A burnable brownish black or black rock composed of carbon and hydrocarbons. It is a non-renewable source of energy, found in abundance in United States, which forms in millions of years. Coal is formed of those partially decomposed plants that lived million of years ago. Then earth was a marshy jungle, the layer of plants under the marsh was covered with dust and water which catch the energy of the plants. Upper layers exert heat and pressure on these plants and the finally turned into their existing form that is coal.
Since 1978, the amount of coal produced in one hour by one miner is tripled due o latest technology and gadgets. Large machines are used to dig coal mines where two methods (surface mining and ground mining) are used. Surface mining generates about two third of the total coal production as most of the coal reserves in United States occur near the surface.
- Surface mining: It is less expensive than the underground mining. The method is used for those coal beds that are not more than 200 feet below. Large machines are used to set aside the layers of rock and soil to expose the coal reserve. The rocks and dust is placed back when the mining is accomplished. This land can be no more used to plant crops, build houses and resort and for animals.
- Underground mining: This method is used to dig out coal beds that are buried some hundred feet below. Elevators are used to ride miners into the coal mine where they extract coal.
- Lignite: The moisture content of this form is very high. Being young these reserves are least exposed to heat and pressure and thus possess least energy content. Having the carbon content of about 25 to 35 per cent, it is used to produce electricity in power plants.
- Sub Bituminous: It can produce more heat than the Lignite as it contains 35 to 45 per cent carbon. The United Sates sub Bituminous reserves are some 100 million years old.
- Bituminous coal: Its heating value is about two to three times greater than Lignite. It contains carbon about 45 to 86 per cent. Its average age is estimated as 100 to 300 million years in United States’ reserves, and fulfilling half of the US demand of coal.
- Anthracite: Its heating value is slightly less than that of Bituminous where carbon composition id from 86 to 97 per cent.
The coal is then projected into the processing plants on a conveyor belt where sulfur, ash, rock, dirt and other impurities are removed to improve the heating value of the coal. After processing the mined coal is ready to ship for the market – the cost of coal travel is more than the cost of mining itself.
How electricity is produced using Coal
The combustion of coal produces tremendous heat which is used to convert water into the steam. The burning of coal gives away heat, pollutants (like smoke and ash) and green house gas. This steam is used to run the turbines which are attached to the electricity producing generators. The electricity thus created is stored in a power station.
There are four types of coal depending on the amount of carbon constituent and the amount of heat generated. The deposits are ranked on the bases of heat and pressure that a plant has suffered for millions of year.
Coal produces about 50 per cent of the total electricity of the United States. The fossil fuel is burned to produce heat that runs the turbine of the power plant to generate electricity.
Disadvantage of Coal
There are numerous disadvantages of coal. If mining is not properly carried than it can destroy not only the land but also contaminate the water reserves. Nowadays the most important part of mining is to restore the lands that are already damaged by the mining. Moreover, the burning of coal gives off the green house gas, e.g. carbon dioxide which is responsible for global warming. Global warming and global dimming are the most haunting issues in the history of mankind and are still lurking to swallow the signs of life on earth. Other pollutants like nitrogen oxide, sulfur and mercury badly affects the water and wind. Sulfur after coming into contact with oxygen form sulfur dioxide which makes the rain acidic and destroys vegetation. Mercury released into air finally settles in water where it became a part of marine habitants and make them misfit as human and animal food.
Industries are looking forward to low-sulfur coal to least affect the environment. Industries are also looking for ways to reduce the existing amount of pollutants from air and water. Coal is now more effectively cleaned before leaving the processing unit. Scrubbers are used by power plant to extract sulfur from the smoke that is going out of the chimney. Nitrogen oxide can be also exempted from same process. Scientists are now working on ways to reduce the mercury content of coal.
Now doubt we need energy sources to meet our day to day needs of energy but it does not mean that we should consult those resources that can damage the ecological system. Incase we do than we must also focus on inventing ways to cope up with the merging problems of pollution to save the planet from the aftermath of human intervention.
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