Energy & Air
Pollution
Introduction
Fossil Fuels: Oil & Gas
Fossil Fuels: Coal
Nuclear Energy
Alternative Energy Resources
Air Pollution
Summary
At the heart of modern society lies an economy driven by energy use.
Unfortunately, the same energy that brings us comfort, convenience, and
prosperity also brings us pollution, impoverishment, and global warming.
Our challenge is to maximize the benefits gained from energy
consumption while minimizing the costs incurred.
Douglas Foy
A fuming smokestack is the perfect symbol of our national dilemma. On
the one hand, it means the jobs and products we need. On the other, it
means pollution.
American Gas Association ad, 1991
Introduction
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Fossil fuels (oil, gas, coal) makeup most of the energy
consumed in the U.S.
Energy use increases with increasing population, land area,
and industrial activity and energy use per capita is greatest
in large, sparsely populated states.
Fossil fuels are non-renewable resources with limited life
span and their combustion contributes to global warming.
Alternative energy sources such as solar and wind power
are renewable and hold the promise of a sustainable energy
future.
U.S. Energy Use
Current U.S. energy use is weighted heavily toward fossil fuels
(oil, natural gas, and coal) that account for approximately 90%
of all energy used in the nation (Fig. 1). Environmental
concerns over air pollution and the potential for global
warming may encourage wider access to alternative energy
sources such as nuclear power and wind or solar energy.
Nuclear power accounts for about a fifth of U.S. electricity
generation but only 5% of total energy consumption.
Alternative energy sources (hydroelectric, wind, solar,
geothermal) generate 5% of U.S. energy production but may
expand that share in the decades ahead.
Energy use within the U.S. varies with population size and
character of energy demand (Fig. 2). States with large
populations, large land area (greater distances to travel), and
Figure 1. U.S. energy
consumption per
energy type, 1949 to
1995. Graph courtesy
of the Energy
Information
Administration.
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energy-intensive industries (e.g., oil refining, chemicals),
typically use the most energy. Large sparsely populated states
such as Wyoming and Alaska rate highly in energy use per
person because transportation consumes large volumes of fuel.
Fossil fuels form from decayed organic material through a
series of chemical reactions that occur gradually over millions
of years under specific physical conditions in a select group of
rocks. These conditions make it possible to predict where oil
and gas may be found but also highlight the fact that fossil
fuels are non-renewable resources that will not be replaced
once used. Reserves of oil and natural gas will probably be
stretched out for another century but we must face the
inevitable conclusion that these finite resources will have to be
replaced with an alternative form of energy in the next 50
years. The inevitable decrease in the availability of fossil fuels
will be felt most acutely in transportation because there is no
viable inexpensive replacement for the refined petroleum
products that fuel automobiles and airplanes.
Figure 2. Distribution
of U.S. energy use.
Energy use at home
and industry is
typically in the form of
electricity generated
by burning coal.
Transportation is
almost exclusively
fueled by forms of
gasoline refined from
petroleum.
Coal represents an alternative fossil fuel with a potentially
longer life span than either oil or gas but it has the unfortunate
distinction of generating more pollution than the other fossil
fuels. Furthermore, coal produces more carbon dioxide during
combustion than either oil or gas, but all three have been
fingered as the primary sources of the greenhouse gas that is
the culprit for global warming.
Advocates of a nuclear future have seized the potential threat
of global warming and the nation's dependence on foreign oil
to advance the nuclear cause. Fifty years ago, scientists
working in the fledgling U.S. nuclear power industry (Fig. 3)
predicted that electricity would be virtually free by the end of
the century because of the electrical benevolence of nuclear
energy. Today, only 17% of the world’s electricity is generated
by nuclear power and that number is unlikely to grow because
of concerns about the safety of nuclear reactors and anxiety
over how to dispose of highly radioactive waste produced
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during power generation. Rarely has a technology shown such
early promise only to fall so rapidly from grace.
Alternative energy resources (hydroelectric, wind, solar,
biomass, geothermal) generate less than 10% of U.S. energy
but have few of the drawbacks of fossil fuels or nuclear power
and hold promise of a sustainable energy future. A veritable
chorus of Pollyannas has sung the praises of alternative energy
since the 1970s but their potential remains ambiguous because
of uncertainties over the rate of technological development and
operating costs. Some of these renewable energy sources have
greater potential than others with solar energy and wind power
holding the most hope for the future.
The industrial air pollution that was once proudly viewed as a
by-product of economic growth is now largely a thing of the
past. No longer will thousands of people die during a weekend
of lethal air pollution as they did in London in 1952. Air
pollution is still widespread but its effects are muted, hidden
among reports of greater incidence of asthma and other
respiratory ailments and studies of acid rain downwind from
industrial centers. The burning of fossil fuels represents a
major source of air pollutants and cleaner air will therefore be
an indirect by-product of any change in energy production in
the years ahead.
Think about it . . .
1. Predict which of the following states consumes the
most energy.
a) California b) Illinois c) New York d) Texas
2. Examine the partially completed graph found at the
end of the chapter that plots gross domestic product
(GDP) per capita vs. energy consumption per capita.
Label the points that represent where you think the
eight named nations would plot on the graph.
3. Draw a time line for energy use before you read any
further in this chapter. Label the time line to indicate
how energy consumption has changed/will change
from 1850 to 2050. Differentiate between domestic
and industrial energy sources and transportation
energy sources.
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Figure 3. Perry
nuclear reactor, 35
miles northwest of
Cleveland, Ohio.
Lake Erie is on the
left of the image.
Image courtesy of the
Nuclear Regulatory
Commission (NRC).
Fossil Fuels: Oil & Gas
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Time and a specific temperature range are necessary for the
generation of oil and gas.
As hydrocarbons become mature they progress from heavy
oils to light oils to natural gas.
Hydrocarbons become concentrated in sedimentary rocks.
The volume of the world’s oil reserves is approximately
1,070 billion barrels.
The U.S. uses 25% of the world’s oil.
Two-thirds of the world’s oil reserves are located in the
Middle East.
Fossil fuels form from decayed organic material. Oil, coal, and
natural gas are the most common products of this process. Oil
and gas form from organic material in microscopic marine
organisms, whereas coal forms from the decayed remains of
land plants. Tar (oil) sands and oil shale are less common
forms of fossil fuels and are less widely used because
extraction of oil from these deposits is more expensive than
producing other forms of fossil fuels.
Generation and Production of Oil and Gas
The two principal requirements in the generation of oil and gas
(also known as hydrocarbons - chemical compounds of
carbon and hydrogen) are time and a specific range of
temperature. The steps in the process are:
1. Organic-rich sediments are deposited and gradually
buried to greater depths and converted to sedimentary rock
(e.g., shale).
2. Chemical reactions occur during burial under conditions
of increasing temperature and pressure. The reactions occur
at temperatures of 50 to 100oC, higher temperatures "boil
off" the hydrocarbons; lower temperatures are not sufficient
to drive the chemical reactions.
3. The reactions change the organic molecules to hydrocarbon
molecules. With increasing time (millions of years) the
hydrocarbons become more mature changing from heavy
oils to lighter oils to natural gas. Fossil fuels are considered
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non-renewable resources because they are consumed much
faster than they can be replaced.
Oil and gas migrate upward through fractures and pore spaces
in permeable rocks and/or sediments. Some hydrocarbons
escape at Earth’s surface through features such as oil seeps.
Others collect below the surface in sedimentary rocks when
their path is blocked by low-permeability rocks (Fig. 4). Rock
structures such as faults and folds may serve to juxtapose
permeable and impermeable units. Oil and gas are trapped in
the permeable rocks and will migrate upward to lie at the
highest elevation in the rock unit.
When an oil field is first drilled the oil is driven into the well
by pressures within the rocks. This primary recovery will
extract about 25% of the oil. Additional oil can be extracted
using enhanced recovery techniques that make it easier for the
oil to enter the well. Such techniques may include artificially
fracturing the rock to create passages for oil migration or
pumping wastewaters from drilling operations into nearby
wells to drive the oil toward the producing well.
Oil Reserves
Oil and gas are not distributed uniformly within Earth's crust
(Fig. 5). Hydrocarbons are initially formed as organic-rich
sediments and the oil and gas subsequently migrate upward,
into younger rocks that are also of sedimentary origin.
Consequently, oil and gas reserves are generally absent in areas
underlain by igneous or metamorphic rocks such as volcanic
island chains like Japan or Hawaii. Even in areas where
sedimentary rocks are present, they must fall within a specific
age range to ensure that the rocks are mature enough to contain
hydrocarbons but not so old that oil and gas would have long
ago escaped.
Oil reserves steadily increased since the first commercial oil
well was drilled in Titusville, Pennsylvania, in 1859 but
estimates of global reserves have remained relatively uniform
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Figure 4. Oil and gas
will migrate through
permeable rocks to
the highest available
elevation. Examples
of traps include folds
(left), and faults
(right).
Figure 5. Locations of
principal North
American oil fields
(left) and other
hydrocarbon
resources (right).
Most oil shales and
oil sands are not
economically viable
now but may play a
more significant role
in energy production
as supplies decrease.
at around a billion barrels over the last decade. Oil reserves
remained stable despite the fact that global population has
doubled in the last thirty years. Reserves haven't declined
because of:
•
Exploration of geologic formations in increasingly remote
areas of the world, including the seafloor, using an array of
new methods that utilize satellites and geophysical
instruments to unravel the geology in regions where few
rocks are visible.
•
Improved technology used by oil companies to extract
greater volumes of oil through enhanced recovery
techniques.
•
Greater efficiency in energy use as a result of higher fuel
prices and stricter pollution standards that caused
manufacturers to build more energy-efficient appliances
and engines.
Further improvements in energy efficiency will continue to
delay the inevitable decline in oil reserves. For example,
recently introduced combination gas-electric cars can be driven
112 km (70 miles) on a gallon of gas. However, even with the
best management and environmental stewardship we must
anticipate that a world that continues to rely on oil will see this
finite resource decline toward the second half of this century.
Known world oil reserves are approximately 1,030 billion
barrels (one barrel is equivalent to 42 gallons). These reserves
would last for nearly 40 years at current global consumption
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rates. The U.S. Geological Survey recently issued a more
optimistic estimate that there actually may be double those
reserves left to be discovered with a potential life span until the
end of this century.
The U.S. uses 25% of the world's oil, much more than any
other nation, and imports over half of the oil it consumes.
Consequently we are vulnerable to disruptions in oil supplies.
Current fluctuations in gasoline prices that result from
relatively modest changes in supply and demand will become
much more exaggerated as the available reserves of oil decline.
The future success of the U.S. economy may rely on the state
of our political relationships with the relatively few nations that
have abundant oil reserves.
Figure 6. Distribution
of global oil and gas
reserves expressed
as a percentage of
global reserves. Twothirds of the world’s
oil and one-third of all
natural gas reserves
are located in the
Middle East. Russia
has 33% of the
world's natural gas
and Saudi Arabia has
25% of the world's oil.
The majority of the oil and other petroleum products currently
imported into the U.S. come from just four nations, Venezuela,
Mexico, Canada, and Saudi Arabia. However, as two-thirds of
all the world's oil reserves are located in the Middle East (Fig.
6), countries such as Saudi Arabia, Kuwait, Iran, and Iraq may
play an increasingly important role in U.S. oil supply in the
decades ahead.
Think about it . . .
1. Use the Venn diagram found at the end of the chapter
to compare and contrast the similarities and
differences between the characteristics of oil and coal
resources.
. . . continued on next page
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2. Similar organic-rich source rocks are present in two
locations. Oil deposits formed in the overlying rocks at
the first location but did not form at the second
location. Which of the following is the best explanation
for this difference?
a) The first location was more deeply buried than the
second.
b) The first location was subjected to lower
temperatures than the second.
c) The first location contains younger rocks than the
second.
d) Rocks at the first location had lower permeability
than rocks at the second site.
Fossil Fuels: Coal
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Figure 7. Progression
of coal rank (maturity)
from carbon-poor
peat to carbon-rich
anthracite. The
relative proportion of
U.S. coal production
by rank is anthracite
2%, bituminous 53%,
sub-bituminous 36%,
and lignite 9%.
•
The carbon content and heat content of coal increase with
increasing maturity.
The volume of ash residue after burning decreases with
increasing coal maturity.
The two principal regions of coal production in the U.S. are
the Appalachian basin and the Great Plains.
Sulfur content of coal is lower in the Great Plains and
higher in the Appalachian basin.
Air pollution, medical expenses, and landfill fees are
external costs of coal use.
Coal, the carbon-rich residue of plants, can be classified by
rank or carbon content. Coal matures by increasing rank with
increasing burial pressure (Fig. 7).
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Peat is the least-mature form of coal, containing a large volume
of fibrous plant matter. With increasing compaction, water is
driven out and carbon becomes increasingly concentrated. Both
carbon content and the amount of heat released during
burning increase with maturity. The carbon content ranges
from around 30% in peat to 99% for anthracite. The higher the
carbon content, the more heat that is released when the coal is
burned. Small amounts of high-carbon coals produce the same
heat as large volumes of low-carbon coal. The volume of ash
that remains after burning decreases with increasing rank. The
ash must be disposed off in a landfill thus increasing expense.
Figure 8. Coalbearing areas of the
U.S. Image courtesy of
Energy Information
Administration.
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There are three principal coal-producing regions in the U.S.
(Fig. 8). The first two, Appalachian basin states (Ohio,
eastern Kentucky, West Virginia, Pennsylvania) and interior
states (Illinois, Indiana, western Kentucky) produce high-rank
bituminous coals and anthracite. These coals are produced
from both surface and underground mines. Unfortunately,
some of the bituminous coals have a high sulfur content (Fig.
9) and therefore contribute to air pollution. Given the stringent
regulations on pollutants, some companies prefer to use lowergrade sub-bituminous coals to avoid costs associated with
installing pollution control devices.
Figure 9. Comparison
of sulfur content and
heat content of coals
from principal U.S.
coal-producing
regions. Western
coals have less sulfur
and lower heat
content.
Figure 10. Thick
seam of subbituminous coal in the
Powder River basin,
northeast Wyoming.
This seam is 60
meter (200 foot) thick
for much of its length
and is less than 15
meters(50 feet) below
the surface at this
location.
Great Plains and Rocky Mountain states (Montana,
Wyoming, North Dakota, South Dakota, Colorado) produce
lignite and sub-bituminous coals from surface mines (Figs. 8,
10). These coals may occur in especially thick seams making
the mining process much less expensive than for underground
mines. Larger volumes of these lower-grade coals must be
burned to generate the same heat as bituminous coal or
anthracite. Companies pay more to haul the extra coal but save
money on production and labor costs. Sub-bituminous coals
were not heavily mined prior to 1970. Subsequent to that date
surface mines have produced more coal than underground
mines and the western coal production has steadily risen to a
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point today where coal production is approximately equal east
and west of the Mississippi River (Fig. 11).
Figure 11. Principal
coal reserves of the
U.S. Lower map
shows top-10 states
for coal reserves that
can be divided
between lignite and
sub-bituminous coals
in the West, and
mainly bituminous
coals and anthracite
east of the Mississippi
River.
Air pollution represents one of the external costs associated
with the combustion of fossil fuels. External costs are the price
we pay indirectly - in taxes, health insurance, medical bills,
landfill fees - because of the use of fossil fuels. The use of coal
would become less economically attractive if these costs were
applied to the original (internal) cost of coal. Electric utilities
account for approximately 90% of all U.S. coal consumption
and are the major source of nitrogen dioxide and sulfur
dioxide, two key air pollutants.
The most potentially significant external cost of using fossil
fuels is the build up of carbon dioxide in Earth's atmosphere.
Scientists predict that fossil fuel emissions will lead to a
warmer "greenhouse" world, initiating a potential cascade of
negative economic repercussions. Consequently, future energy
policy may not be concerned with how much fuel is left, but
may instead focus on how to use it without prompting changes
in global climate.
Coal Reserves
Over 80% of the world's recoverable coal is found in just seven
nations (Fig. 12). The U.S. has the greatest reserves,
accounting for 25% of the world's coal, enough to last for 270
years at current consumption rates. This suggests that we will
have a plentiful supply of electricity into the distant future but
it is of little help as a replacement fuel for refined oil products
(gasoline) unless we can assume that automobiles of the future
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Figure 12. The U.S.
has a quarter of the
world's available coal
reserves and 83% of
all reserves are
divided among just
seven nations.
will run, at least partially, on electricity. Even in this scenario,
we are still left with the potential for additional air pollution
and the threat of global warming.
Think about it . . .
1. Use the Venn diagram found at the close of the
chapter to compare and contrast the characteristics of
oil and coal resources.
2. Examine the map of U.S. coal resources found at the
end of the chapter and predict where the five
numbered points on the graph of sulfur content vs.
BTU might plot on the map.
Nuclear Energy
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Nuclear reactors generate 17% of the world’s electricity
and 5% of total energy.
Nuclear power has fallen from favor because of accidents
like Three Mile Island (1979) and Chernobyl (1986).
There are over 100 operating nuclear reactors in the U.S.,
approximately a quarter of all nuclear power plants
worldwide.
The benefits of nuclear energy are: no air pollution, no
greenhouse effect, and a reduction in dependence on
foreign oil.
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•
•
•
The potential problems are: U.S. reactors are getting old
and there is no currently available site for permanent
nuclear waste disposal.
A potential storage site for nuclear waste is being
investigated at Yucca Mountain, Nevada.
The Yucca Mountain site is isolated, has a dry climate, in
rocks with low porosity and permeability, and is located far
above the groundwater table. However, the area around
Yucca Mountain has experienced earthquakes and
volcanism.
Approximately 17% of the world’s electricity is generated by
nuclear power but that represents only 5% of the world’s
consumption of energy. Clearly there is room for improvement.
Current concerns about global warming have caused some
governments to give nuclear energy another look and has
increased optimism within the nuclear power industry
prompting a series of ads that tout nuclear energy as the
environmentally friendly alternative to dirty fossil fuels. Most
technologies evolve into increasingly sophisticated and cheaper
forms following their introduction and will continue to grow in
popularity until they are replaced by a better alternative. Not so
nuclear power. After a meteoric rise, the nuclear power
industry hit a wall in the latter part of the last century as a
result of problems with their own product.
Nuclear energy originated in the nuclear weapons programs of
World War II. Following the war, control of nuclear research
passed from military to civilian control with the creation of the
Atomic Energy Commission. Early plans to use nuclear
weapons for mega-engineering projects (e.g., excavating a
harbor on the coast of Alaska) were dismissed amid concern
over potential radioactive contamination. The first commercial
nuclear power plants generated electricity in the late 1950s.
Nuclear power generation increased steadily until the 1970s
and appeared to be on the road to acceptance as fuel costs
increased during the 1973 oil crisis. However, the honeymoon
Figure 13. Three Mile
Island Unit 1 reactor,
Pennsylvania, with
Susquehanna River
in background. The
Unit 2 reactor is
nearby but is no
longer in use. Image
courtesy of the Nuclear
Regulatory Commission
(NRC).
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ended amidst with construction costs and a widely reported
accident at the Three Mile Island Unit 2 reactor (1979), near
Harrisburg, Pennsylvania (Fig. 13). Furthermore, the demand
for energy decreased as energy conservation and efficiency
gained popularity.
A dangerous nuclear accident at Chernobyl in the former
Soviet Union (now the Ukraine) in 1986 lessened the chances
for a rebound in nuclear fortunes. The accident resulted from
an unauthorized experiment by operators who were testing the
capabilities of the reactor. Two explosions blew the top of the
power plant. The reactor did not have a containment vessel
(unlike U.S. reactors) allowing the escape of radioactive debris
into the atmosphere. The accident was revealed when Sweden
detected an increase in wind-borne radiation. As a result of the
accident, over 200,000 people had to be moved from the area
surrounding the damaged reactor; 31 workers and emergency
personnel died immediately after accident and an unknown
number of people died later because of exposure to lesser
levels of radioactivity. A concrete "sarcophagus" was built
over the damaged reactor in an unsuccessful effort to contain
any further leaks.
The nuclear industry argues that improved reactor design and
the absence of airborne pollutants associated with fossil fuels
make nuclear power an ideal source for future energy.
The Nuclear Fuel Cycle
The nuclear fuel cycle represents the series of steps that begin
with the mining of uranium, continue through the generation of
electricity, and end with the disposal of nuclear waste.
Uranium Mining and Milling: Uranium is approximately 500
times more abundant in Earth’s crust than gold. The top-five
sources of uranium are Canada (12,029 tonnes, 34% of world
production), Australia, Niger, Namibia, and U.S. (Fig. 14).
Over half of uranium is produced from open-pit mines. The
original uranium ore contains 0.1 to 1% uranium. Uranium is
removed from ore by milling to produce a refined ore that
contains approximately 60% uranium. During the milling
process the uranium is dissolved from the ore and
reprecipitated in a concentrated form known as “yellowcake.”
Uranium Enrichment: Additional processing is required
before the uranium is in a form that can be used in a reactor.
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Natural uranium consists of two isotopes of uranium. The bulk
of natural uranium is U238. Only 0.7% of natural uranium is the
isotope U235 that is capable of undergoing fission, the process
by which energy is produced in a nuclear reactor. Enrichment
increases the concentration of U235 to approximately 4% of
the uranium mixture by removing much of the U238 isotope.
The uranium is formed into pellets that are placed in metal
tubes to form the fuel rods in a reactor fuel assembly.
Nuclear Power Generation: Nuclear reactors generate
electricity from heat much the same way coal- or oil-fired
power plants do. The heat converts water to steam, steam spins
a turbine, and the spinning turbine generates electricity. The
big difference is in how the heat is generated. In power plants
using fossil fuels the fuel of choice is simply burned. In a
nuclear plant, nuclear fission, the splitting of the nucleus of an
atom, is the heat source. Neutrons ejected from the split atom
hit adjacent atoms, causing them to fission. Uranium undergoes
nuclear fission in the fuel rods of a nuclear reactor. Neutronabsorbing control rods may be inserted in the reactor to slow
down the rate of the reaction and produce less heat. Both fuel
rods and control rods are stored in water that serves to cool the
rods and moderate the nuclear fission reactions. The
radioactive material in fuel rods is not sufficiently enriched to
cause a nuclear explosion but a runaway reaction could result
16
Figure 14. U.S.
uranium mining and
production plants.
Image courtesy of
Energy Information
Administration.
Figure 15. Map of the
distribution of U.S.
nuclear reactors.
Image courtesy of the
Nuclear Regulatory
Commission (NRC).
in overheating of the surrounding water and cause a steam
explosion.
Nuclear Reactors: A typical nuclear power plant in the U.S. is
granted a 40-year license for operation but many are taken out
of service (decommissioned) before the end of that time
interval. The oldest currently operating nuclear reactors in the
U.S. started up in 1969. There are over 100 nuclear power
plants operating in the U.S. (Fig. 15; 104 as of November,
1999) but no new plants have been ordered in the last 20 years.
Consequently, as the current plants are decommissioned the
total number of operating nuclear plants will inevitably decline.
Figure 16. Graph of
proportion of
electricity from
nuclear power for
France (58 reactors),
Belgium (7), Sweden
(12), Japan (52), and
U.S. (104). There are
428 nuclear power
plants worldwide
(1999).
Some nations rely heavily on nuclear power to supply the bulk
of their electricity (Fig. 16). France generates over threequarters of its electricity from 58 nuclear power plants and
Lithuania generates 77% of its electricity from just two plants.
In contrast, the U.S. has 104 nuclear reactors that produce
much more electricity than France (96,977 megawatts vs.
61,723 megawatts). However, this represents a smaller
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proportion (19%) of national electricity production than several
other nations. Europe is home to more nuclear reactors than
any other continent (173), and Africa and South America have
only 5 between them.
Nuclear Energy and the Future
There has recently been renewed interest in the use of nuclear
power in some quarters (mainly from advocates in the nuclear
industry). They cite three principal benefits of the use of
nuclear energy:
1. Air pollution and global warming, associated with fossil
fuels, are not produced by nuclear power plants.
2. Electricity from nuclear power would reduce the nation's
dependence on foreign oil which is growing increasingly
scarce.
3. New reactors have safer standardized reactor designs that
markedly reduce the potential for an accident.
However, for nuclear power to become a viable energy
alternative in the immediate future it must first deal with the
following issues:
1. Many existing nuclear power plants are entering old age
and will have to be decommissioned, reducing the energyproduction capacity in the U.S.
2. More nuclear power plants mean more high-level nuclear
waste. The nation still has no repository for this waste and
will not have a disposal site until at least 2010.
Nuclear Waste
Nuclear waste comes in a variety of forms, each with different
storage requirements but it is the disposal of high-level nuclear
waste that presents the greatest challenge for the future.
Although high-level radioactive waste (e.g. used fuel rods)
composes a relatively small volume of all nuclear waste it
represents nearly all (95%) of the radioactivity nuclear wastes
and may remain dangerous for over 10,000 years. Like several
other nations that rely on nuclear energy, the U.S. is attempting
to find a suitable site where it can store nuclear waste safely for
thousands of years. The potential site is located below Yucca
Mountain, Nevada (Fig. 17), about a one hour drive north of
Las Vegas.
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The Department of Energy (DOE) initially identified nine
potential nuclear dump sites but later shortened the list to three
(Fig. 17; Hanford, Washington; Deaf Smith County, Texas;
Yucca Mountain, Nevada). The DOE hoped to investigate the
geology of each site thoroughly to determine which would be
the safest repository for the dangerous waste. However, in
December 1987, Congress saw a chance to save some money
and directed DOE to study just the Yucca Mountain site.
Nevada, which has no nuclear power plants, has fought vainly
against hosting the site.
Figure 17. Three
proposed sites for a
possible high-level
nuclear waste
disposal facility were
considered (map
right) before
Congress chose to
locate the site below
Yucca Mountain,
Nevada (left). Image
courtesy of the Yucca
Mountain Project.
Not only must a high-level nuclear waste disposal facility be
safe from accidental entry and sabotage, potentially for a few
hundred thousand years, it must also be safe from geologic
hazards that may release the radioactive materials. The ideal
site would be geologically stable to ensure that groundwater
could not infiltrate through the waste, and neither earthquakes
nor volcanic eruptions would rupture the containment structure.
Geologic Setting of Yucca Mountain
The waste would be stored in sealed containers in an
underground vault approximately 300 m (1,000 feet) below the
surface (Fig. 18). The site at Yucca Mountain is favorable for
waste disposal because:
•
It is located in the desert of southern Nevada far from
population centers (Las Vegas is ~100 km south).
19
•
The vault would be hollowed out of a layer of volcanic tuff,
a resistant igneous rock with very low porosity (spaces
within the rock that may contain water) and low
permeability (the ability of water to flow through the
rock).
•
In addition, the site gets ~15 cm (6 inches) of precipitation
a year, most of which evaporates in the desert heat. Project
scientists believe that it is unlikely that water could
inundate the disposal facility and transport radioactive
materials into the surrounding environment.
•
Furthermore, the local groundwater source is 240 meters
(~750 feet) below the site, making it difficult for any leaks
to pass quickly (before detection) to the groundwater
supply.
Figure 18.
Approximate position
of the nuclear waste
repository in
impermeable volcanic
tuff rocks below
Yucca Mountain,
Nevada.
However, some scientists point out that certain geologic
features point toward potential problems in the future:
•
Groundwater flow may be accelerated along fractures and
faults that exist in the region, and that evidence points to an
elevated water table (groundwater) in the relatively recent
geologic past (~10,000 years ago).
•
Nevada is one of the most seismically active states after
Alaska and California. Some have suggested that the threat
of a damaging earthquake is too great to take the risk of
building the disposal facility in Nevada. However, although
there have been numerous small earthquakes near the site,
few have been of sufficient magnitude to pose any threat
and a structure could be engineered to withstand the
moderate-size earthquakes that occasionally occur in
southern Nevada.
•
Geologically recent (<10,000 years) volcanic activity has
also occurred nearby but scientists at Yucca Mountain have
estimated that there is little probability that future activity
will impact the disposal facility.
20
The original opening date for the high-level nuclear waste
repository was 1998 but was subsequently changed to 2003 and
then to 2010, reflecting the controversy the site has generated
in Nevada and nationwide. The development of such a site is
essential for the permanent disposal of the nuclear waste that
has already been generated by nuclear power plants. Without a
working disposal facility, the long-term viability of nuclear
power in the U.S. is in jeopardy.
Think about it . . .
Create a concept map that illustrates the issues
surrounding the use of nuclear energy.
Alternative Energy Resources
•
•
•
•
•
Renewable energy is environmentally friendly but its future
potential is dependent upon the rate of technological
development and operating costs.
The potential for the use of renewable energy varies with
location as landscape, climate, and geology.
Biomass, hydropower, and geothermal energy have
drawbacks that make it unlikely that they will increase their
share of U.S. energy significantly in the future.
Passive solar energy requires that structures be oriented to
receive light and heat from sunlight and active solar energy
converts solar radiation to electricity.
Wind energy accounts for 0.5% of all U.S. energy but
could generate up to 20%.
Future energy must come from one of the three principal
energy sources currently in use. Approximately 80% of the
nation's current energy needs are supplied by fossil fuels (oil,
gas, coal) that carry with them the threat of potential energy
shortages as well as associated environmental degradation from
air pollution and concerns about global warming. Nuclear
power supplies less than 10% of total U.S. energy and is
21
unlikely to undergo a resurgence any time soon in the face of
public skepticism over the possibility of a nuclear future.
Renewable energy (hydropower, wind, solar, biomass,
geothermal), therefore, remains the sole potential energy
source that will ensure minimal environmental harm and also
has the potential to free us from reliance on foreign suppliers.
Technological improvements and economies of scale may
reduce costs sufficiently to increase the proportion of U.S.
energy from renewable sources from its current level (Fig. 19;
less than 10%) to at least 30% of total energy use.
Figure 19. Proportion
of U.S. energy
generated by
renewable energy vs.
fossil fuels and
nuclear power.
Controls on Renewable Energy
Unlike fossil fuels, renewable energy must often be used
relatively close to where it is generated. Transmission lines
may conduct electricity up to hundreds of kilometers from its
original source but are not efficient enough to transmit it crosscountry to any location where it is needed. Hydroelectric and
geothermal power are more common in western states because
of the underlying geology. Stream gradients are relatively steep
and thousands of acres of undeveloped lands were available to
be flooded behind massive dams. In addition, recent volcanism
is feed by shallow magma chambers that provide a ready heat
source for circulating groundwater. Climate conditions also
favor greater development of solar and wind power west of the
Figure 20. The most
widely used
renewable energy
sources are biomass
(e.g., burning wood)
and hydroelectric
power.
Mississippi River in regions characterized by high insolation
22
(incoming solar radiation) and/or high consistent wind speeds.
Biomass (wood products) represents the only form of
renewable energy that can be readily transported in its primary
state. The burning of wood (biomass) and hydropower
represent the great majority of current renewable energy use in
the U.S. (Fig. 20).
Figure 21. Area of
land necessary to
generate 1 billion
kilowatts of electricity
per year for different
energy sources.
Renewable sources
require more land per
measure of electricity.
Two of the principal restrictions in the development of
alternative energy sources are the demand for land and the
relative cost (Figs. 21, 22). Fossil fuels require a relatively
small land area to be produced and refined. In contrast,
hydroelectric power requires the flooding of large areas to
ensure a sufficient supply of water. Biomass (burning of
organic material such as fast-growing varieties of wood like
willow) demands the greatest land area to generate a given
amount of electricity (Fig. 21). It is unlikely that sufficient land
area can be converted to forests to produce the wood necessary
to replace fossil fuels in power plants. Most land is already
dedicated to other uses (agriculture, buildings) or does not have
the climate required to develop forests.
Figure 22. Relative
cost to generate one
kilowatt-hour of
electricity. Current
costs of solar energy
are approximately 4
times those of
electricity generated
at a coal-fired power
plant.
The main constraint on use of renewable energy sources today
is cost (Fig. 22). As long as renewable energy is more
expensive than conventional fuels it will not be widely used.
Some forms of renewable energy (wind, hydroelectric) are
competitive with the cost of building nuclear power plants but
only hydroelectric power compares favorably with the main
source of electricity in the U.S., coal.
23
Hydropower production in the U.S. is a close second to the
world's leader (Canada). Energy is generated when water
dropping from higher to lower elevations is used to drive
turbines that rotate generators to produce electricity. Early
settlers used water wheels alongside rapidly flowing streams.
Today, power is generated by the 200-meter (660 foot) drop of
water within giant dams on western rivers such as the Colorado
(Fig. 23) and Columbia.
Although construction of the earliest western dams was viewed
as a blessing in the parched drylands of Arizona and California,
later projects met with increasing opposition because of the
dramatic changes in the physical environment both upstream
(drowned lands, siltation of reservoirs) and downstream
(altered stream channels, uniform [unnatural] streamflow).
Many of the best potential dam sites are now in national
parklands or have competition for land use from farming and
recreation interests. It is therefore considered unlikely that any
new large dams will be built in the U.S. but mini-hydro
projects that serve a relatively small population with minimal
environmental disruption may become increasingly popular.
Figure 23. Left:
Hoover Dam on the
Colorado River with
Lake Mead in the
background. Right:
The Geysers, a
geothermal system
near Calistoga,
California. Image by
David Parsons. Image
courtesy of Dept. of
Energy National
Renewable Energy
Laboratory.
Geothermal power in its most dramatic form uses heat from
sources of underground steam or hot water (hydrothermal
resources) to generate steam used to drive turbines and thus
generate electricity (Figs. 23, 24). Used waters are recycled
back underground to recharge the geothermal reservoir and
continue the process. Groundwater is heated when it percolates
to sufficient depths to be warmed by Earth's geothermal
gradient (~25oC/km) or comes in contact with hot rocks near a
magma chamber. Geothermal power plants are found in several
24
Figure 24.
Geothermal energy
systems exploit
hydrothermal
resources. Heat is
extracted from hot
groundwater and the
cool wastewaters are
returned to the
hydrothermal system.
western states (e.g., California, Nevada, Utah, and Hawaii) and
produce electricity at rates of 5 to 8 cents per kilowatt-hour.
Although it has potential for growth, geothermal power is
unlikely to take a large share of the U.S. energy market
because it is restricted by location to sites in sparsely populated
areas of the West.
Solar and wind energy represent the greatest potential for
technological advances and increasing energy production
among renewable energy sources.
Solar Energy
Solar energy accounts for approximately 1% of all U.S. energy
use. Passive solar energy refers to using the heat from sunlight
to warm buildings (Fig. 25) and was first used in Greek homes
over 1,500 years ago. It is estimated that sunlight could be used
to supply up to 90% of home heat, depending upon location.
Figure 25. Modern
house with passive
solar design, near
Denver, Colorado.
House combines
passive (south-facing
windows) and active
solar technologies.
Image by Dave
Parsons. Image
courtesy of Department
of Energy National
Renewable Energy
Laboratory.
25
Passive solar energy has greater potential in the sunny desert
Southwest than the overcast Pacific Northwest. The use of
passive solar energy can be readily incorporated into the
construction of new homes that can be built with windows
facing south to receive maximum insolation. Unfortunately,
such techniques are less useful in older homes.
Active (direct) solar energy can be used in two forms. Water
or oil may be heated in solar collectors that use mirrors to focus
the sunlight onto the liquid (Fig. 26). The hot liquid is then
used for heating. In contrast, photovoltaic cells convert
sunlight directly to electricity (Fig. 27).
Figure 26. Solar One,
California; the tower
in center of image is a
10-megawatt solar
receiver. Image by
Sandia National
Laboratories, courtesy
of Department of
Energy National
Renewable Energy
Laboratory
(DOE/NREL).
Solar energy still has some hurdles to overcome before it can
be used extensively. At present some solar energy systems are
too inefficient for widespread use. For example, when coal is
burned approximately half the heat generated can be converted
to electricity. Current models of photovoltaic cells convert less
than 10% of sunlight into electricity. Some developing nations
are at the forefront of solar energy because it may be more
economical to use photovoltaic cells to generate electricity in
remote locations instead of having to build transmission lines
Figure 27. Left:
Woman in India uses
a photovoltaicpowered pump to
collect water. Image
by Harin Ullal. Right:
Homes in a rural
Brazilian village use
photovoltaic cells to
provide light. Image by
Roger Taylor. Images
courtesy of Department
of Energy National
Renewable Energy
Laboratory.
26
to conduct electricity large distances to serve relatively small
populations (Fig. 27).
Wind Power
Wind power accounts for approximately 0.5% of U.S.
electricity (Fig. 28). Technological advances are making wind
power increasingly competitive with costs ranging from 1 to 10
times those of fossil fuels. Suitable wind velocities (over 20
km/hr) are consistently present over about 13% of the U.S. and
estimates suggest wind power could generate as much as 20%
of U.S. energy in the future.
Figure 28. A series of
100 kW wind turbines
near Altamont Pass,
California. Image by
Ed Linton. Image
courtesy of Department
of Energy National
Renewable Energy
Laboratory
(DOE/NREL).
The areas with the greatest potential for wind power are
determined by the patterns of prevailing winds that consistently
exhibit sufficient velocity and reliability only over the Great
Plains states. Unfortunately, these states are hundreds of miles
from population centers were the power would be needed. New
or improved transmission lines necessary to get the power to
suitable markets are unlikely to be built until it can be
demonstrated that the region can generate sufficient energy.
However, there is little incentive to invest in huge wind farms
without such a delivery system in place. The great majority of
U.S. wind turbines are located in California (Fig. 28).
Think about it . . .
1. Use the Venn diagram found at the end of the chapter
to compare and contrast the characteristics of nuclear
energy and renewable energy resources.
2. The graph located at chapter end compares projected
plots of the generation of wind energy vs. time (19852025) with nuclear energy capacity vs. time (19602000). Make some predictions on the future of wind
energy using the evolution of nuclear power as a
model.
27
Air Pollution
•
•
•
•
•
Toxic air pollution killed thousands in the relatively recent
past.
Industrial emissions are recorded annually by the EPA's
Toxic Release Inventory.
The concentrations and emissions of six criteria pollutants
are regularly measured against a set of national standards.
National air quality is improving despite increases in
population, transportation, and economic growth.
In addition to various health effects, air pollution also
causes acid rain and can reduce visibility.
Air quality diminished in big cities following the Industrial
Revolution and declined further as the popularity of the
automobile increased during the last century. Air pollution at
Earth's surface is at least partially dependent upon weather
conditions. The combination of tall smokestacks and steady
prevailing winds will generally ensure that emissions are
dispersed and diluted.
Air temperature decreases upward under normal atmospheric
conditions and emissions rise upward. However, atmospheric
conditions may sometimes be reversed creating a situation
where cold air is trapped below warm air, creating a
temperature inversion (Fig. 29). Under such conditions the
cold air will remain stagnant, unable to rise, until dispersed by
changing weather conditions. Dense concentrations of
pollutants trapped close to the ground surface may create lethal
air pollution similar to that which caused 5,000 deaths in a
single weekend in London, 1952. Twenty people died and
hundreds became ill as a result of toxic air pollution in
Donora, Pennsylvania, in October 1948. Emissions from a
zinc wire plant were trapped close to ground level by a
temperature inversion. Most of those affected were elderly.
28
Figure 29. Normal
atmospheric
conditions (left) and
conditions
responsible for a
temperature inversion
(right). A temperature
inversion occurs
when warm air lies
above cold air,
preventing the
dispersion of
pollutants.
Criteria Pollutants
National Ambient Air Quality Standards have been determined
for only seven pollutants; particulates, sulfur dioxide, carbon
monoxide, nitrogen oxides, lead, hydrocarbons, and
photochemical oxidants (ozone). The EPA recognizes six
common "criteria" pollutants:
Criteria Pollutants
Carbon monoxide
Nitrogen dioxide
Sulfur dioxide
Particulates
Ozone
Lead
Source
Auto emissions
Auto emissions, electric utilities
Electric utilities, industry
Various (e.g., electric utilities, wood stoves)
NOx + volatile organic compounds + sunlight
Leaded gasoline, lead smelters
Concentrations of criteria pollutants measured in comparison to
National Ambient Air Quality Standards (NAAQS). The six
criteria pollutants have decreased in concentration nationwide
over the last few decades (Fig. 30), and the volume of
Figure 30. Trends in
emissions of sulfur
dioxide (blue),
nitrogen oxides
(green), and volatile
organic compounds
(red) from 1900 to
1997. Original graph
from U.S. EPA National
Air Quality and
Emissions Trends
Report, 1997.
emissions of these pollutants has also declined. However, one
related group of pollutants, nitrogen oxides, has shown a slight
increase in emissions over the last decade. Recent air
regulations are aimed at reducing this last holdout.
Concentrations are linked to the direct emissions of pollutants
or associated gases (e.g., volatile organic compounds, nitrogen
oxides). The bulk of U.S. air pollution comes from the
combustion of fossil fuels and industrial processes (Fig. 31).
These activities are concentrated in urban areas where millions
of people live in close proximity and devour prodigious
amounts of energy. Most emissions have decreased despite
29
economic growth and increases in population and
transportation but some locations still are above NAAQS for
individual pollutants or groups of pollutants. The U.S. EPA
estimates that ~80 million people live in counties that exceed
one or more air quality standards.
Figure 31. States
containing top-10
sources of each of
the criteria pollutants
with a listing of the
types of sources that
generate each type of
pollutant. Information
from U.S. EPA's
Airsdata website.
National efforts to reduce air pollution initially centered on
improving automobile fuel efficiency standards (greater
distance on fewer gallons of gas) or modifying gasoline
composition (unleaded gas). Mass transit systems have been
added in densely populated cities in an effort to get people out
of their cars and into buses or trains. These steps were able to
reduce emissions of almost all major pollutants but
improvements have recently slowed as more fuel-efficient cars
have been overtaken in popularity by minivans and sports
utility vehicles that have lower fuel-efficiency standards (27.5
vs. 20.5 miles per gallon).
Criteria Pollutant Health Effects
Carbon monoxide
Nitrogen dioxide
sulfur dioxide
Particulates
Ozone
Lead
30
Reduces oxygen availability
Respiratory illnesses
Respiratory illnesses, cardiovascular disease
Respiratory illnesses
Respiratory illnesses
Anemia, kidney disease, neurological problems
Although some extreme air pollution events, like those in
London in 1952, can be directly linked to severe illness or
death, the health effects associated with less-profound pollution
events are more ambiguous. Health researchers point to a 56%
increase in asthma cases for U.S. residents aged under 18 from
1982 to 1991 and suggest there is a correlation between
pollution levels and illness and mortality rates.
Figure 32. Good (left)
and poor (right)
visibility at the Grand
Canyon, Arizona, as
a result of air
pollution. From an
original series of 15
slides at the Grand
Canyon Visibility
Transport Commission.
In addition to health effects, air pollution can also result in acid
rain and decreased visibility. Acid rain is precipitated
downwind from areas with sulfur dioxide and nitrogen oxide
emissions. Acid rains leach nutrients from soils, damage
forests, and may cause the acidification of lakes. Recent data
have highlighted decreasing sulfate levels (less acid rain)
because of decreasing emissions of contributing pollutants. Air
pollutants absorb and scatter light to create a haze that limits
visibility (Fig. 32).
Summary
1. What is the source for the majority of energy used in the
U.S.?
Fossil fuels account for the bulk of U.S. energy use. Coal,
natural gas, and petroleum are burned to generate electricity
and refined petroleum products (e.g., gasoline) are used in
transportation. Nuclear energy and alternative (renewable)
energy sources (hydroelectric power, biomass) account for the
31
remainder of electricity generation and approximately 10% of
all U.S. energy consumption.
2. What factors influence energy use in different locations?
States with large populations, large land area (greater distances
to travel), and energy-intensive industries (e.g. oil refining,
chemicals), typically use the most energy. Texas is the most
energy-hungry state because it combines all three of the above
components. States such as Wyoming and Alaska rate highly in
energy use per person because gas consumption is high in these
large, sparsely populated states. The U.S. uses more energy
than any other nation because it also combines a large
population (third in the world) with a large land area, and an
extensive industrial base.
3. How do fossil fuels form?
Fossil fuels form from decayed organic material. Oil, coal and
natural gas are the most common products of this process. Oil
and gas form from organic material in microscopic marine
organisms, whereas coal forms from the solid resins and waxes
that characterize land plants. Tar sands and oil shale are less
common and are less widely used because extraction of oil
from these deposits is more expensive than producing the other
forms of fossil fuels.
4. How are oil and gas deposits formed?
The two principal requirements in the generation of oil and gas
are time and a specific range of temperature. The first
requirement is an organic-rich source of sediments that are
converted to sedimentary rock. Next, chemical reactions occur
during burial under conditions of increasing temperature and
pressure. The reactions occur at temperatures of 50 to 100oC.
The reactions change the organic molecules to hydrocarbon
molecules. With increasing time the hydrocarbons become
more mature changing from heavy oils to lighter oils and
finally, to natural gas. Fossil fuels are considered nonrenewable resources because it is not possible to replenish
consumed reserves at geological rates of formation.
Commercial hydrocarbon deposits are not found in relatively
old (Precambrian) rocks because these rocks have been around
for too long and organic remains would long ago have been
converted to gas and have escaped from the rocks. Likewise,
deeply buried rocks have typically undergone temperatures that
are too high to allow hydrocarbons to remain.
5. Where are the world's oil and gas deposits located?
32
Global oil reserves are made up of over 1,000 billion barrels of
oil, approximately two-thirds of which is present in countries
of the Middle East (e.g., Saudi Arabia, Iran, Iraq, Kuwait).
Major gas deposits are found in the same nations as well as
Russia. Nations with the largest oil reserves typically use
relatively little oil; in contrast, countries that use a lot of oil
(e.g., U.S., Japan, Germany) may have relatively small oil
reserves.
6. How is coal formed?
The two principal requirements in the generation of coal are
time and a carbon-rich organic source made up of the solid
resins and waxes of plants. With increasing burial, water is
expelled from the organic material and carbon content
increases.
7. What is coal rank and how does it vary?
Coal rank is a measure of the carbon content. Rank increases
from a minimum of 30% carbon content for peat to a maximum
of 99% or more for anthracite. Burned coal releases more heat
with increasing rank and less ash remains following
combustion. In order of increasing rank, coal type varies as
follows; peat, lignite, sub-bituminous coal, bituminous coal,
and anthracite. Sub-bituminous and bituminous coals are the
most common coal types.
8. What other properties of coal are important?
The sulfur content of coal is a key factor in determining what
type of coal is used to generate electricity. High-sulfur
bituminous coals contribute to air pollution but yield more heat
per ton of coal than low sulfur sub-bituminous coal. Utility
companies must balance the cost of guarding against pollution
with the extra cost of transporting more low-grade coals that
generate more waste (ash) following combustion. Air pollution
represents an external cost associated with the combustion of
fossil fuels. The use of coal would become less economically
attractive if these costs were applied to the original (internal)
cost of coal. Scientists predict that fossil fuel emissions will
lead to a warmer "greenhouse" world, initiating a potential
cascade of negative economic repercussions. Consequently,
future energy policy may not be concerned with how much fuel
is left, but may instead focus on how to use it without
prompting changes in global climate.
9. How are coal resources distributed?
33
The world's coal resources are distributed more evenly than oil
and gas resources and favor some of the largest nations. The
U.S. and China contain approximately half of the world's coal.
Within the U.S., there are two regions that contain most of the
nation's coal. Appalachian basin states (e.g., Ohio, Kentucky,
Pennsylvania, West Virginia) produce high-rank bituminous
coals and anthracite. These coals are typically produced from
underground mines. Great Plains states (Montana, Wyoming,
North Dakota, South Dakota, Colorado) produce subbituminous coals from relatively inexpensive surface mines.
10. How has technology changed the generation of energy?
Fossil fuel use dominated the first half of the century in all
sectors of energy consumption. Nuclear power held much
promise for electricity generation at the mid-century but
nuclear accidents have continued to raise public concerns about
the safety of nuclear plants. New technologies associated with
solar and wind energy hold hope for the future as they have
few of the drawbacks associated with other energy sources
(pollution, safety). However, renewable energy sources will be
limited by climate and have little potential for replacing
petroleum as the energy source of choice for transportation.
11. How is nuclear energy generated?
Uranium ore contains is a small fraction of the uranium isotope
(U235). The radioactive isotope becomes more concentrated
following milling and enrichment. The uranium isotopes split,
releasing neutrons, when placed in fuel rods in a reactor
assembly and the neutrons are absorbed by other U235 isotopes,
causing further fission. Splitting of the isotopes also generates
heat that converts water to steam and drives a turbine to
generate electricity.
12. Which nations rely most heavily on nuclear energy?
Thirty-three nations generate electricity using nuclear power.
The U.S. uses more electricity from nuclear reactors than
anyone else (28% of global electricity generated by nuclear
power) but this represents a relatively small proportion of the
nation's total electricity use (19%). Some small countries
generate the bulk of their electricity with a few nuclear plants
(Lithuania, 2 nuclear reactors, 77% of electricity; Belgium 7
and 55%; Switzerland 5 and 41%). Some of the world's most
heavily populated nations have either no operating nuclear
power plants (e.g., Indonesia) or very few relative to the size of
their populations (China has 3; India, 10; Brazil, 1).
34
13. What are the advantages to using nuclear power to generate
electricity?
Nuclear advocates typically identify three principal benefits of
the use of nuclear energy: (1) a reduction in air pollution and
decrease in the potential for global warming associated with
fossil fuel use, (2) electricity from nuclear power would reduce
the nation's dependence on foreign oil, (3) new reactors have
safer standardized reactor designs that markedly reduce the
potential for an accident.
14. Sounds pretty convincing, why don't utility companies
build more nuclear reactors?
Assuming that people could be convinced of the safety of
nuclear reactors - a big “if” at present, there are still two issues
that must be dealt with before nuclear energy becomes viable
in the long term. First, many existing nuclear power plants are
approaching the time when they have to be retired from use
(decommissioned) and it will undoubtedly cost companies a lot
of money to dismantle these plants in the relatively near future
leaving fewer funds for building new reactors. Second, more
nuclear power plants mean more high-level nuclear waste and
there is still nowhere to permanently (100,000's years) store the
waste until it is no longer harmful. And just wait until they start
trucking waste cross-country to Yucca Mountain.
15. Why are they trying to dump nuclear waste under a
mountain in Nevada?
Locating a dump for highly radioactive waste requires a
balance be struck between suitable geologic conditions and
cultural and political forces. Nevada's geology and climate
makes it a suitable site for a repository and its relatively small
population makes it politically feasible to site the dump in the
state. Any suitable site must have low-porosity/permeability
rocks that will protect the waste from groundwater infiltration
and must be remote enough so that people are unlikely to
accidentally expose the material during future development.
Ideally, the site would also be far from potential hazards that
might damage the integrity of the repository. Nevada is less
than ideal on this score because it has frequent earthquakes
(small-moderate) and relatively recent volcanic activity.
However, few places are without some form of risk and
scientists will analyze the site to determine if the potential
hazards make it an unsound choice.
16. What is renewable energy?
35
Renewable energy comes in a variety of forms that remain
undiminished with use. It also has the potential to have less of
a negative impact on the environment than fossil fuels or
nuclear power. The principal types of renewable energy
include geothermal, hydroelectric, biomass, solar, and wind.
17. What forms of renewable energy are currently significant
contributors to U.S. energy?
Biomass (burning of wood) and hydroelectric power
(electricity generated from dams) account for most of the
renewable energy generated in the U.S. today but neither has
much potential for growth because there are few rivers left to
dam and limited area to convert to tree plantations to generate
biomass.
18. What forms of renewable energy hold the greatest promise
for the future?
Solar and wind power. Wind power generation is increasing
rapidly worldwide (~20% annually) and photovoltaic cells are
cost-effective in locations that are too distant to be supplied by
a traditional power grid. Solar power will grow more rapidly as
advancing technology reduces the cost of new photovoltaic
cells.
19. What is a temperature inversion?
A temperature inversion occurs when cold air lies below warm
air. Under normal conditions, the temperature of air decreases
with increasing altitude. A parcel of warm air will rise through
the overlying colder air, diluting pollution as it is carried higher
in the atmosphere. Pollutants become concentrated below a
blanket of warm air when cold air lies immediately above the
ground surface. The cold air remains trapped near the surface
until changing weather conditions restore normal conditions.
20. What are criteria pollutants?
These are the six regulated pollutants that are generally
products of the combustion of fossil fuels. The concentration of
particulates, sulfur dioxide, carbon monoxide, nitrogen dioxide,
lead, and ozone are compared to national standards. Locations
that have elevated concentrations must take steps to reduce
them to within the range of the standards.
21. Where does most air pollution come from?
The primary source of air pollution is from the combustion of
fossil fuels. Almost half the energy consumed in the U.S. is
from petroleum and over half the electricity used comes from
36
burning coal. These activities are concentrated in urban areas
where millions of people live in close proximity and devour
prodigious amounts of energy.
37
Energy Consumption vs. GDP
GDP is a measure of the total production and consumption of
goods and services, think of it as the wealth of the nation.
Energy consumption is the amount of energy used for
transportation, industry, domestic use, commerce, etc. Note
that both measures used in this exercise are per capita (per
person).
1. Examine the partially completed graph of gross domestic
product (GDP) per capita vs. energy consumption per
capita below. Label the points that represent where you
think the following nations would plot on the graph. Note:
China, India, Indonesia, and Brazil are ranked 1, 2, 4, and 5
in the world in total population (the U.S. is third).
China
Japan
India
Australia
Indonesia
Saudi Arabia
Brazil
Nigeria
2. Can you suggest explanations for the distribution of the
nations on the graph?
38
Venn Diagram: Oil vs. Coal Resources
Use the Venn diagram, below, to compare and contrast the
similarities and differences between the characteristics of oil
and coal resources. Print this page and write features unique to
either group in the larger areas of the left and right circles; note
features that they share in the overlap area in the center of the
image.
Oil
Coal
39
Sulfur Content vs. Heat Content of U.S. Coal
Examine the map of U.S. coal resources below and predict
where the five numbered points on the graph of sulfur content
vs. BTU might plot on the map.
40
Venn Diagram: Nuclear Energy vs. Renewable
Energy
Use the Venn diagram, below, to compare and contrast the
similarities and differences between the characteristics of
nuclear energy and renewable energy resources. Print this page
and write features unique to either group in the larger areas of
the left and right circles; note features that they share in the
overlap area in the center of the image.
Nuclear Energy
Renewable Energy
41
The Future of Wind Energy
Read the statements below and examine the graph before
answering the questions that follow.
Wind energy has grown more rapidly than any other energy
source in recent years. Approximately 9.6 gigawatts of energy
were generated by wind power in 1998, up from 1 gigawatt in
1985. From 1990 to1998, the global annual rate of growth for
the following energy sources was: wind power 22.2%, oil
1.8%, nuclear power 0.6%, coal 0.0%.
Nuclear power generated approximately 1 gigawatt of energy
in 1960. The use of nuclear energy expanded rapidly in the
1970s before becoming less appealing as a result of some wellpublicized nuclear accidents between 1979 and 1986. Nuclear
energy generation has leveled off at about 340 gigawatts/year
in recent years.
The graph below compares projected plots of the generation of
wind energy vs. time (1985-2025) with nuclear energy capacity
vs. time (1960-2000). The graph projects current trends in the
growth of wind energy into the future at 10%, 15%, and 20%
growth rates.
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1. If we assume a comparable growth rate, approximately how
long will we have to wait until wind energy can produce
the same amount of energy as is currently generated by
nuclear power?
a) 3-6 years
c) 21-24 years
b) 10-12 years
d) 35-40 years
2. What factors might cause wind energy generating capacity
to level off (wind power growth rate would fall to near
zero) in the future.
3. Will wind energy be as productive as nuclear power?
Explain your answer.
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