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