Fossil Energy Study Guide:
300 million years ago
Before the dinosaurs, many giant
plants died in swamps.
WHAT IS COAL?
Coal looks like a shiny black rock.
Coal has lots of energy in it.
When it is burned, coal makes heat and light energy. e cave men
used coal for heating, and later for cooking.
Burning coal was easier
have to be collected as often.
because coal burned longer than wood and, therefore, did not
People began using coal in the 1800s to
heat their homes. T
rains and ships used coal
for fuel. Factories used coal to make iron
and steel. Today, we burn coal mainly to
make electricity.
COAL IS A FOSSIL FUEL
Coal was formed millions of years ago,
before the dinosaurs. Back then, much of the
earth was covered by huge swamps. ey were lled with giant ferns and
plants. As the plants died, they sank to the bottom of the swamps.
Over the years, thick layers of plants were covered by dirt and
water. ey were packed down by the weight. After a long time, the
heat and pressure changed the plants into coal. Coal is called a fossil
fuel because it was made from plants that were once alive! Since
coal comes from plants, and plants get their energy from the sun, the
energy in coal also came from the sun.
e coal we use today took millions of years to form. We can’t make
more in a short time. at is why coal is called nonrenewable.
100 million years ago
Dirt
Dead Plants
Water
Over millions of years, the plants were
buried under water and dirt.
Rocks and Dirt
Coal
Today
Heat and pressure turned the
dead plants into coal.
Fossil Energy Study Guide: Coal
COAL IS OUR MOST ABUNDANT FUEL
e United States has more coal reserves than any other country in
the world. In fact, one-fourth of all the known coal in the world is in the
United States. e United States has more coal that can be mined than
the rest of the world has oil that can be pumped from the ground. We
have enough to last more than 250 years!
Currently, coal is mined in 25 of the 50 states.
Coal is used primarily in the United States to generate electricity.
In fact, it is burned in power plants to produce more than half of the
electricity we use. 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!
Coal is not only our most abundant fossil fuel, it is also the one with
perhaps the longest history.
key
Fossil Energy Study Guide: Coal
A BRIEF HISTORY OF COAL
Coal is the most plentiful fuel in the fossil family and it has the
longest and, perhaps, the most varied history.
Coal has been used for
heating since the cave man. Archeologists have also found evidence that
the Romans in England used it in the second and third centuries (100-
200 AD).
In the 1700s, the English found that coal could produce a fuel that
burned cleaner and hotter than wood charcoal.
During the 1300s in North America, the Hopi Indians 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.
e Industrial Revolution played a major role in expanding the
use of coal.
A man named
James Watt invented the steam engine which
made it possible for machines to do work previously done by humans
and animals. Mr. Watt used coal to make the steam to run his engine.
During the rst half of the 1800s, the Industrial Revolution spread
to the United States. Steamships and steam-powered railroads were
main 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, and is not the same as Coca-
Cola!) replaced charcoal as the primary fuel for iron blast furnaces to
make steel.
e 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 rst
used to generate electricity for homes and factories. By 1961, coal had
become the major fuel used to generate electricity in the United States.
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.
Today we use a lot of coal, primarily because we have a lot of it and
we know where it is in the United States.
Fossil Energy Study Guide: Coal
COAL MINING
AND TRANSPORTATION
Most coal is buried under the ground. If coal is near the surface,
miners dig it up with huge machines. First, they scrape o the dirt and
rock, then dig out the coal. is is called surface mining.
After the coal is mined, they put back the dirt and rock. ey
plant trees and grass. e land can then be used again. is is called
reclamation.
If the coal is deep in the ground, tunnels called mine shafts are dug
down to the coal. Machines dig the coal and carry it to the surface.
Some mine shafts are 1,000 feet deep. is is called deep mining, or
underground mining.
We Dig for Coal
In the mine, coal is loaded in small coal cars or on conveyor belts
which carry it outside the mine to where the larger chunks of coal are
loaded into trucks that take it to be crushed (smaller pieces of coal are
easier to transport, clean, and burn).
e crushed coal can then be sent by truck, ship, railroad, or barge.
You may be surprised to know that coal can also be shipped by pipeline.
Crushed coal can be mixed with oil or water (the mixture is called a
slurry) and sent by pipeline to an industrial user.
5.
e spinning turbine is used to power a generator, a
machine that turns mechanical energy into
electric energy.
is happens when
magnets inside a copper coil in the
generator spin.
7.
e water returns to the boiler,
and the
cycle begins again.
Fossil Energy Study Guide: Coal
CONVERTING COAL INTO ELECTRICIT
Y
Nine out of every 10 tons of coal mined in the United States today
are used to make electricity, and nearly half of the electricity used in this
country is coal-generated electricity.
Electricity from coal is the electric power made from the energy
stored in coal. Carbon, made from ancient plant material, gives coal
most of its energy. is energy is released when coal is burned.
We use coal-generated electricity for:
heating,
cooling,
e process of converting coal into electricity has multiple steps
and is similar to the process used to convert oil and natural gas into
electricity:
1. A machine called a pulverizer grinds the coal into a ne
powder.
2. e coal powder mixes with hot air, which helps the coal burn
more eciently, and the mixture moves to the furnace.
3. e burning coal heats water in a boiler, creating steam.
4. Steam from the boiler spins the blades of an engine called a
turbine, transforming heat energy from burning coal into
mechanical energy that spins the turbine engine.
6.
cooking ,
lighting ,
transpor tation,
communic ation,
farming ,
industry ,
healthcare ,
and much more!
Turning Coal into
Electricity
The steps for converting coal into electricity
are shown here, and described above. An actual
photo of a turbine is shown in the circle.
Turbines have fan-like blades attached to a shaft
that spin to generate power. Practically every
form of electric power is generated by a turbine.
Even the Space Shuttle uses a gas turbine!
A condenser cools the steam moving
through the turbine.
As the steam is
condensed, it turns back into water.
Transformer changes
the voltage of electricity
HIGH
LOW
Transmission lines
carry electricity
long distances
Electricity-generating plants send
out electricity
Distribution lines
How Electricity
carry electricity
Gets to Your House
to your house
Fossil Energy Study Guide: Coal
DELIVERING ELECTRICITY
Electricity-generating plants send out electricity using a
transformer, which changes the electricity from low voltage to high
voltage. is is an important step, as it gives electricity the jolt it needs
to travel from the power plant to its nal destination. Voltages are often
as high as 500,000 volts at this point.
Electricity ows along transmission lines to substation
transformers. ese transformers reduce the voltage for use in the local
areas to be served.
From the substation transformers, electricity travels along
distribution lines, which can be either above or below the ground, to
cities and towns. Transformers once again reduce the voltage—this time
to about 120 to 140 volts—for safe use inside homes and businesses. e
delivery process is instantaneous. By the time you have ipped a switch
to turn on a light, electr
icity has been delivered.
COAL’S ROLE IN OUR ELECTRICAL SUPPLY
Natural gas and oil are also used to make electricity.
How does coal
compare to these other fossil fuels? In terms of supply, coal has a clear
advantage. e United States has nearly 300 billion tons of recoverable
coal. at is enough to last more than 250 years if we continue to use
coal at the same rate as we use it today.
But what about costs? e mining, transportation, electricity
generation, and pollution-control costs associated with using coal are
increasing, but both natural gas and oil are becoming more expensive to
use as well. is is, in part, because the United States must import much
of its oil supply from other countries.
It has enough coal,
however, to take care of its electricity needs, with enough
left over to export some coal as well.
e cost of using coal should continue to be ev
en
more competitive, compared with the rising cost of other
fuels. In fact, generating electricity from coal is cheaper
than the cost of producing electricity from natural gas.
In the United States, 23 of the 25 electric power plants
with the lowest operating costs use coal. Inexpensive
electricity, such as that generated by coal, means lower
operating costs for businesses and for homeowners. is
advantage can help incr
ease coal’s competitiveness in the
marketplace.
Fossil Energy Study Guide: Coal
CLEANING UP COAL
Coal is our most abundant fossil fuel. e United States has
more coal than the rest of the world has oil. ere is still enough coal
underground in this country to provide energy for the next 250 years or
more.
But coal is not a perfect fuel.
Trapped inside coal are traces of impurities like sulfur and nitrogen.
When coal burns, these impurities are released into the air.
While oating 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. Scientists call it “acid rain.”
ere are also tiny specks of minerals—including common dirt—
mixed in coal. ese tiny particles don’t burn and make up the ash left
behind in a coal combustor. Some of the tiny particles also get caught
up in the swirling combustion gases and, along with water vapor, form
the smoke that comes out of a coal plant’s smokestack. Some of these
particles are so small that 30 of them laid side-by-side would barely
equal the width of a human hair!
Also, coal like all fossil fuels is formed out of carbon.
All living
things—even people—are made up of carbon. (Remember—coal started
out as living plants.) But when coal burns, its carbon combines with
oxygen in the air and forms carbon dioxide. Carbon dioxide is a colorless,
odorless gas, but in the atmosphere, it is one of several gases that can
trap the earth’s heat. Many scientists believe this is causing the earth’s
temperature to rise, and this warming could be altering the earth’s climate.
Sounds like coal is a dirty fuel to burn. Many years ago, it was.
But things have changed. Especially in the last 20 years, scientists have
developed ways to capture the pollutants trapped in coal before they can
escape into the air.
We also have new technologies that cut back on the release of carbon
dioxide by burning coal more e ciently.
Many of these technologies belong to a family of energy systems
called “clean coal technologies.”
HOW DO YOU MAKE COAL CLEANER?
Actually there are several ways.
One way is to clean the coal before it arrives at the power plant. is
is done by simply crushing the coal into small chunks and washing it.
Another way is to use “scrubbers” that remove the sulfur dioxide (a
pollutant) from the smoke of coal-burning power plants.
Fossil Energy Study Guide: Coal
HOW DO SCRUBBER S WORK?
Most scrubbers rely on a very common substance found in nature
called “limestone.” We literally have mountains of limestone throughout
the United States. When crushed and processed, limestone can be made
into a white powder. Limestone can be made to absorb sulfur gases
under the right conditions—much like a sponge absorbs water.
In most scrubbers, limestone (or another similar material called
lime) is mixed with water and sprayed into the coal combustion gases
(called “ ue gases”). e limestone captures the sulfur and “pulls” it out
of the gases. e limestone and sulfur combine with each other to form
either a wet paste (it looks like toothpaste!), or in some newer scrubbers,
a dry powder. In either case, the sulfur is trapped and prevented from
escaping into the air.
THE CLEANEST COAL TECHNOLOGY A REAL GAS!
We can even turn coal into a gas—using lots of heat and water—in
a process called gasi cation. When coal is turned into a gas, we can
burn it and use it to spin a gas turbine to generate electricity. e 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. But why go to all the trouble to turn the coal into gas if all
you are going to do is burn it?
A big reason is that the pollutants in coal—like sulfur, nitrogen
and carbon dioxide —can be almost entirely cleaned up when coal is
changed into a gas. In fact, scientists have ways to remove 99.9 percent
of the sulfur and small dirt particles from coal gas. Gasifying coal is one
of the best ways to clean pollutants out of coal.
Another reason is that the coal gases don’t have to be burned. ey
can also be used as valuable chemicals. Scientists have developed ways to
turn coal gases into everything from liquid fuels for cars and trucks to
plastic toothbrushes!
Fossil Energy Study Guide: Coal
COAL AND CLIMATE CHANGE
Carbon dioxide (CO
2
) is a colorless, odorless gas that is produced
naturally when humans and animals breathe. e main source of man-
made CO
2
emissions, however, is the burning of fossil fuels (oil, natural
gas and coal) for energy production. Carbon dioxide is important
for plants and animals, but if too much of it is produced, it can build
up in the air and trap heat near the earth’s surface. is is called the
greenhouse e ect.
To clean CO from power plants, scientists have been studying how
2
to capture the CO
2
coming up a power plant’s smokestack before it
gets into the air. e CO can then gathered, transported, and eventually
2
stored deep underground or in the ocian, where it’s supposed to sit for a
long, long time. Scientists are even studying ways to recycle the CO into
2
new materials. e technical name for this process is carbon capture and
storage, or carbon sequestration.
It is expected that coal and other fossil fuels will remain a major
energy source for years to come. Many environmentalists believe that
capturing and storing CO
2
from power plants, combined with other
eorts, could help ght climate change.
Scientists continue to research and develop carbon sequestration
technologies. It is important to make sure these new processes are
environmentally acceptable and safe. For example, scientists must
determine that CO
2
will not escape from under the ground, or
contaminate drinking water supplies. Carbon capture and storage is an
exciting area of research and development for today’s scientists.
CARBON STORAGE
CO
2
