ENERGY IN CONTEXT: A FOSSIL FUEL PRIMER - Hydrofracking: What Everyone Needs to Know - page 3

people's homes. But as the nation industrialized, those fuels were largely replaced
by fossil fuels—coal replaced wood, and eventually petroleum eclipsed coal—to
power the steam engines that led to the Industrial Revolution. In the nineteenth
century, animal oils, especially whale oil, used to produce light in oil lamps, were
replaced by petroleum.
Today, the US Energy Information Administration (EIA) estimates that 25 per-
cent of America's energy comes from petroleum, 22 percent from coal, and 22 per-
cent from natural gas. Nuclear power accounts for 8.4 percent, and “renewable”
energy—such as wind, solar, geothermal, or hydropower—supplies 8 percent. 2
What Is Coal?
Coal is a combustible, brown or black sedimentary rock made of carbon, hydrogen,
oxygen, nitrogen, and sulfur. Plentiful and cheap, it is the most abundant fossil fuel
produced in the United States. 3 Coal is used around the world to fuel power plants
and is an important resource for the iron and steel industries. But it is also highly
polluting. According to the Union of Concerned Scientists, coal plants are the na-
tion's primary source of CO 2 , the leading greenhouse gas. A typical coal plant gen-
erates 3.5 million tons of CO 2 per year; in 2011, utility coal plants in the United
States emitted 1.7 billion tons of CO 2 . 4
There are four major types of coal: anthracite, bituminous, sub-bituminous, and
lignite. They are classified by the type and amount of carbon they contain, and by
the amount of heat energy they produce:
• Anthracite is a scarce coal found only in Pennsylvania. It is the hardest coal, and has
a high carbon content (86-97 percent) that provides more energy than other coals.
• Bituminous is the most abundant type of coal, containing 45-86 percent carbon, and
is between 100 and 300 million years old. It is found in West Virginia, Kentucky, and
Pennsylvania.
• Sub-bituminous coal is the second-most abundant type of coal in the United States. It
contains 35-45 percent carbon, is over 100 million years old, and is mined in Wyom-
ing.
• Lignite is the youngest and softest coal, and tends to be high in moisture. It contains
only 25-35 percent carbon, but is high in hydrogen and oxygen. It is mainly used by
power plants and is found in Texas and North Dakota.