COAL AND ELECTRICITY GENERATION
Chris Petrauskis and Craig Pierce
Since the industrial
revolution, coal has been fundamental to the creation of electricity in
the United States. In 2002,
51.8% of the electricity generated in the United States came from the use
of coal as an energy source. Nuclear,
the next most substantial energy source, accounted for 19.8% of the total.
At 16.1%, the combustion of natural gas contributed the third
greatest amount of electricity
[1]
. Although coal is
the primary supplier of electricity for the country as a whole, energy
sources vary among the different states.
This variance occurs due to a number of geographical, geological,
and economic factors, which will be addressed in more detail.
For example, Kentucky and Indiana depended upon coal for 96% and
94%, respectively, of their electricity production in 1999.
In contrast, California used coal for a mere 1% of its 1999
electricity production, depending much more upon natural gas (46%) and
hydroelectric power (22%) as sources for electricity.
In Wisconsin, 69% of electricity production in 1999 depended upon
coal
[2]
.
Due
to industrial, technological, and economic expansion, the demand for
electricity from coal within the United States has grown dramatically
throughout the past few decades. Since
1970, the amount of electricity from coal consumed within the
United States surged 148% from 1,532 billion kilo-Watt-hours (kWh) to
3,792 billion kWh in 2002. Furthermore,
according to the EIA, the consumption of electricity from coal is expected
to be 42% higher in 2020 than in 2000.
[3]
While the overall
consumption of coal will increase over the next few decades, the national
reliance as a percentage of the whole is projected to decrease as
renewable energy sources fill in the gaps.
Stages
of the Fuel Cycle
The
process of converting the dense energy of coal into the useful form of
electricity can occur in a number of different ways.
Most of these processes, however, contain the same basic elements.
Following is a brief explanation of the basic steps shared by
the most prevalent coal combustion plants: First,
coal must be extracted from the Earth.
Trapped for millions of years, large coal deposits exist in
thirty-eight of the fifty United States, lying beneath 13% of the country’s
area. Depending on the
location and composition of these deposits, coal can typically be
classified into four different types.
Lignite is the most abundant form of coal in the world and
is widespread across the Western United States.
Yet, due to its young ecological age, the low energy content of
lignite limits this source of coal as a realistic source for combustion.
Subbituminous coal, an older coal also found across the
West, has been the most widely used type across the United States
[4]
. Nearly one-third
of all the coal used in United States coal powers plants is extracted from
the state of Wyoming. Wyoming’s
subbituminous coal contains approximately 18 million Btu/ton and produces
only .58 lbs. of SO2/ton
[5]
. Forming
approximately 150 million years ago beneath fresh water reservoirs,
subbituminous coal contains a relatively small percentage of both energy
and sulfur. A third form of
coal, bituminous, is older and has a higher energy content than
subbituminous coal. This
coal, found primarily in the Midwest and East, contains approximately 24
million Btu/ton. Finally, anthracite,
a highly sulfuric coal found mostly in Pennsylvania, contains
approximately 23 million Btu/ton and gives off 1.58 lbs of SO2
upon combustion. The higher
energy and sulfur content is due to the formation of this natural resource
beneath salt-water oceans over 300 million years ago.
For
a coal plant seeking the most economical coal resource, three primary
factors must be considered – energy content, geographic location, and
purity. As evident from its
prevalent usage, subbituminous coal is considered the most cost-effective
type of coal in the United States. Although anthracite holds the highest
concentrated energy per Btu, power plants opt to pay shipment fees for a
less concentrated subbituminous coal source due to ultimate savings on SO2
control
[6]
.
The
mining process physically removes coal from natural coal deposits. Depending
on the location of the deposits, coal can be mined by one of two major
methods: surface mining and underground mining.
Surface, or strip, mining extracts coal from deposits located just
beneath the Earth’s outer crust. Surface
mines typically spread over a large area, as miners use bulldozers and
large augers to dig downward toward the coal deposits.
Underground mining focuses on coal deposits that are located
hundreds of meters beneath the Earth’s surface.
In order to extract this fuel, miners must dig deep beneath the
Earth’s surface using cutting, drilling, and blasting.
This method usually depends heavily upon deep shafts and complex
mine development to extract the coal.
Following extraction, coal is typically transported via truck or
train to facilities than crush, pulverize, and clean the rock
[7]
. Finally,
the coal is shipped by truck, ship, railroad, barge, or pipeline to the
individual power plants. “Hundreds
of coal trains and barges run day and night, delivering coal at a rate of
2.5 million metric tons per day to power plants and factories around the
country.”
[8]
Upon
reaching a coal plant, a number of steps are taken to transform the
concentrated energy within the coal into electricity.
First, the clean and pulverized coal enters a boiler.
Within this boiler, the coal begins to combust at a very hot
temperature. This combustion
creates heat, as well as several other gases.
This heat and gas can then be used to move turbines and generate
electrical energy. The heat
produced from coal combustion typically boils water to create this steam
which drives a steam turbine. In
some coal plants, this process is pressurized and the gases released
during combustion power gas turbines as well.
Finally, the remaining steam is condensed back to water and either
recycled back to the boiler or released to the environment
[9]
.
Environmental
Problems
Despite
its negative impact upon the environment, the coal combustion power plant
is the most common method of generating electricity.
In order to explore the downsides of the coal plant, one must first
understand the environmental effects caused by each of the four primary
pollutants. As explained
previously, each type of coal contains a different sulfur content,
depending on how the fossil fuel was formed.
In the combustion reaction, sulfur combines with excess oxygen fuel
to form sulfur dioxide (SO2).
Without proper regulation, SO2 escapes into the
atmosphere, where it can combine with water vapor in the air to form a
mildly acidic substance, or acid rain.
Besides its ability to accelerate the corrosion of many materials,
acid rain in high concentration can change the acidity of a body of water,
disrupting a delicate aquatic habitat.
A second bi-product of the combustion process is the formation of
nitrogen oxides (NOx). NOx
also forms through reactions with excess oxygen in the heat producing
combustion reaction, and contributes to acid rain along with the formation
of local smog. The formation
and release of carbon dioxide into the atmosphere is the growing problem
for coal as a sustainable energy source, for CO2 in the
atmosphere is a catalyst for the constant warming of the earth.
[10]
To
fully understand the environmental effects of coal power, one must
consider the full spectrum of its impact.
The Union of Concerned Scientists presented a study of the
ecological impact of a 500-megawatt coal plant.
A plant this size would typically produce 3.5 billion kilo-watt
hours per year, burn 1,430,000 tons of coal, use 2.2 billion gallons of
water, and provide enough electricity to power a city of about 140,000
people. For example, during
one year of service, such a plant puts out 10,000 tons of SO2,
10,200 tons of NOx, 1.7 million tons of CO2, 500
tons of small particles, 220 tons of hydrocarbons, and 720 tons of CO.
Furthermore, the plant would output large quantities of sludge,
ash, lead, and other metals. Additional
impacts include radioactive emissions, ecosystem alteration, ground water
contamination, transportation problems, and human injury and death.
[11
Alternate
Technologies
In
order to address growing environmental concerns regarding coal power
plants, the United States Department of Energy initiated the Clean Coal
Technology Demonstration Program (CCT) in 1985.
This program was designed to “create a partnership between
government, several states, and private companies to test new methods
developed by scientists to make coal burning much cleaner.”
Since its inauguration in 1985, the CCT has received over $2
million from the United States government, and over $4 million from states
and private companies. Today,
the CCT has developed technology that can filter our nearly 99% of air
particles and 95% of acid-rain pollutants during the coal combustion
process
[12]
. Currently,
several Clean Coal Technologies are being implemented within coal power
plants to reduce SO2, NOx, and other emissions.
The first major step to improving the cleanliness of coal
combustion involves a simple cleansing process.
Typically, before combustion, coal is crushed and pulverized into
tiny chunks. Then, this coal
is fed into large water tanks. The
small coal particles float to the top of the tank, while other substances
and impurities fall to the bottom. This
process is a simple and somewhat effective way of removing coal’s basic
impurities. In fact,
facilities across the country, named ‘coal preparation plants,’
specialize in this very process. Unfortunately,
cleansing coal does not remove all of coal’s impurities.
The process of removing sulfur from coal becomes a bit more
difficult. Although the
cleansing process removes much of the coal in sulfur, the remaining traces
still have a significant effect upon the environment.
In order to further purify coal, many plants use flue gas
desulfurization units, also known as scrubbers, to absorb SO2.
These scrubbers inject powdered limestone into the combustion
chamber. This limestone
serves as a sponge to absorb SO2 and form calcium sulfates
(gypsum) that are wet and pasty, but not released into the air.
Coal plants can then remove these calcium sulfates from the
combustion units without releasing any sulfur into the air.
Today, scrubbers are capable of typically eliminating 90% of sulfur
emissions
[13]
. The CCT is also
testing for new and improved scrubber technologies as well
[14]
.
Additional developments have also been implemented in order to
reduce NOx emissions. Nitrogen,
a natural occurring element, composes 80% of the atmospheric air.
When these nitrogen compounds (N2) are heated to a very
high level, the nitrogen breaks apart to form bonds with oxygen, creating
the pollutant NOx. How can
this reaction be prevented? The
solution is called ‘staged production,’ a process that uses multiple
combustion burners that use much more fuel that oxygen.
As a result, all of the present oxygen is used to fuel the
combustion process. This
leaves far fewer remaining oxygen available to react with nitrogen and
form NOx gases. Then,
with the ‘staged production’ method, the remaining unburned fuel is
moved to another chamber with a limited amount of oxygen.
The remaining unburned fuel from this combustion chamber then moves
to another combustion chamber, and the process continues until all of the
fuel is burnt. Although the
staged production process is extremely cost effective, it typically
results in only a 50% maximum reduction in emissions.
Currently over one-half of United States coal plants implement this
staged combustion technology. Many
plants also utilize NOx scrubbers, similar to the SOx
scrubbers described above, to further improve emission levels.
A more cutting edge technology, the fluidized bed boiler, builds
upon the scrubber technology. Unlike
traditional combustion chambers, the fluidized bed boiler depends upon
upward-blowing jets of air that suspends and appears to ‘fluidize’ the
burning coal. This
fluidization process reduces emissions in two major ways.
First, the tumbling allows the powdered limestone to better mix
with the limestone. As a
result, the limestone is able to absorb more potential pollutants.
Secondly, the presence of air jets greatly cools the combustion
process. In fluidized bed
boilers, the temperature inside the chamber drops from an average of 3000
degrees Fahrenheit to an average of 1400 degrees Fahrenheit.
As a result, the air is typically not hot enough for NOx
to form. Fluidized bed
boilers have been shown to reduce up to 90-95% of SO2 emissions
and 90% of NOx emissions.
Additionally, these chambers can be pressurized to utilize both
steam and gas turbines
[15]
. This
pressurization can enhance the efficiency of coal plants by up to 45-50%
[16]
.
Perhaps the most innovative CCT system in use today is the
oxygen-based integrated gasification combined cycle (IGCC) technology.
This process is completely non-combustive and depends upon the
actual gasification of coal. First,
crushed coal and limestone are added to the fluidized bed gasifier, where
a portion of the sulfur mixes with limestone to form calcium sulfide.
No combustion takes place within this chamber, but the coal is
heated to a high temperature and blasted with hot steam.
The heat and steam then gasify the coal into a mixture of carbon
monoxide and hydrogen. This
gas can then be used to spin gas and steam turbines.
The gases can first be burnt to generate electricity with the gas
turbine. Secondly, the heat
and exhaust gases coming out of the gas turbine can also be used to spin a
steam turbine. By gasifying
the coal, scientists can now remove 99.9% of sulfur and other particles
from coal
[17]
. Tests also show that IGCC plants emit 37.13 less lb/mWh of SO2,
8.55 less lb/mWh of NOx, and .09 lb/mWh less of CO2
than an original pulverized coal plant
[18]
. Although coal plants are far from eco-friendly, new technology and
innovation are greatly reducing the ecological impact of coal power.
Limitations
and Advantages
Referencing previously discussed aspects of this report, two facts
jump out which severely limit the feasibility of coals power as the energy
of the future. At best
estimates, efficiency capabilities for the coal plant are expected to
reach only 60% in the foreseeable future.
Also, despite the impressive advancements in clean-coal
technologies, few affordable methods of CO2 sequestering or
prevention have been discovered. If
global warming does progress as predicted, the demand for electricity
produced without the release of greenhouse gasses is sure to rise.
On the other hand, under the current political and economic
situation of the United States, coals stands as the nation’s most
crucial natural resource to ensure that increasing energy demands are met.
To begin, there is an abundance of extractable coal within the
borders of the United States, making it a secure source of energy over the
next few decades. The U.S.
imports only 12.5 million tons per year, less than 1% of annual total coal
consumption, which highlights the negligible reliance upon foreign
countries for this fossil fuel. The
stocks of coal have been projected to last 265 more years at current rate
of usage and 93 more years at an annual rate of growth of 2%
[19]
. Growth over the
next twenty years has been projected at 1.35%
[20]
. Because of these
advantages, coal is a very affordable source of energy also, costing only
$1.22 per million Btu over the 2002 nine-month weighted average
[21]
.
Over the past 25 years, the federal government has played a
significant role in shaping how coal is combusted to produce electricity,
especially by addressing the environmental regulation of coal-production.
As part of the 1978 Clean Air Act Amendments, the emission
standards were raised for all coal plants built after the date of issue.
Under the New Source Review (NSR) aspect of the amendments, plants
built prior to 1978 did not have to meet tougher standards unless
undergoing significant modifications or additions.
For the past 25 years, some plants have taken advantage of this
loophole to avoid modernizing pollution control, by increasing quantity of
coal combusted inefficiently rather than updating existing facilities and
facing NSR. Currently, 36% of
older units emit SO2 at levels above NSR standards, and 73% of
these pre-1978 facilities continue to emit NOx at levels above
NSR standards
[22]
. The other most
substantial piece of legislation affecting coal plants is the Bush
Administration Clear Skies Initiative, which some praise for clarifying
the complicated EPA timeline for tightening emission standards and others
criticize for delaying increased air pollution control by ten years
[23]
. (See
Appendix V.) The
National Coal Council recognizes the confusion of those in the industry
who need a clear vision of future emission guidelines, especially those
amidst a design and construction process for a new coal plant which
typically takes 6 years.
[24]
Additional
Issues
As Professor John Karcneck mentioned during his lecture, many
cities within Europe operate coal combustion electric plants at impressive
total thermodynamic efficiencies, through the utilization of post-turbine
steam as a heat source for residential and industrial use.
Yet, this ‘cogeneration’ is convenient only on those situations
where there is a constant and significant demand for heating, thus in
colder climates or for industrial application.
As electricity production becomes further deregulated, there may be
a greater potential within the United States for the implementation of
smaller combined heat and power plants.
[25]
NATURAL GAS AND ELECTRICITY GENERATION
Megan Cain and Andy Zychowicz
There are four traditional methods of generation electricity using
natural gas as the fuel source. The
first, and most basic method is steam generation.
Steam generation uses natural gas combustion energy to heat a
boiler. The steam produced
then turns a turbine, which powers the generator to produce electricity.
These types of systems are located in large power plants and are
generally base load type plants that supply a steady stream of electricity
but cannot be turned on and off quickly to accommodate peaks and valleys
in the power grid. Natural
gas is used less often in these steam generation units than are coal and
oil. These types of units,
which use the high heat capacity of water to optimize thermal output,
typically achieve 33 to 35 percent of thermal efficiency, meaning that
about a third of the heat generated is converted into electrical energy.
Thermal energy is not total energy stored in the natural gas, only
that portion of the energy that is converted to heat.
The two thirds of heat generated that is not used to produce
electricity is exchanged with the environment surrounding the plant and is
lost as far as function al work is concerned.
The second traditional method for generating electricity from
natural gas is the centralized gas turbines.
Centralized gas turbines do not utilize steam but instead turn the
turbine with the hot gasses directly produced from combustion of natural
gas. Since there is no need to wait for water to be converted to steam,
the turbines begin turning as soon as heat is produced from the combustion
process. This property lends
gas turbines to primarily peak load production where short
ignition-to-electricity times are vital.
The cost of this advantage over steam generation units is lowered
thermal efficiency. Natural
gas is used widely in this peak load generation strategy due to its
ability to be quickly and easily ignited.
Another strategy for electricity production using natural gas is
the combustion engine. This
type of unit works much the same way that any motor vehicle’s internal
combustion engine works. The
fuel source (natural gas or gasoline vapors in cars) is combusted within a
cylinder creating heat that expands the gas within the cylinder.
This expansion drives a piston, which then turns a shaft that will
in our case drive a generator to produce electricity.
This method also yields a short ignition-to-electricity time that
is best utilized in peak load production.
However, this advantage of quick production again leads to a loss
in efficiency compared to a steam generation plant.
The final traditional method of generating electricity using
natural gas is combined cycle units.
These systems use a combination of both steam and gas turbines that
allow for use of previously wasted heat.
The gas turbines work in much the same manner as mentioned above
but the waste heat from the system is used to produce steam to turn
another turbine and hence recovering some thermal efficiency.
Combined cycle plants can be turned on quickly and achieve thermal
efficiencies of up to 60 percent. These
designs are the obvious choice for most proposed power plants.
[26]
These natural gas fired power plants have come online and are the
fastest growing source of electricity production in the United States.
Approximately one quarter of the energy consumed in the U.S. is
derived from natural gas. However
only a small, but rapidly growing, portion of the national natural gas
consumption is used in electricity production.
In Wisconsin less than one percent of the electricity generated is
from natural gas sources.
[27]
The total
national reliance on natural gas for electricity consumption varies
greatly. For the fourth
quarter of 2002 almost 17 percent of natural gas demand was satisfied by
electricity generation. These
differences are due to fluctuations in both peak load demands and natural
gas market prices.
[28]
Stages
of the Fuel Cycle
The fuel cycle for natural gas begins with exploration and
drilling. Most natural gas
deposits currently being exploited are found in one of two places.
The first and most conventional method of tapping natural gas
begins with the exploration for oil.
The formation of both natural gas and oil are very similar and
natural gas differs only in the fact that it has undergone stresses of
heat and pressure greater than that of oil and allowed the carbon
containing material to be broken down to a single or couple carbon atoms.
This thermogenic natural gas is formed deeper than the oil
deposits. As the light gas
rises through rock formations, it is trapped above the oil deposits by
impervious rock formations. This
gas is under positive pressure and will rise to the surface without added
energy once the capping rock structure has been tapped.
The second, less conventional source of natural gas currently being
exploited is coal bed methane. Coal
bed methane is natural gas that has seeped into cracks or veins in coal
beds. This form of natural
gas is generally under pressure form the water table slightly above it and
to allow the methane to rise to the surface, water must be pumped out of
the area reducing the pressure on the gas.
The water pumped out from the ground is generally non-potable water
contaminated with salts and a host of dissolved particulate matter and
minerals. This water is
sometimes pumped back into the ground but wastewater pits are often times
constructed to cut costs. Seismic
imaging is used to detect the location, size, and depth of both forms of
gas deposits. Once the
natural gas is discovered, the next step is to build the infrastructure
necessary to extract the fuel. Most
new formations are found in non-developed areas.
Therefore roads and electrical lines must be erected to not only
support construction of the wells but also to support the maintenance of
wells, powering of compressor stations, and regulation of production.
Once the natural gas has been tapped and brought to the surface via
wells it must be transported to a consumer.
This is accomplished via the interstate natural gas pipeline
system. The 272,000 miles of
high strength steel pipe that comprise the nation’s interstate gas
pipeline provide transportation form the wellhead to the power plant.
The gas is processed at plants along this pipeline to remove trace
elements of sulfur, liquid butane and propane, water, carbon dioxide and
other trace gasses that could reduce efficiencies at power plants or
produce harmful chemicals when combusted.
Along this pipeline every 50-60 miles, compressor stations are
needed to keep pressure in the system optimal and therefore keep the gas
moving along the pipeline.
[29]
The last stop
before entering a utility is the gate station where gas pressure is
reduced to levels usable by the utility, gas is metered to allow for
measurement of total gas consumed by the utility, and a “rotten egg”
odorant is added to allow for easy detection of gas leaks.
[30]
Once the gas has entered the particular utility it is generally
combusted with oxygen to produce wastes of heat and carbon dioxide.
Other wastes such as nitrogen oxides (100 lbs/mbtu), sulfur
dioxides (0.6 lbs/mbtu), and other wastes are produced in very small
quantities compared to other fossil fuels and some have been practically
eliminated in previous handling (gate stations and processing plants).
The main waste product of natural gas combustion is carbon dioxide.
Natural gas produces 115,000 pounds of carbon dioxide emissions per
million Btu combusted.
[31]
There are no
solid wastes from natural gas electricity generation.
Natural gas is a very potent greenhouse gas, even more dangerous
than carbon dioxide and leaks or main breaks may also be considered waste
products.
Environmental
Problems
The
environmental problems associated with natural gas all seem to stem from
exploration and extraction of natural gas.
The first issue raised by the exploration for new gas deposits is
the locations of natural gas reserves.
We have already tapped and nearly exhausted all natural gas
deposits in developed areas. This
forces the exploration and exploitation of new reserves to pristine
wildlife areas that have not been developed.
The impacts up on native wildlife can be devastating.
The exploration for and possible development of natural gas and
other fossil fuel reserves in the Powder River Basin of the Shoshone
National Forest in Wyoming and Montana, part of the Greater Yellowstone
Ecosystem, poses the greatest threat to one of it’s keystone predators
the grizzly bear. According
to a 1991 study by Dave Mattson and Richard Knight of the Interagency
Grizzly Bear Study Team, the roads that will have to be built impose a
five times greater mortality rate among the already endangered keystone
species. The study shows that
the bears tend to avoid habitat within 2.4 miles of a road regardless of
food, water, or other resources located within this habitat.
The outcome of the decision to develop this wilderness for it’s
coal bed methane gas could set a precedent that could effect one of the
nations last pristine western wildlife reserves.
[32]
Another source of environmental concern is wrapped up in the
problem of western land rights. A
large portion of the land west of the Mississippi River that is owned by
the individual residents confers only the surface rights to that land and
rights to the subsurface resources are owned by the government.
These land rights practices are remnants of the Homestead Act that
attracted the first settlers from the east.
The government also owns access rights to those resources.
This disparity in land use has caused many problems for the
residents of land holding natural gas reserves.
The main uses of western land containing gas reserves are ranching
and agriculture. When natural
gas is discovered on the land used by private citizens, conflicts erupt.
One major problem is the use of water by natural gas utilities.
To allow the methane to collect and rise to the surface, massive
amounts of water must be pumped from the ground.
In New Mexico’s San Juan Basin, 5.8 billion gallons of water have
been pumped out of the ground in natural gas production.
A majority of this water was pumped back deep into the ground
recharging the aquifer. While
this abundance of water may seem like a boon for ranchers and
agriculturalists starved of water in the arid west, this water is often
not pure. The water pumped
out can have a very high salinity and kill crops or grazing land if used
for irrigation. For some
utilities, the solution to these adverse environmental effects is the
construction of wastewater pits. However,
this approach also causes concern with locals because of loss of
aesthetics and the possibility of wastewater leaching into surface or
ground waters. Farmers and
ranchers downstream that rely on the water for irrigation are upset by the
increased salinity of the rivers. This
problem also greatly effects aquatic wildlife that depends on relatively
low, constant salinity levels.
Pumping massive amounts of water has effects beyond surface
conflicts. Water table levels
are lowered by this practice and can have drastic effects upon the local
human population and the local/regional ecosystems in general.
People living on the relatively undeveloped land do not have the
convenience of clean, local, pressurized municipal water that high-density
living provides city dwellers. Instead,
they must rely on wells and the natural aquifers to not only purity their
water, but also to pressurize it occasionally and allow it to naturally
flow to the surface. The
lowering of the water table due to coal bed methane drilling not only
dries up those natural springs but also disrupts the hydrological cycle
that replenishes, transports, and purifies water for human use.
Lowering of the water table and its effects upon hydrological
system elements also has effects upon the non-human constituents of the
ecosystem both in the short term and long term effects upon regional
aquifers and flora that may not be understood or realized for decades or
longer.
The dual nature of land rights and land use in the west combined
with the activities necessary and some unnecessary undertaken by utilities
has also brought landowners and utilities head to head.
[33]
Cattle ranchers
have cited the callous energy companies with killing cattle with
machinery, poising livestock with wastewater overflow, and excessive noise
intrusion upon their normally quiet comfortable rural existences.
As one representative of the utilities indicated, the utilitarian nature of their industry
has local impacts but great national benefits. “There
is little or no constituency for producing energy products that have
national benefits but only local impacts," Ken
Wonstolen of Colorado Oil and Gas
Association stated, "but we’re going to have to
drill more wells…or this economy is going to shut down."
[34]
Limitations
and Advantages
The main limitations as described above are the environmental and
social impacts of exploration and production of natural gas.
However there are two other large disadvantages for natural gas as
an energy source for electricity production.
These are the intimately linked ideas of supply and price.
The supply of thermogenic natural gas is obviously finite within a
human lifetime or several generations.
We have been consuming natural gas since it was originally used to
light streetlights and have only increased our consumption as it has been
fitted as a fuel source for an increasing number of applications.
We are not only consuming more than we are producing but the vast
stores of concentrated, “cheap” natural gas have mostly been tapped
and are close to running dry. Not
only does this raise the long-term question of sustainability of reserves
for the future but also the short-term problem of skyrocketing prices.
Natural gas has historically been seen as an attractive alternative
to other energy sources due to its low price.
In the past year gas prices have risen 130 percent and show no
signs of reversing course.
[35]
These price
hikes, resulting from a harsher winter, rise in other fossil fuel prices
(especially oil), and instability in the international community, have
caused natural gas subscribers to dig much deeper into the pocket book
this year and caused utilities to shift away from their gas fired power
plants.
[36]
There are however several advantages to using natural gas.
Paradoxically the main advantage to natural gas is it’s
comparative environmental benefits. The
main component of natural gas, methane (CH4), possesses more
energy per carbon atom than any other fossil fuel or possible arrangement
of hydrocarbons. Not only
does it release the smallest possible amount of carbon per unit but also
the nature of gas allows it to be free of most solid sulfur containing
compounds that cause coal to be so “dirty”.
This gives it the distinction as the cleanest burning fossil fuel.
[37]
The domestic nature of natural gas reserves gives it a two-prong
benefit. The fact that the
majority of the natural gas consumed in the U.S. is produced domestically
frees us from international geopolitical tangles and trade volatility.
Transportation is another benefit of domestic production.
Natural gas is easy to transport across the interstate pipeline
system and environmental disasters on the magnitude of oil barge spills
are almost an impossibility. Price
was mentioned as a disadvantage but also can be an advantage in two ways.
The high prices currently being experienced allow a lower
opportunity cost for utilities to explore non-conventional reserves which
may be more environmentally benign and to invest in more efficient capture
and use of natural gas. Natural
gas prices fluctuate with the market forces placed on them.
Natural gas has been used in systems where cogeneration with
different fuel sources has allowed for greater flexibility to different
market prices of the fuels.
[38]
Alternative
Technologies
Methane is produced by a number of methods other than thermogenesis.
For example, methane is produced by several bacterial organisms
that breakdown organic material such as biomass.
WE Energies in Wisconsin is currently using landfills and cow
manure to produce methane for use in power plants.
[39]
Recent discovery
of catalysts have provided a positive energy yielding chemical formula
that can produce methane, ethane, ethylene, propane, propylene, and butane
from the greenhouse gas carbon dioxide and hydrogen chloride.
This reaction could be placed in smokestack scrubbers to remove
carbon dioxide and convert it into methane usable to generate electricity.
Another reaction that could possibly be used in scrubbers to remove
carbon dioxide is biological reactions.
Methanococcus jannaschiik, a bacterium recently isolated from
thermal vents, produces methane from carbon dioxide and available hydrogen
and is viable in harsh conditions.
[40]
Great deposits of natural gas also lie frozen in cages of ice.
Gas hydrates are methane molecules trapped within ice lattices and
are found in relatively high densities off the continental shelves of
North America.
[41]
These formations
could possibly contain 270,000,000 trillion ft3 of methane that
could provide the world with enough energy at current growth rates for
well over a century. The
drilling and extraction techniques however are in their infancy at best.
Knowledge of the effects upon the environment are also unknown,
however this very well may be the answer to the supply problem.
[42]
In addition to the traditional model of electricity production with
a centralized utility power plant designs for distributed generation
provide hope for a more efficient future in electricity generation.
Distributed generation refers to smaller power plants providing
electricity for a block of homes or industrial/commercial complex.
These systems utilize small gas turbines, combined cycle units,
fuel cells or combustion engines and employ combined heat and power (CHP)
systems that are able to use the waste heat from electricity generation to
heat homes, hot water, or industrial boilers improving thermal efficiency
up to 80 percent. This means
that we use up less of our limited reserves and in the case of fuel cells,
powered by methane, are able to capture the carbon dioxide and prevent its
emission into the environment.
NUCLEAR POWER AND ELECTRICITY GENERATION
Lindsay Leiterman and Karin Schindel
We
first must look at how much the United States already uses nuclear power
as an energy source and which states are the main generators.
The United States as a whole relies approximately 20% on nuclear
power for their electrical power. Most
of the producers are located in the Midwest and Eastern United States.
The leading states include Vermont with 67% reliance, South
Carolina with 55%, and Illinois with 50%.
[43]
Uranium
is the starting material for nuclear energy so it is important to see
where it is mined. The
nuclear fuel cycle uses far less starting material than do the typical
fossil fuel cycles. For
example a 1000MW coal plant requires approximately 3 million tons a year
of coal a year where a 1000MW nuclear plant requires only 25 tons of
Uranium dioxide each year for the same result.
It is still important to look at the world reserves.
Australia has 25.7% left in world reserve, Africa has 24% and North
America has 21.9%.
[44]
Stages
of the Fuel Cycle
The
nuclear fuel cycle is a very important part of nuclear energy because it
does not rely on combustion which makes this so different than other
fossil fuel types of energy production. A 1000MW coal plant produces
approximately 7 million tons of waste gases into the atmosphere each year
in the form of carbon and sulfur dioxides as well as 150-200,000 million
tons of solid wastes such as fly ash and sulfur.
Without the combustion, many of the harmful emissions are not a
part of nuclear energy production. With
the reprocessing process the waste can be reduced to approximately 1 ton
per year. Instead of waste in
the form of emissions, nuclear plants produce radioactive waste which will
needs a disposal methods that can secure it because it can be harmful for
thousands of years. It is
very important in this process that it designed to prevent significant
water contamination to the public.
[45]
The
first step is the mining and milling process.
The uranium is mined either by surface or underground mining
techniques. The major mines
in the United States are located in New Mexico and Wyoming with Colorado
and Utah closely following.
[46]
The uranium is
then sent to a mill where it is crushed and made into a slurry. Once it is
in this liquid it is leached to sulfuric acid and precipitated out as
Uranium Oxide. Mill tailings,
the residual wastes from the mining, are also made in this step.
These have proven harmful to the environment so during the mining
process they are pumped into an impoundment.
[47]
The
Uranium Oxide is then converted into the gas Uranium Hexafloride.
This is only done at plants in Europe and the United States so they
have to transport it between the milling and conversion step.
The
uranium naturally consists of roughly .7% of the U-235 isotope and 99.3%
of the U-238 isotope. The
enrichment process uses a centrifuge method to increase the U-235
concentration to 3.5%-5%. The
increased amounts of U-235 increases the energy created from the nuclear
process because the U-235 is what drives the reaction.
The
enriched U-235 then goes to the fuel fabrication where it is converted in
uranium dioxide pellets. These
pellets go into steel rods which are bundled together and inserted
into the core of the nuclear reactor.
Within
the reactor, the U-235 are struck by atomic particles which causes the
U-235 to split and then release their own particles to strike other U-235,
all causing a large chain reaction. Some of the U-238 turns in Plutonium
which yields about one third of the plant’s output.
Only one third of the plant’s spent fuel needs to be replaced
each year.
The
spent fuel is highly radioactive so it is stored in spent fuel storage
ponds to reduce radioactivity and heat.
It must cool for long periods of time because after the nuclear
reaction the fuel is very hot and radioactive. After the spent fuel cools,
it can either be reprocessed or slated for permanent disposal. “Spent
fuel still contains approximately 96% of its original uranium, of which
the fissionable U-235 content has been reduced to less than 1%. About 3%
of spent fuel comprises waste products and the remaining 1% is plutonium.”
[48]
The Uranium and
Plutonium can be separated from the waste by chopping up the fuel rods and
dissolving them in acid. The
recovered Uranium can be sent to the conversion plant so that they can be
reprocessed.
To
immobilize the radioactivity, at a high temperature, high level waste can
be heated to produce a dry powder which can be incorporated into
borosilicate, a form of glass. The
glass is poured into stainless steel canisters which could be buried in
stable rock such as granite, volcanic tuff, salt, or shale.
At
the end of the useful life of a nuclear reactor, the plant must then be
decommissioned. The plant is
shut down and radioactive components are disposed of so that the public is
not affected. First all the
spent fuel must be removed from the site and then there are four options
of what can be done with the rest of the plant.
The first option is SAFSTOR or mothballing which involves some
decontamination, the plant is closed, and the plant is perpetually
guarded. The ENTOMB or
entombment option involves concrete or steel barriers around the most
radioactive equipment to prevent the release of radioactivity again with
guards for an indefinite time. DECON
or immediate dismantlement where decontamination is followed by
destruction. All materials
are sent to a low level waste sight.
The forth option of delayed dismantlement is the same as the DECON
method except with a several year break in between decontamination and
destruction to reduce personnel exposure.
[49]
Concerns
and Limitations
Nuclear
power is also a very efficient power.
Because it does not use combustion and so much energy is not lost
as waste heat. An average
plant is said to have a 33% thermal efficiency.
The table below clearly shows that nuclear power produces
substantial amounts of electrical power for the small amount of Uranium
used compared with other sources.
[50]
|
Firewood
|
16
MJ/kg
|
|
Brown
coal
|
9
MJ/kg
|
|
Black
coal (low quality)
|
13-20
MJ/kg
|
|
Black
coal
|
24-30
MJ/kg
|
|
Natural
Gas
|
39
MJ/m3
|
|
Crude
Oil
|
45-46
MJ/kg
|
|
Uranium*
- light water reactor
|
500,000
MJ/kg
|
(MJ
= Megajoules) *Natural Uranium
Research
into reprocessing should be continued because, if utilized correctly, it can
minimize the amount of spent fuel waste.
The United States has had problems with the reprocessing process
because of several incidents of the fuel causing everything it came into
contact with becoming radioactive. This meant even higher amounts of waste
disposal. Several other
countries such as France, Germany and Japan have succeeded in efficient
use of reprocessing spent fuel. The
lack of spent fuel, although still radioactive with long-term waste
disposal needed, from a nuclear plant that reprocesses should be compared
with the amount of waste that the same size coal plant would produce.
Comparing a 1000MWe coal plant to a 1000MWe nuclear plant the
nuclear plant if the participate in reprocessing end up with considerably
less waste. The nuclear plant
needs only 25 UO2 to for that plant and will produce 27 tons of
spent fuel but 97% can be reprocessed leaving only about 700kg of spent
fuel. The coal plant needs
about 3 million tons of coal per year and produces as much as 7 million
tons of carbon dioxide, 200,000 tons of sulfur dioxide, and 200,000 tons
of fly ash. All of these are
quite harmful to the environment. Reprocessing
can also be seen as an attempt as proliferation of nuclear weapons because
the plutonium being recycled can be the fundamental material for nuclear
weapons.
[51]
A
main focus of issues surrounding nuclear power is that of safety.
This concern encompasses many aspects throughout the entire process
of nuclear fission as a means for energy production.
Mining of the uranium can be done with very little risk and
basically no negative environmental impacts.
However, once the fuel reaches the plants, disturbances are more
likely to occur. The high
temperatures in which the process of fission takes place have the
potential of allowing a radiation release by melting the metal enveloping
the uranium fuel, known as a “meltdown.”
This release of radioactive particles would pollute the atmosphere,
possibly groundwater, and all things relying on this air, water, and land.
A further issue that may evolve once an accident has already
occurred is the boiling away, or evaporation, of the water used in the
reactor for heat transfer. This
again would result in the release of radiation into the atmosphere.
[52]
There
is also the safety concern involved with the transportation of the spent
nuclear fuel. “The United
States Department of Energy ships highly radioactive materials between
former production sites, research reactors, power reactors, storage, and
other facilities throughout the United States.”
[53]
The spent fuel in this comes from commercial nuclear power
plants, foreign and domestic research reactors, and U.S. nuclear powered
warships. The nuclear fuel is
shipped across the United States by railway or specified trucking routes.
Since 1964, 3000 shipments of spent fuel have been shipped over 1.7
million miles and no container has ever leaked.
The Nuclear Regulatory Committee and the Department of
Transportation decide on the most direct route that avoids all major
cities. The governor is required to be notified before the trip and
usually the driver will drive the route ahead of time to assure that he is
comfortable with the route. The
fuel container consists of many layers of shielding inside a thick steel
cylinder and undergoes many tests to make sure it is invulnerable to
impact flames, submersion, and puncture.
[54]
Health
concerns are frequently related to nuclear power, specifically those of
humans. While many people
believe processing nuclear fuel exposes humans to high and unsafe levels
of radiation that enter the atmosphere, the opposite is true.
Radiation from the nuclear fuel cycle only contributes 0.1% of the
total radiation in the environment to which humans are exposed
consistently. Instead, the
majority of radiation, 82%, is derived from unavoidable and natural
sources such as radon and surface rock.
Another 11% of total radiation experienced by people is internal,
that is the radiation comes from their own body.
Numerous studies have further proven there to be no connection
between the nuclear fuel cycle and radiation levels noted in humans by
noting no connection between those living and working for long periods of
time near a nuclear plant to leukemia or cancer levels.
[55]
There
are also risks from the uranium mining process if the mill tailings are
not properly dealt with. The
mill tailing contain waste and can contaminate ground water as well as are
linked the increased release of radon gas which is harmful to humans.
These mining sites are now required to decommissioned by properly
containing all of these mill tailings before the site is left permanently.
Because they contain some levels of radioactivity, mill tailings
are placed in impoundments that account for geology, seismic activity,
ground water levels, availability of naturally occurring clay and
potential flooding. During the mining wildlife and unnecessary humans are
kept off the land and after mining is complete they are covered with rock
and soil ten feet deep to protect against radon emissions.
Water quality is also taken into account when burring the mill
tailings.
[56]
Perhaps
the best known example of a nuclear power accident is that which occurred
at the Chernobyl plant in the Ukraine, April 26, 1986.
Large amounts of radioactive particles were ejected into the
atmosphere after a reactor was destroyed when a loss of coolant led to an
explosion from within. The
immediate concern was to prevent the fire from spreading to further
reactors at the site. Unfortunately
this led to the deaths of many firefighters from the direct exposure to
such intense levels of radiation. While
the on-site cleanup was thorough and included encasing the burned reactor
in 300,000 tons of concrete, scrubbing buildings and roads of the
radioactive dust, and removing contaminated soils, the negative impacts of
this disaster will be faced by Europeans and Ukrainians for many decades.
The radiation spread unpredictably throughout the northern
hemisphere, with some of the heaviest sections falling in France, Norway,
Sweden, the Mediterranean Sea, the Atlantic Ocean and of course, near the
actual site. Large areas of
farmland and forests were contaminated and will not be able to be used as
resources for well over a century. This
loss of agriculture resulted in a local economic fall.
The inhabitants of many areas of Ukraine are still not able to
safely consume local water, milk, meat, fish, fruits, or vegetables and
over 170,000 people were forced to permanently relocate.
Furthermore, those exposed to the high radiation areas mentioned
above, continue to experience increases in death rate, birth defects,
leukemia, organ cancers, mental retardation, and immune abnormalities.
[57]
The
ensuing investigation was able to ascertain the initial cause for this
calamity to be a flaw in the reactor.
The reactor, known as the RBMK reactor, was not stable at low
power, which led to the explosion, nor was the reactor enclosed in a
containment building thus, the immediate release of radiation could not be
prevented. While the RBMK
reactor is not used in North America or in Western Europe, 15 operating
RBMK reactors can be found throughout Russia, the Ukraine, and other
neighboring countries.
[58]
The
second cause for the disaster was human error.
Significant errors in reaction to the initial incident were made by
the plant operators due to their lack of understanding and preparation for
such occurrences. The
employees within the plant were not knowledgeable on a scientific or a
technical level as to the plant they were operating.
[59]
Another
well-known nuclear plant incident occurred at the Three Mile Island Plant
in Pennsylvania, 1979. A
failure in the cooling system combined with human error in response to
this failure, led to a 50% melt down of the reactor core.
Unlike Chernobyl, a very minimal radioactive release occurred since
the reactor was housed in a containment building, preventing nearly all
radiation from escaping. No
significant environmental damages occurred, nor did any immediate
casualties result.
[60]
Another
concern of utilizing nuclear power as a main energy source is economic
based. Nuclear energy had
been predicted to be significantly cheaper than traditional fossil fuels
by the year 2000. Unfortunately,
this prediction did not hold true in the United States.
However, in France, where almost 80% of their electricity is
generated by nuclear power, this energy source is 27% cheaper than coal
generated electricity. There
are several reasons for this significant difference in usage and cost.
The main reason is due to the large subsidies which the French
government supplies for research, development, proper waste disposal, and
even insurance coverage against plant related accidents.
Secondly, France develops their plants using a uniform design in
order to save money.
[61]
The
United States has not built a nuclear plant since 1976 and the opening of
any new plants in the near future is not being heavily considered for
several reasons. The plants
take years to plan and build to ensure safety.
During the construction various permits must be obtained which is a
slow and expensive process, often delaying construction even further.
Some states have deregulated their electricity market, allowing
users to purchase energy from the least expensive source, these not being
the aging nuclear plants. Most
often closing a plant is more cost effective than attempting to make
necessary repairs. However,
the combination of these early closing plants and the plants whose
licenses expire is projected to decrease the nation’s nuclear reliance
from 20% to 7%, with the last plant predicted to close in 2035.
[62]
Yet
another focus of concern is the handling of wastes, as noted by the Union
of Concerned Scientist, stating, “In addition to safety issues, nuclear
plants continue to be problematic because of their spent fuel rods and
other radioactive waste. By 1995, US nuclear plants had produced almost
32,000 metric tons of high-level radioactive waste.
[63]
Finding a way to keep this waste out of the environment for
the thousands of years it remains radioactive has proven difficult.
Problems such as groundwater contamination led to four of the six
commercial facilities that store low-level radioactive waste being closed.
[64]
” Currently the
nation’s low-level wastes are being stored in South Carolina and Nevada,
however these sites are quickly reaching capacity levels which will then
force states to dispose of low-level wastes on an individual basis.
Intermediate wastes resulting from nuclear weapons production are
being stored in underground salt beds in Carlsbad, New Mexico.
This waste primarily consists of nuclear weapons.
In
1987, Yucca Mountain was identified by the United States Congress as a
candidate site for permanent high-level waste storage from commercial
nuclear power plants. For
further information on this selection please consult The United States
General Accounting Office Report “Nuclear Waste: Uncertainties About the
Yucca Mountain Repository Project” GAO-02-765T, May 23, 2002, which
states “in February [2002], the Secretary of Energy endorsed the Yucca
Mountain site, and the President recommended that Congress approve the
site”. The area lies 90
miles northwest of the tourist city of Las Vegas and would be expected to
hold 70,000 tons of spent fuel waste.
Many concerns arise in selecting this mountain as a holding site.
Scientists agree that the spent fuel waste will not be able to be
fully contained until it has decomposed and that eventual leakage will
occur. This leakage could be
worsened or accelerated by any activity of the quake fault lines on which
the mountain is located. An
earthquake would lead to a rise in the water table which would result in
radioactive contamination of air and groundwater.
Further, since the majority of nuclear reliant states are located
far east of Nevada, the average spent fuel wastes will have to travel
2,300 miles. The nation’s
spent fuel wastes will cross through 43 states in order to reach this
final site which further increases the risk of accidents occurring in
transportation.
[65]
Alternate
Technologies
An
alternative to requiring a high-level radioactive permanent storage
facility is reprocessing all the spent fuel and in the future using
alternative methods such as fusion to generate electricity.
A type of reprocessing can occur by breeder nuclear fission which
uses the U-238 in combination with Pu-239, a fissionable, human-made
isotope, in order to avoid the enrichment process of obtaining the U-235.
If all the U-238 currently being stored in waste sites were to be
used in this method, the product would supply the United States with
electricity for over 100 years. However,
immense safety issues arise in using the breeder nuclear fission since it
requires liquid sodium instead of water for cooling purposes.
Liquid sodium, being a very violent compound, can burn
spontaneously in the presence of air at high temperatures and react
explosively when in contact with water.
Also, governments, as well as, the public commonly dislike breeder
fission because the plutonium isotope required is additionally the fuel
for nuclear weapons. The last
breeder fission plant closed in France in 1997 due to economic reasons and
no future use of this method is being examined.
[66]
Fusion is continuing to be researched as a more efficient way to
gain nuclear power. This
process involves the combining of two light atomic nuclei under intense
heat and pressure. During
this reaction, immense quantities of energy are produced in the form of
heat which is then transformed into electricity.
The energy output during the fusion process is much greater than
that which results from burning fossil fuels, so much so, that almost 9
million mL of gasoline are required to equal the energy potential of 1 mL
of fusion fuel. The fuel
source for fusion is easily obtainable considering it is merely various
isotopes of the hydrogen atom. The
typical isotopes used are Deuterium, found in water, and Tritium, formed
by adding neutrons to atoms found in salt water and some types of surface
rock, Lithium-6. Progress is
being made to overcome the challenges that inhibit frequent use of this
process. One such obstacle is
that the heat under which atoms fuse is in the millions of degrees.
Another impediment is the confining of the fuel at such high
temperatures as the ionized gas becomes plasma.
[67]
Currently,
experimental reactors using both magnetic fusion and inertial fusion are
being assessed.
[68]
These
alternatives to a standard fuel container would prevent the nuclei from
losing energy when they come in contact with the container walls.
Instead, for instance in the magnetic confinement, the plasma would
circulate in a ring shaped chamber allowing the atoms to combine with each
other.
[69]
The use of
magnetic or inertial fusion is predicted to be operating commercial power
plants by 2050.
[70]
OIL AND ELECTRICITY GENERATION
Joe Pedersen and Joe Rowley
A
small percentage of the petroleum that is used in this country is
designated for the purpose of generating electricity, but it is still an
important resource for energy production in many areas of the country.
This report will analyze the ethical implications of oil production
and its use as a source of electric energy production, taking into account
the consequences that occur at each stage.
Oil
is used to generate electricity, through a process of combustion, heating
water, and producing steam. As
the liquid water molecules are heated, they expand and produce increased
pressure that is harnessed to rotate a turbine that in turn causes a
generator to produce electricity. This
method is inefficient due both to the loss of heat, and the inability to
capture the electrical energy being produced by the generator for future
use. Most energy plants that
use this method of steam powered turbine generators actually employ coal
because it is a much cheaper fuel. Only
2.9% of the nation’s electric energy is derived from the combustion of
oil.
[71]
Stages
of the Fuel Cycle
Extraction: The
extraction process consists of the stage of the fuel cycle in which the
oil is located and removed from the reservoir.
Various methods of exploration are employed to determine where
suitable pockets of oil can be found.
One modern method of exploration uses sound waves.
Once found, a well is established that allows the oil to be
extracted.
When first established, oil wells often remain pressurized and oil
naturally flows out of the ground. This
natural flow of oil is called primary production.
Often, much oil remains in the ground after primary production, but
this leftover oil is much harder to remove.
[72]
Transportation: Once
extracted, the oil must be channeled through different means of
transportation to refineries where it is converted from “crude” to
multiple usable products. On
land, oil is transported by pipe, rail, and road, and by sea, oil tankers
are used.
Refinement: By heating
the crude oil, refineries separate the oil into many different usable
products, based on their different boiling points.
After the crude oil has been heated it is separated in a
fractionation tower, which may be 30.5 meters (100 feet) tall.
The lower the boiling point of the component of the crude oil, the
higher the component rises within the tower.
These components (petrochemicals) can be used for a wide variety of
applications, from heating the kitchen stove to producing asphalt for the
roads on which we drive.
[73]
Consumption: At the
electricity generating plant, oil is combusted to convert liquid water
into steam, creating pressure and turning the turbines that produce
electricity. When combusted,
the oil produces exhaust (CO2,
SOx, NOx, carbon monoxide) and solid waste
(CO2 and sludge) which have divers negative effects on the
environment.
Environmental
Problems
According
to the Natural Resource Defense Council, oil companies disregard the
stringent policies developed to minimize the ecological impact of
extracting the oil from the ground because government agencies fail to
enforce environmental protection laws.
[74]
Each year, accidents
and illnesses occur that are connected with production of materials needed
for plant, oil field development, and transportation.
[75]
Transportation is especially hazardous, as illustrated by the
table below.
|
|
Death
|
Fire/Explosion
|
Injury
|
|
Truck
|
87.3
|
34.7
|
2.3
|
|
Rail
|
2.7
|
8.6
|
0.1
|
|
Barge
|
0.2
|
4.0
|
3.6
|
|
Tank
Ship
|
4.0
|
1.2
|
3.1
|
Comparisons
based on calculated rates per ton-mile. (Source: Allegro Energy Group)
Throughout
each stage in the use of oil, exhaust is produced as some of the oil is
burned to power each process. Exhaust
is an inevitable byproduct that has been found to significantly increase
the risk of cancer in oil refinery workers.
Air pollutants (SOx, NOx, carbon monoxide)
resulting from the other phases of the oil cycle, including oil field
development and transportation,
[76]
have detrimental effects on the associated workers.
The consequences to the environment from the oil production cycle
can be just as significant. Loss
of forests, crops, and animals occurs due to absorption of oil
combustion-derived air pollutants (particulate matter), released during
power plant operation,
[77]
while marine habitat can be affected negatively by the
transportation of petroleum using oil tankers and the associated spillage
that results. At a global
level, increased concentrations of greenhouse gases (CO2, SOx,
NOx) dispersed throughout the atmosphere by each phase of oil
use threaten the integrity of the world climate by causing global warming.
Global warming potentially encompasses wide-ranging consequences
including fluctuating temperatures, extreme droughts, floods, and storms,
shift of climate zones and loss of habitat, raised sea levels from melting
polar ice caps, and increased respiratory and heat related illness.