It is expressed as mass per unit volume (kg/m³). This parameter is required for designing a solid waste management program. A reduction in volume by 75% is achieved through normal compaction equipment, so that an initial density of 100kg/m³ may readily be increased to 400 kg/m³. Significant changes in the density occur as waste moves from sources to disposal site, as A result of scavenging, handling, wetting, and drying by the Weather and vibration during transport. Density is critical in the design of sanitary landfill as well as for storage, collection and transport of wastes. Efficient operation of landfill requires compaction of wastes to optimum density.
Values greater than 40% are also not common. Moisture increases the weight of the solid wastes and therefore the cost of collection and transport increases. Consequently waste should be insulated from rain or other extraneous water source. Moisture content is critical determinant in the economic feasibility of waste treatment by incineration. During incineration energy must be supplied for evaporation of water and raising the temperature of vapour.
Information of chemical characteristics is important in evaluating alternative processing and recovery options. Typically waste is considered as combination of combustible and noncombustible components. If solid waste is to be used as a fuel or for any other use we should know its chemical components.
These are included in the class of fats, oils and grease. The principal sources of lipids in the garbage are cooking oil and fats. Lipids have high heating values about 38,000 Kj/Kg (kilojoules/kilograms), which makes the waste with high lipid content suitable for energy recovery. Since lipids become liquids at temperature slightly above ambient they add to the liquid content during waste decomposition. They are biodegradable, but they have low solubility in water and hence the rate of biodegradation is slow.
These are primarily originated from the food sources rich in starch and celluloses. These readily biodegrade into carbon dioxide, water and methane. Decomposition of carbohydrates attracts the flies and rats and hence should not be left exposed for long duration.
These are the compounds containing carbon, hydrogen, nitrogen and oxygen and organic acid with amino groups. They are primarily found in food and garden wastes, but their partial decomposition result in the production of amines, which impart unpleasant odors.
These are the natural products contain cellulose and lignins that are relatively resistant to biodegradation. These are found in paper products, food and yard wastes. Paper is almost100% cellulose, cotton over 95% and wood products over 40-50%. These are highly combustible products most suitable for incineration. The calorific value of oven dried paper products are in the range 12000-18000 kj/kg.
Synthetic Organic Materials
In the recent years plastics have become a
significant components of solid waste,
accounting for 1-10%. They are highly resistant to the biodegradation;
hence their presence in the waste
is objectionable. Currently much attention is
given to reduce this component at disposal sites. Plastics have a
high heating value, about 32000 kj/kg,
which makes them very suitable for
incineration. However, among the plastics Polyvinyl chloride
(PVC) when burnt produces dioxin and acid gas. The trace
gases produced during the burning
of plastic are proved to be
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