Sample essay on the Treatment and Disposal of Solid Bio Degradable Wastes

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Agriculture, industrial or domestic activities of man produce huge quantities of solid wastes. Production of about 50 million tons of rice creates about 17 million tons of paddy husk and 2.8 million tons of rice bran. A cigarette making industry using about 7.8 million kg of tobacco leaves produces about 0.39 million kg of solid wastes.

About 10,000 kg of cotton turned into cloth creates about 800 kg, while tanning and dyeing 1000 hides generate about 1200 kg of solid refuse. The amount of waste solids produced per person per day in Indian cities varies from about 300 to 600 gm. On global scale all this adds upto an enormous quantity, disposal of which is a tough task.

Bio-degradable wastes pose little problems. Much of agricultural wastes is used to feed the live stock population. In India about 410 million tons of manure is produced every year from organic waste produced by bovine population. Large compost pits are dug and organic wastes are dumped in it to stay there for a long time. Pits are covered with a layer of soil. Organic wastes, if dry may be soaked with water which helps in their rapid decomposition.

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The process of degradation under anaerobic conditions changes the physical structure of the waste material. Its mass is drastically reduced. The time required for adequate decomposition depends upon the nature of organic wastes, moisture content, temperature etc. The residual matter is exceedingly rich in mineral nutrients. It is used as manure in agricultural fields.

Problems arise when the mass of organic wastes is enormous. As biodegradation is a slow process, land once used as dumping ground or compost pits is engaged for a long time. Lower temperatures and scanty moisture content delay the process considerably and in very cold climates the decomposition of organic wastes is negligible. In temperate and tropical regions as well, the growing amount of organic wastes is causing concern. More and more land has to be used to accommodate the dumping grounds for solid wastes as human establishments expand. Useful land has to be converted to ugly looking waste-land.

A rather quick method of getting rid of the enormous bulk of solid wastes is to burn it under controlled conditions. The heat produced may be utilized for some useful purpose. Ashes left after burning are dumped in water or disposed of in fields. They represent only about 8-10% of the total mass of waste material thus burnt.

When organic wastes are subjected to high temperatures in absence of oxygen large molecules are broken down into smaller ones. The process is known as pyrolysis. Gases like CO2, CO, CH4, C2 H2, C2H4, black tar like liquid and charcoal is produced. These can be used as fuel. However, heat treatment yields plenty of gaseous pollutants which add to the atmospheric burden of gaseous pollutants. Rising concentration of these gases in the atmosphere shall have far reaching consequences such as global warming, stratospheric ozone depletion etc. Hence the practice of burning organic wastes is not a very sound practice.

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The combustion of organic matter releases, quickly, mineral elements which appear as ashes, These are either dumped on open land or disposed of in streams and rivers. Flowing waters carry the precious mineral nutrients down to the ocean from where little returns to the land. Natural bio- geochemical cycles are cut short. If the period of residence of mineral elements in the bio-sphere is shortened, the soil becomes poorer as it receives little recycled mineral nutrients and has to obtain it from virgin sources.

Quick depletion of nutrients occurs. The practice of burning cow-dung cakes has resulted in wide spread depletion of nitrogen and phosphorus in many Indian fields. The mineral content in the faecal matter produced by catties could have helped to maintain proper soil structure and nutrient status. But instead it is burned to produce heat and ashes which are quickly leached away during rainy seasons. The soil becomes poorer after every rain.

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