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
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 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.
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
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
||Gas Grills, Torches
||Gas & Liquid
*State at Room Temperature, and 1 atmosphere of pressure
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
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.
Commercially, natural gas is often used for heating purposes. It can be used to fuel a
steam turbine as coal, or as a way to sterilize medical equiptment. Domestically, it is
often used to power furnaces, gas stoves, clothes driers, and more. These devices maintain
a small flame, called a pilot light, and then use it to ignite a stream of natural gas to
create a constant, controlled flame.
Many scientists and enviromentalists are encouraging the use of natural gas because it
is not as harmful to the enviroment as coal and petroleum.