Coal

On this page:

What is coal?
How is coal formed?
History of usage of coal.
How is coal extracted?
How do we use coal and why?
What are coal reserves?
Why should we be conservative in our use of coal?
What can be done to improve the way we use coal?
Conclusion
Sources

What is coal?

Coal

Coal is a hard, black colored, rock-like substance. It is made up of carbon, hydrogen, oxygen, nitrogen and varying amounts of sulfur. There are three main types of coal – anthracite, bituminous and lignite. Anthracite coal is the hardest and has more carbon, which gives it higher energy content. Lignite is the softest and is low in carbon but high in hydrogen and oxygen content. Bituminous is in between. Today, the precursor to coal—peat—is still found in many countries and is also used as an energy source.

How is coal formed?

Coal, oil and gas are called “fossil fuels” because it’s generally accepted that they formed from the organic remains of prehistoric plants and animals and by exposure to heat and pressure in the Earth’s crust over millions of years. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years.

The main deposits of fossil fuels are from the Carboniferous Period which occurred from about 360 to 286 million years ago. It was part of the Paleozoic Era. “Carboniferous” gets its name from carbon, the basic element in coal and other fossil fuels.

The huge trees, ferns and other large leafy plants which covered the land at that time are at the origin of today’s coal deposits. As they died and sank to the bottom of the swamps they formed layers of a spongy material called peat. Over many hundreds of years, the peat was covered by sand and clay and other minerals, which turned into a type of rock called sedimentary.

More and more rock piled on top of more rock, and it weighed more and more. It began to press down on the peat. The peat was squeezed and squeezed until the water came out of it and it eventually, over millions of years, it turned into coal.

History of usage of coal:

Smith using coal to heat metal

The use of coal as a fuel predates recorded history. Coal has been used for heating since the cave man. The earliest known use of coal was in China. Coal from the Fu-shun mine in northeastern China may have been used to smelt copper as early as 3,000 years ago. The Chinese thought coal was a stone that could burn.

Coal was used to run furnaces for the melting of metal ore.

Archeologists have also found evidence that the Romans in England used it in the second and third centuries (100-200 AD). In North American, the Hopi Indians during the 1300s in what is now the U.S. Southwest used coal for cooking, heating and to bake the pottery they made from clay. Coal was later rediscovered in the United States by explorers in 1673. However, commercial coal mines did not start operation until the 1740s in Virginia.

In the 1700s, the English found that coal could produce a fuel that burned cleaner and hotter than wood charcoal. Later on a man named James Watt invented the steam engine which made it possible for machines to do work previously done by humans and animals. The widescale use of fossil fuels, coal at first and petroleum later, to fire these steam engines enabled the Industrial revolution. During the first half of the 1800s, the Industrial Revolution spread to the United States. Steamships and steam-powered railroads were becoming the chief forms of transportation, and they used coal to fuel their boilers. In the second half of the 1800s, more uses for coal were found. During the Civil War, weapons factories were beginning to use coal. By 1875, coke (which is made from coal) replaced charcoal as the primary fuel for iron blast furnaces to make steel. The burning of coal to generate electricity is a relative newcomer in the long history of this fossil fuel. It was in the 1880s when coal was first used to generate electricity for homes and factories. Long after homes were being lighted by electricity produced by coal, many of them continued to have furnaces for heating and some had stoves for cooking that were fueled by coal.

How is coal extracted?

Coal is found in many of the lower 48 states of U.S. and throughout the rest of the world. Coal is mined out of the ground using various methods. Some coal mines are dug by sinking vertical or horizontal shafts deep under ground, and coal miners travel by elevators or trains deep under ground to dig the coal. Other coal is mined in strip mines where huge steam shovels strip away the top layers above the coal. The layers are then restored after the coal is taken away.

The coal is then shipped by train and boats and even in pipelines. In pipelines, the coal is ground up and mixed with water to make what’s called a slurry. This is then pumped many miles through pipelines. At the other end, the coal is used to fuel power plants and other factories.

How do we use coal and why?

Burning coal is a fairly cheap way to produce significant amounts of energy.

Burn coal to create energy

The United States has more coal reserves than any other single country in the world. In fact, just over 1/4 of all the known coal in the world is in the United States. The United States has more coal that can be mined than the rest of the world has oil that can be pumped from the ground. China and many other countries also have huge coal reserves. Calculations show that there’s enough coal in the world to provide energy for at least one hundred years and probably more. Today (Jan, 2012) coal provides around 31% of global energy. However this percentage changes all the time, so if you want an exact number please check current percentages. In the United States more than half of the electricity we use is generated by burning coal. A stove uses about half a ton of coal a year. A water heater uses about two tons of coal a year. And a refrigerator, that’s another half-ton a year. Even though you may never see coal, you use several tons of it every year!

What are coal reserves?

Coal reserves are years of production left in the ground with the current proved reserves. At present this is estimated at 148 years in the worst case scenarios, and up to 417 years with the most optimistic proved reserve estimates.

The calculation above assumes that coal will continue to be consumed at our actual rate. In reality, consumption of coal has been increasing. This suggests that coal will be used up more quickly.

The calculation also assumes that coal could be produced at a constant level for that number of years and that all of the proved reserves could be recovered.

In reality, the production curve is much more akin to a bell curve. At some point in time, the production of each resource within an area, country, or globally will reach a maximum value, after which, the production will decline until it reaches a point where is no longer economically feasible or physically possible to produce.

Therefore it is quite likely the lower estimates are nearer the truth. As coal and other fossil fuel supplies diminish, prices will rise. Therefore it may then become economically feasible to exploit hitherto unexploited reserves. It is also likely that renewable energy supplies will then become more in demand as they may turn out to be cheaper than the exploitation of fossil fuels reserves. Alternative sources of energy include nuclear, hydroelectric, solar, wind and geothermal.

Why should we be conservative in our use of coal?

Mining coal can be difficult and dangerous.

Strip mining destroys large areas of the landscape.

coal-mining-strip-mining

Coal fired power stations need huge amounts of fuel, which means train-loads of coal almost constantly. In order to cope with changing demands for power, the station needs reserves. This means covering a large area of countryside next to the power station with piles of coal.

Trapped inside coal are traces of impurities like sulfur and nitrogen. When coal burns, these impurities are released into the air. While floating in the air, these substances can combine with water vapor (for example, in clouds) and form droplets that fall to earth as weak forms of sulfuric and nitric acid. This is called “acid rain.”

Burning coal also generates large amounts of bottom ash and fly ash. Fortunately these materials are used in a wide variety of applications. For example, about 43% of U.S. produced fly ash is recycled and used among others, as a supplement in concrete production. Bottom ash may be used as an aggregate in road construction and concrete.

Burning coal produces more carbon dioxide than burning oil or gas. Carbon dioxide is a colorless, odorless gas, but in the atmosphere, it is one of several gases that can trap the earth’s heat. It is therefore called a greenhouse gas. Many scientists believe this is causing the earth’s temperature to rise, and this warming could be altering the earth’s climate.

What can be done to improve the way we use coal?

In the last 20 years, scientists have developed ways to capture the pollutants trapped in coal before the impurities can escape into the atmosphere. Today, we have technology that can filter out 99 percent of fly ash and remove more than 95 percent of the acid rain pollutants in coal. We also have new technologies that cut back on the release of carbon dioxide by burning coal more efficiently. Because less fuel is used to produce the same amount of power, the amount of carbon dioxide released from coal-burning power plants using these new technologies is reduced.

One of the most promising new techniques involves turning coal into gas. When you think of coal as a mass of atoms it is easy to understand how this works. Most of the atoms are carbon. A few are hydrogen. And there are some others, like sulfur and nitrogen, mixed in. Heat coal hot enough inside a big metal vessel, blast it with steam, and it breaks apart. The carbon atoms join with oxygen that is in the air (or pure oxygen can be injected into the vessel). The hydrogen atoms join with each other. The result is a mixture of carbon monoxide and hydrogen – a gas. You can then burn the hydrogen and use the hot combustion gases to spin a gas turbine to generate electricity. The exhaust gases coming out of the gas turbine are hot enough to boil water to make steam that can spin another type of turbine to generate even more electricity. This way you use the same source of energy twice. This way it is possible to generate 50% more electricity with the same amount of coal! Thus reducing the amount of Carbon Dioxide released into the air.

clean-coal-burning-plantA major reason to use this technique is that the impurities in coal – like sulfur, nitrogen and many other trace elements – can be almost entirely filtered out when coal is changed into a gas (a process called gasification). In fact, scientists have ways to remove 99.9% of the sulfur and small dirt particles from the coal gas. Gasifying coal is one of the best ways to clean pollutants out of coal.

Another reason is that carbon monoxide and hydrogen – the gases formed from coal – don’t have to be burned. They can also be used as valuable chemicals. Scientists have developed chemical reactions that turn carbon monoxide and hydrogen into everything from liquid fuels for cars and trucks to plastic toothbrushes! For more information on “Clean coal technology” please click here.

There are many ways to encourage the use and development of technologies of the kind discussed above. Environmental regulations use a variety of approaches to limit pollution, such as command-and-control (which mandates the amount of pollution or the technology used), economic incentives, or voluntary programs. It will be necessary to implement a lot of regulations worldwide, in order to reduce the amount of carbon dioxide we release into the atmosphere .

In economic terms, pollution from fossil fuels is costing quite a lot of money and may become much more expensive in the future. Up until now governments and therefore, taxpayers, have been footing the bill. Taxation is considered one way to make the producer of pollution pay for its negative effects rather than citizens. This would be a way to ‘internalize’ the cost of pollution. There are several advantages to this approach. Fossil fuels would become more expensive, thereby reducing their use and the amount of pollution associated with them, along with raising the funds necessary to counteract these factors.

Conclusion:

Fossil fuels are non-renewable resources because they take millions of years to form, and reserves are being depleted much faster than new ones are being made. Although there seems to be enough coal to last for at least a hundred years and probably more we should remember that our energy needs increase constantly. A global movement toward the generation of renewable energy is therefore under way to help meet increased energy needs. If we manage to use remaining fossil fuels in a much cleaner way, while supplying increased energy needs from renewable energy sources, we may be ready to entirely switch to renewable energy sources by the time fossil fuels run out. It is therefore important to develop both techniques side by side. Cleaning up the way we use fossil fuels while supplementing our energy needs with renewable energy will also reduce the amount of Carbon Dioxide released into the air. This in turn will have a significant positive effect on our efforts to stop global warming.  

Sources:
http://www.fe.doe.gov/education/energylessons/coal/index.html
http://www.fe.doe.gov/education/energylessons/coal/gen_howformed.html
http://www.fe.doe.gov/education/energylessons/coal/coal_history.html
http://en.wikipedia.org/wiki/Fossil_fuel
http://www.energyquest.ca.gov/story/chapter08.html
http://environment.about.com/od/greenhouseeffect/a/volcano-gas.htm
http://epa.gov/climatechange/science/stateofknowledge.html

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