Coal

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Coal
 
Coal has been used longer than any other form of fossil fuel. Even early
Coal has been used longer than any other form of fossil fuel. Even early
cavemen used coal (known as black rock) for heating purposes. In the
cavemen used coal (known as black rock) for heating purposes. In the
Line 11: Line 10:
and other metals. Th e coal byproduct, coke, was widely used in glass
and other metals. Th e coal byproduct, coke, was widely used in glass
blowing, brick and tile manufacturing, and production of high purity
blowing, brick and tile manufacturing, and production of high purity
-
metals that transformed the fi eld of metallurgy.21 Another byproduct of
+
metals that transformed the field of metallurgy ([[#Additional Comments|a]]). Another byproduct of
-
coal, the coal gas, revolutionized the fi eld of lighting, fi rst on the streets
+
coal, the coal gas, revolutionized the field of lighting, first on the streets of London and soon thereafter in other large European cities (See box “Coal Gas”). As more and more coal was extracted, the need for better
-
of London and soon thereaft er in other large European cities (See box
+
drilling equipment, safety devices, and hauling carts increased. Th is led to important innovations ranging from reciprocating pumps to atmospheric
-
“Coal Gas”). As more and more coal was extracted, the need for bett er
+
-
drilling equipment, safety devices, and hauling carts increased. Th is led to
+
-
important innovations ranging from reciprocating pumps to atmospheric
+
engines and wagon tramways.
engines and wagon tramways.
 +
In the early twentieth century, coal accounted for 90% of all energy
In the early twentieth century, coal accounted for 90% of all energy
supplies in the world, before it lost its dominance as an energy source
supplies in the world, before it lost its dominance as an energy source
Line 23: Line 20:
combustion engines. Today, coal accounts for a quarter of the world’s
combustion engines. Today, coal accounts for a quarter of the world’s
primary energy consumption, and generates 40% of all electricity. Similar
primary energy consumption, and generates 40% of all electricity. Similar
-
fi gures for the US are 25% and 50%.22
+
figures for the US are 25% and 50% ([[#References|1]]).
-
21 Coke is produced by carbonization of coal in an oxygen-defi cient environment and high temperatures.
+
 
-
22 2004 estimates; a. World Coal Institute (htt p://www.worldcoal.org); b. US Geological Survey (htt p://energy.usgs.gov/coal.html).
+
==Types of Coal==
-
161
+
 
-
Chapter 7 - Fossil Fuels
+
The quality of coal is typically categorized by its rank and grade. Th e rank of the coal represents its morphological development from peat to lignite (or brown coal), sub-bituminous, bituminous (soft coal), and anthracite (hard coal). The higher the coal is ranked, the greater is its carbon content,resulting in more energy being liberated when it is burned (Table 1). The grade of the coal determines its purity. Coal is of a better grade if its sulfur content is less and burns with lower emissions; coal is classified into low, medium, and high grades.
-
Types of Coal
+
 
-
Th e quality of coal is typically categorized by its rank and grade. Th e rank
+
:{| border='1' {{table}}
-
of the coal represents its morphological development from peat to lignite
+
|-
-
(or brown coal), sub-bituminous, bituminous (soft coal), and anthracite
+
| colspan="4" | Table 1. Coal Ranks and their Properties.
-
(hard coal). Th e higher the coal is ranked, the greater is its carbon content,
+
|-
-
resulting in more energy being liberated when it is burned (Table 7-6).
+
|| Rank || Age<br />(million years) || Carbon Content || Heating Value<br />(kJ/kg)*
-
Th e grade of the coal determines its purity. Coal is of a bett er grade if its
+
|-
-
sulfur content is less and burns with lower emissions; coal is classifi ed into
+
|| Anthracite || 350 || 85-95% || 34,000 and up
-
low, medium, and high grades.
+
|-
-
Table 7-6. Coal Ranks and their Properties.
+
|| Bituminous || 300 || 45-85% || 25,000-35,000
-
Rank Age
+
|-
-
(million years)
+
|| Sub-bituminous || 100 || 35-45% || 20,000-25,000
-
Carbon Content Heating Value
+
|-
-
(kJ/kg)*
+
|| Lignite || 60 || 25-35% || 10,000-20,000
-
Anthracite 350 85-95% 34,000 and up
+
|-
-
Bituminous 300 45-85% 25,000-35,000
+
| colspan="4" | *Higher Heating Values.
-
Sub-bituminous 100 35-45% 20,000-25,000
+
|}
-
Lignite 60 25-35% 10,000-20,000
+
 
-
*Higher Heating Values.
+
[[Image:Major Recoverable Coal.jpg|thumb|500 px|alt=Table 2 Major Recoverable Coal. |Table 2 Major Recoverable Coal.]]
 +
 
Whether coal ranks higher or lower depends largely on how it was formed.
Whether coal ranks higher or lower depends largely on how it was formed.
-
Th e fi rst stage of coal formation involves the compression of vegetation
+
The first stage of coal formation involves the compression of vegetation
-
under the heavy weights of water and ground materials. Th ese materials
+
under the heavy weights of water and ground materials. These materials
gradually turn into a dark-brown, compact organic material known as
gradually turn into a dark-brown, compact organic material known as
peat. Over time, peat is compressed and heated to form lignite. Lignite is
peat. Over time, peat is compressed and heated to form lignite. Lignite is
Line 56: Line 54:
the texture of the original wood may even be found in pieces of lignite. At
the texture of the original wood may even be found in pieces of lignite. At
greater depths, lignite is transformed into sub-bituminous, bituminous, and
greater depths, lignite is transformed into sub-bituminous, bituminous, and
-
ultimately anthracite coal. Th erefore, it is expected to fi nd anthracite in the
+
ultimately anthracite coal. Therefore, it is expected to find anthracite in the very old deposits that reside in the deep layers and to find lignite in the younger deposits and in those closer to the surface.
-
very old deposits that reside in the deep layers and to fi nd lignite in the
+
 
-
younger deposits and in those closer to the surface.
+
==Reserves and Resources==
-
Reserves and Resources
+
 
-
As Table 7-7 indicates, just fi ve countries, the US, Russia, China, India,
+
As Table 2 indicates, just five countries, the US, Russia, China, India,
and Australia, own about 70% of the total world coal reserves – estimated
and Australia, own about 70% of the total world coal reserves – estimated
at 976 billion metric tons. Despite what one might expect, with the
at 976 billion metric tons. Despite what one might expect, with the
exception of Iran, there are no coal mines in the Middle East.
exception of Iran, there are no coal mines in the Middle East.
-
Coal Gas
+
 
-
FYI ...
+
[[Image:US actual and projected coal production.jpg|thumb|500 px|alt=Figure 1 US actual and projected coal production. |Figure 1 US actual and projected coal production.]]
-
Coal gas (also called town gas or synthetic gas) is produced by heating the coal or exposing it to hot steam in the
+
 
-
absence of air to carbon monoxide and hydrogen. During the 19th century coal gas was used primarily in cooking and
+
[[Image:World coal consumption outlook by region.jpg|thumb|500 px|alt=Figure 2 World coal consumption outlook by region. |Figure 2 World coal consumption outlook by region.]]
-
heating and later in the gas-lanterns used by most major cities. Because of its low caloric value and problems with tars, oil,
+
 
-
and other pollutants, it was replaced by petroleum when the source was discovered.
+
-
Coal gas can be burned directly or converted to methane, gasoline, or other petroleum products such as plastics and
+
-
photographic film.
+
-
Table 7-7. Major Recoverable Coal
+
-
Resources Worldwide (2002 data)*
+
-
Country Total
+
-
Recoverable
+
-
Reserves
+
-
(Billion metric
+
-
tons)
+
-
Percentage
+
-
of the total
+
-
US 243 25.0
+
-
Russia 157 16.2
+
-
China 103 10.6
+
-
India 90 9.3
+
-
Australia 72 7.4
+
-
Rest of
+
-
the World
+
-
306 31.5
+
-
Total 971 100
+
-
*EIA,2003 Internati onal Energy Annual Report,
+
-
DOE/EIA-0219 (2003)
+
-
162
+
Large coal deposits are found in 38 US states, with more than half of these
Large coal deposits are found in 38 US states, with more than half of these
in only three states: Wyoming, West Virginia, and Kentucky. Anthracite is
in only three states: Wyoming, West Virginia, and Kentucky. Anthracite is
most commonly found in Pennsylvania and accounts for only 1% of the
most commonly found in Pennsylvania and accounts for only 1% of the
US’s coal reserves. About 70% of coal is bituminous; the rest is essentially
US’s coal reserves. About 70% of coal is bituminous; the rest is essentially
-
lignite. Eastern and Mid-continent coalfi elds contain mostly bituminous
+
lignite. Eastern and Mid-continent coalfields contain mostly bituminous
coal, while sub-bituminous coal is predominantly found in the Western
coal, while sub-bituminous coal is predominantly found in the Western
states. Most lignite is mined in Texas, Montana, and North Dakota.
states. Most lignite is mined in Texas, Montana, and North Dakota.
 +
Worldwide coal production, which reached 4.8 billion metric tons in
Worldwide coal production, which reached 4.8 billion metric tons in
2004, accounted for more than a quarter of all energy sources and about
2004, accounted for more than a quarter of all energy sources and about
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primary consumption to petroleum and natural gas, coal production (and
primary consumption to petroleum and natural gas, coal production (and
consumption) leveled off until 1972, whereupon the rate started to rise
consumption) leveled off until 1972, whereupon the rate started to rise
-
again.23 Th e latest fi gures indicate coal consumption at one billion metric
+
again ([[#References|2]]). Th e latest figures indicate coal consumption at one billion metric
-
tons in 2004. Th e US’s proven, identifi ed, and ultimate (identifi ed and
+
tons in 2004. Th e US’s proven, identified, and ultimate (identified and
undiscovered) coal reserves are estimated at 247 billion, 1557 billion, and
undiscovered) coal reserves are estimated at 247 billion, 1557 billion, and
-
3968 billion metric tons, respectively.24 Th e actual and projected US coal
+
3968 billion metric tons, respectively ([[#References|3]]). Th e actual and projected US coal
-
productions are shown in Figure 7-14.
+
productions are shown in Figure 1.
 +
 
Although the US has the most coal reserves in the world, it is China
Although the US has the most coal reserves in the world, it is China
-
that produces (and consumes) the most coal. Th e trend is expected to
+
that produces (and consumes) the most coal. The trend is expected to
continue, and in the next two decades, coal use is projected to increase
continue, and in the next two decades, coal use is projected to increase
by another 36%, with the largest increases projected for China and India
by another 36%, with the largest increases projected for China and India
-
(Figure 7-15). In Europe, however, substantial declines in coal use are
+
(Figure 2). In Europe, however, substantial declines in coal use are
-
projected in favor of cleaner natural gas.25
+
projected in favor of cleaner natural gas ([[#References|4]]).
-
Environmental Concerns
+
 
 +
==Environmental Concerns==
 +
 
 +
[[Image:Impact of various energy technologies.jpg|thumb|500 px|alt=Figure 3 Impact of various energy technologies on global warming and overall air quality. |Figure 3 Impact of various energy technologies on global warming and overall air quality.]]
 +
 
Coal is probably the dirtiest of all fossil resources; it produces more
Coal is probably the dirtiest of all fossil resources; it produces more
carbon per unit energy content, has the highest percentage of sulfur, and
carbon per unit energy content, has the highest percentage of sulfur, and
produces more nitric oxides. Th e relative impact on global warming and
produces more nitric oxides. Th e relative impact on global warming and
overall air quality is considered to be the greatest, producing twice carbon
overall air quality is considered to be the greatest, producing twice carbon
-
dioxide as oil for the same amount of energy (See Figure 7-16).
+
dioxide as oil for the same amount of energy (See Figure 3).
Depending on how deep the coal is buried, coal can be extracted by digging
Depending on how deep the coal is buried, coal can be extracted by digging
tunnels or strip-mining. Hazards associated with tunnel operation include
tunnels or strip-mining. Hazards associated with tunnel operation include
cave-ins, explosions from dust buildup, carbon monoxide poisoning, and
cave-ins, explosions from dust buildup, carbon monoxide poisoning, and
-
lack of suffi cient ventilation. Although tunneling operations harm miners
+
lack of sufficient ventilation. Although tunneling operations harm miners
the most, strip-mining has the greatest environmental impacts. Th ese
the most, strip-mining has the greatest environmental impacts. Th ese
include the destruction of fertile surface-soil, permanent changes in the
include the destruction of fertile surface-soil, permanent changes in the
landscape, and the possibility of acidic or alkaline drainage to the surface
landscape, and the possibility of acidic or alkaline drainage to the surface
-
(Figure 7-17). In many industrial countries, public and environmentalist
+
(Figure 4). In many industrial countries, public and environmentalist
pressure has forced local governments to require coal mining companies
pressure has forced local governments to require coal mining companies
to reclaim the land and restore it to its original form aft er strip-mining.
to reclaim the land and restore it to its original form aft er strip-mining.
-
Figure 7-14
+
 
-
US actual and projected coal production.
+
[[Image:Shale oil.jpg|thumb|500 px|alt=Figure 4 Shale oil can potentially meet a great portion of the future energy demand. |Figure 4 Shale oil can potentially meet a great portion of the future energy demand.]]
-
Source: Historical data, EIA 2006.
+
 
-
23 Barlett , A., “Fundamentals of the Energy Crisis,” Th e American Journal of Physics, 40, September 1978. pp. 876-888.
+
-
24 EIA Website (htt p://www.eia.doe.gov/cneaf/coal/reserves/chapter1.html).
+
-
25 Enery Information Agency Fact Sheet (htt p://www.eia.doe.gov).
+
-
Figure 7-15
+
-
World coal consumption outlook by region
+
-
(1990-2025).
+
-
Source: Energy Informati on Agency, 2003.
+
-
Figure 7-16
+
-
Impact of various energy technologies on
+
-
global warming and overall air quality.
+
-
Air Pollution Impact
+
-
Greenhouse gas impact
+
-
HIGH
+
-
LOW
+
-
LOW HIGH
+
-
Wind
+
-
Nuclear
+
-
Biomass
+
-
Natural gas
+
-
Petroleum
+
-
Coal
+
-
163
+
-
Chapter 7 - Fossil Fuels
+
-
26 Lumpkin, R.E., “Recent Progress in the Direct Liquefaction of Coal,” Science, 239, p. 873, 1988.
+
-
27Hatfi eld, C. B., “How long oil supply grow?” M. King Hubbet Center for Petroleum Supply Studies, Newslett er #97/4-1-6, October 1997.
+
Since coal is formed primarily underneath swamp beds, it contains a large
Since coal is formed primarily underneath swamp beds, it contains a large
amount of sulfur. To remove the sulfur, coal is crushed into small chunks
amount of sulfur. To remove the sulfur, coal is crushed into small chunks
and washed inside large water tanks. Since sulfur is heavier than coal,
and washed inside large water tanks. Since sulfur is heavier than coal,
-
most sink to the bott om and is removed. Some of the sulfur is chemically
+
most sink to the bottom and is removed. Some of the sulfur is chemically
bonded to carbon (organic sulfur) and cannot be washed off this way; it
bonded to carbon (organic sulfur) and cannot be washed off this way; it
must be removed by adding chemicals that react with sulfur and break it
must be removed by adding chemicals that react with sulfur and break it
loose.
loose.
 +
Although most sulfur is removed by physical and chemical processes, the
Although most sulfur is removed by physical and chemical processes, the
coal burned in power plants still contains considerable amounts of sulfur
coal burned in power plants still contains considerable amounts of sulfur
Line 175: Line 131:
before it is released into the atmosphere. In wet scrubbers, limestone
before it is released into the atmosphere. In wet scrubbers, limestone
slurry is sprayed onto the fl ue gases where it combines with sulfur to form
slurry is sprayed onto the fl ue gases where it combines with sulfur to form
-
a paste that is left behind. Dry scrubbers consist of a fi xed sorbent bed
+
a paste that is left behind. Dry scrubbers consist of a fixed sorbent bed
of activated carbon, char, and alumina impregnated with copper. Large
of activated carbon, char, and alumina impregnated with copper. Large
-
bag houses remove larger particles while electrostatic precipitators fi lter
+
bag houses remove larger particles while electrostatic precipitators filter
smaller particulates.
smaller particulates.
 +
In addition to ecological concerns, coal extraction can be quite dangerous.
In addition to ecological concerns, coal extraction can be quite dangerous.
It is estimated that several thousand miners are killed each year as a
It is estimated that several thousand miners are killed each year as a
Line 185: Line 142:
widespread, the number of mine accidents and fatalities are expected to
widespread, the number of mine accidents and fatalities are expected to
increase.
increase.
 +
Of course, coal has a number of advantages. It is relatively cheap; it can be
Of course, coal has a number of advantages. It is relatively cheap; it can be
transported by truck, ship, and rail; it is easy to store and burn, and can be
transported by truck, ship, and rail; it is easy to store and burn, and can be
-
liquefi ed to produce synthetic oil. Every ton of coal will yield about 5.5
+
liquefied to produce synthetic oil. Every ton of coal will yield about 5.5
-
barrels of liquid fuel.26 It should be noted, however, that although there
+
barrels of liquid fuel ([[#References|5]]). It should be noted, however, that although there
exists a large quantity of coal reserves to be exploited, if coal is used to
exists a large quantity of coal reserves to be exploited, if coal is used to
substitute the current demand for petroleum, the coal supply would serve
substitute the current demand for petroleum, the coal supply would serve
-
as only a very temporary solution to the problem.27
+
as only a very temporary solution to the problem ([[#References|6]]).
==References==
==References==
 +
 +
(1) 2004 estimates; a. World Coal Institute (http://www.worldcoal.org); b. US Geological Survey (http://energy.usgs.gov/coal.html).
 +
 +
(2) Barlett , A., “Fundamentals of the Energy Crisis,” Th e American Journal of Physics, 40, September 1978. pp. 876-888.
 +
 +
(3) EIA Website (htt p://www.eia.doe.gov/cneaf/coal/reserves/chapter1.html).
 +
 +
(4) Energy Information Agency Fact Sheet (http://www.eia.doe.gov).
 +
 +
(5) Lumpkin, R.E., “Recent Progress in the Direct Liquefaction of Coal,” Science, 239, p. 873, 1988.
 +
 +
(6) Hatfield, C. B., “How long oil supply grow?” M. King Hubbet Center for Petroleum Supply Studies, Newsletter #97/4-1-6, October 1997.
 +
 +
(7) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005
 +
 +
==Additional Comments==
 +
 +
(a) Coke is produced by carbonization of coal in an oxygen-deficient environment and high temperatures.
==Further Reading==
==Further Reading==
 +
 +
Berkowitz, N., Fossil Hydrocarbons: Chemistry and Technology,
 +
Elsevier Academic Press, 1997.
 +
 +
Deff eyes, K. S., Hubbert’s Peak: Th e Impending World Oil Shortage,
 +
Princeton University Press, Princeton, N. J., 2001.
 +
 +
Campbell, C. J., Th e Coming Oil Crisis, Multi-Science Publishing
 +
Company, 2004.
 +
 +
Tariq Ali, Th e Clash of Fundamentalisms: Crusades, Jihads and
 +
Modernity, Verso, 2002.
 +
 +
Pelletiere, S., Iraq and the International Oil System: Why America
 +
Went to War in the Gulf, Praeger Publishing, 2001.
 +
 +
Oil and Gas Journal, Technology, news, statistics, special reports, and
 +
analysis (http://ogj.pennnet.com).
 +
 +
Journal of Petroleum Technology, The official journal of Society of
 +
Petroleum Engineers, Dallas.
 +
 +
The Petroleum Engineer, Petroleum Engineer Pub. Co.
 +
 +
Journal of Petroleum Science and Engineering, Elsevier, covers the
 +
fields of petroleum (and natural gas) exploration, production and
 +
flow.
==External Links==
==External Links==
 +
 +
National Energy Technology Laboratory: Th e Strategic Center for
 +
Coal (http://www.netl.doe.gov/coal).
 +
 +
National Petroleum Technology Office (http://www.npto.doe.gov).
 +
 +
US Geological Survey (http://www.usgs.gov).
 +
 +
Organization of Petroleum Exporting Countries (OPEC) (http://www.opec.org).
 +
 +
Society of Petroleum Engineers (http://sae.org).

Current revision as of 16:47, 21 July 2010

Coal has been used longer than any other form of fossil fuel. Even early cavemen used coal (known as black rock) for heating purposes. In the United States and many other industrial countries, fuel wood was the dominant energy source until the sixteenth century. In the early seventeenth century, aft er many forests had been cleared and wood became scarce, coal substituted wood as the main source of fuel. Th e coal extracted from shallow streams was high in sulfur and burned with an irritating smell but also had some advantages. It burned at higher temperatures than wood and was more desirable for the smelting of irons and other metals. Th e coal byproduct, coke, was widely used in glass blowing, brick and tile manufacturing, and production of high purity metals that transformed the field of metallurgy (a). Another byproduct of coal, the coal gas, revolutionized the field of lighting, first on the streets of London and soon thereafter in other large European cities (See box “Coal Gas”). As more and more coal was extracted, the need for better drilling equipment, safety devices, and hauling carts increased. Th is led to important innovations ranging from reciprocating pumps to atmospheric engines and wagon tramways.

In the early twentieth century, coal accounted for 90% of all energy supplies in the world, before it lost its dominance as an energy source to petroleum, a liquid fossil fuel that could easily be used in internal combustion engines. Today, coal accounts for a quarter of the world’s primary energy consumption, and generates 40% of all electricity. Similar figures for the US are 25% and 50% (1).

Contents

Types of Coal

The quality of coal is typically categorized by its rank and grade. Th e rank of the coal represents its morphological development from peat to lignite (or brown coal), sub-bituminous, bituminous (soft coal), and anthracite (hard coal). The higher the coal is ranked, the greater is its carbon content,resulting in more energy being liberated when it is burned (Table 1). The grade of the coal determines its purity. Coal is of a better grade if its sulfur content is less and burns with lower emissions; coal is classified into low, medium, and high grades.

Table 1. Coal Ranks and their Properties.
Rank Age
(million years)
Carbon Content Heating Value
(kJ/kg)*
Anthracite 350 85-95% 34,000 and up
Bituminous 300 45-85% 25,000-35,000
Sub-bituminous 100 35-45% 20,000-25,000
Lignite 60 25-35% 10,000-20,000
*Higher Heating Values.
Table 2 Major Recoverable Coal.
Table 2 Major Recoverable Coal.

Whether coal ranks higher or lower depends largely on how it was formed. The first stage of coal formation involves the compression of vegetation under the heavy weights of water and ground materials. These materials gradually turn into a dark-brown, compact organic material known as peat. Over time, peat is compressed and heated to form lignite. Lignite is a soft , brownish-black coal, containing about 30% carbon. It is also the lowest quality and the most abundant type of coal in the world. Traces of the texture of the original wood may even be found in pieces of lignite. At greater depths, lignite is transformed into sub-bituminous, bituminous, and ultimately anthracite coal. Therefore, it is expected to find anthracite in the very old deposits that reside in the deep layers and to find lignite in the younger deposits and in those closer to the surface.

Reserves and Resources

As Table 2 indicates, just five countries, the US, Russia, China, India, and Australia, own about 70% of the total world coal reserves – estimated at 976 billion metric tons. Despite what one might expect, with the exception of Iran, there are no coal mines in the Middle East.

Figure 1 US actual and projected coal production.
Figure 1 US actual and projected coal production.
Figure 2 World coal consumption outlook by region.
Figure 2 World coal consumption outlook by region.

Large coal deposits are found in 38 US states, with more than half of these in only three states: Wyoming, West Virginia, and Kentucky. Anthracite is most commonly found in Pennsylvania and accounts for only 1% of the US’s coal reserves. About 70% of coal is bituminous; the rest is essentially lignite. Eastern and Mid-continent coalfields contain mostly bituminous coal, while sub-bituminous coal is predominantly found in the Western states. Most lignite is mined in Texas, Montana, and North Dakota.

Worldwide coal production, which reached 4.8 billion metric tons in 2004, accounted for more than a quarter of all energy sources and about 90% of all electricity generated. In the United States, coal production grew exponentially from 1860 to 1910. As we switched our source of primary consumption to petroleum and natural gas, coal production (and consumption) leveled off until 1972, whereupon the rate started to rise again (2). Th e latest figures indicate coal consumption at one billion metric tons in 2004. Th e US’s proven, identified, and ultimate (identified and undiscovered) coal reserves are estimated at 247 billion, 1557 billion, and 3968 billion metric tons, respectively (3). Th e actual and projected US coal productions are shown in Figure 1.

Although the US has the most coal reserves in the world, it is China that produces (and consumes) the most coal. The trend is expected to continue, and in the next two decades, coal use is projected to increase by another 36%, with the largest increases projected for China and India (Figure 2). In Europe, however, substantial declines in coal use are projected in favor of cleaner natural gas (4).

Environmental Concerns

Figure 3 Impact of various energy technologies on global warming and overall air quality.
Figure 3 Impact of various energy technologies on global warming and overall air quality.

Coal is probably the dirtiest of all fossil resources; it produces more carbon per unit energy content, has the highest percentage of sulfur, and produces more nitric oxides. Th e relative impact on global warming and overall air quality is considered to be the greatest, producing twice carbon dioxide as oil for the same amount of energy (See Figure 3). Depending on how deep the coal is buried, coal can be extracted by digging tunnels or strip-mining. Hazards associated with tunnel operation include cave-ins, explosions from dust buildup, carbon monoxide poisoning, and lack of sufficient ventilation. Although tunneling operations harm miners the most, strip-mining has the greatest environmental impacts. Th ese include the destruction of fertile surface-soil, permanent changes in the landscape, and the possibility of acidic or alkaline drainage to the surface (Figure 4). In many industrial countries, public and environmentalist pressure has forced local governments to require coal mining companies to reclaim the land and restore it to its original form aft er strip-mining.

Figure 4 Shale oil can potentially meet a great portion of the future energy demand.
Figure 4 Shale oil can potentially meet a great portion of the future energy demand.

Since coal is formed primarily underneath swamp beds, it contains a large amount of sulfur. To remove the sulfur, coal is crushed into small chunks and washed inside large water tanks. Since sulfur is heavier than coal, most sink to the bottom and is removed. Some of the sulfur is chemically bonded to carbon (organic sulfur) and cannot be washed off this way; it must be removed by adding chemicals that react with sulfur and break it loose.

Although most sulfur is removed by physical and chemical processes, the coal burned in power plants still contains considerable amounts of sulfur which, when burned, produce sulfur dioxide. In addition to sulfur dioxide, nitrogen oxides and particulates are produced. Modern power plants use wet or dry scrubbers to remove the remaining sulfur in their smokestacks before it is released into the atmosphere. In wet scrubbers, limestone slurry is sprayed onto the fl ue gases where it combines with sulfur to form a paste that is left behind. Dry scrubbers consist of a fixed sorbent bed of activated carbon, char, and alumina impregnated with copper. Large bag houses remove larger particles while electrostatic precipitators filter smaller particulates.

In addition to ecological concerns, coal extraction can be quite dangerous. It is estimated that several thousand miners are killed each year as a result of mine explosions, cave-ins, and carbon monoxide poisoning. As the energy crunch becomes tighter and the use of coal becomes more widespread, the number of mine accidents and fatalities are expected to increase.

Of course, coal has a number of advantages. It is relatively cheap; it can be transported by truck, ship, and rail; it is easy to store and burn, and can be liquefied to produce synthetic oil. Every ton of coal will yield about 5.5 barrels of liquid fuel (5). It should be noted, however, that although there exists a large quantity of coal reserves to be exploited, if coal is used to substitute the current demand for petroleum, the coal supply would serve as only a very temporary solution to the problem (6).

References

(1) 2004 estimates; a. World Coal Institute (http://www.worldcoal.org); b. US Geological Survey (http://energy.usgs.gov/coal.html).

(2) Barlett , A., “Fundamentals of the Energy Crisis,” Th e American Journal of Physics, 40, September 1978. pp. 876-888.

(3) EIA Website (htt p://www.eia.doe.gov/cneaf/coal/reserves/chapter1.html).

(4) Energy Information Agency Fact Sheet (http://www.eia.doe.gov).

(5) Lumpkin, R.E., “Recent Progress in the Direct Liquefaction of Coal,” Science, 239, p. 873, 1988.

(6) Hatfield, C. B., “How long oil supply grow?” M. King Hubbet Center for Petroleum Supply Studies, Newsletter #97/4-1-6, October 1997.

(7) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005

Additional Comments

(a) Coke is produced by carbonization of coal in an oxygen-deficient environment and high temperatures.

Further Reading

Berkowitz, N., Fossil Hydrocarbons: Chemistry and Technology, Elsevier Academic Press, 1997.

Deff eyes, K. S., Hubbert’s Peak: Th e Impending World Oil Shortage, Princeton University Press, Princeton, N. J., 2001.

Campbell, C. J., Th e Coming Oil Crisis, Multi-Science Publishing Company, 2004.

Tariq Ali, Th e Clash of Fundamentalisms: Crusades, Jihads and Modernity, Verso, 2002.

Pelletiere, S., Iraq and the International Oil System: Why America Went to War in the Gulf, Praeger Publishing, 2001.

Oil and Gas Journal, Technology, news, statistics, special reports, and analysis (http://ogj.pennnet.com).

Journal of Petroleum Technology, The official journal of Society of Petroleum Engineers, Dallas.

The Petroleum Engineer, Petroleum Engineer Pub. Co.

Journal of Petroleum Science and Engineering, Elsevier, covers the fields of petroleum (and natural gas) exploration, production and flow.

External Links

National Energy Technology Laboratory: Th e Strategic Center for Coal (http://www.netl.doe.gov/coal).

National Petroleum Technology Office (http://www.npto.doe.gov).

US Geological Survey (http://www.usgs.gov).

Organization of Petroleum Exporting Countries (OPEC) (http://www.opec.org).

Society of Petroleum Engineers (http://sae.org).