Geologic Resources
Chapter 15
General Mining Law 1872
Encouraged mineral explorationHelp develop the West – selling land
Mining provides – jobs, resources, stimulation of economy
Environmentalist want – lease not ownership, pay royalty, clean up
Resources
Metallic – nickel, iron, gold, aluminumNonmetallic – salt, gypsum, clay, soilEnergy – coal, oil, natural gas, uranium
Ore – rock containing a metallic mineralReserve – known deposit of mineral that can be extracted for a profit
Resources in the ocean
Black smokers – hydrothermal vents that deposit minerals in tall chimneylike stacks
Manganese nodules – found on the ocean floor, they contain 30-40% manganese and other important minerals
Magma
Black smoker
Sulfidedeposit
White crab White clam
Tube worms
Whitesmoker
Fig. 14.3, p. 322
Removing mineral resources
Shallow deposits are removed through surface mining
Open-pit miningDredgingArea strip miningContour strip mining
Deep deposits through subsurface mining
Contour Strip Mining
Fig. 14.4d, p. 324
Area Strip Mining Fig. 14.4c, p. 324
Dredging Fig. 14.4b, p. 324
Open Pit Mine Fig. 14.4a, p. 324
Fig. 14.5b, p. 325 Room-and-pillar
Underground Coal Mine Fig. 14.5a, p. 325
Fig. 14.5c, p. 325 Longwall Mining of Coal
Mining
Overburden is removed to expose mineral, disposed of as spoil
Surface mining accounts for about 90% of non fuel mining and 60% of coal
Surface Mining Control and Reclamation Act 1977 – companies had to restore most of the surface to pre-mining conditions
Environmental effects of mining
Scarring and disruption of land surfaceCollapse and subsiding of landWind and water caused toxin-laced mining wastesAcid mine drainage
Sulfuric acid from rain water combinationRun-off to streamsDestroys aquatic life
Toxic chemical emission into air
Percolation to groundwater
Leaching of toxic metalsand other compounds
from mine spoil
Acid drainage fromreaction of mineralor ore with water
Spoil banks
Runoff ofsediment
Surface MineSubsurfaceMine Opening
Leaching may carryacids into soil andgroundwater
supplies
Fig. 14.7, p. 326
Steps Environmental Effects
exploration, extraction
MiningDisturbed land; mining accidents;health hazards; mine waste dumping;oil spills and blowouts; noise;ugliness; heat
Solid wastes; radioactive material;air, water, and soil pollution;
noise; safety and healthhazards; ugliness; heat
Processing
transportation, purification,manufacturing
Use
transportation or transmissionto individual user,
eventual use, and discarding
Noise; uglinessthermal water pollution;
pollution of air, water, and soil;solid and radioactive wastes;
safety and health hazards; heat
Fig. 14.6, p. 326
After mining
Ore contains desired metal and waste called gangue
Removed gangue is piled into heaps called tailings
Smelting is then used to separate the metal minerals
Smelting
Smelters create a large quantity of air pollution
They also produce liquid and solid hazardous waste that must be disposed
Companies are trying to reduce pollution, lower costs, and decrease liability
How much is there?
Depletion time is the time it takes to use up 80% of the reserve (profitable)
Reserve to production ratio – how long will the known reserves last at current rates of production
Present Depletiontime A
Depletiontime B
Depletiontime C
Time
Pro
du
ctio
n
C
B
A
Recycle, reuse, reduceconsumption; increasereserves by improvedmining technology,higher prices, andnew discoveries
Recycle; increase reservesby improved miningtechnology, higher prices,and new discoveries
Mine, use, throw away;no new discoveries;rising prices
Fig. 14.9, p. 329
The big three
US, Germany, and Russia
Only 8% of the population
Use 75% of the most common metals
US uses 25% of the fossil fuels (cars)
Fig. 14.10, p. 329
Ocean mining
Will the ocean supply us with enough minerals?They are there, but too expensive currently
Energy resources
99% of energy used to heat the earth and all the buildings comes from the sun
The sun also creates renewable energy resources – wind, flowing water, biomass
The rest
The last 1% comes from fuel resources
Fossil fuels make up the vast majority
Petroleum, coal, and natural gas
A small portion also comes from nuclear sources
Mined coal
Pipeline
Pump
Oil well
Gas well
Oil storage
CoalOil and Natural Gas Geothermal Energy
Hot waterstorage
Contourstrip mining
PipelineDrillingtower
Magma
Hot rock
Natural gasOil
Impervious rock
Water Water
Oil drillingplatformon legs
Floating oil drillingplatform
Valves
Undergroundcoal mine
Water is heatedand brought upas dry steam or
wet steam
Waterpenetratesdownthroughtherock
Area stripmining
Geothermalpower plant
Coal seam
Fig. 14.11, p. 332
Shifts in energy usage worldwide
During the 20th century
Coal use dropped from 55 to 22%Oil increased from 2 to 30%Natural gas rose from 1 to 23%Nuclear rose from 0 to 6%Renewable (wood and water ) dropped from 42 to 19%
Way to go US
The U.S. is the world’s largest energy consumerWe use 25% of the world’s energy (even though we only have 4.5% of the total population)India with 17% of the population only uses 3% of the world’s commercial energy91% of the U.S.’s energy in nonrenewable
EnergyNet energy refers to the amount of useful energy minus the energy needed to find, extract, process, concentrate, and transport to the users
Nuclear energy has a low net energy ratio because it is expensive to extract and process uranium, convert it into a fuel, build and operate the plant, and dismantle and deal with radioactive plants and waste
Oil, Oil everywhere and not a drop to drink
Extracted as crude oil or petroleum, a thick liquid consisting of hydrocarbons, and some sulfur, oxygen and nitrogen impurities
Produced from decayed plant and animal material over millions of years
Oil continued
Normally crude oil is not found in underground pools, but is spread out in the pores and cracks within rock deep beneath the ground
Primary recovery – drill a hole and pump out the light weight crude that fills the hole
Oil continued
Secondary recovery – pumping water into the well to force oil out of the pores The oil and water mixture is separated after pumping
Only about 35% of the oil is removed by primary and secondary recovery
Oil continued
Tertiary recovery – either a heated gas or a liquid detergent is pumped into the well to help remove more oil
Tertiary is expensive
Oil continued
At the refinery oil is converted into petrochemicals and used as a resource to create industrial organic chemicals, pesticides, plastics, synthetic fibers, paints, medicines and more.
OPEC – organization of petroleum exporting countries control 67% of the worlds oil and maintain control over pricing
Diesel oil
Asphalt
Greaseand wax
Naphtha
Heating oil
Aviation fuel
Gasoline
Gases
FurnaceFig. 14.16, p. 337
Heatedcrude oil
Low land use
Easily transportedwithin and between countries
High netenergy yield
Low cost (withhuge subsidies)
Ample supply for42–93 years
Advantages
Moderate waterpollution
Releases CO2 when burned
Air pollutionwhen burned
Artificially low price encourageswaste and discourages search for alternatives
Need to findsubstitute within50 years
Disadvantages
Fig. 14.21, p. 340
Oil continuedOil shale is a fine grained sedimentary rock containing solid combustible organic material called kerogen
Shale oil is made from heating oil shale
Tar sand contains bitumen another combustible organic materialBoth are more expensive than crude recovery
Advantages Disadvantages
Moderate existingsupplies
Large potentialsupplies
High costs
Low net energyyield
Large amount ofwater needed toprocess
Severe land disruption fromsurface mining
Water pollution from mining residues
Air pollution when burned
CO2 emissionswhen burned
Fig. 14.25, p. 342
Natural Gas
Mostly CH4 methane with some ethane, propane and butane and small amounts of hydrogen sulfide (toxic)
LPG (liquefied petroleum gas) the propane and butane are removed from natural gas and stored under pressure
How long will it last?
Natural gas should last about 125 years worldwide
About 75 years in the US
Overall about 200-300 years with rising prices, better technology, and more discoveries
Advantages Disadvantages
Good fuel forfuel cells andgas turbines
Low land use
Easily transportedby pipeline
Moderate environ-mental impact
Lower CO2 emissions thanother fossil fuels
Less air pollutionthan otherfossil fuels
Low cost (withhuge subsidies)
High net energyyield
Ample supplies(125 years)
Sometimes burned off andwasted at wellsbecause of lowprice
Shipped acrossocean as highlyexplosive LNG
Methane(a greenhouse gas) can leakfrom pipelines
Releases CO2
when burned
Fig. 14.26, p. 342
The future of power plants
There is currently being developed a combined cycle natural gas electric power plant with 60% efficiency
This is much better than 32-40% efficiency of others (coal, oil, nuke)
What other reasons make it better?
Coal
Solid fuel of combustible carbon, most formed 285-360 million years agoPeat – 1st, low heat contentLignite – 2nd, low heat and low sulfurBituminous Coal – 3rd, high heat and abundant supply, high sulfurAnthracite – 4th, high heat, low sulfur, limited supply
Increasing moisture content
Increasing heat and carbon content
Peat(not a coal)
Lignite(brown coal)
Bituminous Coal(soft coal)
Anthracite(hard coal)
Heat
Pressure Pressure Pressure
Heat Heat
Partially decayedplant matter in swampsand bogs; low heatcontent
Low heat content;low sulfur content;limited supplies inmost areas
Extensively usedas a fuel becauseof its high heat contentand large supplies;normally has ahigh sulfur content
Highly desirable fuelbecause of its highheat content andlow sulfur content;supplies are limitedin most areas
Fig. 14.27, p. 344
Coal for energy
Coal provides about 22% of the commercial energy in the world
It is used to create 62% of the worlds electricity75% of the worlds steelChina is the largest user followed by USUS creates 52% of energy with coal
Advantages Disadvantages
Low cost (with huge subsidies)
High net energyyield
Ample supplies(225–900 years)
Releases radioactive particles and mercury into air
High CO2 emissionswhen burned
Severe threat tohuman health
High land use (including mining)
Severe land disturbance, air pollution, andwater pollution
Very high environmentalimpact
Fig. 14.28, p. 344
The cost of coalLand disturbanceAir pollution (especially sulfur dioxide)Co2 emissionsWater pollution
Electricity production (coal) is the second largest producer of toxic emissions
The most deadly emission is mercury
Wonderful coal
60,000 babies annually are born with brain damage due to mercury exposure, typically from pregnant mothers eating mercury in fish
Coal also releases more radioactive particles into the atmosphere than nuclear power plants
Also, acid rain and methane release
Coal in the US
Air pollutants kill thousands (estimates are from 60,000 – 200,000)Cause at least 50,000 cases of respiratory diseaseCost several billion dollars in property damage
The good news
Fluidized bed combustion is reducing the amount of pollution
Hot air is blown under a mix of crushed limestone and coal while it is burntThis removes most sulfur dioxide, reduces Nox and burns the coal more efficiently and cheaply
Calcium sulfateand ash
Air
Air nozzles
Water
Fluidized bed
Steam
Flue gases
Coal Limestone
Fig. 14.29, p. 345
Coal gasification
Solid coal can be converted into synthetic natural gas (SNG)
It can also be made into synfuels (liquids) through coal liquefaction
Neither is expected to play a major role in our future energy needs
Raw coal
Pulverizer
Air oroxygen
Steam
Pulverized coalSlag removal
Recycle unreactedcarbon (char)
Raw gases CleanMethane gas
Recoversulfur
Methane(natural gas)
2CCoal
+ O2 2CO
CO + 3H2 CH4 + H2O
Remove dust,tar, water, sulfur
Fig. 14.30, p. 345
Advantages Disadvantages
Large potentialsupply
Vehicle fuel
Low to moderatenet energy yield
Higher cost thancoal
High environmentalimpact
Increased surfacemining of coal
High water use
Higher CO2 emissions than coal
Fig. 14.31, p. 346
Nuclear Energy
Uranium 235 and plutonium 239 are split (nucleus) to release energyThe reaction rate is controlledThe energy heats water and turns it to steamSteam spins turbines connected to generators which create electricity
LWR light water reactors
All US reactors are of this type, so know it
Periodic removaland storage of
radioactive wastesand spent fuel assemblies
Periodic removaland storage of
radioactive liquid wastes
Pump
Steam
Small amounts of Radioactive gases
Water
Black
Turbine Generator
Waste heat Electrical power
Hot water output
Condenser
Cool water input
Pump
Pump Wasteheat
Useful energy25 to 30%
WasteheatWater source
(river, lake, ocean)
Heatexchanger
Containment shell
Uranium fuel input(reactor core)
Emergency coreCooling system
Controlrods
Moderator
Pressurevessel
Shielding
Coolantpassage
Fig. 14.32, p. 346
CoolantCoolant
Hot coolantHot coolant
Nuclear is out of favor
The US has not ordered a new nuclear facility since 1978, and 120 ordered since 1973 were cancelledMost countries are phasing out nuclear plants or are not continuing to expand their programs, except China who is trying to move away from dependence on coal
Why is nuclear not meeting expectations?
Multi-billion dollar cost of constructionStrict govt. safety regulationsHigh operating costsMore malfunctions than expectedPoor managementPublic concern after Chernobyl, and Three Mile IslandInvestor concern about economic feasibility
Low risk of accidents because of multiplesafety systems(except in 35 poorly designed and run reactors in former SovietUnion and Eastern Europe)
Moderate land use
Moderate landdisruption andwater pollution(without accidents)
Emits 1/6 asmuch CO2 as coal
Lowenvironmentalimpact (withoutaccidents)
Large fuelsupply
Spreads knowledge and technology for building nuclear weapons
No acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants
Catastrophic accidents can happen (Chernobyl)
High environmental impact (with major accidents)
Low net energy yield
High cost (even with large subsidies)
Advantages Disadvantages
Fig. 14.35, p. 349
Coal
Ample supply
High net energyyield
Very high airpollution
High CO2emissions
65,000 to 200,000deaths per yearin U.S.
High land disruption fromsurface mining
High land use
Low cost (with huge subsidies)
Nuclear
Ample supplyof uranium
Low net energyyield
Low air pollution(mostly from fuelreprocessing)
Low CO2emissions(mostly from fuelreprocessing)
About 6,000deaths per year in U.S.
Much lower landdisruption fromsurface mining
Moderate land use
High cost (with huge subsidies)
Fig. 14.36, p. 349
ChernobylIn the former Soviet Union, April 26, 1986 the reactor core went out of control and exploded sending a cloud of radioactive dust into the atmosphere3,576 – 32,000 people died400,000 forced to evacuate62,000 square miles still contaminatedMore than 500,000 people exposed to high level radiationCost the govt. $385 billion
Three Mile Island
March 29, 1979 in Harrisburg, Penn.Coolant failed and core meltedRadioactive material escaped into air50,000 people evacuatedLuckily the radiation release was believed to be too low to cause death or cancerCleanup has cost $1.2 billion so far
What do we do with the waste?
Low level radioactive waste must be stored for 100-500 years until it reaches a safe level (does not give off harmful ionizing radiation)This was done by sealing the waste in steel drums and dumping it in the oceanToday some countries (US) stores the waste at govt. run landfills, but no one wants to live anywhere near them
Waste container
Steel wall
Steel wall
Severalsteel drumsholding waste
Lead shielding
2 meters wide2–5 meters high
Fig. 14.38a, p. 351
Clay bottom
Up to 60deep trenchesdug into clay.
As many as 20flatbed trucksdeliver wastecontainers daily.
Barrels are stackedand surroundedwith sand. Coveringis mounded to aidrain runoff.
Fig. 14.38b, p. 351
And the bad stuff?
High level radioactive waste must be stored for 10,000 to 240,000 years until it reaches a safe levelCurrently most is stored at the reactor site, sealed in drums, in pools of water
Proposed methods of disposal
Bury deep underground – this is the leading strategy currentlyShoot it into space/SunBury it deep in the Antarctic ice sheetDump it into descending subduction zonesBury in deep mud deposits on ocean floorConvert into less harmful isotopes (currently we do not have the technology)
Fig. 14.39a
, p. 352
Slide 52
Personnel elevator
Air shaft
Nuclear waste shaft
2,500 ft.(760 m)deep
Fig. 14.39b, p. 352
Slide 53
Storage Containers
Fuel rod
Primary canister
Overpack container sealed
Fig. 14.39c, p. 352
Radioactive contamination
The EPA suggests that there are 45,000 sites in the US (20,000 belong to the DOE)It is expected to cost over $230 billion over the next 75 yearsMore than 144 highly contaminated weapons construction sites will never be completely cleaned