ENVIRONMENTAL SCIENCE 13e
CHAPTER 13:
Energy
Core Case Study: Amory Lovins and
the Rocky Mountain Institute (1)
• 1984: home and office building in
Snowmass, CO
• Heat:
– Sun
– Heavy roof insulation
– Thick stone walls
– Energy-efficient windows
– Waste-heat recovery
Core Case Study: Amory Lovins and
the Rocky Mountain Institute (2)
• Sun
– 99% of heat and hot water
– 95% of daytime lighting
– 90% of household electricity
• Energy-efficient electrical appliances
and computers
• Rocky Mountain Institute
– Promotes energy-efficient buildings and
transportation
Fig. 13-1, p. 296
13-1 What Major Sources of
Energy Do We Use?
• Concept 13-1A About three-quarters of
the world’s commercial energy comes
from nonrenewable fossil fuels, and the
rest comes from nonrenewable nuclear
fuel and renewable sources.
• Concept 13-1B Net energy is the amount
of high-quality energy available from a
resource minus the amount of energy needed
to make it available.
• What do we need to consider when
evaluating energy resources?
Evaluating Energy Resources
• The supply
• The environmental impact
• How much net useful energy they
provide
Commercial energy use by source
What can be said about renewable vs non-renewable?
Fig. 13-2, p. 298
Science Focus: Net Energy
• It takes energy get energy.
• What steps are involved in the oil industry that require
energy?
• Second law of thermodynamics (what happens to the
energy at each step?)
• Net energy: The usable amount of high quality
energy available from a given quantity of an energy
resource minus the energy needed to find, extract,
process, and get that energy to consumers
• Net energy ratio
• Ex. Nuclear fuel cycle, how much energy we get out vs
how much energy we put in
13-2 What Are the Advantages and
Disadvantages of Fossil Fuels?
• Concept 13-2 Oil, natural gas, and
coal are currently abundant and
relatively inexpensive, but using
them causes air and water
pollution, degrades large areas of
land, and releases greenhouse
gases to the atmosphere.
Dependence on Oil (1)
• Petroleum (crude oil)
– Also called light oil
– Trapped underground or under ocean with
natural gas
– Fossil fuels
• Extraction
– U.S. peak production
– Global peak production: the point in time when we reach the
maximum overall rate of crude oil production for the whole world.
Once we pass this point, what will happen to global oil
production?
Dependence on Oil (2)
• Transportation
• Refining
• Petrochemicals
Lowest Boiling Point
Gases
Gasoline
Aviation
fuel
Heating oil
Diesel
oil
Naphtha
Grease
and wax
Heated
crude oil
Asphalt
Furnace
Highest Boiling Point
Fig. 13-3, p. 300
Fig. 13-3, p. 300
Supplement 9, Fig. 3, p. S40
How Long Will Crude Oil Supplies Last?
• Crude oil is the single largest source of
commercial energy in world and U.S.
How Long Will Crude Oil Supplies Last?
• Crude oil is the single largest source of
commercial energy in world and U.S.
• Proven oil reserves
– Identified deposits that can be extracted
profitably at today’s prices with today’s
technology
How Long Will Crude Oil Supplies Last?
• Crude oil is the single largest source of
commercial energy in world and U.S.
• Proven oil reserves
– Identified deposits that can be extracted
profitably at today’s prices with today’s
technology
– Geologists predict known and projected global
reserves of crude oil will be 80% depleted
between 2050 and 2100 depending on
consumption rates
What are our options?
What are our options?
• Look for more oil
• Use and waste less oil
• Use other energy options
• Yes, yes, and yes!
14
13
Barrels of oil per year (billions)
12
11
10
Projected U.S.
oil consumption
9
8
7
6
5
4
3
2
Arctic refuge oil
output over 50 years
1
0
2000
2010
2020
2030
Year
2040
2050
Fig. 13-4, p. 301
*United States Oil Production
and Use (1)
• U.S.
– 93% of energy from fossil fuels
– 39% from crude oil
– Produces 9% of world’s crude oil
– Uses 25% of world production
– Has 2% of proven crude oil reserves
United States Oil Production
and Use (2)
• Domestic oil production
– Off-shore drilling
– Alaska
• Future U.S. production
• Consumption versus production
• Oil imports
– 2008: imported 58% of crude oil
Trade-Offs
Conventional Oil
Advantages
Disadvantages
Ample supply for
42–93 years
Need to find
substitutes within 50
years
Low cost
Large government
subsidies
High net energy
yield
Environmental costs
not included in
market price
Easily transported
within and
between countries
Low land use
Technology is well
developed
Efficient
distribution system
Artificially low price
encourages waste
and discourages
search for alternatives
Pollutes air when
produced and burned
Releases CO2 when
burned
Can cause water
pollution
Fig. 13-5, p. 301
Oil Sand
• Oil sand (tar sand): mixture of clay, water
and bitumen
• Bitumen: thick, sticky, tar like heavy oil
with high sulfur content
• Northeastern Alberta in Canada has ¾ world’s
tar sands resources
• Under boreal forest
• Huge environmental cost
Tar sands
• http://www.good.is/post/think-nuclearor-coal-is-bad-tar-sands-mining-iscoming-to-utah/
• http://www.youtube.com/watch?v=Yk
woRivP17A&feature=related
Oil shale
• Contain kerogen
• Shale Oil
• About 72% of world’s estimated oil shale
reserves buries in government owed land
in US states of Colorado, Wyoming, and
Utah in Green River formation
• What are the problems? Low net energy,
requires huge amount of water to produce (Colorado River System),
severe water pollution, air pollution, CO2 emission …
Fig. 13-6, p. 303
Trade-Offs
Heavy Oils from Oil
Shale and Tar Sand
Advantages
Disadvantages
Moderate cost
(tar sand)
High cost (oil shale)
Low net energy yield
Large potential
supplies, especially
tar sands in
Canada
Easily transported
within and
between countries
Efficient
distribution
system in place
Technology
well-developed
(tar sand)
Environmental costs
not included in
market price
Large amounts of
water needed for
processing
Severe land
disruption
Severe water
pollution
Air pollution and
CO2 emissions
when produced
and burned
Fig. 13-7, p. 303
Natural Gas Is a Useful and
Clean-burning Fossil Fuel (1)
•
•
•
•
•
Natural gas
Conventional natural gas
Unconventional natural gas
Liquefied petroleum gas (LPG)
Less carbon dioxide emitted per unit
of energy than with crude oil, tar
sand, shale oil
Natural Gas Is a Useful and
Clean-burning Fossil Fuel (2)
• Liquefied natural gas (LNG)
• World supply of conventional natural
gas –
62-125 years
• Unconventional natural gas
– Coal-bed methane gas
– Methane hydrate
Trade-Offs
Conventional Natural Gas
Advantages
Disadvantages
Ample supplies
Nonrenewable resource
High net energy yield
Releases CO2 when burned
Low cost
Government subsidies
Less air pollution than
other fossil fuels
Lower CO2 emissions than
other fossil fuels
Environmental costs not
included in market price
Methane
(a greenhouse gas) can
leak from pipelines
Easily transported by
pipeline
Difficult to transfer from
one country to another
Low land use
Good fuel for fuel cells,
gas turbines, and motor
vehicles
Can be shipped across
ocean only as highly
explosive LNG
Fig. 13-8, p. 304
Coal Is a Plentiful But Dirty Fuel
(1)
• Used in electricity production
• World’s most abundant fossil fuel
• U.S. reserves should last about 250
years
• Sulfur and particulate pollutants
• Mercury and radioactive pollutants
Coal Is a Plentiful But Dirty Fuel
(2)
• Heavy carbon dioxide emissions
• Pollution control and environmental
costs
• China major builder of coal plants
Increasing moisture content
Peat
Lignite
(not a coal)
(brown coal)
Heat
Pressure
Partially decayed plant
matter in swamps and
bogs; low heat content
Increasing heat and carbon content
Bituminous
(soft coal)
Anthracite
(hard coal)
Heat
Heat
Pressure
Pressure
Low heat content; low
sulfur content; limited
supplies in most areas
Extensively used as a fuel
because of its high heat
content and large supplies;
normally has a high sulfur
content
Highly desirable fuel
because of its high
heat content and
low sulfur content;
supplies are limited
in most areas
Fig. 13-9, p. 305
Waste heat
Coal burning power plant
Coal bunker
Cooling tower
transfers
waste
heat to
atmosphere
Turbine
Generator
Cooling
loop
Stack
Pulverizing
mill Boiler
Condenser
Filter
Toxic ash disposal
Fig. 13-10, p. 306
TVA Coal fired power plant
• http://www.tva.com/power/coalart.htm
• http://www.newsweek.com/photo/2009/07/
21/photos--the-worst-man-madeenvironmental-disasters.html
Fig. 13-10, p. 306
Coal-fired
electricity
286%
Synthetic oil and
gas produced
from coal
150%
Coal
100%
Tar sand
92%
Oil
86%
Natural gas
Nuclear power
fuel cycle
Geothermal
CO2 Emissions per unit of
electrical energy
58%
17%
10%
Stepped Art
Fig. 13-11, p. 306
Trade-Offs
Coal
Advantages
Disadvantages
Ample supplies (225–900 years)
Severe land disturbance,
air pollution, and water
pollution
High net energy yield
Severe threat to human
health when burned
Environmental costs not
included in market price
Low cost
Large government
subsidies
Well-developed technology
High CO2 emissions
when produced and
burned
Air pollution can be reduced with
improved technology
Radioactive particle and
toxic mercury emissions
Fig. 13-12, p. 307
Case Study: The Growing
Problem of Coal Ash
• Highly toxic
• Often stored in ponds
– Ponds can rupture
• Groundwater contamination
• EPA: in 2009 called for classifying
coal ash as hazardous waste
– Opposed by coal companies
TVA coal ash spill
• http://earthfirst.com/americas-top-10worst-man-made-environmental-disasters/
Clean Coal Campaign
• Coal industry
– Rich and powerful
– Fought against labeling carbon dioxide a
greenhouse gas
• “Clean coal” touted by coal industry
– Mining harms the environment
– Burning creates carbon dioxide and
toxic chemicals
• Plan to capture and store carbon
dioxide
Converting Coal into Gaseous
and Liquid Fuels
• Synfuels
• Coal gasification
– Synthetic natural gas (SNG)
• Coal liquefaction
– Methanol or synthetic gasoline
• Extracting and burning coal more
cleanly
Trade-Offs
Synthetic Fuels
Advantages
Disadvantages
Large potential supply
Low to moderate net energy yield
Higher cost than coal
Requires mining 50% more coal
Vehicle fuel
Environmental costs not included
in market price
Moderate cost
High environmental impact
Large government subsidies
Lower air pollution
than coal when
burned
High water use
Higher CO2 emissions than coal
Fig. 13-13, p. 309
13-3 What Are the Advantages and
Disadvantages of Nuclear Energy?
• Concept 13-3 The nuclear power
fuel cycle has a low environmental
impact and a very low accident risk,
but its use has been limited because
of high costs, a low net energy
yield, long-lived radioactive
wastes, vulnerability to sabotage,
and the potential for spreading
nuclear weapons technology.
How Does a Nuclear Fission
Reactor Work?
• Nuclear fission
• Light-water reactors
• Boil water to produce steam to turn
turbines to generate electricity
• Radioactive uranium as fuel
• Control rods, coolant, and
containment vessels
TVA
• http://www.tva.gov/power/nuclear/watt
sbar_howworks.htm
• http://www.tvakids.com/videos/pressu
rized_water_animation.htm
Small amounts of
radioactive gases
Uranium
fuel input
(reactor core)
Control rods
Containment shell
Heat exchanger
Waste heat
Steam Turbine
Generator
Hot
coolant
Pump
Pump
Pump
Coolant
Moderator
Shielding
Pressure Coolant
vessel
passage
Periodic removal and
storage of radioactive
wastes and spent
fuel assemblies
Hot
water
output
Water
Periodic removal
and storage of
radioactive
liquid wastes
Pump
Cool
water
input
Useful
electrical
energy
About 25%
Waste heat
Condenser
Water source
(river, lake, ocean)
Fig. 13-14, p. 310
Fig. 13-14, p. 310
Safety and Radioactive Wastes
• On-site storage of radioactive wastes
• Safety features of nuclear power
plants
• Nuclear fuel cycle
• Reactor life cycle
• Large amounts of very radioactive
wastes
Fig. 13-15, p. 311
Fig. 13-15, p. 311
Nuclear Fuel Cycle
Decommissioning
of reactor
Fuel assemblies
Enrichment
of UF6
Conversion
of U3O8
to UF6
Reactor
Fuel fabrication
(conversion of enriched
UF6 to UO2 and fabrication
of fuel assemblies)
Uranium-235 as
UF6 Plutonium239 as PuO2
Temporary storage
of spent fuel assemblies
underwater or in dry
casks
Spent fuel
reprocessing
Low-level radiation
with long half-life
Mining uranium ore
(U3O8 )
Open fuel cycle today
Recycling of nuclear fuel
Geologic
disposal
of moderate
and high-level
radioactive
wastes
Fig. 13-16, p. 312
What Happened to Nuclear
Power?
• Optimism of 1950s is gone
• Comparatively expensive source of
power
• No new plants in U.S. since 1978
• Disposing of nuclear waste is difficult
• Three Mile Island (1979)
Japan’s Nuclear Disaster
• http://www.guardian.co.uk/world/video/201
1/mar/14/japan-tsunami-amateur-footagevideo
Case Study: Chernobyl Disaster
• Ukraine (1986)
• Explosions and partial meltdown
• Huge radioactive release to
atmosphere
• Estimated death toll: 9,000–212,000
• Radioactive fallout and long-term
health effects
• Lesson – worldwide consequences
Trade-Offs
Conventional Nuclear Fuel Cycle
Advantages
Disadvantages
Large fuel supply
Cannot compete
economically without huge
government subsidies
Low environmental
impact (without
accidents)
Low net energy yield
High environmental impact
(with major accidents)
Emits 1/6 as much CO2
as coal
Moderate land disruption
and water pollution
(without accidents)
Moderate land use
Environmental costs not
included in market price
Risk of catastrophic accidents
No widely acceptable solution
for long-term storage of
radioactive wastes
Subject to terrorist attacks
Low risk of accidents
because of multiple
safety systems (except for
Chernobyl-type reactors)
Spreads knowledge and
technology for building
nuclear weapons
Fig. 13-17, p. 313
Trade-Offs
Coal vs. Nuclear
Coal
Nuclear
Ample supply
Ample supply of
uranium
High net energy
yield
Very high air
pollution
High CO2
emissions
High land
disruption from
surface mining
Low net energy yield
Low air pollution
Lower CO2 emissions
Much lower land
disruption from
surface mining
High land use
Moderate land use
Low cost (with
huge subsidies)
High cost (even with
huge subsidies)
Fig. 13-18, p. 314
Nuclear Power Is Vulnerable to
Terrorist Acts
• Insufficient security
• On-site storage facilities
• U.S.: 161 million people live within 75
miles of an above-ground nuclear
storage site
Dealing with Radioactive
Wastes
• High-level radioactive wastes
• Long-term storage: 10,000–240,000
years
• Deep burial
• Detoxify wastes?
Case Study: Dealing with Radioactive
Wastes in the United States
• Yucca Mountain, Nevada
• Concerns over groundwater
contamination
• Possible seismic activity
• Transportation accidents and
terrorism
• 2009: Obama ends Yucca funding
What Do We Do with Worn-Out
Nuclear Power Plants?
• Decommissioning old nuclear power
plants
• Dismantle power plant and store
materials
• Install physical barriers
• Entomb entire plant
What Is the Future for Nuclear
Power?
•
•
•
•
•
Reduce dependence on foreign oil
Reduce global warming
Advanced light-water reactors
Nuclear fusion
How to develop relatively safe nuclear
power with a high net energy yield?
13-4 Why Is Energy Efficiency
an Important Energy Source?
• Concept 13-4 The United States
could save as much as 43% of all the
energy it uses by improving the
energy efficiency of industrial
operations, motor vehicles, and
buildings.
Improving Energy Efficiency
• Energy efficiency
– How much work we get from each unit
of energy we use
• Reducing energy waste
– 41% of all commercial energy in U.S. is
wasted unnecessarily
• Numerous economic and
environmental advantages
Energy Inputs
System
Outputs
9%
7%
41%
85%
U.S.
economy
43%
8%
4%
3%
Nonrenewable fossil fuels
Useful energy
Nonrenewable nuclear
Petrochemicals
Hydropower, geothermal,
Wind, solar
Biomasss
Unavoidable energy
waste
Unnecessary energy
Fig. 13-19, p. 319
Examples of Energy-Wasting
Devices
•
•
•
•
Incandescent light bulb
Internal combustion engine
Nuclear power plants
Coal-burning power plants
Saving Energy and Money in
Industry
• Cogeneration/Combined Heat and
Power (CHP) systems
• Recycling
• Energy-saving electric motors
• Fluorescent lighting
• Smart grid electricity
Saving Energy and Money in
Transportation
• 2/3 of U.S. oil consumption
• Low fuel-efficiency standards for
vehicles
• Hidden costs: $12/gallon of gas
• Raise gasoline taxes/cut payroll and
income taxes
• Tax breaks for fuel-efficient vehicles
Hybrid and Fuel-Cell Cars
•
•
•
•
•
Super-efficient and ultralight cars
Gasoline-electric hybrid car
Plug-in hybrid electric car
Hydrogen fuel cells
Accessible mass-transit systems as
alternative
Cars
20
Cars, trucks, and SUVs
Trucks and SUVs
15
10
1975 1980
1985
1990 1995
Year
2000
2005
Miles per gallon (mpg) (converted to U.S. test equivalents)
Average fuel economy (miles per gallon)
25
50
45
Europe
40
Japan
China
35
Canada
30
25
United
States
20
2002
2004
2006
2008
Year
Stepped Art
Fig. 13-21, p. 320
Conventional hybrid
Fuel tank
Plug-in hybrid
Fuel tank
Battery
Battery
Internal
combustion
engine
Transmission Electric motor
Internal
combustion
engine
Transmission Electric motor
Stepped Art
Fig. 13-22, p. 321
Saving Energy and Money in
New Buildings
• Green architecture
• Solar cells, fuel cells, eco-roofs,
recycled materials
• Super insulation
• Straw bale houses
Saving Energy in Existing
Buildings
•
•
•
•
•
•
Insulate and plug leaks
Use energy-efficient windows
Heat houses more efficiently
Heat water more efficiently
Use energy-efficient appliances
Use energy-efficient lighting
Fig. 13-23, p. 322
Attic
• Hang reflective foil near
roof to reflect heat.
• Use house fan.
• Be sure attic insulation is
at least 30 centimeters
(12 inches).
Bathroom
• Install water-saving toilets,
faucets, and shower heads.
• Repair water leaks promptly.
Kitchen
• Use microwave rather than
stove or oven as much as
possible.
• Run only full loads in
dishwasher and use low- or
no-heat drying.
• Clean refrigerator coils
regularly.
Basement or utility room
• Use front-loading clothes washer. If possible run only full loads with warm or
cold water.
• Hang clothes on racks for drying.
• Run only full loads in clothes dryer and use lower heat setting.
• Set water heater at 140° if dishwasher is used and 120° or lower if no
dishwasher is used.
• Use water heater thermal blanket.
• Insulate exposed hot water pipes.
• Regularly clean or replace furnace filters.
Outside
Plant deciduous trees to block
summer sun and let in winter
sunlight.
Other rooms
• Use compact fluorescent
lightbulbs or LEDs and avoid
using incandescent bulbs
wherever possible.
• Turn off lights, computers, TV,
and other electronic devices
when they are not in use.
• Use high efficiency windows;
use insulating window covers
and close them at night and
on sunny, hot days.
• Set thermostat as low as you
can in winter and as high as
you can in summer.
• Weather-strip and caulk doors,
windows, light fixtures, and
wall sockets.
• Keep heating and cooling
vents free of obstructions.
• Keep fireplace damper closed
when not in use.
• Use fans instead of, or along
with, air conditioning.
Stepped Art
Fig. 13-24, p. 324
Why Are We Still Wasting So
Much Energy?
• Energy costs relatively little
• Lack of government support and
economic incentives
• Inadequate building codes
• Inadequate appliance standards
• Lack of information about saving
energy
13-5 What Are Advantages/Disadvantages
of Renewable Energy Resources?
• Concept 13-5 Using a mix of
renewable energy sources –
especially sunlight, wind,
flowing water, sustainable
biomass, and geothermal
energy – can drastically reduce
pollution, greenhouse gas emissions,
and biodiversity losses.
Renewable Energy
• Sustainability mostly depends on
solar energy
– Direct form: from the sun
• Indirect forms
– Wind
– Moving water
– Biomass
• Geothermal
Benefits of Shifting to Renewable
Energy Resources (1)
•
•
•
•
More decentralized, less vulnerable
Improve national security
Reduce trade deficits
Reduce air pollution
Benefits of Shifting to Renewable
Energy Resources (2)
• Create jobs
• Save money
• Renewable energy handicapped by
– Unbalanced, intermittent subsidies
– Inaccurate pricing
Using Solar Energy to Heat
Buildings and Water
• Passive solar heating system
• Active solar heating system
Fig. 13-25, p. 325
Fig. 13-25, p. 325
Summer
sun
Vent allows
hot air to
escape in
summer
Heavy
insulation
Winter
sun
Superwindow
Superwindow
Stone floor and wall for heat storage
PASSIVE
Fig. 13-25, p. 325
Supplement 9, Fig. 5, p. S41
Trade-Offs
Passive or Active Solar Heating
Advantages
Disadvantages
Energy is free
Need access to sun 60%
of time
Net energy is moderate
(active) to high (passive)
Quick installation
Sun can be blocked by
trees and other structures
Environmental costs not
included in market price
No CO2 emissions
Need heat storage system
Very low air and water
pollution
Very low land disturbance
(built into roof or windows)
Moderate cost (passive)
High cost (active)
Active system needs
maintenance and repair
Active collectors
unattractive
Fig. 13-26, p. 326
Solar Energy for HighTemperature Heat and Electricity
•
•
•
•
Solar thermal systems
Solar thermal plant
Solar cookers
Photovoltaic (solar) cells
Trade-Offs
Solar Energy for High-Temperature
Heat and Electricity
Advantages
Disadvantages
Moderate environmental
impact
Low efficiency
No CO2 emissions
Low net energy
High costs
Environmental costs not
included in market price
Fast construction
(1–2 years)
Costs reduced with
natural gas turbine
backup
Needs backup or storage
system
Needs access to sun most of
the time
May disturb desert areas
Fig. 13-27, p. 326
Single solar cell
Solar-cell roof
Boronenriched
silicon
Junction
Phosphorusenriched silicon
Roof options
Panels of
solar cells
Solar
shingles
Fig. 13-29, p. 328
Fig. 13-30, p. 328
Trade-Offs
Solar Cells
Advantages
Disadvantages
Fairly high net energy yield
Need access to sun
Work on cloudy days
Low efficiency
Quick installation
Need electricity storage
system or backup
Easily expanded or moved
No CO2 emissions
Low environmental impact
Last 20–40 years
Environmental costs not
included in market price
High costs (but should
be competitive in 5–15
years)
Low land use (if on roof or
built into walls or windows)
High land use (solar-cell
power plants) could
disrupt desert areas
Reduces dependence on
fossil fuels
DC current must be
converted to AC
Fig. 13-31, p. 328
Producing Electricity from
Flowing Water
• Hydropower
– Leading renewable energy source
– Much unused capacity
• Dams and reservoirs
– Turbines generate electricity
– Eventually fill with silt
• Micro-hydro generators
Trade-Offs
Large-Scale Hydropower
Advantages
Disadvantages
Moderate to high net energy
High construction costs
High efficiency (80%)
High environmental
impact from flooding land
to form a reservoir
Large untapped potential
Low-cost electricity
Long life span
No CO2 emissions during
operation in temperate areas
Can provide flood control
below dam
Environmental costs not
included in market price
High CH4 emissions from
rapid biomass decay in
shallow tropical reservoirs
Danger of collapse
Uproots people
Decreases fish harvest
below dam
Provides irrigation water
Reservoir useful for fishing
and recreation
Decreases flow of natural
fertilizer (silt) to land
below dam
Fig. 13-32, p. 329
Producing Electricity from Wind
• Indirect form of solar energy
• World’s second fastest-growing
source of energy
• Vast potential
– Land
– Offshore
Supplement 9, Fig. 8, p. S43
Trade-Offs
Wind Power
Advantages
Disadvantages
Moderate to high net
energy yield
Steady winds needed
High efficiency
Backup systems needed when
winds are low
Moderate capital cost
Low electricity cost (and
falling)
Very low environmental
impact
Plastic components produced
from oil
Environmental costs not
included in market price
No CO2 emissions
High land use for wind farm
Quick construction
Visual pollution
Easily expanded
Can be located at sea
Noise when located near
populated areas
Land below turbines can
be used to grow crops or
graze livestock
Can kill birds and interfere
with flights of migratory birds
if not sited properly
Fig. 13-34, p. 331
Energy from Burning Biomass
• Biomass
– Wood
– Agricultural waste
– Plantations
– Charcoal
– Animal manure
• Common in developing countries
• Carbon dioxide increase in atmosphere
Converting Plant Matter to
Liquid Biofuel
• Biofuels
– Ethanol and biodiesel
– Crops can be grown in most countries
– No net increase in carbon dioxide
emissions
– Available now
• Sustainability
Trade-Offs
Biodiesel
Advantages
Disadvantages
Reduced CO
emissions
Increased NOx emissions
and more smog
Reduced CO2
emissions (78%)
Higher cost than
regular diesel
High net energy
yield for oil palm
crops
Environmental costs not
included in market price
Moderate net
energy yield for
rapeseed crops
Reduced
hydrocarbon
emissions
Low net energy yield for
soybean crops
May compete with
growing food on
cropland and raise food
prices
Better gas
mileage (40%)
Loss and degradation of
biodiversity from crop
plantations
Potentially
renewable
Can make engines hard
to start in cold weather
Fig. 13-35, p. 333
Fig. 13-36, p. 334
Trade-Offs
Ethanol Fuel
Advantages
Disadvantages
High octane
Lower driving range
Low net energy yield (corn)
Some reduction in CO2
emissions
(sugarcane bagasse)
High net energy yield
(bagasse and switchgrass)
Higher CO2 emissions (corn)
Much higher cost
Environmental costs not
included in market price
May compete with growing
food and raise food prices
Can be sold as a mixture of
gasoline and ethanol or as
pure ethanol
Higher NOx emissions and
more smog
Corrosive
Potentially renewable
Can make engines hard to
start in cold weather
Fig. 13-37, p. 335
http://articles.cnn.com/2008-0401/tech/algae.oil_1_algae-research-fossilfuels-nrel?_s=PM:TECH
Energy by Tapping the Earth’s
Internal Heat
• Geothermal energy
• Geothermal heat pumps
• Hydrothermal reservoirs
– Steam
– Hot water
• Deep geothermal energy
Supplement 9, Fig. 9, p. S43
Supplement 9, Fig. 10, p. S44
Trade-Offs
Geothermal Energy
Advantages
Disadvantages
Very high efficiency
Scarcity of suitable sites
Moderate net energy at
accessible sites
Lower CO2 emissions than
fossil fuels
Can be depleted if used too
rapidly
Environmental costs not
included in market price
CO2 emissions
Low cost at favorable sites
Moderate to high local air
pollution
Low land use and
disturbance
Noise and odor (H2S)
Moderate environmental
impact
High cost except at the most
concentrated and accessible
sources
Fig. 13-38, p. 336
Can Hydrogen Replace Oil?
• Hydrogen is environmentally friendly
• Problems
– Most hydrogen is in water
– Net energy yield is negative
– Fuel is expensive
– Air pollution depends on production
method
– Storage
Trade-Offs
Hydrogen
Advantages
Can be produced from
plentiful water
Fuel
cell
Disadvantages
Not found as H2 in nature
Energy is needed to produce fuel
Low environmental impact
Negative net energy
Renewable if produced
from renewable energy
resources
CO2 emissions if produced from
carbon-containing compounds
No CO2 emissions if
produced from water
Environmental costs not included
in market price
Good substitute for oil
Nonrenewable if generated by
fossil fuels or nuclear power
Competitive price if
environmental and social
costs are included in cost
comparisons
High costs (that may eventually
come down)
Easier to store than
electricity
Safer than gasoline and
natural gas
Will take 25 to 50 years to
phase in
Short driving range for current
fuel-cell cars
Nontoxic
No fuel distribution system
in place
High efficiency (45–65%)
in fuel cells
Excessive H2 leaks may deplete
ozone in the atmosphere
Fig. 13-39, p. 337
Science Focus: The Quest to
Make Hydrogen Workable
• Bacteria and Algae
• Electricity from solar, wind,
geothermal
• Storage: liquid and solid
• Preventing explosions
13-6 How Can We Make the Transition to
a More Sustainable Energy Future?
• Concept 13-6 We can make a
transition to a more sustainable
energy future by greatly improving
energy efficiency, using a mix of
renewable energy resources, and
including environmental costs of
energy resources in their market
prices.
Transition to a More
Sustainable Energy Future (1)
• For each energy alternative:
– How much available next 25-50 years?
– Estimated net energy yield
– Total costs
– Necessary subsidies and tax breaks
– How affect economic and military
security
– Vulnerability to terrorism
– Environmental effects
Decentralized Power System
Bioenergy power plants
Wind farm
Small solar-cell
power plants
Fuel cells
Solar-cell
rooftop
systems
Rooftop solarcell arrays
Smart electrical
and distribution
system
Commercial
Residential
Small
wind
turbine
Industrial
Microturbines
Stepped Art
Fig. 13-40, p. 339
Transition to a More
Sustainable Energy Future (2)
• Gradual shift from centralized
macropower to decentralized
micropower
• Greatly improved energy efficiency
• Temporary use of natural gas
• Decrease environmental impact of
fossil fuels
Solutions
Making the Transition to a More Sustainable Energy Future
Improve Energy Efficiency
Increase fuel-efficiency
standards for vehicles,
buildings, and appliances
More Renewable Energy
Mandate government purchases
of efficient vehicles and other
devices
Include environmental costs in prices for all energy
resources
Provide large tax credits or
feebates for buying efficient
cars, houses, and appliances
Offer large tax credits for
investments in energy efficiency
Reward utilities for reducing
demand for electricity
Greatly increase energy
efficiency research and
development
Greatly increase use of renewable energy
Provide large subsidies and tax credits for use of
renewable energy
Encourage government purchase of renewable energy
Greatly increase renewable energy research and
development
Reduce Pollution and Health Risk
Cut coal use 50% by 2020
Phase out coal subsidies and tax breaks
Levy taxes on coal and oil use
Phase out nuclear power subsidies, tax breaks,
and loan guarantees
Fig. 13-41, p. 340
Economic, Political, and Educational
Strategies to Sustainable Energy
• Requires government strategies
• Keep prices low in selected resource
to encourage use
– Same strategy for fossil fuels and
nuclear power
• Keep prices high in selected resource
to discourage use
• Emphasize consumer education
Three Big Ideas from This
Chapter - #1
Energy resources should be evaluated
on the basis of their potential
supplies, how much net useful energy
they provide, and the environmental
impact of using them.
Three Big Ideas from This
Chapter - #2
Using a mix of renewable energy –
especially sunlight, wind, flowing
water, sustainable biofuels, and
geothermal energy – can drastically
reduce pollution, greenhouse gas
emissions, and biodiversity losses.
Three Big Ideas from This
Chapter - #3
Making the transition to a more
sustainable energy future requires
sharply reducing energy waste, using
a mix of environmentally friendly
renewable energy resources, and
including the harmful environmental
costs of energy resources in their
market prices.