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Ch. 11: Fossil Fuels
Objectives:
 Define fossil fuel and distinguish among coal, oil, and natural gas.
 Describe the processes that formed coal, oil, and natural gas.
 Relate fossil fuels to the carbon cycle.
 Distinguish between surface mining and subsurface mining.
 Summarize the environmental problems associated with using coal.
 Define resource recovery and fluidized bed combustion.
 Explain why many new coal plants will be designed to capture carbon
dioxide.
Fossil Fuel Overview
 combustible deposits, formed from the remnants of ancient photosynthesizers,
compressed in an oxygen-free environment
o the Earth is constantly forming new fossil fuels, although formation cannot
keep pace with use
o deposits are not evenly distributed over the planet, resulting in some
countries having more resources than others
 formation
o coal is the remnants of ancient 300 mya) swamp plants
 these ancient plants died and fell into the water, which drastically
slowed decomposition
 plants built up, and over time, were covered with sediments
 heat and pressure converted the non-decomposed material into
carbon-rich carbon and the sediments into sedimentary rock
o oil and natural gas are the remnants of ancient aquatic microorganisms
 the mechanism of formation is generally the same as with coal
 oil is a liquid mixture of hydrocarbons, while natural gas is primarily
methane (formed at higher temperatures than oil)
 burning of fossil fuels has released carbon dioxide accumulated over millions of
years in a period of a couple hundred years
o carbon dioxide equilibrium in the carbon cycle has thus been disrupted
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Coal
 used primarily for electrical and steel production
 different grades of coal, starting with the precursor, peat  more heat and
pressure during formation leads to coal that is drier, harder, with a higher
heating value
o lignite (“soft coal”)  brown/brown-black, wood-like texture
 moist, doesn’t produce much heat, although it is often used to make
electricity
 mostly found out west in the U.S.
o subbituminous coal
 low heat value, but also a low sulfur content
 found primarily in Alaska
o bituminous coal  dull to bright black
 the most common  used a lot to make electricity
 makes a lot of heat, but contains the most sulfur
 found in the middle U.S.
o anthracite  dark, brilliant black
 burns hottest and cleanest
 largely depleted in the U.S., but most common in PA
(*show pictures of coal grades, explain what charcoal is, show students example of
anthracite)
 reserves are mostly in the Northern Hemisphere
o 50% of the world’s coal is in the U.S., Russia, and China, with other large
reserves in Australia, India, Germany, and South Africa
o current reserves should last about 200 more years
 mining
o surface mining is used if the coal is relatively close (100 ft) to the surface
 strip mining is fairly common, where trenches are dug and the
overburden from one trench is put into an old one, creating a spoil
bank
o subsurface mining is used when the coal is deeper in the ground
 40% of mining is done this way, even though it is more expensive
and more hazardous for the miners (cave-ins, 2000 deaths per year
due to cancer and black lung), as well as typically less efficient
 it is, however, not as hazardous to the environment
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(*show video on subsurface mining and processing
http://science.discovery.com/tv-shows/how-do-they-do-it/videos/how-do-theydo-it-coal-mining.htm)
 environmental impacts of mining
o Surface Mining Control and Reclamation Act (SMCRA; 1977)
 prior to 1977, mines were usually abandoned and left exposed to the
elements
 erosion of topsoil downhill and into streams and toxins in the
soil prevented plants from recolonizing
 sulfuric acid (rain + iron sulfide in mine wastes) and dissolved
materials, such as lead, arsenic, and cadmium, get washed into
nearby waterways  acid mine drainage
 landslides were common
 coal preparation plants dump tailings near the site, increasing
acid mine drainage
 SMCRA requires reclamation (restoration) of mines by the coal
companies, as well as permits/inspections, prohibition of mining in
sensitive areas, and taxes to pay for abandoned pre-1977 mines
 did not prevent mountaintop removal (surface mining done with a
dragline) because the technology wasn’t as advanced in 1977 and so
it wasn’t as damaging to the environment
 was limited in 2002 because it violates the Clean Water Act by
filling streams in valleys with debris
(*show student-made video on SMCRA)
 pollution associated with transporting coal
 environmental impacts of burning coal
o various air pollutants (all typically more than oil and natural gas)
 soot
 carbon dioxide 
 climate change
 ocean acidification
 mercury (1/3 of all comes from U.S.)
 biomagnifies through ecosystems  neurotoxin
 SOx, NO, and NO2 react with water in the atmosphere to produce
acid deposition  decline of aquatic species, as well as forests
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 can we make coal cleaner?
o yes, although it’s not really “clean”
 scrubbers (desulfurization systems) are required by the Clean Air Act
(cost 15% of total construction costs of power plant)
 lime + water neutralize 98% of the acidic, sulfur containing
gases  calcium sulfate sludge (now a waste product, usually
dumped in a landfill)
o resource recovery is when we make a waste some type of
marketable product
o calcium sulfate sludge can be used to make wallboard or
a soil conditioner (helps to neutralize acid in soil and
increases water-holding capacity)
 use fabric filters to remove 99% of the particulates (fly ash can
be used to make lightweight concrete)
 also help to cut NOx emissions, but NOT CO2 emissions
 fluidized-bed combustion
 mixes crushed coal with particles of limestone DURING burning
 lower temperature (more efficient)  less NOx and CO2
 don’t need scrubbers, costs about the same, government
incentives to use this
 if pressurized, it becomes even cleaner (although more
expensive)
 carbon capture and storage (CCS)  NEW technology
 the removal of carbon from fossil fuel combustion and storage
of the carbon, usually underground
 should it be required in the future?