APES Chapter 15 presentation.ppt

Chapter 15

Geologic Resources:

Mineral Resource

• Concentration of naturally occurring

material in or on the earth’s crust that can

be extracted and processed into useful

Nonrenewable resources

• Not renewed in our lifetime • Metallic minerals – Fe, Cu, Al

ore- rock containing enough metallic mineral to be mined profitably

• Nonmetallic minerals – Salt, clay, sand phosphates, soil

General Classification of Nonrenewable

Mineral Resources

• The U.S. Geological Survey classifies mineral resources into four major categories:

– Identified: known location, quantity, and quality or existence known based on direct evidence and measurements.

– _{Undiscovered: potential supplies that are}

assumed to exist.

– _{Reserves: identified resources that can be}

extracted profitably.

Getting More Minerals from the Ocean

• Hydrothermal

deposits form

when mineral-rich

superheated water

shoots out of vents

in solidified

Locating Mineral Resources

• Arial photos, satellites

• Aircraft with radiation measuring equipment (for uranium) and magnetometers (for iron)

• Deep well drilling • Seismic surveys

Types of Mining Techniques

• Minerals are removed through a variety of methods that vary widely in their costs, safety factors, and levels of environmental harm.

• A variety of methods are used based on mineral depth.

Surface Mining

• Mechanized equipment strips away the

overburden

(layer of soil and rock

overlying a mineral deposit) and discards it

as

spoils

• Accounts for 60% of coal in US

Surface Mining:

Open-pit Mining

• Machines dig

holes and

remove ores,

sand, gravel,

and stone.

• Toxic

groundwater

Open Pit Mining

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Dredging

• Chain buckets,

Area Strip Mining

• Earth movers

strips away

overburden, and

giant shovels

removes mineral

deposit.

• Often leaves

highly erodible hills

of rubble called

Strip Mining

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Contour Strip Mining

• Used on hilly or

mountainous

terrain.

• Unless the land is

restored, a wall of

dirt is left in front

of a highly

erodible bank

called a

Mountaintop Removal

• Machinery

removes the tops

of mountains to

expose coal.

Restoration of Surface Mined Land

• Achievable in all but arid and semiarid areas • Expensive and not done in many countries

• Surface mining Control and Reclamation Act of 1977: requires mining companies to restore

Subsurface Mining

• Dig vertical shaft, blast subsurface

tunnels, use machinery to remove ore and

transport to top

• Disturbs less land than surface mining

• Produces less waste, but leaves much of

resource in ground

• More expensive and dangerous

• Dangers: collapse of roof & walls,

explosions of dust & natural gas

ENVIRONMENTAL EFFECTS OF

USING MINERAL RESOURCES

• The extraction, processing, and use of

Effects

• Scarring, disruption of land surfaces • Collapse or subsidence of land

• Wind, water erosion of toxin-laced mining wastes • Acid mine drainage – produced when aerobic

bacT act on iron sulfide minerals in spoils,

contaminates water supply, damages aquatic life • Emission of toxic chems into atmosphere

Mining Impacts

• Metal ores are

smelted or treated

with (potentially

Ore Processing

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Life cycle of Metal Resource

• Gangue – waste • Tailings – waste

material

• Smelting – separation of desired metal from ore

• Uses massive energy • Air, water pollution

SUPPLIES OF MINERAL

RESOURCES

• Never completely run out of a mineral

resource but economically deplete it.

•

Economic depletion

- Costs more to find,

SUPPLIES OF MINERAL

RESOURCES

• Depletion curves

for a renewable

resource using

three sets of

assumptions.

SUPPLIES OF MINERAL

RESOURCES

• New technologies can increase the mining of

low-grade ores at affordable prices, but

harmful environmental effects can limit this

approach.

• Most minerals in seawater and on the deep

ocean floor cost too much to extract, and

SUPPLIES OF MINERAL

RESOURCES

• The future supply of a resource depends on

its affordable supply and how rapidly that

supply is used.

USING MINERAL RESOURCES MORE

SUSTAINABLY

• Scientists and engineers are developing new types of materials as substitutes for many

metals. Silicon, ceramics, plastics

Solutions

Sustainable Use of Nonrenewable Minerals • Do not waste mineral resources.

• Recycle and reuse 60–80% of mineral resources.

• Include the harmful environmental costs of mining and processing minerals in the prices of items (full-cost pricing).

• Reduce subsidies for mining mineral resources.

• Increase subsidies for recycling, reuse, and

finding less environmentally harmful substitutes.

• Redesign manufacturing processes to use less mineral resources and to produce less pollution and waste.

• Have the mineral-based wastes of one manufacturing process become the raw materials for other processes.

• Sell services instead of things.

TYPES OF ENERGY

RESOURCES

• About 99% of the energy we use for heat

comes from the sun and the other 1%

comes mostly from burning fossil fuels.

– Solar energy indirectly supports wind power, hydropower, and biomass.

• About 76% of the commercial energy we

use comes from nonrenewable fossil fuels

(oil, natural gas, and coal) with the

• Cultural changes and technological

advances have greatly increased energy

use per person

Trends in Energy Resources

• Global use of coal has declined – most polluting and climate-disrupting fossil fuel.

• US- largest user followed by China

• Use of oil climbs (?low prices, abundance and ease of use) Many fluctuations – post Katrina

• Natural gas use increasing - ? Ample supplies. Cleanest and least climate disrupting of fossil fuels

• Nuclear power leveled off – may change soon

• Biomass- in developing countries (fuel wood and charcoal made from wood) Leads to unsustainable

US Trends

• Largest user 24% with 4.6% of world’s pop

• 92% US energy from nonrenewable resources • World and US dependence on nonrenewable

Developing Energy Policies for the Future

• How much is available long and short term • What is net energy yield

• Cost of development and use • Gov’t role

• Effect on national and global & economic security • Vulnerability to terrorism

Net Energy

• the amount of high-quality usable energy

available from a resource after subtracting

the energy needed to make it available.

• Expressed as ratio – the higher the ratio

the greater the net energy

Fig. 16-4, p. 358

Space Heating

Space Heating

Passive solar _5.8

Natural gas

Oil _4.5

Active solar _1.9 Coal gasification _1.5 Electric resistance heating (coal-fired plant) _0.4

0.4

Electric resistance heating (nuclear plant) _0.3

High-Temperature Industrial Heat

High-Temperature Industrial Heat

28.2 Surface-mined coal

Underground-mined coal _25.8

Natural gas _4.9

Oil 4.7

Coal gasification _1.5 Direct solar (highly concentrated by mirrors,

heliostats, or other devices) 0.9

Transportation

Transportation

Natural gas _4.9

Gasoline (refined crude oil) _4.1 Biofuel (ethyl alcohol) _1.9

Coal liquefaction 1.4 Oil shale 1.2 Electric resistance heating (natural-gas-fired plant)

Example: Compare passive solar to nuclear plant

• Passive solar – high net energy – very little energy expended

• Nuclear – low net energy – requires much

OIL

• Crude oil (petroleum) is a thick liquid

containing hydrocarbons that we extract from

underground deposits and separate into

products such as gasoline, heating oil and

asphalt.

– Only 35-50% can be economically recovered from a deposit.

– As prices rise, about 10-25% more can be

recovered from expensive secondary extraction techniques.

OIL

• Refining crude oil:

– Based on boiling

points, components are removed at

various layers in a giant distillation

column.

OIL

• Eleven OPEC (Organization of Petroleum

Exporting Countries) have 78% of the

world’s proven oil reserves and most of the

world’s unproven reserves.

• After global production peaks and begins a

slow decline, oil prices will rise and could

threaten the economies of countries that

Case Study: U.S. Oil Supplies

• The U.S. – the world’s largest oil user –

has only 2.9% of the world’s proven oil

reserves.

• U.S oil production peaked in 1974

(halfway production point).

Trade-Offs

Conventional Oil

Advantages Disadvantages Ample supply for

42–93 years Need to find

substitutes within 50 years

Low cost (with huge subsidies)

Artificially low price encourages waste and discourages search for alternatives

High net energy yield

Easily transported within and between countries

Air pollution when burned

Low land use

Releases CO₂ when burned

Technology is well developed

Efficient distribution

system Moderate water

Heavy Oils from Oil Sand and Oil

Shale: Will Sticky Black Gold Save

Us?

• Heavy and tarlike oils from oil sand and oil

shale could supplement conventional oil, but

there are environmental problems.

– High sulfur content.

– Extracting and processing produces:

• Toxic sludge

• Uses and contaminates larges volumes of water

Oil Shales

• Oil shales

contain a solid

combustible

mixture of

Trade-Offs

Heavy Oils from Oil Shale and Oil Sand

Advantages Disadvantages

Moderate cost (oil sand)

High cost (oil shale)

Low net energy yield

Large potential supplies,

especially oil sands in

Canada Large amount _{of water needed} for processing Easily transported within and between countries Severe land disruption Severe water pollution Efficient distribution system in place Air pollution when burned

CO₂ emissions when burned Technology is

NATURAL GAS

• Natural gas, consisting mostly of methane, is often found above reservoirs of crude oil.

– When a natural gas-field is tapped, gasses are liquefied and removed as liquefied petroleum gas (LPG).

NATURAL GAS

• Russia and Iran have almost half of the

world’s reserves of conventional gas, and

global reserves should last 62-125 years.

• Natural gas is versatile and clean-burning

fuel, but it releases the greenhouse gases

carbon dioxide (when burned) and

NATURAL GAS

• Some analysts see

natural gas as the

best fuel to help us

make the transition

to improved energy

efficiency and

greater use of

COAL

COAL

• Coal reserves in the United States,

Russia, and China could last hundreds to

over a thousand years.

– The U.S. has 27% of the world’s proven coal reserves, followed by Russia (17%), and

China (13%).

COAL

• Coal is the most

abundant fossil fuel, but compared to oil and natural gas it is not as versatile, has a high environmental

COAL

• Coal can be converted into synthetic

natural gas (SNG or syngas) and liquid

fuels (such as methanol or synthetic

gasoline) that burn cleaner than coal.

– Costs are high.

COAL

NUCLEAR ENERGY

• Isotopes of uranium and plutonium undergo controlled nuclear fission

• Fuel - uranium oxide consists of about 97%

nonfissionable uranium-238 and 3% fissionable uranium-235.

– Concentration of uranium-235 is increased through an enrichment process.

– Dangerous to mine and purify- workers exposed to radon (lung ca)

Nuclear Fission

• Atom such as uranium-235 or plutonium-239 is split by no and massive amounts of energy are

released in a controlled chain reaction

• Reaction is moderated to control heat and

energy by cooling solution (absorbs neutrons) and by control rods (made of B or Cd)

Light Water Reactors

Fig. 16-16, p. 372 Small amounts of

radioactive gases Uranium fuel input (reactor core) Control rods Containment shell Heat exchanger

Steam Turbine _Generator

Waste heat Electric power Hot coolant Useful energy 25%–30% Hot water output Pump Pump

Coolant _{Pump Pump}

Moderator Cool water input Waste heat Shielding Pressure vessel Coolant passage Water _Condenser Periodic removal and

storage of radioactive wastes and spent fuel assemblies

Periodic removal and storage of radioactive liquid wastes

Nuclear Energy

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Types of Reactors

1. PWR – pressurized water, >70% of reactors

• Water circulates around fuel rods to remove heat primary coolant

• Primary coolant flows through tube in steam generator and produces high energy steam (heat transfer)

• Energy turns turbine (kinetic energy to mechanical energy)

• Steam leaving turbine is condensed and pumped back to steam generator

• Reactors encased in thick-walled concrete and steel • Operating properly, releases less radioactivity than a

coal-fired power plant.

2. Boiling water reactor

• More dangerous design

• Boiling water from reactor core is used to drive the turbine generators

• Highly radioactive water and steam leave the containment building

3. Canadian deuterium reactors CANDU

• Use heavy water D₂O as cooling agent and moderator

• Can use naturally found unconcentrated uranium, eliminates expense of enrichment

4. Graphite

• Used as moderator and structural material for reactor core

• Britain – MAGNOX – cooling accomplished by CO₂

• Soviet Design – similar but low pressure cooing water circulates through core in small metal

tubes

Disasters with Graphite Reactors

• Involved fires in graphite cores

• Nuclear fuel melted and escaped into the

atmosphere

• 1956 in England

Safety Concerns

• Biggest danger is cooling water system failure • Nuclear fuel can overheat, and meltdown can

result that releases deadly radioactive material (Chernobyl)

• Misconception – nuclear power plants don’t explode

• 2002 inspectors found that leaking boric acid

Alternative Reactor Designs

• PBMR Pebble Bed Modular reactor

• Uses uranium in ceramic-coated pellets surrounded by helium as cooling gas

• Can reload pellets during operations

• Problems with fires in control buildings and turbine-generators

• Can create 10X more radioactive wastes than traditional

Breeder Reactors

• Produce own fuel rather than consume it converts uranium-238 into plutonium-239 • Safety problems

• Uses liquid sodium as coolant – explosive component if contacts water

• Immediate meltdown if coolant is lost • Excess Pu could be used for bombs

• 1986 France put breeder reactor into operation, but closed after 1 year when crack was

Nuclear Fuel Cycles

• Each part produces low-level and high level waste

• Low level must be stored for 100 – 500 years before decaying to safe levels (generally

consider 10 - ½ lives)

• Contaminated tools, clothing, building materials • Before 1970, put into steel drums and dumped

into ocean

High level Radioactive Waste

• Must be stored safely for 10,000 years (uranium) and 240,000 years (if plutonium is not removed) • Spent fuel rods, wastes from nuclear weapons

manufacturing

• Presently fuel assemblies stored in deep water pools on site at nuclear power plants (read page 371)

• As pools fill, assemblies are stored in large metal dry casks outside power plants

Yucca Mountain, Nevada

• 1987 high level radioactive waste repository • Waste to be stored deep underground

• Scheduled to open 2010, but Obama administration says “NO”

• Requirements for High Level radioactive waste repository:

No geologic faults (no earthquakes) Low groundwater table

Fig. 16-18, p. 373 Decommissioning of reactor Fuel assemblies Reactor Enrichment

of UF₆ Fuel fabricationFuel fabrication

(conversion of enriched UF

(conversion of enriched UF₆₆

to UO

to UO₂₂ and fabrication of and fabrication of fuel assemblies)

fuel assemblies) Temporary storage of _{Temporary storage of}

spent fuel assemblies

spent fuel assemblies

underwater or in dry

underwater or in dry

casks

casks Conversion of

U₃O₈ to UF₆

Uranium-235 as UF

Uranium-235 as UF₆₆

Plutonium-239 as PuO

Plutonium-239 as PuO₂₂

Spent fuel Spent fuel reprocessing reprocessing Low-level radiation Low-level radiation

with long half-life

with long half-life

Geologic disposal of moderate & high-level radioactive wastes Open fuel cycle today

NUCLEAR

ENERGY

• In 1995, the World Bank said nuclear

power is too costly and risky.

• In 2006, it was found that several U.S.

Coal vs. Nuclear

Trade-Offs

Coal Nuclear

Ample supply Ample supply of uranium

High net energy yield Low net energy yield

Very high air pollution Low air pollution (mostly _{from fuel reprocessing)}

High CO₂ emissions Low CO₂ emissions (mostly

from fuel reprocessing)

High land disruption from

surface mining Much lower land disruption

from surface mining

Low cost (with huge subsidies) High cost (even with huge subsidies)

What Happened to Nuclear Power?

• After more than 50 years of development and

enormous government subsidies, nuclear power has not lived up to its promise because:

– Multi billion-dollar construction costs.

– Higher operation costs and more malfunctions than expected.

– Poor management.

Case Study: The Chernobyl

Nuclear Power Plant Accident

• The world’s worst nuclear power plant

accident occurred in 1986 in Ukraine.

• The disaster was caused by poor reactor

design and human error.

• By 2000, 8,000 people had died from

radiation –related diseases

NUCLEAR ENERGY

• Terrorists could attack nuclear power plants,

especially poorly protected pools and casks that store spent nuclear fuel rods.

• Terrorists could wrap explosives around small amounts of radioactive materials that are fairly easy to get, detonate such bombs, and

Nuclear Fusion

• Nuclear fusion is a nuclear change in which two isotopes are forced together.

– No risk of meltdown or radioactive releases. – May also be used to breakdown toxic material. – Still in laboratory stages. Uses deuterium and

tritium – isotopes of hydrogen

– Requires more energy to accomplish than would produce