Transcript Environmental Effects of Energy Production and Use

Environmental Effects of
Energy Production and Use
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Effects of fossil fuel production
Effects of fossil fuel combustion
"Acid rain"
CFC emissions from HVAC equipment
Stratospheric ozone depletion
Global Warming/The "Greenhouse Effect"
Energy conservation as a pollution and
greenhouse gas reduction strategy
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Effects of Fossil Fuel Production
 Fossil fuels are produced by mining or drilling.
 Considerable environmental damage results from
mining and drilling...
 Surface ("strip") mining for coal often results in
vegetation loss, stream and soil acidification,
road damage, etc.
 Underground mining is extremely hazardous, and
old mines sometime catch fire and burn for
years/decades, causing surface subsidence and
damage.
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Abandoned
coal strip
mine pit
near
Brookwood,
Alabama on
Hwy 216
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Fuel Production Effects (Cont’d)
 Drilling for petroleum and natural gas often results
in release of briny water onto surface and into
streams causing damage to the stream life and
sometimes rendering the water unfit for human
consumption (even after ordinary treatment).
 Petroleum refining to produce gasoline, kerosene,
jet fuel, diesel oil, fuel oil, etc. often results in the
release of carcinogenic and ecologically
damaging hydrocarbons into the environment.
 Most fossil fuel extraction technologies are
themselves fairly energy intensive.
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Fossil fuel processing has
environmental consequences…
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Effects of Fossil Fuel Combustion
 Fossil fuels are hydrocarbons containing traces of
nitrogen, sulfur and other elements.
 Typical combustion reaction: CwHxOzNaSb + O2 +
N2 CO2+ CO + H2O + NOx + SO2 + HC + …
 Only H2O is essentially benevolent...
 CO and many HC's are toxic to humans.
 NOx and SO2 combine with rainwater to form nitric
and sulfuric acids, i.e., "acid rain".
 CO2 is the primary culprit in global warming, but
other gases are important.
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Important Combustion Processes
 The three most important combustion processes
for energy production are natural gas flames for
heating furnaces and water heaters, boiler
flames, and internal combustion engine flames.
 Burning natural gas for heating produces some
NOx, significant CO2 (but less than coal or oil).
 Boiler combustion of coal and fuel oil for
industrial and electric power produces significant
quantities of CO2, NOx and SO2
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Combustion Processes (Cont’d)
 Because boiler flames are at relatively low
temperature (compared to IC engines), most
NOx is formed from oxidation of fuel nitrogen.
 IC engine flames are very hot, which leads to
dissociation of N2 and O2, thus, most NOx in
engines is formed from the oxidation of nitrogen
introduced with the combustion air.
 IC engines are also significant producers of CO2,
CO (spark-ignited), SO2 (diesel) and
hydrocarbons.
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CFC from HVAC Equipment
 Refrigerators, air conditioners and heat pumps
have used chlorofluorocarbons (CFC's) as their
working fluids (refrigerants).
 CFC's at normal conditions are extremely inert,
stable and non-toxic. Their use leads to good
equipment efficiency and safety.
 Because they are so inert, CFC's are not
destroyed in the lower atmosphere and eventually
rise to the upper atmosphere (stratosphere).
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CFC Problem
 UV light in the stratosphere breaks down the
CFC molecule, releasing chlorine ions.
 The Cl- ion attacks ozone (O3) molecules,
converting them to O2 and O.
 The Cl- ions are released after breaking down an
O3 molecule, and both the O and the Cl- are free
to attack other O3 molecules.
 Release of CFCs has already caused significant
stratospheric ozone depletion, particularly in the
South and North Polar regions.
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Stratospheric Ozone Depletion
 Ozone is a good absorber of
solar ultraviolet radiation,
and depletion of upper
atmosphere ozone results in
increased surface levels of
UV radiation.
 Increased levels of UV at
the surface enhance global
warming, but more
importantly, can result to
increased human skin
cancer and plant damage.
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The ozone hole at its peak
in 2003 over Antarctica
Ozone Depletion (Cont’d)
 The Montreal Protocols, signed in 1987, called
for a 50% reduction in the most damaging CFC'S
(including R-11 and R-12) by 2000.
 Because of new findings of polar ozone depletion
and scientific demonstration of its cause, the
London Montreal Protocol meeting of 1990
raised the cutback to 100%, and the
Copenhagen meeting of 1992 moved the
deadline to 1996.
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Ozone Depletion (Cont’d)
 Hydrochlorofluorocarbons (CHFC's), such as R22, are scheduled for phaseout by 2020 by the
1992 agreement (maybe 2010 or 2012 now).
 The ozone depletion index of R-22 (home air
conditioners and heat pumps is about 0.05,
where R-12 has an ODI of 1.0
 The discoverers of the ozone depletion link to
stratospheric ozone received the Nobel Prize in
chemistry in 1995.
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Global Warming
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Glass is selective...
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A Greenhouse...
 Sunlight at  = 0.5 m
mostly passes through the
glass
 Re-emitted radiant energy
from the ~300 K interior is
at   0.5 m
 The glass is opaque to this
infrared wavelength, so reemitted energy cannot
radiate away
 The greenhouse warms up
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Principal Greenhouse Gases
 CO2- (55% greenhouse effect)- Primarily
from combustion of carbon-containing fuels
(fossil fuels).
 CFCs- 24 % of warming (R-11 and R-12:
17% and other CFCs: 7%). From HVAC
equipment, foams, chip manufacturing, etc.
(e.g., lens blower and asthma inhaler)
“Developing” nations have 10 yr setback on
Montreal Protocols- some problems with
black market R-12, etc.
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Greenhouse Gases (Cont’d)
 Methane- (15% of warming) – Some “natural”
biological emissions, such as ruminant animal
flatulence and “releases” from termites, but these
are enhanced by man’s activities (farming,
logging). Some sources are purely manmade,
such as unburned methane in natural gas
combustion and gas line leaks (huge leaks in
Russia).
 Compared to a CO2 molecule, one CH4 molecule
has 25 times the global warming potential (GWP)
and one R-12 molecule has 21,000 times the
GWP!
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Man’s agricultural and
logging activities result in
enhanced emissions of
greenhouse gas from
natural sources. Ruminant
and termite “emissions” are
significant sources of CO2
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Greenhouse Gases (Cont’d)
 Nitrous oxide (6% of warming)- From combustion
and natural sources.
 With the exception of the CFCs, there has been
little worldwide agreement on how to reduce
greenhouse gases, including the most recent
Kyoto Conference in 12/97.
 Industrialized countries w/ 20% of population
account for 75% of greenhouse gas emissions.
 The U.S. accounts for 20% of the world's
manmade CO2 emissions.
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How Can Global Warming Be Reduced?
 Increased energy efficiency. This is simplest
and most cost-effective.
 Substitution of natural gas for coal and oil
(short term, limited supplies).
 Reforestation and reduction of deforestation.
 Safe nuclear power (fission).
 Alternative renewable energy: OTEC, wind,
solar thermal, solar photovoltaic, biofuels.
 Hydrogen transportation fuel (needs research).
 Fusion power (needs development).
 Other alternatives???
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