. Advatages: Syngas and slag are produced, while sulfuric acid is obtained from sulfur containing waste [18]. Disadvantages: it produces highly toxic polyhalogenated organics as a product, high amount of coal is required [18].

3.5 Composting

This is a process of aerobic biological decomposition of organic waste under controlled conditions, such as temperature, humidity, and pH. The indigenous microorganisms (thermophile and mesophile) transform organic matter into compost, a stable product [21]. The resulting compost functions as a soil conditioner and has uses in landscaping, agriculture, and horticulture [22]. Due to the gradual involvement of microorganisms during the breakdown process, composting is a “batch” process. Composting is a safe and ecofriendly process [21].

3.6 Hydrothermal carbonization

Carbonization is a relatively new thermal conversion method that turns solid waste into carbonaceous residues by heating it to a temperature between 180 and 350 C in a water-based environment (i.e., hydrochar). This process is exothermic in nature, moisture-rich waste materials are used, and energy requirements to run the device are low. But it is a costly method [18].

4. Waste management system

There are six different systems that are considered as waste management system, Figure 5:

1. Industrial Symbiosis/Inhouse waste handling: In this techniques, waste of one industry is used as a resource of production in another industry. For examples, waste wood of match industry is utilized as a resource in Chip-board industry. While waste of paper mill is used in packaging industry for packing of eggs, fruits and vegetables etc. [23].

2. Industrial waste management system

3. Littering/unmanaged waste Handling

4. Return system: used cans or bottles are returned to the company or industries for its reuse after the recycling of their respective waste (Figure 6).

5. Hazardous waste management system

6. Public or private Municipal Waste Management System [25].

Figure 5.

A model of WM system [5].

Figure 6.

SWM model for return system [24].

5. Challenges to solid waste management (SWM)

There are the following challenges which come across the SWM.

5.1 Waste generation and characterization

Waste generation rate is directly depending upon the population of an area. People disposed of their waste openly or discarded inappropriately. The most meaningful way of waste management is to educate people to reduce waste. Because of the modern era industries and institutions are going towards modern food packaging which itself is a big problem leading towards the generation of waste [26]. Solid wastes are characterized in terms of corrosive, ignitability, reactive and toxicity [4] and are also categorized on the basis of biodegradable, nonbiodegradable, organic inorganic and natural wastes [26].

5.2 Lack of funding

Overpopulation has necessitated the provision of sophisticated infrastructure for urban areas, and landfill selection is essential. Dumping zones are the main issue in dumping sites and a lack of government funding for urban local governments (ULBs) to effectively manage generated solid waste. We lack the facilities necessary to conduct a suitable process for SWM, due to lack of funding [26].

5.3 Lack of awareness

Govt, do not taking entrust towards the awareness programs of locality and their participatory approach towards SWM. The modern techniques of SWM should be adopted on large scale by adopted nations [18].

5.4 Institutional setup

There is less interaction between the federal and state governments causes a delay in reporting information from one to the other, which delays proper implementation at the sub-national level. Major barriers include a lack of collaboration with urban municipal governments for specific action plans and a weak implementation of policy [26].

5.5 Segregation of waste

Solid wastes contain every type of material when they are openly dumped. We need properly managed and scientific system for their safe disposal. Improper waste segregation is hazardous and causes serious health problems [21].

5.6 Involvement of other sectors

Many organizational sectors were established to improve the process of collecting MSW and source segregation it, but due to societal ignorance these approaches are ignored [26]. Rag-pickers might be employed by the organized sector to increase MSW collection efficiency and source segregations. Nevertheless, this enormous potential has gone untapped because there aren’t enough recycling industries and people do not accept recycling.

6. Solid waste management and sustainable development goals (SDGs)

The importance of maintaining health and protecting the environment through proper solid waste management in cities has increased because of seventeen Sustainable Development Goals (17SDGs). The SDG agenda promotes higher reuse and recycling as well as decreased waste generation. It mentions SDGs 3 (ensure people’s health and promote well-being), 6 (water and sanitation), 11 (make cities inclusive, safe, resilient, and sustainable), and 13 (combating climate change and its impact) [17]. SDG-11 is closely related to solid waste management: “percentage of solid waste that is well-managed and collected on a regular basis.” Yet, just like all prior social development programmes, operationalization and implementation may be where the problem lies. The management of solid waste is not mainstreamed, is funded poorly, and has never met expectations in many developing nations [27].

7. Conclusion

The mechanism of collection of solid waste and its safe disposal is a generic environmental problem worldwide. In this respect, the 3Rs-principle is considered to be the cheapest and most efficient way for solid waste management. In the majority of developing countries, there is no system for waste recovery at the collection and disposal sites. The recycling potential is not satisfactory. The practice of open burning of plastic and rubber items is the most common practice that causes air pollution. The waste management control mechanism is limited. Due to the lack of treatment facilities, people generally face unhygienic environments. Therefore, proper management must be done for solid waste management strategies.

Abbreviation

SW	solid waste
SWM	solid waste management
ISWM	integrated solid waste management
MSW	municipal solid waste
3Rs	reduce, reuse, recycle
USA	United States of America
Cd	cadmium
Cr	chromium
Cu	copper
Ni	nickel
Pb	lead
SOx	oxides of sulpher
NOx	oxides of nitrogen
CO	carbon monooxide
CH4	methane
H2	hydrogen
SDGs	sustainable development goals