This lecture will help you understand · •People in developing nations suffer war and...
Transcript of This lecture will help you understand · •People in developing nations suffer war and...
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This lecture will help you understand:• Mineral resources and their contributions to society
• Mining methods
• Social and environmental impacts of mining
• Sustainable use of mineral resources
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Central Case: Mining for … cell phones?• Cell phones and other hightech products contain tantalum
Coltan = columbite + tantalum
• The Democratic Republic of the Congo was at war
Since 1998, 5 million died and millions more fled
• Soldiers controlled mining operations and forced farmers and others to work, while taking most of the ore
People entered national parks, killing wildlife and clearing rainforests
Profits from coltan sales financed the war
• Most tantalum from the Congo goes to China
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Minerals and mining• We extract raw minerals from beneath our planet’s surface
Turn them into products we use everyday
• Rock and resources from the lithosphere contribute to our economies and lives
• Rock = a solid aggregation of minerals
• Mineral = a naturally occurring solid chemical element or inorganic compound
It has a crystal structure, specific chemical composition, and distinct physical propertiesMinerals are nonrenewable, so we need to be aware of
their finite and decreasing supplies
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Minerals are everywhere in our products
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We obtain minerals by mining• We obtain minerals through the process of mining
• Mining = in the broad sense, it is the extraction of any resource that is nonrenewable
We mine minerals, fossil fuels, and groundwater
• Mining = in relation to minerals, it is the systematic removal of rock, soil, or other material to remove the minerals of economic interest
• Because minerals occur in low concentrations, concentrated sources must be found before mining
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We extract minerals from ores• Metal = an element that is lustrous, opaque, and malleable and can conduct heat and electricity
• Ore = a mineral or grouping of minerals from which we extract metals
• Economically valuable metals include copper, iron, lead, gold, aluminum
Tantalite ore is mined, processed into tantalum, and used in electronic devices
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We process metals after mining ore• Most minerals must be processed after mining
• After mining the ore, rock is crushed and the metals are isolated by chemical or physical means
The material is processed to purify the metal
• Alloy = a metal is mixed, melted, or fused with another metal or nonmetal substance
Steel is an alloy of iron and carbon
• Smelting = heating ore beyond its melting point then combining it with other metals or chemicals
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Processing minerals has costs• Processing minerals has environmental costs
Most methods are water and energyintensive
• Chemical reactions and heating to extract metals from ores emit air pollution
• Tailings = ore left over after metals have been extracted
Pollutes soil and water
They may contain heavy metals or acids (cyanide, sulfuric acid)
Water evaporates from tailings ponds, which may leach pollutants into the environment
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We also mine nonmetallic minerals and fuels• Nonmetallic minerals include sand, gravel, phosphates, limestone, and gemstones
$7 billion/year of sand and gravel are mined in the U.S.
Phosphates provide fertilizer
“Blood diamonds” are mined and sold to fund, prolong, and intensify wars in Angola and other areas
• Substances are mined for fuel
Uranium for nuclear power
Coal, petroleum, natural gas are not minerals (they are organic), but they are also extracted from the Earth
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Economically useful mineral resources
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Mining methods and their impacts• People in developing nations suffer war and exploitation because of the developed world’s appetite for minerals
• In 2009, raw materials from mining gave $57 billion to the U.S. economy
After processing, minerals contributed $454 billion
28,000 Americans were directly employed for mining
• Large amounts of material are removed during mining
• Disturbing lots of land
• Different mining methods are used to extract minerals
Economics determines which method to use
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Strip mining removes surface soil and rock• Strip mining = layers of soil and rock are removed to expose the resource
• Overburden = overlying soil and rock that is removed by heavy machinery
After extraction, each strip is refilled with the overburden
• Used for coal, oil sands, sand, gravel
• Destroys natural communities over large areas and triggers erosion
• Acid drainage = sulfide minerals form sulfuric acid and flow into waterways
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Strip mining destroys the environment
Strip mining removes soil Discolored water is a sign of acid drainage
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A mining method: subsurface mining• Accesses deep pockets of a mineral through tunnels and shafts
The deepest mines are 2.5 mi
• Zinc, lead, nickel, tin, gold, diamonds, phosphate, salt, coal
• The most dangerous form of mining
Dynamite blasts, collapsed tunnels
Toxic fumes and coal dust
• Acid drainage, polluted groundwater
Sinkholes damage roads, homes, etc.
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A mining method: open pit mining• Used with evenly distributed minerals
Terraced so people and machines can move about
• Copper, iron, gold, diamonds, coal
• Quarries = open pits for clay, gravel, sand, stone (limestone, granite, marble, slate)
• Huge amounts of rock are removed to get small amounts of minerals
• Habitat loss, aesthetic degradation, acid drainage
• Abandoned pits fill with toxic water
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Bingham County, Utah open pit mineThe mine is 2.5 mi across and 0.75 mi deep; almost half a million tons of ore and rock are removed each day. If it were a stadium, it could seat 9
million people
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A mining method: placer mining• Using running water, miners sift through material in riverbeds
Coltan miners, California’s Gold Rush of 1849
• Used for gold, gems
• Debris washed into streams makes them uninhabitable for wildlife
• Disturbs stream banks, causes erosion
• Harms riparian plant communities
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A mining method: mountaintop removal• Entire mountaintops are blasted off
• The waste is dumped into valleys
• For coal in the Appalachian Mountains of the eastern U.S.
• Economically efficient
“Valley filling” = dumping rock and debris into valleys
• Degrades and destroys vast areas
• Pollutes streams, deforests areas,
erosion, mudslides, flash floods
An area the size of Delaware has already been removed
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Mountaintop removal is socially devastating
• Mine blasting cracks foundations and walls
• Floods and rock slides affect properties
• Overloaded coal trucks speed down rural roads
• Coal dust and contaminated water cause illness
• Local politicians do not help
• Highefficiency mining reduces the need for workers
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A mining method: solution mining• Solution mining (insitu recovery) = resources in a deep deposit are dissolved in a liquid and siphoned out
• Salts, lithium, boron, bromine, potash, copper, uranium
• Less environmental impact than other methods
• Less surface area is disturbed
• Acids, heavy metals, uranium
can accidentally leak
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A mining method: undersea mining• We extract minerals (e.g., magnesium) from seawater
• Minerals are dredged from the ocean floor
Sulfur, phosphate, calcium carbonate (for cement), silica (insulation and glass), copper, zinc, silver, gold
• Manganese nodules = small, ballshaped ores scattered across the ocean floor
Mining them is currently uneconomical
• Hydrothermal vents may have gold, silver, zinc
• Mining would destroy habitats and organisms and release toxic metals that could enter the food chain
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Restoration of mined sites• Governments in developed countries require companies to reclaim (restore) surfacemined sites
Other nations (e.g., Congo) have no regulations at all
• Reclamation aims to bring a site to a condition similar to its premining condition
Remove structures, replace overburden, replant vegetation
• The U.S. 1977 Surface Mining Control and Reclamation Act mandates restoration
Companies must post bonds to ensure restoration
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Restoration of mined sites• Even on restored sites, impacts may be severe and longlasting
• Complex communities are simplified
Forests, wetlands, etc. are replaced by grasses
• Essential symbioses are eliminated and often not restored
• Water can be reclaimed
Remove heavy metals
pH is moderated
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The General Mining Act of 1872• Encourages metal and mineral mining on federal land
Any citizen or company can stake a claim on any public land open to mining for $5 per acre
The public gets no payment for any minerals found
• Once a person owns the land, that land can be developed for any reason, having nothing to do with mining
• Supporters say it encourages a domestic industry that is risky and provides essential products
• Critics say it gives land basically free to private interests
Efforts to amend the act have failed in Congresshttp://www.blm.gov/or/programs/minerals/locatingminingclaims.php
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Minerals are nonrenewable and scarce• We must recover and recycle our limited supplies
• Once known reserves are mined, minerals will be gone
For example, indium, used in LCD screens, might only last 32 more years
Gallium (for solar power) and platinum (fuel cells) are also scarce
• Reserve estimates are uncertain
New discoveries, technologies, consumption patterns, and recycling affect mineral supplies
As minerals become scarcer, demand and price rise
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Years remaining for selected minerals• Scarcity increases prices
• Industries will spend more to reach further deposits
The red represents remaining years the metals are estimated to be economically recovered at current prices
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Factors affecting how long deposits last• Discovery of new reserves increases known reserves
Minerals worth $900 billion were discovered in Afghanistan in 2010
• New extraction technologies reach more minerals at less expense
• Changing social and technological dynamics modify demand in unpredictable ways
Lithium batteries are replacing cadmiumnickel ones
• Changing consumption patterns affect how fast we exploit reserves (e.g., a recession depresses demand)
• Recycling extends the lifetimes of minerals
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We can use minerals sustainably• Recycling addresses:
Finite supplies
Environmental damage
• 35% of metals were recycled in 2008 from U.S. municipal solid waste
7 million tons
Steel, iron, platinum, gold, nickel, germanium, tin, and chromium
Reduces greenhouse gases by 25 million metric tons
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We can recycle rare metals from ewaste• Electronic waste (ewaste) from computers, printers, cell phones, etc. is
rising rising
• Recycling keeps hazardous wastes out of landfills while conserving mineral resources
• 1.2 billion cell phones sold each year contain 200 chemicals and precious metals
Phones can be refurbished and resold or dismantled and their parts reused or recycled
Only 10% of cell phones are recycled
• Recycling reduces demand for virgin ores and reduces pressure on ecosystems
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Conclusion• We depend on minerals and metals to make the products we use
• Mineral resources are mined by various methods
• Contributing to material wealth
• But causing extensive environmental damage (habitat loss, acid drainage, etc.)
• Restoration and regulations help minimize the environmental and social impacts of mining
• Maximize recycling and sustainable use of minerals