The information on this page was prepared by:
| Joseph Ruhl | jruhl@usc.edu | Computer Engineering and Computer Science |
| TianLi Woon | twoon@usc.edu | Electrical Engineering |
Coal: Environmental Impacts
Environmental Protection Agency (EPA) reported that, as of 1999, emissions of criteria air pollutants (those related to human health) had dropped a full 31% below 1970 levels. This dramatic improvement in air quality is all the more remarkable when you consider that, during the same period, the U.S. population grew by 33%, the U.S. economy grew by 147%, and the use of coal to generate electricity increased by 188%.
http://www.ceednet.org/educ/environment2.htm
Although abundant and cost-effective, coal has some environmental challenges to overcome. Coal has a reputation as a dirty fuel source, one that can pollute the air and damage the landscape.
So that coal might live up to its potential as a significant source of energy, the coal industry is working hard to ensure that the mining and use of coal does not permanently damage land or pollute air. The coal industry restores mined land to its original condition or prepares it for more productive uses, and it has incorporated technological advances to keep the air clean and safe.
LAND RECLAMATION
In the past, coal mining often left behind landscapes that were unattractive and unproductive. Animals and plant life that once thrived in an area could no longer survive in conditions produced by coal mining. Today, thanks to land reclamation, it can be difficult to tell the difference between land that has been mined and land that has not.
Land reclamation is the process of protecting, restoring, or improving land before, during, and after surface mining. This means that the land is preserved, nature is protected, and water and soil are conserved. Ultimately, the land can become productive farmland, be restored to forest, or undergo development as a lake.
First, geologists study rock formations to find possible coal reserves. Test holes are drilled so that samples of coal can be examined for evidence of quality, quantity, and location beneath the surface.
Then, the reclamation plan is made. This involves studying the area’s geology, plants, water, soil, and wildlife. Information is recorded so that potential problems during the mining process can be identified and so that conditions may be restored after the mining has been completed. In addition, the mining site is examined for artifacts from past cultures. If any are found, they are removed and preserved.
Next, the timeline for mining and reclamation is set. The coal mining company works with federal and state government agencies and local officials to ensure that all regulations are being followed.
Once the planning phase has been completed and the required permits obtained, mining may begin. The topsoil, subsoil, earth, and rock are removed and set aside, and the coal that lies just below the surface is mined.
During the mining process, water is tested to ensure that it is not polluted. If water is found to be contaminated, it is treated before it leaves the mine area.
Finally, the area is refilled with the overburden (the earth and rock that were removed) and soils. To the extent possible, the area is restored to its original condition or improved. This often means planting, seeding, and irrigating the land�a process completed over many years.
AIR POLLUTION
When coal is burned, it releases impurities such as sulfur, nitrogen, and fly ash. These can pollute the air or contribute to conditions that can lead to “acid rain,” precipitation that damages forests and pollutes rivers and lakes. Today, though, advances in technology mean that about 99 percent of the chemicals that can pollute the air and more than 95 percent of the chemicals that can cause acid rain are removed.
These technological advances are part of an effort referred to as the Clean Coal Technology (CCT) Program, which began in 1985. Since that time, the federal government has contributed more than $2 billion toward this program to make the burning of coal cleaner and safer. The coal industry has contributed more than $4 billion toward this goal.
There are several ways coal can be made cleaner. Coal can be crushed and washed before it is burned. The washing process often goes a long way in removing harmful sulfur, but it does not remove all of the sulfur.
While the coal burns, special combustion processes can remove more sulfur and nitrogen. Devices called flue gas desulfurization systems, or “scrubbers,” remove more than 90 percent of the sulfur dioxide emissions from the burning process. The flue gas is sprayed with a mixture of water and lime or limestone, which reacts with the sulfur dioxide to form a wet sludge or, in some cases, a dry powder that can be disposed of or made into pellets for roadbeds or into plasterboard or concrete blocks.
Another method for tackling air pollution involves using devices called electrostatic precipitators, which give coal dust particles an electric charge so they can be attracted to a collector plate.
Other methods of removing pollutants involve the way the coal is actually burned. This includes Fluidized Bed Combustion and Gasification as mentioned under the power plants topic.
http://www.teachcoal.org/aboutcoal/articles/coalenv.html