The Definitions Of Solid Waste Management Environmental Sciences

As clarified in the introductory part of this study, Solid Waste Management (SWM) is defined as the collection, transportation, processing or treatment, recycling or disposal and finally monitoring of waste materials. The term is usually related to the materials produced by various activities undertaken by humans and is generally carried out to reduce their negative effects on their health, environment and aesthetics. Waste management is also undertaken to recover resources for further commercial or economic benefits. Waste management can involves the managing of solid, liquid, gaseous or radioactive waste materials, and for which there are various methods and fields of expertise for each type. As the subject of this research suggests, we will be focusing on the management of solid waste only.

Waste management practices differ for developed and developing nations, for urban and rural areas, and for residential and industrial producers. Management for non-hazardous residential and institutional waste in metropolitan areas around the world, is usually the responsibility of the local government authorities, while management for non-hazardous commercial and industrial waste is usually the prime responsibility of the producer.

Waste is an unavoidable by-product of most human activity. Economic development and rising living standards in the Asian and Pacific Region have led to an increase in the quantity and complexity of generated waste, while industrial diversification and the provision of expanded health-care facilities have added substantial quantities of industrial hazardous waste and biomedical waste into the waste stream which will potentially have severe environmental and human health consequences. In the following paragraphs, we will be discussing the generation and types of growing volume of solid waste, which poses formidable challenges to the world.

TYPES OF WASTE & THEIR DIFFERENTIATIONGENERATION AND CHARACTERISTICS

A clear appreciation of the quantities and characteristics of the waste being generated is a key component in the development of strong and cost-effective solid waste management strategies. In some of the more developed countries, the quantification and characterization of waste forms the basis for management and intervention, while in the developing world little priority is given to the systematic surveying of waste generation and management and future trends of waste generation are poorly understood. Although there is a lack of comprehensive or consistent information, at the country level, some broad trends and common elements are apparent while discussing the generation and types of solid waste.

In general, the developed countries generate much higher quantities of waste per capita compared to the developing countries of the region. However, in certain circumstances the management of even small quantities of waste poses a significant challenge. For example, in the small islands of the South Pacific sub region, small populations and modest economic activity have ensured that relatively low quantities of waste are generated. However, many of these countries, particularly small countries such as Kiribati, Tuvalu and the Marshall Islands, face considerable waste management challenges due to their small land areas and resultant lack of disposal options.

Throughout the world, the principal sources of solid waste are residential households and the agricultural, commercial, construction, industrial and institutional sectors. For the purposes of this study, these sources are defined as giving rise to four major categories of waste: municipal solid waste, industrial waste, agricultural waste, hospital waste and hazardous waste. Each of these waste types is examined separately below.

Municipal Solid Waste

Municipal solid waste (MSW) is generated from households, offices, hotels, shops, schools and such other institutions. The major components are food waste, paper, plastic, rags, metal and glass. Although demolition and construction debris is often included in collected waste, as are also small quantities of hazardous waste, such as electric light bulbs, batteries, automotive parts and discarded medicines and chemicals.

Generation rates for MSW vary from city to city and from season to season and have a strong correlation with levels of economic development and activity. High-income countries (such as Australia, Japan, Hong Kong, China, Republic of Korea, and Singapore) produce between 1.1 and 5.0 kg/capita/ day; middle-income countries (such as Indonesia, Malaysia and Thailand) generate between 0.52 and 1.0 kg/capita/day, whilst low-income countries (such as Bangladesh, India, Viet Nam, Pakistan and Myanmar) have generation rates of between 0.45 and 0.89 kg/capita/ day. Taken as a whole, the Asian and Pacific Region currently produces some 1.5 million tons of MSW each day and this is expected to more than double by 2025 (World Bank, 1999).

The amount of human feces in the MSW is significant in squatter areas of many Asian and Pacific cities where "wrap and throw" sanitation is practiced or bucket latrines are emptied into waste containers. The latter is common in many cities (such as Calcutta, Dhaka and Hanoi) of the region where there are minimal or ineffective sewerage systems.

Industrial Solid Waste

Industrial solid waste in the Asian and Pacific Region, as elsewhere, encompasses a wide range of materials of varying environmental toxicity. Typically this range would include paper, packaging materials, waste from food processing, oils, solvents, resins, paints and sludge, glass, ceramics, stones, metals, plastics, rubber, leather, wood, cloth, straw and abrasives.

As with municipal solid waste, due to the absence of a regularly up-dated and systematic database on industrial solid waste, the exact rates of generation are largely unknown. Industrial solid waste generation varies, not only between countries at different stages of development but also between developing countries. In People's Republic of China, for example, the generation ratio of municipal to industrial solid waste is one to three. In Bangladesh, Sri Lanka and Pakistan, however, this ratio is much lower. In high-income, developed countries, such as Australia and Japan, the ratio is one to eight. However, based on an average ratio for the Asian and Pacific region, the industrial solid waste generation is equivalent to 1,900 million tons per annum. This amount is expected to increase substantially and at the current growth rates, it is estimated that it will double in less than 20 years. As the existing industrial solid waste collection, processing and disposal systems of many countries are grossly inadequate; such incremental growth will pose very serious challenges.

Agricultural Waste and Residues

Expanding agricultural production has naturally resulted in increased quantities of livestock waste, agricultural crop residues and agro-industrial by-products. Among the countries in the Asian and Pacific Region, People's Republic of China produces the largest quantities of agriculture waste and crop residues followed by India. In People's Republic of China, some 587 million tons of residues are generated annually from the production of rice, corn and wheat alone. In Pakistan, about 56.22 million tons of different crop residues are generated annually, of which 12.46 million tons originate from cotton, 2.90 million tons from maize, 12.87 million tons from sugarcane, 8.16 million tons from rice and 19.83 million tons from wheat. In addition, Pakistan produces other wastes amounting to some 28 million tons of which 58% are animal waste, 40% is sugarcane bagasse and the remaining 2% comprises a mix of jute, mustard stalks, sesame sticks, castor seed stalks, sunflower stalks and tobacco stalks (ESCAP 1997).

Hospital/ Hazardous Waste

Hospital waste is generated during the diagnosis, treatment, or immunization of human beings or animals or in research activities in these fields or in the production or testing of biological materials. It may include wastes like solid waste, disposables, anatomical waste, cultures, discarded medicines and chemical wastes. These are in the form of disposable syringes, swabs, bandages, body fluids and human excreta. This waste is highly infectious and can be a serious threat to human health if not managed in a scientific and discriminate manner. It has been roughly estimated that of the 4 kg of waste generated in a hospital at least 1 kg would be infected.

In Punjab, Pakistan, 75 tons of clinical waste is produced daily. The rate of generation per bed per day is 1.8 kg. There are 35 hospitals in Lahore, which generate 6 tons of clinical waste daily.

Most hazardous waste is the by-product of a broad spectrum of industrial, agricultural and manufacturing processes, nuclear establishments, hospitals and health-care facilities. Primarily, high-volume generators of industrial hazardous waste are the chemical, petrochemical, petroleum, metals, wood treatment, pulp and paper, leather, textiles and energy production plants (coal-fired and nuclear power plants and petroleum production plants). The principal types of hazardous waste generated in the Asian and Pacific Region, include waste solvents, chlorine bearing waste and pesticideorganophosphate-herbicide-urea-fungicide bearing waste. In particular, solvents are extensively used and, as a consequence, large quantities of waste solvents are produced.

Table 1: Sources of solid wastes, typical waste generators and types of solid waste generated

(Adapted from Pakistan State of the Environment Report 2005, draft, p. 113)

METHODS OF DISPOSAL OF SOLID WASTE

There are a variety of ways in which solid waste can be disposed off. Following are some of the methods of solid waste disposal.

Figure 1: The Solid Waste Management Hierarchy

Source: Waste Hierarchy: Who's on Top in the Game of Trash? By Raquel Fagan

1. Landfill

A landfill, also called a dump or a rubbish dump is a site for the final disposal of waste materials by burial and is the oldest and most widespread form of waste treatment. Historically, landfills have been the most common methods of organized waste disposal and remain so in many places around the world.

Landfills may include both the waste disposal sites around cities (where a producer of waste carries out their own waste disposal at the place of production) and as well as sites used by many producers. Many landfills are also used for other waste management purposes, such as the temporary storage, consolidation and transfer, or processing of waste material (sorting, treatment, or recycling).

Disposing of waste in a landfill involves the burying of waste and they are often established or located in abandoned or unused large ditches, mining voids or burrow pits. A properly designed and well-managed landfill can be a hygienic and relatively inexpensive method of disposing of waste materials. Older or poorly designed and managed landfills can create a number of unfavorable environmental impacts such as wind-blown litter, attraction of pests, and generation of liquid leachate. Another common byproduct of landfills is gas (mostly composed of methane and carbon dioxide), which is produced when organic waste breaks down anaerobically. This gas can create stench problems, kill surface plant life, and is a greenhouse gas.

Figure 2: A Landfill in ActionSource: RE3.org (Posters), Reduce, Reuse, Recycle

The design characteristics of a modern landfill should include measures to contain leachate such as a soil or plastic lining material. Deposited waste is normally compressed to increase its density and stability, and is covered to prevent attracting pests (such as mice or rats). Many landfills also have gas extraction systems fixed to remove the gas produced in the waste. Gas is then pumped out of the landfill using perforated pipes and flared off or burnt in a gas engine to generate electricity.

2. Incineration

Incineration is another waste disposal method which involves the burning of waste material. Incineration and similar other high temperature waste treatment systems are sometimes described as "thermal treatment" methods. Incinerators convert waste materials into heat, gas, steam, and ash.

Incineration is undertaken both on a private scale by individuals and on a large scale by industries. It is used to dispose of all types of solid, liquid and gaseous waste. It is recognized as quite a useful method of disposing of certain hazardous waste materials (such as biological medical waste). Incineration can be a controversial method of waste disposal, due to issues such as emission of gaseous pollutants.

Incineration is common in countries such as Japan where land is not openly available, as these facilities generally do not require as much area as landfills. Waste-to-energy (WtE) or energy-from-waste (EfW) are broad terms for facilities that burn waste in a furnace or boiler to generate heat, steam and/or electricity. Combustion in an incinerator is not always perfect and there have been concerns about micro-pollutants in gaseous emissions from incinerator stacks. Particular concern has focused on some very persistent organics such as dioxins, furans, PAHs (poly aromatic hydrocarbons) that may be created within the incinerator and afterwards in the incinerator plume, which may have serious environmental consequences in the area immediately around the incinerator. On the other hand, this method or the more benign anaerobic digestion produces heat that can be used as energy.

Figure 3: Basic layout of a state of the art municipal solid waste incineration plantSource: vonRoll Inova: Grate combustion systems. Zurich.3. Composting

Compost is an organic material which is a combination of decomposed plants and animal materials and other organic materials that are being decomposed largely through aerobic decomposition into a rich black soil. The process of composting is simple and practiced privately by individuals in their homes, agriculturally by farmers on their lands and industrially by industries and cities.

Compost soil is very rich and is used for many purposes. A few of the places that it is used are in gardens, landscaping, horticulture and agriculture. The compost of soil itself is beneficial for the land in many ways, including as soil conditioner, as fertilizer to add vital humus or humic acids, and as a natural pesticide. In ecosystems, compost soil is useful for erosion control, land and stream reclamation, wetland construction and as landfill cover.

As concern about landfill space increases, worldwide interest in recycling by means of composting is growing, since it is a process for converting decomposable organic materials into useful stable products.

4. Plasma Gasification

Plasma is a highly electrically charged gas. An example in nature is lightning, capable of producing temperatures exceeding 12,600 °F (6,980 °C). A gasifier vessel utilizes proprietary plasma torches operating at +10,000 °F (5,540 °C) (the surface temperature of the Sun) in order to create a gasification zone of up to 3,000 °F (1,650 °C) to convert solid or liquid wastes into a syngas (Alliance Federated Energy, http://www.afeservices.com/tech_what.php). Syngas (from synthesis gas) is the name given to a gas mixture that contains varying amounts of carbon monoxide and hydrogen. When municipal solid waste is subjected to this extreme heat within the vessel, the waste's molecular bonds break down into basic components. The process thus results in elimination of waste and hazardous materials. Plasma gasification offers countries new opportunities for waste disposal, and more importantly for renewable power generation in an environmentally sustainable manner.

THE MODEL FOR INTEGRATED SWM

The Model for the Integrated Solid Waste Management has been presented by researchers, Joe E. Heimlich, Kerry L. Hughes and Ann D. Christy at the Ohio State University, USA, as part of its Community Development Initiative.

Figure 4: The Integrated SWM Model

Source: Community Development Initiative, Ohio State University, USA

The strategy behind the development of this model is to identify the level or levels at which the highest values of individual and collective materials can be recovered.

No single solution completely answers the question of what to do with our waste. Every community or region has its own unique profile of solid waste. The composition of solid waste also varies, depending on diverse variables such as urbanization, commercial enterprises, manufacturing and service sector activities. Similarly the attitudes of people in different regions of any country vary regarding waste management practices. This is often referred to as Waste Management Ethics and includes the recycling ethic and litter ethic of a community as subcategories. Community diversity and waste diversity are the two main reasons why no single method of waste disposal has been accepted as the best method.

However, all communities also have the same alternatives to waste disposal as well. For this reason, the Integrated Waste Management starts with reduction (using less) and reusing more, thereby saving material production, resource cost and energy. At the bottom of the list, lies the Landfill, which is the ultimate method of Waste Disposal around the world.

THE THREE R'S

REDUCE: Conserving resources and environment by reducing the quantity of waste that is produced. Reducing the waste generation is the most desirable waste management method as it does away with the need to handle, transport, recycle, or disposal of waste in the first place.

REUSE: Reconditioning unwanted manufactured products. Mostly carried out by scavengers in developing countries. It basically means using a product more than once, either for the same purpose or for a different one. For example, using durable coffee mugs, towels, napkins, refilling bottles etc.

RECYCLE: Recovering and reusing materials by various treatments. Mostly paper and tins. It includes recycling of organic wastes to make new or similar products but excludes recovery of energy from waste materials

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