Energy - Fossil Fuels- Coal
EVPP 111 Lecture
Dr. Largen
OUTLINE
Renewable vs. Non-Renewable Energy
Fossil fuels - general
formation
resources vs. reserves
Coal
formation
types
reserves
extraction
use patters
use issues
Nonrenewable vs. renewable energy sources
Nonrenewable resources
available in finite, limited quantities
are depleted by use
- natural processes do not replenish nonrenewable resources within a reasonable period of time
- on the human time scale
Nonrenewable vs. renewable energy sources
Nonrenewable resources
include
- minerals
- copper, tin, aluminum, radioactive ores
- fossil fuels
- coal
- oil
- natural gas
Nonrenewable vs. renewable energy sources
Renewable resources
available in potentially unlimited quantities
- term is not used exclusively to describe energy resources
replaced by natural fairly rapidly
- on a scale of days to decades
can be used forever as long as they are not overexploited in the short term
- they must be used in a sustainable manner that gives them time to replace or replenish themselves
Nonrenewable vs. renewable energy sources
Renewable resources
include
- non-energy
- trees
- fishes
- fertile agricultural soil, fresh water
- energy
- solar
- wind
- geothermal
- hydroelectric
Nonrenewable energy: resources vs. reserves
Nonrenewable resources
must differentiate between deposits that can be extracted and those that cannot
Nonrenewable energy: resources vs. reserves
Nonrenewable resources
resource
a naturally occurring substance
of potential use to humans
can potentially be extracted using current technology
reserve
known deposits that can be extracted profitably with existing technology
under certain economic conditions
Nonrenewable energy: resources vs. reserves
Nonrenewable resources
resource
total amount changes only by the amount that is used each year
reserve
an economic concept
amount changes as
technology advances
as new deposits are discovered
as economic conditions vary
reserves are smaller than resources
Fossil fuels
general
definition
formation
specific types
formation
resources and reserves
use patterns
use issues
Fossil fuels
General definition
the partially decayed remains of plants, animals and microorganisms that lived millions of years ago
Fossil fuels
General formation
~300 million years ago
- much of earth’s climate was mild and warm
- plants grew year round in vast swamps
- as swamp plants and aquatic microorganisms died
- they fell into or sunk in water
- where they decomposed very little due to lack of oxygen
- they were covered by layers of sediment
Fossil fuels
General formation
over great periods of time
- the heat and pressure that accompanied the burial of the organic material by sediments
- converted the non-decomposed organic material into a carbon-rich materials we now call fossil fuels
Fossil fuels
Types
coal
oil
natural gas
Fossil fuels
Coal
formation
- ~300 million years ago tropical freshwater swamps covered many regions of the earth
- conditions in these swamps favored extremely rapid plant growth
- resulting in the accumulations of dead plant material under the water
- where decay was inhibited due to low oxygen concentrations
Fossil fuels
Coal
formation
- partially decayed accumulated plant material was covered by sediments
- especially when geologic changes in the earth caused some swamps to be submerged by seas
- over vast periods of time, the heat and pressure that accompanied burial
- converted the non-decomposed plant material into a carbon-rich rock called coal
Fossil fuels
Coal
occurs in different types, or grades, which are dependent on
- the varying amounts of heat and pressure to which it was exposed during formation
Fossil fuels
Coal exposed during formation to
higher heat and pressure
- drier (lower water content)
- more compact (harder)
- higher heating value (=higher energy content)
lower heat and pressure
wetter (higher water content)
less compact (softer)
lower heating value (=lower energy content)
Fossil fuels
Coal
three most common grades
- lignite
- bituminous
- anthracite
Fossil fuels
Coal - three most common grades
lignite
characteristics
moist, water content of ~45%
soft, woody texture
produces little heat compared to other types of coal
- heat value of 7000 BTU/pound
dark brown in color
contains ~20 noncombustible compounds
contains ~35% carbon
Fossil fuels
Coal - three most common grades
lignite
uses
often used to fuel electric power plants
deposits
sizable deposits found in western US
largest US producer is North Dakota
cost to mine (1997) $10.91/2000 pounds
Fossil fuels
Coal - three most common grades
bituminous
characteristics
moderately dry, water content of 5-15%
moderately hard
- although its also called a soft coal
produces nearly twice the amount of heat as lignite
- heat value of 12,000 BTU/pound
dull to bright black with dull bands
contains ~20-30 noncombustible compounds
contains ~55-75% carbon
Fossil fuels
Coal - three most common grades
bituminous
uses
extensively by electric power plants
- because it produces a lot of heat
deposits
found in US in Appalachian region, near Great Lakes, in Mississippi Valley, in central Texas
cost to mine (1997) $24.64/2000 pounds
Fossil fuels
Coal - three most common grades
anthracite
highest grade of coal
characteristics
very dry, water content of 4%
very compact
produces twice the heat of lignite
- heat value of 14,000 BTU/pound
dark, brilliant black in color
contains ~1noncombustible compound
contains ~95% carbon
Fossil fuels
Coal - three most common grades
anthracite
uses
electric power generation and other industrial uses such as production of steel
deposits
in US, most is located east of Mississippi River, particularly in PA
Fossil Fuels
Coal deposits and reserves
coal is most abundant fossil fuel in world
found mostly in Northern Hemisphere
found in seams or veins
- underground layers that vary in thickness from 2.5cm to >30m in thickness
easily located
- so geologists believe most (if not all) major deposits have been located
Fossil Fuels
Coal deposits and reserves
known, proven world reserves
- location
- 66% located in US, Russia, China and India
- with US accounting for 24% of those
- could last
- ~200 years at present rate of consumption
- ~65 years if rate of consumption increases by 2% per year
Figure 10.4: Distribution of coal deposits, Raven & Berg
Fossil Fuels
Coal deposits and reserves
known US reserves
- location
- throughout US
- more in eastern 1/2 of continental US
- could last US
- ~300 years at present rate of consumption
Fossil Fuels
Coal deposits and reserves
unknown, unproven world reserves
- additional coal reserves that are currently too expensive to develop
- for example, deposits at depths greater than 5000 feet would cost more to extract than would be offset by current price of coal
Fossil Fuels
Coal deposits and reserves
unknown, unproven world reserves
- location
- ~85% are located in US
- could last
- ~1000 years at present rate of consumption
- ~149 years if rate of consumption increases by 2% per year
Fossil Fuels
Coal deposits and reserves
unknown, unproven US reserves
- could last US
- ~400years at present rate of consumption
Fossil Fuels
Coal deposits and reserves
known AND unknown world reserves
- could last
- ~200-1000 years depending on rate of consumption
Fossil Fuels
Coal extraction
two basic types of coal mines
- surface mines
- subsurface mines
Fossil Fuels
Coal extraction
surface mines
also called strip mining
used when the overburden is 30-100 meters thick
overburden is the rock/earthen material on top of a vein/seam of coal
results in best utilization of coal reserves
it removes most of the coal in a vein
can be profitably used in a vein as thin as 1/2 meter
Fossil Fuels
Coal extraction
surface mines
has increased globally
in US, from 30% of coal extracted in 1970 to 60% of coal extracted currently
advantages over subsurface mining
less expensive
safer for miners
allows more complete removal of coal
disadvantage over subsurface mining
disrupts land more extensively
- adverse environmental impacts
Fossil Fuels
Coal extraction
subsurface mines
employed when overburden is thick, >~30-100 meters
account for ~40% of current coal extraction
advantage over surface mining
- disrupts land less extensively
- less potential for adverse environmental impacts
disadvantages over surface mining
- more expensive
- less safe for miners
- less complete removal of coal
Fossil Fuels
Coal use patterns
provides
- ~21% of world’s commercial energy
- ~22% of US’s commercial energy
used to
- generate
- ~62% of world’s electricity
- ~53% of US’s electricity
- make
- ~75% of world’s steel
Figure 10.9: World commercial energy sources, 1997, Raven & Berg
Fossil Fuels
Coal use patterns
many analysts project a decline in coal use over the next 40-50 years because of
- its high CO2 emissions
- harmful human health effects
- availability of less environmentally harmful ways to produce electricity
Fossil Fuels
Coal use issues
coal contains
- small amounts of sulfur
- which is released into the atmosphere as SO2 when coal is burned
- trace amount of mercury and radioactive materials
- which are released into the atmosphere when coal is burned
Fossil Fuels
Coal use issues
coal is the fossil fuel that is most abundant & produces highest environmental impact from
- land disturbance
- air pollution
- greenhouse gas emissions (SO2 CO2)
- release of toxic mercury particles
- release of thousands of times more radioactive particles into atmosphere per unit energy produced than does a normally operating nuclear power plant
- water pollution
Fossil Fuels
Coal use issues
human health impacts
- occupational
- coal mining is one of most dangerous jobs in world
- during 20th century, ~90,000 American coal miners died in mining accidents
- though death rates declined in latter part of century
- between 1870 and 1950, 30,000 miners died in PA alone
- equivalent of one man per day for 80 years
Fossil Fuels
Coal use issues
human health impacts
- occupational
- miners have increased risk of black lung disease
- lungs become coated with inhaled coal dust restricting oxygen exchange, causing ~2000 deaths per year
Fossil Fuels
Coal use issues
land disturbance
- in US, thousands of square kilometers have been disturbed by mining
- only about 1/2 of that has been reclaimed
Fossil Fuels
Coal use issues
land disturbance
- types
- open trenches
- topsoil removal/erosion
- landslides caused by lack of vegetation
- mountaintop removal
- land subsidence
- trailing dumps
Fossil Fuels
Coal use issues
land disturbance
- acid mine drainage
- is produced when rainwater seeps through iron sulfide minerals exposed in waste mines and
- carries sulfuric acid to nearby streams and lakes
Fossil Fuels
Coal use issues
air pollution
- many elements taken up by ancient plants were concentrated in the coal formation process
- such as uranium, lead, cadmium, mercury, rubidium, thallium, zinc
- are released when coal is burned
- as gas into atmosphere
- are concentrated as in fly ash and bottom slag
- coal is responsible for ~25% of all atmospheric mercury pollution in US
Fossil Fuels
Coal use issues
air pollution
- acid deposition
- both sulfur oxides (SOx) and nitrogen oxides (NOx) form acids when they react with water
- SOx and NOx emissions react with water in the atmosphere to form
- an acid which falls from atmosphere to surface, known as acid deposition or acid precipitation
Fossil Fuels
Coal use issues
greenhouse gases
- coal contains up to 10% sulfur by weight
- unless sulfur is removed by washing or flue-gas scrubbing
- it is released during burning and oxidizes to sulfur dioxide (SO2) or sulfate (SO4)
- ~18 million metric tons Sox released annually in US (~75% of total US emissions)
Fossil Fuels
Coal use issues
greenhouse gases
- high temperatures and rich air mixtures used in coal-fired burners also
- oxidize nitrogen compounds (mostly from the atmosphere) into nitrogen oxides (NOx)
- ~5 metric tons of NOx released annually in US (~30% of total US emissions)
Fossil Fuels
Coal use issues
greenhouse gases
- combustion of coal produces CO2
- ~one trillion metric tons released annually in US (~50% of total US emissions)
Fossil Fuels
Coal use issues
making coal a cleaner fuel
- desulfurization systems
- clean power plants’ exhausts
- chemicals react with the pollution and the pollution sttles out (precipitates)
- modern "scrubbers" remove ~98% of the sulfur
- expensive, add to coast of coal energy
Fossil Fuels
Coal use issues
clean coal technologies
- new methods for burring coal such as fluidized bed combustion
- mixes crushed coal with particles of limestone in a strong air current during combustion
- takes place at lower temperatures so there are fewer nitrogen oxides produced
- sulfur reacts with calcium in limestone and precipitates out
Fossil Fuels
Coal use issues
clean coal technologies
- new methods for burring coal such as fluidized bed combustion
- process is more efficient than traditional coal burning
- produces more heat for a given amount of coal
- therefore, reduces CO2 emissions
Figure 10.8: Fluidized-bed combustion of coal, Raven & Berg
Fossil Fuels
Coal use issues
converting goal into gaseous and liquid fuels
- solid coal can be converted into synfuels
- into synthetic natural gas (SNG)
- by the process of coal gasification
- into liquid fuel such as methanol of synthetic gasoline
- by the process of coal liquefaction
- most analysts expect synfuels to play only a minor role as a energy resource in the next 30-50 years
Figure 10.16: Coal gasification, Raven & Berg