Introduction

Fossil Fuels are some of the most important energy sources in our world today. They are responsible for everything from heating our houses to fueling our automobiles. Coal, Oil or Petroleum, and Natural Gas are considered the three, basic fossil fuels. They are created by the fossilization of plants and animals. These decay, and revert into their most basic forms. Carbon in it's pure form is coal, and petroleum and natural gas are hydrocarbons (molecules formed primarily from hydrogen and carbon atoms) formed during the decaying process. The only difference between natural gas and petroleum is their relative sizes. Since the natural gasses tend to be much smaller molecules, they are lighter, and exist in a gaseous state at room temperature, whereas petroleum molecules are heavier, and are liquid at room temperature. The premise behind the use of fossil fuels for energy conversion is the idea of combustion, more commonly called burning.  Combustion is the chemical process where molecules containing carbon are exposed to oxygen and heat, which creates a chain reaction, producing more heat to continue fueling the reaction.  The reaction will only cease when either the supply of oxygen or the supply of carbon runs out.  A simple, common example of this is the burning of methane, natural gas.  The process is shown below:

In this example, 4 molecules of methane and 7 molecules of oxygen react with heat to form 4 molecules of carbon dioxide and 6 molecules of water.  Carbon dioxide and water are often the result of combustion reactions.  This reaction is called exothermic, because it creates a large amount of heat, most commonly manifested in a flame.

Around 400,000 years ago in China, prehistoric man made one of the most important discoveries -- how to control fire.  The could then use fire to heat their homes, and also as a weapon.  This was the earliest use of combustion, the burning of wood to create heat for personal warmth.  For many, many centuries, this was the major source of heat and light. Eventually, people learned that burning fossil fuels was more efficient than wood, so they used oil to fuel their lamps, and coal to feed their fires. As technology advanced, so did the science of fossil fuels. Scientists had to find new and more efficient ways to produce power and later to produce electricity. The following sections discuss different fossil fuels used in this process.

Coal

Coal is a widely used fossil fuel, who is losing much of its market to petroleum and natrual gas. In order for coal to be formed, many geologic steps must occur. The first stage is the creation of peat from the decomposition of different organisms. Peat is not an acceptable fossil fuel because it can absorb large quantities of water. In order for peat to become more dense, a protective layer of sediment must form over top of the peat. This protective layer serves to shield the peat, and also to press the moisture from it. Depending upon the length of time, different types of coal can be formed. The three classifications, ranked from lowest to highest quality, are lignite, bituminous, and anthracite. The higher the quality, the larger percentage of carbon it contains. With fewer other components, the coal burns cleaner and more efficiently.

In order to obtain coal for the purpose of energy conversion, it must first be mined. The coal we use today was originally formed between 100 and 300 million years ago, depending upon the quality. Huge deposits all over the world are mined, and the coal is shipped internationally. The first recorded coal mining occurred in China, in the twelfth century. Since then, the methods of mining coal have changed drastically. In the eighteenth century, most mining was done with picks, shovels, and wheelbarrows. Then, in the nineteenth century, with the advent of the mine cars, coal mining became much easier. Modern methods often include heavy machinery and explosives to more efficiently extract the coal. Not all mining is done underground, however. Today, nearly sixty percent of all coal mining is done on the surface, called strip mining.

In order to use coal to produce electricity for modern uses, it is usually used as fuel for a steam engine. Basically, the coal is burned, producing heat. This heat is used to boil water, producing steam. This steam then turns a turbine, which is connected to a generator, which produces electricity.

The efficiency of using coal as an energy source depends entirely upon the efficiency of the steam engine. Efficiency ratings of modern facilities range from seventy to ninety percent efficient. Most critics of coal as an energy source object to the environmental ramifications of the smoke created from the combustion. These effects can vary, depending upon the quality of coal used. All current day facilities require certain environmental standards to be met. All exhaust is filtered to remove anything harmful to the environment.

Petroleum

The petroleum industry is another very important business in the world today. Everything from the gas that fuels our automobiles to the plastic fork we use to eat with at lunch starts as a hydrocarbon called petroleum. Geologists agree that petroleum is created by the decay of small aquatic organisms in oceanic rocks billions of years ago. The decay is accelerated by the heat of the earth and small bacteria. The process by which petroleum pools together is still not fully understood. Scientists believe it travels through a porous rock, where it is trapped in a rock chamber. Once the petroleum is collected in these pools, they only await discovery. Once found, the oil can be pumped out, purified, and used commercially.

Scientists have developed many ways to determine the presence of petroleum pools, such as seismic testing. Seismic testing involves sending sound waves into the earth, and measuring their deflections. This procedure can give very detailed information about a prospective oil pool. Newer technologies, such as the use of lasers and satellites will improve this accuracy in the foreseeable future. No matter how much technology we have, we still need to drill to verify the existence of a significant amount of commercial grade petroleum.

Drilling technology has greatly improved in recent years. Since many of the petroleum deposits are as deep as 1500 meters in the ocean, special techniques have been devised. New oil rigs are capable of drilling 1800 meters deep from the surface of the water. The drills are special created to drill straight down, expelling the rocks through the opening. It creates a pressure differential which keeps the oil from seeping out, and the water from seeping in. It also has special tubes to transport the petroleum through the drill bit, up through a tube to the oil rig. Often times, extensive drilling is required to determine the exact size and boundaries of the oil deposit. Once all this information is gathered, commercial extraction can begin.

Once all the oil has been gathered onto the oil rig, it needs to be separated. Many times, deposits not only contain oil, but also natural gasses. The different types of petroleum all need to be separated. For information on the basic hydrocarbons, see the table below:

*State at Room Temperature, and 1 atmosphere of pressure

Once the oil is collected, it needs to be transported. This is first accomplished by the oil rig, if the drilling was offshore, but then it is often transported across land in an oil pipeline. There are many such pipelines in the world, such as the Alaskan Pipeline, which transports oil from Alaska, to the mainland United States. This 800 mile trans-Alaskan oil pipeline began operation in 1977, and it connects the Prudhoe Bay fields on the northern coast of Alaska to Valdez on Prince William Sound. In addition to using pipelines, smaller shipments can be accomplished using oil tankers, trucks, and railroad cars.

Although most oil rigs will separate gas from liquid, the different types of liquid need to be separated. To do this, the crude oil is transported to a refinery. Oil refineries use very tall distillation towers to accomplish this. The crude oil is pumped into the tower, and the temperature is increased. As the temperature increases, the lightest liquid, usually butane, will vaporize. As the vapor raises higher into the tower, it cools, and condenses on the walls of the tower, where it is collected. The temperature is then raised again, and the process is repeated to collect the next lightest hydrocarbon. Some more advanced refineries can actually break down heavy molecules into smaller, more valuable ones.

The chief products from such refineries are gasoline, kerosene, jet fuels, heating fuels, and diesel fuels.

The major use of petroleum in our society is as a fuel for automobiles. Automobile fuel is generally created from a mixture of heptane, octane, and nonane, depending on where in the world you live. The closer to the equator you live, the more nonane, and the further away, the more heptane. The reason for this is to maintain a constant viscosity. Gasoline tends to be more viscous in the colder climates, so a lighter mixture is used.

The major energy conversion process for petroleum is used by a car's internal combustion engine. The force created by the combustion of the gasoline is used to drive the piston. The fuel intake line on the engine is regulated by a valve. The valve opens, allowing fuel to flow into the chamber. The valve then closes, the spark plug ignites the fuel, forcing the piston down, and the exhaust valve opens so the exhaust can escape. The exhaust valve closes, and the procedure then repeats itself. The piston, constantly moving up and down, turns an axle, which propels the car. Many automobiles have between four and eight of these chambers, called cylinders, which propel the car.

Critics of petroleum based energy conversion claim the process releases harmful pollutants into the atmosphere. Most harmful exhaust pollutants are filtered by the automobile's catalytic converter; however, some harmful pollutants escape into the atmosphere as a result of internal combustion engines. Many environmentalist believe these chemicals are depleting the ozone layer, so some scientists are urging for alternative fuels, such as gasohol.

Natural Gas

Natural gas is made up primarily of methane. It is commonly made up of 90% Methane, 6% ethane, and 4% other gasses. Its main advantage over coal and petroleum is that it burns cleanly -- there are no pollutants formed during combustion.

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