Nonrenewable Resources : Oil and Natural Gas

Nonrenewable Resources : Oiland Natural Gas

Fossil Fuel Reserves

1. Enough coal to last us around 112 years at currentrates of production (Could last longer)

The largestcoal reservesare found inthe U.S. (1st),Russia (2nd),and China(3rd). Thisaccounts forabout 50% ofall provencoalreserves.

Coal Is a Plentiful but Dirty Fuel

1. Coal: solid fossil fuel

2. Mined: by strip or subsurface mining

Mining causes habitat degradation

Coal contains a lot of sulfur compounds; rainwater runningthrough spoilage heaps causes ground water contamination

3. Burned in power plants; generates 42% of the world’selectricity

Inefficient average coal-fired power plants is onlyabout 30% efficient

4. Three largest coal-burning countries

China

United States

Canada

Problems with Abandoned CoalMines

1. Spoil piles contain a lot of toxic chemicals

2. Rainwater mixes and dissolves chemicals whichleach out and can contaminate groundwater,surface water, the soil, etc.

Spoil heap of anun-reclaimedmine

Coal Is a Plentiful but Dirty Fuel

1. World’s most abundantfossil fuel

U.S. has 28% of provenreserves

2. Environmental costs ofburning coal

Severe air pollution

Sulfur released as SO2

Large amount of soot

CO2

Trace amounts of Hg andradioactive materials

20 of the world’s worstpolluted cities are inChina!---Acid Rain

The majority of atmosphericmercury is produced bycoal burning power plants

Increasing moisture content

Increasing heat and carbon content

Peat

(not a coal)

Lignite

(brown coal)

Bituminous

(soft coal)

Anthracite

(hard coal)

Heat

Pressure

Partially decayed plantmatter in swamps andbogs; low heat content

Low heat content; lowsulfur content; limitedsupplies in most areas

Extensively used as a fuelbecause of its high heatcontent and large supplies;normally has a high sulfurcontent

Highly desirable fuelbecause of its high heatcontent and low sulfurcontent; supplies arelimited in most areas

Fig. 15-14, p. 382

Stages in Coal Formation over Millionsof Years

Waste heat

Coal bunker

Turbine

Cooling towertransfers wasteheat toatmosphere

Generator

Cooling loop

Stack

Pulverizing mill

Condenser

Filter

Boiler

Toxic ash disposal

Science: Coal-Burning Power Plant

Coal Consumption in China & theUnited States, 1980-2008

Figure 8, Supplement 9

Acid rain is primarily caused by burning coal! (A lot ofSO2 is given off)

Coal Deposits in the U.S.

Figure 19, Supplement 8

Fig. 15-18, p. 384

Advantages

Disadvantages

1. Ample supplies inmany countries

1. Severe landdisturbance andwater pollution

2. Fine particle andtoxic mercuryemissions threatenhuman health

2. High netenergy yield

3. Emits large amountsof CO2, SO2, Mercury,and other pollutantswhen produced andburned

3. Low cost whenenvironmental costsare not included

Advantages and Disadvantages of UsingCoal as an Energy Source

The Problem of Coal Ash

1. Types of coal ash:

Ash from burning coal

Ash that contains toxic chemicals as a result ofremoving toxic pollutants from emissions

2. Highly toxic

Arsenic, cadmium, chromium, lead, mercury

Ash left from burning and from emissions

3. Some used as fertilizer by farmers

4. Most is buried or put in ponds

Leachate can contaminate groundwater

The Clean Coal and Anti-CoalCampaigns

1. Coal companies and energy companies fought

Classifying carbon dioxide as a pollutant

Classifying coal ash as hazardous waste

Air pollution standards for emissions

2. 2008 clean coal campaign

But no such thing as clean coal

We Can Convert Coal into Gaseousand Liquid Fuels

1. Coal gasification

Converts solid coal into a gas - Synthetic naturalgas (SNG)

Removes sulfur & most other impurities from coal

2. Coal Liquefaction

Converts solid coal into a liquid such asmethanol or synthetic gasoline

3. SNG and methanol are Synfuels

Fig. 15-19, p. 385

Advantages

Disadvantages

1. Large potentialsupply in manycountries

1. Low to moderate netenergy yield

2. Vehicle fuel

2. Requires mining 50%more coal with increasedland disturbance, waterpollution and water use

3. Lower airpollution than coal

3. Higher CO2 emissionsthan coal

Advantages and Disadvantages of UsingSynthetic Fuels

How Does a Nuclear FissionReactor Work?

1.Controlled nuclear fission reaction in a reactor

Light-water reactors

Very inefficient

2. Fueled by uranium ore & packed as pellets infuel rods & fuel assemblies

Control rods absorb neutrons

3. Water is the usual coolant

4. Containment shell around the core for protection

5. Water-filled pools or dry casks for storage ofradioactive spent fuel rod assemblies

Fig. 15-20a, p. 387

Small amounts ofradioactive gases

Uranium fuelinput (reactorcore)

Containment shell

Waste heat

Control rods

Heat exchanger

Steam

Turbine

Generator

Hotcoolant

Usefulelectricalenergy

about 25%

Hotwateroutput

Coolant

Moderator

Coolwaterinput

Waste heat

Shielding

Pressurevessel

Coolantpassage

Water

Condenser

Periodic removal andstorage of radioactivewastes and spent

fuel assemblies

Periodic removaland storage

of radioactive

liquid wastes

Water source

(river, lake, ocean)

Fig. 2-9b, p. 43

Nuclearfission

Uranium-235

Neutron

Energy

Fission

fragment

Energy

Fission

fragment

Radioactive isotope Radioactive decay occurs when nuclei of unstable isotopes

spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energyradiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or acombination of the three items shown in the diagram.

What Is the Nuclear Fuel Cycle?

1.Mine the uranium

2.Process the uranium to make the fuel

3.Use it in the reactor

4.Safely store the radioactive waste

5.Decommission the reactor

Fig. 15-21, p. 388

Fuel assemblies

Decommissioning

of reactor

Enrichment

of UF6

Reactor

Fuel fabrication

(conversion of enriched UF 6

to UO2 and fabrication of fuelassemblies)

(conversion of enriched UF 6

to UO2 and fabrication of fuelassemblies)

Temporary storage

of spent fuel assembliesunderwater or in dry casks

Temporary storage

of spent fuel assembliesunderwater or in dry casks

Conversion

of U3O8

to UF6

Spent fuelreprocessing

Uranium-235 as UF6Plutonium-239 as PuO2

Low-level radiation withlong half-life

Mining uranium

ore (U3O8)

Mining uranium

ore (U3O8)

Geologic disposalof moderate-

and high-levelradioactivewastes

Geologic disposalof moderate-

and high-levelradioactivewastes

Open fuel cycle today

Recycling of nuclear fuel

What Happened to NuclearPower?

1. Slowest-growing energy source and expected todecline more

2. Why?

Economics

Poor management

Low net yield of energy of the nuclear fuel cycle

Safety concerns

Need for greater government subsidies

Concerns of transporting uranium

Global Energy Capacity of NuclearPower Plants

Figure 10, Supplement 9

Nuclear Power Plants in theUnited States

Figure 21, Supplement 8

Storing Spent Radioactive Fuel RodsPresents Risks

1. Fuel rods must be replaced every 3-4 years

2. Cooled in water-filled pool

3. Placed and stored in dry casks

4. Must be stored for thousands of years

5. Vulnerable to terrorist attack

Chernobyl

April 26, 1986

In Chernobyl, Ukraine

Series of explosions caused the roof of a reactor building to blow off

Partial meltdown and fire for 10 days

Huge radioactive cloud spread over many countries and eventuallythe world

350,000 people left their homes

Effects on human health, water supply, and agriculture

chernobyl map Caesium-137 contaminated areas in European countries

Radioactive Wastes Produced byNuclear Power

1. High-level radioactivewastes

Must be stored safely for 10,000–240,000 years

2. Where to store it

Deep burial: safest and cheapestoption

Would any method of burial last longenough?

There is still no facility

Shooting it into space is toodangerous

Yucca Mountain wasthe proposed site forthe storage ofnuclear waste

What Do We Do with Worn-OutNuclear Power Plants?

1. Decommission or retire the power plant

2. Some options

Dismantle the plant and safely store the radioactivematerials

Enclose the plant behind a physical barrier with full-time security until a storage facility has been built

Enclose the plant in a tomb

•Monitor this for thousands of years

Can Nuclear Power Lessen Dependence onImported Oil & Reduce Global Warming?

1. Nuclear power plants: no CO2 emission

2. Nuclear fuel cycle: emits CO2

3. Opposing views on nuclear power

–Nuclear power advocates

–2007: Oxford Research Group

4. Need high rate of building new plants, plus astorage facility for radioactive wastes

Fig. 15-22, p. 389

Conventional Nuclear Fuel Cycle

Low environmentalimpact (withoutaccidents)

Very low net energyyield and high overallcost

Advantages

Disadvantages

Emits 1/6 as muchCO2 as coal

Produces long-lived,harmful radioactivewastes

Low risk of accidents inmodern plants

Promotes spread ofnuclear weapons

Trade-Offs

Trade-Offs: Coal versus Nuclear toProduce Electricity

Fig. 15-23, p. 389