Solid wastes may be defined as garbage from home resulting from commercial and industrial activities and waste substances created by agriculture, mining and water purification plants.
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The waste products are classified on the basis of their nature and moisture content and how much thermal energy is obtained from them as follows:-
Classification
Garbage:
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It includes kitchen waste and vegetables, fruits and. meat waste. It contains 70 percent moisture and products heat as an amount of 6 x 106 joule 1kg.
Rubbish:
It includes lime and mortar of broken buildings and some household un-useful materials such as paper, wood, rubber, and glass, ceramic and different kinds of metals. It contains 25 per cent moisture and produces heat at an amount of 15 x 155 joule/kg.
Pathological wastes:
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It includes the used gauge, bandage of hospital and nursing room used materialism surgery, excess stools, urine, bloods is pathological laboratory etc. It contains 85 percent moisture and produces heat at an amount of 25 x 10° joule/kg.
Agricultural wastes:
It includes plant waste products such as paddy husks, straw baggage wood dust, jute sticks, etc. and animal waste products such as urine, conducing, bones etc. This waste product when used in the soil, increase the fertility of the soil and help in the growth of the plant.
Industrial wastes:
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It includes flyash of thermal power own it, different chemical substances, sludge of steel industry metals of are extraction industry, paints etc.
Mining wastes:
It includes the difficult waste products produced at the time of lifting coal from colliery.
Radioactive waste:
It includes the different liquid and gaseous products produced in the different stages of the cycle of atomic fuel. It is most dangerous products and it creates different problems in the environment.
Packing wastes:
The amount of packing wastes e.g., polythene bag, paper, cardboards, gory bags etc. are increasing more now-a-days and these creates problem in the locality.
Uses of Solid Wastes:
A solid waste causes the environmental pollution. But different beneficial materials are possible to produce from it by a least effort as follows:
Production of energy:
Energy can be produced by burning of straw of paddy and wheat, baggage, wood and other fuel and it can be used in different activities.
Production of fuel:
Solid waste under goes thermal decomposition by the consumption of it in the method of paralysis i.e. combustion without oxygen and produces gaseous matter, water insoluble oil, methanol and other matters. The solid portion of waste remains as residence which can be used as fuel. This method has some advantages as follows.
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The fuel obtained by this way produces less smoke on burning.
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The fuel obtained by this way produces more heat.
Production of fuel gas:
The combustible gas is possible to produce by burning the solid waste with the help of gas fear machine. This method has some advantages as follows:
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Disposal of solid wastes is advantageous.
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The gas produced from solid wastes is same in nature and for this it can be used as fuel.
Besides this combustible gas, methane CH4 can be produced by bio-chemical method with the bacteria. The combustible gas is possible to produce by two bio-chemical technologies as follows:
Landfall gas Project:
The municipal soil wastes are deposited in a place away from the town by collecting them from different places. The bacteria decomposes the organic matter and different gases such as methane, carbon dioxide, small amount hydrogen sulphide, ammonia etc. are produced and remains fixed in the soil. The landfill gas is collected by pouring pipe into the soil. This gas can be used for different functions is cooking, lighting etc.
Biogas project (Gorbar gas project):
Gobar gas plant is a system comprising of a gas holder and a digestion chamber, in which, ‘Gober cowdung can be treated aerobically to produce to important and useful items, namely,
Fuel gas and organic manure. India was the finest country in the world to have developed a biogas plant on an experimental basis as early as 1939 followed by the installation of a commercial model in 1954. Later the Khadi and Village Industries Commission (KVIC) adopted the biogas programme in 1962 and were instrumental for initiating biogas plants in India.