environmental science

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

Fig. 13-2, p. 298

Commercial energy use by source

What can be said about renewable vs non-renewable?

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

Asphalt

GasesLowest Boiling Point

Highest Boiling Point

Gasoline

Aviation fuel

Heating oil

Dieseloil

Heatedcrude oil

Furnace

Naphtha

Greaseand wax

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.



• Proven oil reserves– Identified deposits that can be extracted

profitably at today’s prices with today’s technology



• 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!

Fig. 13-4, p. 301

2050

Year

Bar

rels

of

oil

per

yea

r (b

illi

on

s)

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Projected U.S.oil consumption

Arctic refuge oiloutput over 50 years

2000 2010 2020 2030 2040

*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

Fig. 13-5, p. 301

DisadvantagesNeed to findsubstitutes within 50years

Large governmentsubsidies

Environmental costsnot included inmarket price

Artificially low priceencourages wasteand discouragessearch for alternatives

Pollutes air whenproduced and burned

Releases CO2 whenburned

Can cause waterpollution

Ample supply for42–93 years

Low cost

High net energyyield

Easily transportedwithin andbetween countries

Low land use

Technology is welldeveloped

Efficientdistribution system

Trade-Offs

Conventional OilAdvantages

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-nuclear-or-coal-is-bad-tar-sands-mining-is-coming-to-utah/

• http://www.youtube.com/watch?v=YkwoRivP17A&feature=related

http://www.good.is/post/think-nuclear-or-coal-is-bad-tar-sands-mining-is-coming-to-utah/



http://www.youtube.com/watch?v=YkwoRivP17A&feature=related

http://www.youtube.com/watch?v=YkwoRivP17A&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

Fig. 13-7, p. 303

Heavy Oils from OilShale and Tar Sand

High cost (oil shale)

Low net energy yield

Environmental costsnot included inmarket price

Large amounts ofwater needed forprocessing

Severe land disruption

Severe waterpollution

Air pollution and CO2 emissions when produced and burned

Technologywell-developed(tar sand)

Efficientdistribution system in place

Easily transportedwithin andbetween countries

Large potentialsupplies, especiallytar sands inCanada

Moderate cost(tar sand)

Trade-Offs

Advantages Disadvantages

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

Fig. 13-8, p. 304

Conventional Natural Gas

Nonrenewable resource

Releases CO2 when burned

Government subsidies

Environmental costs notincluded in market price

Methane(a greenhouse gas) canleak from pipelines

Difficult to transfer fromone country to another

Can be shipped acrossocean only as highlyexplosive LNG

Ample supplies

High net energy yield

Low cost

Less air pollution thanother fossil fuels

Lower CO2 emissions thanother fossil fuels

Easily transported bypipeline

Low land use

Good fuel for fuel cells,gas turbines, and motorvehicles

Trade-Offs


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

Highly desirable fuel because of its high heat content andlow sulfur content; supplies are limited in most areas

Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content

Low heat content; lowsulfur content; limitedsupplies in most areas

Partially decayed plantmatter in swamps andbogs; low heat content

Peat(not a coal)

Lignite(brown coal)

Bituminous(soft coal)

Increasing heat and carbon content Increasing moisture content

Heat Heat Heat

Pressure Pressure Pressure

Anthracite(hard coal)

Fig. 13-9, p. 305

Stack

Waste heat

Cooling towertransfers wasteheat to atmosphere

Pulverizing mill

TurbineCoal bunker

GeneratorCooling loop

Condenser

Boiler

Filter

Toxic ash disposal

Fig. 13-10, p. 306

Coal burning power plant

TVA Coal fired power plant

• http://www.tva.com/power/coalart.htm

• http://www.newsweek.com/photo/2009/07/21/photos--the-worst-man-made-environmental-disasters.html

http://www.tva.com/power/coalart.htm

http://www.newsweek.com/photo/2009/07/21/photos--the-worst-man-made-environmental-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 58%

Nuclear power fuel cycle 17%

Geothermal 10%Stepped Art

Fig. 13-11, p. 306

CO2 Emissions per unit of electrical energy

Fig. 13-12, p. 307

DisadvantagesSevere land disturbance,air pollution, and waterpollution

Severe threat to humanhealth when burned


Large governmentsubsidies

High CO2 emissionswhen produced andburned

Radioactive particle andtoxic mercury emissions

Air pollution can be reduced withimproved technology

Well-developed technology

Low cost

High net energy yield

Ample supplies (225–900 years)

Trade-Offs

Coal

Advantages

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-10-worst-man-made-environmental-disasters/

http://earthfirst.com/americas-top-10-worst-man-made-environmental-disasters/

http://earthfirst.com/americas-top-10-worst-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

Fig. 13-13, p. 309

DisadvantagesLow to moderate net energy yield

Higher cost than coal

Requires mining 50% more coal

Environmental costs not includedin market price

High environmental impact

Large government subsidies

High water use

Higher CO2 emissions than coal

Large potential supply

Vehicle fuel

Moderate cost

Lower air pollutionthan coal whenburned

Trade-Offs

Synthetic Fuels

Advantages

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 FissionReactor 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/wattsbar_howworks.htm

• http://www.tvakids.com/videos/pressurized_water_animation.htm

http://www.tvakids.com/videos/pressurized_water_animation.htm




Coolwaterinput

Small amounts ofradioactive gases

Periodic removal andstorage of radioactive

wastes and spentfuel assemblies

Periodic removaland storage of

radioactiveliquid wastes

Control rods

Heat exchanger

Containment shell

Steam

Water

Uraniumfuel input(reactor core)

Hotcoolant

Coolant

Moderator

Coolantpassage

Shielding

Waste heat

Water source(river, lake, ocean)

Useful electricalenergy

About 25%

GeneratorTurbine

Hotwateroutput

Condenser

Pressurevessel

Fig. 13-14, p. 310

Pump

Waste heatPump

Pump

Pump

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

Fuel assemblies

Fuel fabricationEnrichmentof UF6

Temporary storageof spent fuel assemblies

underwater or in dry casks

Low-level radiationwith long half-life

Geologic disposalof moderate and high-levelradioactive wastes

(conversion of enrichedUF6 to UO2 and fabricationof fuel assemblies)

Uranium-235 as UF6 Plutonium-239 as PuO2

Decommissioningof reactor

Reactor

Spent fuelreprocessing

Conversionof U3O8

to UF6

Fig. 13-16, p. 312

Open fuel cycle today

Recycling of nuclear fuel

Mining uranium ore (U3O8 )

Nuclear Fuel Cycle

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/2011/mar/14/japan-tsunami-amateur-footage-video

http://abcnews.go.com/Technology/video/japan-nuclear-crisis-at-fukushima-daiichi-plant-13137908



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

Fig. 13-17, p. 313

Conventional Nuclear Fuel Cycle

Cannot competeeconomically without hugegovernment subsidies


High environmental impact(with major accidents)


Risk of catastrophic accidents

No widely acceptable solutionfor long-term storage ofradioactive wastes

Subject to terrorist attacks

Spreads knowledge andtechnology for buildingnuclear weapons

Large fuel supply

Low environmentalimpact (withoutaccidents)

Emits 1/6 as much CO2

as coal

Moderate land disruptionand water pollution(without accidents)

Moderate land use

Low risk of accidentsbecause of multiplesafety systems (except forChernobyl-type reactors)

Trade-Offs

DisadvantagesAdvantages

Fig. 13-18, p. 314

Coal vs. Nuclear

Ample supply ofuranium


Low air pollution

Lower CO2 emissions

Much lower landdisruption fromsurface mining

Moderate land use

High cost (even withhuge subsidies)

Ample supply

High net energyyield

Very high airpollution

High CO2

emissions

High landdisruption fromsurface mining

High land use

Low cost (withhuge subsidies)

Coal Nuclear

Trade-Offs

Nuclear Power Is Vulnerable toTerrorist 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

OutputsSystemEnergy Inputs

43%

7%

9%

3%4%

41%85%

8%

U.S.economy

Fig. 13-19, p. 319

Nonrenewable fossil fuels

Nonrenewable nuclear

Hydropower, geothermal,Wind, solarBiomasss

Useful energy

Petrochemicals

Unavoidable energywasteUnnecessary energy

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

Stepped Art

Fig. 13-21, p. 320

25Cars

20 Cars, trucks, and SUVs

Trucks and SUVs15

Ave

rag

e f

uel

eco

no

my

(mil

es

per

gal

lon

)

10

1975 1980 1985 1990 1995 2000 2005

Year

50

45 Europe

40 Japan

35China

Mil

es p

er g

allo

n (

mp

g)

(co

nve

rted

to

U.S

. te

st e

qu

ival

ents

)

30 Canada

25United States20

2002 2004 2006 2008

Year

Stepped Art

Conventional hybrid Fuel tank

Battery

Internal combustion engine

Transmission Electric motor

Plug-in hybrid

Fuel tank

Battery

Internal combustion engine

Transmission Electric motor

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

Fig. 13-24, p. 324

Outside Plant deciduous trees to blocksummer sun and let in wintersunlight.

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.

Bathroom• Install water-saving toilets, faucets, and shower heads.• Repair water leaks promptly.

Stepped Art

Attic• Hang reflective foil near roof to reflect heat.• Use house fan.• Be sure attic insulation is at least 30 centimeters (12 inches).

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.

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

PASSIVE

Summersun

Wintersun

Vent allowshot air toescape insummer

Superwindow

Superwindow

Stone floor and wall for heat storage

Heavyinsulation

Fig. 13-25, p. 325

Fig. 13-26, p. 326

Passive or Active Solar Heating

Need access to sun 60%of time

Sun can be blocked bytrees and other structures


Need heat storage system

High cost (active)

Active system needsmaintenance and repair

Active collectorsunattractive

Energy is free

Net energy is moderate(active) to high (passive)

Quick installation

No CO2 emissions

Very low air and waterpollution

Very low land disturbance(built into roof or windows)

Moderate cost (passive)


Trade-Offs

Solar Energy for High-Temperature Heat and Electricity• Solar thermal systems

• Solar thermal plant

• Solar cookers

• Photovoltaic (solar) cells

Fig. 13-27, p. 326

Trade-Offs

Low efficiency

Low net energy

High costs


Needs backup or storagesystem

Needs access to sun most ofthe time

May disturb desert areas

Costs reduced withnatural gas turbinebackup

No CO2 emissions

Fast construction(1–2 years)

Moderate environmentalimpact


Solar Energy for High-TemperatureHeat and Electricity

Boron-enrichedsilicon

Phosphorus-enriched silicon

Junction

Single solar cell Solar-cell roof

Panels of solar cells

Solar shingles

Roof options

Fig. 13-29, p. 328

Fig. 13-30, p. 328

Fig. 13-31, p. 328

Solar Cells

Need access to sun

Low efficiency

Need electricity storagesystem or backup


High costs (but should be competitive in 5–15 years)

High land use (solar-cellpower plants) coulddisrupt desert areas

DC current must beconverted to AC

Reduces dependence onfossil fuels

Low land use (if on roof orbuilt into walls or windows)

Last 20–40 years

Low environmental impact

No CO2 emissions

Easily expanded or moved

Quick installation

Work on cloudy days

Fairly high net energy yield

Trade-Offs


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

Fig. 13-32, p. 329

Large-Scale Hydropower

High construction costs

High environmentalimpact from flooding landto form a reservoir


High CH4 emissions fromrapid biomass decay inshallow tropical reservoirs

Danger of collapse

Uproots people

Decreases fish harvestbelow dam

Decreases flow of naturalfertilizer (silt) to landbelow dam

Moderate to high net energy

High efficiency (80%)

Large untapped potential

Low-cost electricity

Long life span

No CO2 emissions duringoperation in temperate areas

Can provide flood controlbelow dam

Provides irrigation water

Reservoir useful for fishingand recreation


Trade-Offs

Producing Electricity from Wind

• Indirect form of solar energy

• World’s second fastest-growing source of energy

• Vast potential– Land

– Offshore

Fig. 13-34, p. 331

Trade-Offs

Steady winds needed

Backup systems needed whenwinds are low

Plastic components producedfrom oil


High land use for wind farm

Visual pollution

Noise when located nearpopulated areas

Can kill birds and interferewith flights of migratory birdsif not sited properly

Moderate to high netenergy yield

High efficiency

Moderate capital cost

Low electricity cost (andfalling)

Very low environmentalimpact

No CO2 emissions

Quick construction

Easily expanded

Can be located at sea

Land below turbines canbe used to grow crops orgraze livestock


Wind Power

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

Fig. 13-35, p. 333

Increased NOx emissionsand more smog

Higher cost thanregular diesel


Low net energy yield forsoybean crops

May compete withgrowing food oncropland and raise foodprices

Loss and degradation ofbiodiversity from cropplantations

Can make engines hardto start in cold weather

Reduced COemissions

Reduced CO2

emissions (78%)

High net energyyield for oil palmcrops

Moderate netenergy yield forrapeseed crops

Reducedhydrocarbonemissions

Better gasmileage (40%)

Potentiallyrenewable

Trade-Offs


Biodiesel

Fig. 13-36, p. 334

Fig. 13-37, p. 335

Lower driving range

Low net energy yield (corn)

Higher CO2 emissions (corn)

Much higher cost


May compete with growingfood and raise food prices

Higher NOx emissions andmore smog

Corrosive

Can make engines hard tostart in cold weather

High octane

Some reduction in CO2

emissions(sugarcane bagasse)

High net energy yield(bagasse and switchgrass)

Can be sold as a mixture ofgasoline and ethanol or aspure ethanol

Potentially renewable

Trade-Offs


Ethanol Fuel

http://articles.cnn.com/2008-04-01/tech/algae.oil_1_algae-research-fossil-fuels-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

Fig. 13-38, p. 336

Very high efficiency Scarcity of suitable sites

Can be depleted if used toorapidly


CO2 emissions

Moderate to high local airpollution

Noise and odor (H2S)

High cost except at the mostconcentrated and accessiblesources

Moderate environmentalimpact

Low land use anddisturbance

Low cost at favorable sites

Lower CO2 emissions thanfossil fuels

Moderate net energy ataccessible sites

Trade-Offs


Geothermal Energy

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

Fig. 13-39, p. 337

Not found as H2 in nature

Energy is needed to produce fuel

Negative net energy

CO2 emissions if produced fromcarbon-containing compounds

Environmental costs not includedin market price

Nonrenewable if generated byfossil fuels or nuclear power

High costs (that may eventuallycome down)

Will take 25 to 50 years tophase in

Short driving range for currentfuel-cell cars

No fuel distribution systemin place

Excessive H2 leaks may depleteozone in the atmosphere

Can be produced fromplentiful water

Low environmental impact

Renewable if producedfrom renewable energyresources

No CO2 emissions ifproduced from water

Good substitute for oil

Competitive price ifenvironmental and socialcosts are included in costcomparisons

Easier to store thanelectricity

Safer than gasoline andnatural gas

Nontoxic

High efficiency (45–65%)in fuel cells

Trade-Offs


Hydrogen

Fuelcell

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

Bioenergy power plants

Smart electricaland distributionsystem

Small solar-cellpower plants

Solar-cellrooftopsystems

Commercial

Fuel cells

Rooftop solar-cell arrays

Residential

Small windturbine

Stepped ArtIndustrial Microturbines

Wind farm

Fig. 13-40, p. 339

Decentralized Power System

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

Fig. 13-41, p. 340

Increase fuel-efficiency standards for vehicles, buildings, and appliances

Mandate government purchases of efficient vehicles and other devices

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

Improve Energy Efficiency

Making the Transition to a More Sustainable Energy Future

Solutions

Phase out nuclear power subsidies, tax breaks, and loan guarantees

More Renewable Energy

Greatly increase use of renewable energy

Provide large subsidies and tax credits for use of renewable energy

Include environmental costs in prices for all energy resources

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

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.


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.


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.

environmental science

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