Question
Explain and write about the classification of solid waste and management of waste disposal.
✓
Answer
There are several different ways of classifying solid waste. However, one way is based on whether the waste is biodegradable or not.
Biodegradable solid wastes are those that can be broken down (decomposed) into their constituent elements by bacteria and other micro-organisms. Food waste, manures and waste from producing crops are the main biodegradable wastes. Besides methane, the decomposition may also produce offensive and irritating smells.Waste that decomposes in the presence of an adequate air supply (aerobically) under controlled conditions can produce compost, which can be used to improve the quality of soils.
Non-biodegradable solid wastes are those that are not decomposed by microbial action. These wastes include plastic containers, scrap metal, food and drink cans and plastic bags. Materials in solid wastes can also be classified as combustible or non-combustible, depending on whether they will burn or not.
Depending on the inherent dangers associated with its physical and chemical properties, solid waste can be classified as either hazardous or non-hazardous. Hazardous wastespose substantial or potential threats to public health or the environment. For example, toxic, infectious and corrosive (acidic or alkaline) substances are all likely to be classed as hazardous. Non-hazardous wastes are those that do not possess hazardous characteristics, although they can still be harmful to people or the environment.
Management of Solid Wastes :
1. Dumping : This is the most popular solid waste disposal method used today. Garbage is basically spread out in thin layers, compressed and covered with soil or plastic foam. Modern landfills are designed in such a way that the bottom of the landfill is covered with an impervious liner, which is usually made of several layers of thick plastic and sand. This liner protects the groundwater from being contaminated because of leaching or percolation. When the landfill is full, it is covered with layers of sand, clay, topsoil and gravel to prevent sewage of water.
2. Incineration : This method involves the burning of solid wastes at high temperatures until the wastes are turned into ashes. Incinerators are made in such a way that they do not give off extreme amounts of heat when
burning solid wastes.
Incinerators that recycle heat energy through furnace and boiler are called waste-to-energy plants. These waste-to-energy systems are more expensive to set up and operate compared to plain incinerators because they require special equipment and controls, highly skilled technical personnel, and auxiliary fuel systems.
This method of solid waste management can be done by individuals, municipalities and even institutions. The good thing about this method is the fact that it reduces the volume of waste up to 20% or 30% of the original volume.
3. Recovery and Recycling : Recycling or recovery of resources is the process of taking useful but discarded items for the next use. Plastic bags, tins, glass and containers are often recycled automatically since, in many situations, they are likely to be scarce commodities. Traditionally, these items are processed and cleaned before they are recycled. The process aims at reducing energy loss, consumption of new material and reduction of landfills. The most developed countries follow a strong
tradition of recycling to lower volumes of waste.
4. Composting : Due to a lack of adequate space for landfills, biodegradable yard waste is allowed to decompose in a medium designed for the purpose. Only biodegradable waste materials are used in composting.
It is a biological process in which micro-organisms, specifically fungi and bacteria, convert degradable organic waste into substances like humus. This finished product, which looks like soil, is high in carbon and nitrogen. Good quality environmentally friendly manure is formed from the compost that is an excellent medium for growing plants and can be used for agricultural purposes.
5. Pyrolysis : This is a method of solid waste management whereby solid wastes are chemically decomposed by heat without the presence of oxygen. It usually occurs under pressure and at temperatures of up to $430^{\circ} \mathrm{C}$. The solid wastes are changed into gasses, solid residue of carbon and ash and small quantities of liquid.
Biodegradable solid wastes are those that can be broken down (decomposed) into their constituent elements by bacteria and other micro-organisms. Food waste, manures and waste from producing crops are the main biodegradable wastes. Besides methane, the decomposition may also produce offensive and irritating smells.Waste that decomposes in the presence of an adequate air supply (aerobically) under controlled conditions can produce compost, which can be used to improve the quality of soils.
Non-biodegradable solid wastes are those that are not decomposed by microbial action. These wastes include plastic containers, scrap metal, food and drink cans and plastic bags. Materials in solid wastes can also be classified as combustible or non-combustible, depending on whether they will burn or not.
Depending on the inherent dangers associated with its physical and chemical properties, solid waste can be classified as either hazardous or non-hazardous. Hazardous wastespose substantial or potential threats to public health or the environment. For example, toxic, infectious and corrosive (acidic or alkaline) substances are all likely to be classed as hazardous. Non-hazardous wastes are those that do not possess hazardous characteristics, although they can still be harmful to people or the environment.
Management of Solid Wastes :
1. Dumping : This is the most popular solid waste disposal method used today. Garbage is basically spread out in thin layers, compressed and covered with soil or plastic foam. Modern landfills are designed in such a way that the bottom of the landfill is covered with an impervious liner, which is usually made of several layers of thick plastic and sand. This liner protects the groundwater from being contaminated because of leaching or percolation. When the landfill is full, it is covered with layers of sand, clay, topsoil and gravel to prevent sewage of water.
2. Incineration : This method involves the burning of solid wastes at high temperatures until the wastes are turned into ashes. Incinerators are made in such a way that they do not give off extreme amounts of heat when
burning solid wastes.
Incinerators that recycle heat energy through furnace and boiler are called waste-to-energy plants. These waste-to-energy systems are more expensive to set up and operate compared to plain incinerators because they require special equipment and controls, highly skilled technical personnel, and auxiliary fuel systems.
This method of solid waste management can be done by individuals, municipalities and even institutions. The good thing about this method is the fact that it reduces the volume of waste up to 20% or 30% of the original volume.
3. Recovery and Recycling : Recycling or recovery of resources is the process of taking useful but discarded items for the next use. Plastic bags, tins, glass and containers are often recycled automatically since, in many situations, they are likely to be scarce commodities. Traditionally, these items are processed and cleaned before they are recycled. The process aims at reducing energy loss, consumption of new material and reduction of landfills. The most developed countries follow a strong
tradition of recycling to lower volumes of waste.
4. Composting : Due to a lack of adequate space for landfills, biodegradable yard waste is allowed to decompose in a medium designed for the purpose. Only biodegradable waste materials are used in composting.
It is a biological process in which micro-organisms, specifically fungi and bacteria, convert degradable organic waste into substances like humus. This finished product, which looks like soil, is high in carbon and nitrogen. Good quality environmentally friendly manure is formed from the compost that is an excellent medium for growing plants and can be used for agricultural purposes.
5. Pyrolysis : This is a method of solid waste management whereby solid wastes are chemically decomposed by heat without the presence of oxygen. It usually occurs under pressure and at temperatures of up to $430^{\circ} \mathrm{C}$. The solid wastes are changed into gasses, solid residue of carbon and ash and small quantities of liquid.
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