Coal is a leading fossil fuel consumed for fulfilling energy demands across the globe. However, like oil and natural gas, it is also a source of adding obnoxious pollutants to the environment. Since it is richer in carbon content, burning of pulverized coal in electric power plants results in more environmental damage compared to oil and natural gas.
Global Warming due to Coal Combustion
Carbon dioxide emissions are the essential outcome of coal combustion in power plants; it has been indicated that the current level of carbon dioxide emissions in the air are enough to disrupt earth’s carbon dioxide equilibrium. Carbon dioxide has been identified as a heat trapping gas; it retains the infrared radiations returning from earth to sun, thus causing the global temperature to rise.
The global warming resulting from carbon dioxide and other greenhouse gases may have several catastrophic impacts upon the environment. These impacts include melting of polar ice, rise in sea-levels and the consequent flooding of coastal areas. In addition, it may increase erosion of coastal lands subjecting coastal buildings and their residents to increased risks of violent storms.
Acid Deposition Due to Coal Burning
Bituminous coal used in most power plants contains small amounts of sulfur and nitrogen. Combustion of coal in power plants converts them to sulfur and nitrogen oxides respectively. These oxides, upon reaction with water in the atmosphere, result in precipitation of acid, sometimes also called acid rain. Acid rain is often prevalent downwind from coal burning power plants, indicating the connection between acid formation and airborne emissions caused by coal-fired power plants.
Acidification of lakes and streams results in decline of aquatic animal populations. In addition, crop damage, forest degradation, impaired visibility and chemical weathering of monuments are the major results of acid deposition. Furthermore, presence of acidic substances in air entails human health risks such as asthma and bronchitis.
Particulate Matter and Ground-Level Ozone
The coal-fired power plants release solid and liquid particles that remain suspended in the air and appear in the form of smog (combination of smoke and fog). These suspended particulates are dangerous for human health and may cause respiratory illnesses. The airborne nitrogen oxide emissions associated with coal burning cause urban smog which is a respiratory irritant. Moreover, increased ground level ozone due to nitrogen oxides reduces agricultural and commercial forest yields.
Mercury Emissions from Coal Burning
Most coal-fired power plants are major mercury emitters; mercury is present in coal in small traces and is released to the atmosphere during combustion. Although, it is emitted in a non-hazardous elementary form, its accumulation in the environment can be hazardous for humans and wildlife. It is a neurotoxin and if deposited in an aquatic environment in the form of methyl mercury, it can accumulate in invertebrates and fish and may affect their neural tissues.
Controlling Environmental Impacts of Coal Burning
Several solutions have been proposed for reducing the environmental impacts of coal burning in power plants: increasing the efficiency of electric power plants, retrofitting old plants with newer and more efficient technology alternatives, carbon sequestration, switching to low sulfur and nitrogen coals and use of clean coal burning technologies such as fluidized bed combustors and installation of scrubbers in flue gas streams can be effective control measures.