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Chapter 23 Materials management. Resource use. How much is left?. Mining. Is used to extract valuable minerals from the earth Is dependent on crustal abundance Elements and minerals are not equally represented or distributed in the earth’s crust Countries and companies have mineral reserves
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Mining • Is used to extract valuable minerals from the earth • Is dependent on crustal abundance • Elements and minerals are not equally represented or distributed in the earth’s crust • Countries and companies have mineral reserves • Known quantity that can be realistically recovered by mining Relative crustal abundance of most common minerals
Mined Materials • Sand and gravel • Metals • Phosphates • Salts • Sodium • Sulfur • Gemstones • Fuel sources • Coal • Uranium
Ore • Concentrated accumulations of minerals formed from geologic processes • Can also contain waste material • Must usually be processed to produce a pure form of the mineral • Can occur in veins • Localized high concentrations of a mineral • Can occur in disseminated deposits • Large, widely spread lower concentrations of a mineral
Types of Mining • Surface Mining • Placer • Strip • Mountaintop Removal • Open Pit • Subsurface Mining • Shaft • Solution • Ocean Mining
Placer Mining • Used when a resource accumulates in riverbed deposits • Running water is used to sift lighter materials from the heavier resource materials • Also called panning • Disturbs large amounts of sediment
Strip Mining • Used when a resource exists in layers near the Earth’s surface • Rock and soil above the resource (overburden) is removed from a strip of land • Mined material is removed and overburden is replaced
Mountaintop Mining • Used when a resource occurs in seams near mountain ridges • Entire mountaintops are bulldozed and blasted away to reveal the seam • Overburden is replaced on the remaining mountain, and may fall or be dumped into adjacent valleys
Open Pit Mining • Used when a resource is in an area unsuitable for tunneling, or when it is spread evenly and close to the surface • Also called a quarry
Subsurface Mining • Used when a resource occurs deep underground • Vertical shafts are dug into the ground • Horizontal tunnels are dug to follow the seam or deposit being mined • Material is removed and sent to the surface for processing
Solution Mining • Also called in-situ recovery • Used when a resource is buried deep, and can be dissolved in liquid • A hole is drilled to the resource, and water or acid is poured into the hole • The resource is sucked out and processed to remove it from the fluid
Ocean Mining • Used when resource deposits exist on or under the sea floor, or in seawater • Resources are “vacuumed” off the sea floor • Research is underway to extract or evaporate resources from seawater
Problems with Mining • All mining uses machinery and transportation that produces pollution • All mining produces tailings, or mineral waste that can damage ecosystems • The processing of ore can produce toxic byproducts • Extraction of gold uses cyanide • Miners are exposed to some of the most hazardous working conditions on the planet
Acid Drainage • Most harmful form of environmental damage from mining • Occurs when newly exposed rock that contain sulfur reacts with water and oxygen to form sulfuric acid
Acid Drainage • Sulfuric acid leaches metals from nearby rock and soil • Forms toxic acidic liquid called leachate • Cleanup involves neutralizing the acid and removing the metals
Brownfields • Abandoned sites polluted with hazardous waste • Includes abandoned mines • Dangerous and difficult to clean up for reuse • Fall under EPA Superfund sites
Mine Restoration or Reclamation • Goal is to restore a mined site to as close to its original condition as possible • Involves: • Filling in shafts and holes • Removing mining structures and equipment • Replacing overburden • Replanting • Ecosystems never fully recover from mining disruption
General Mining Act of 1872 • Any individual or company can stake an exclusive claim on federal land open for mining • Land can be patented, or bought outright, for about $5/acre • No payments are made to the government, even if profits are realized • Includes gemstones, metals, uranium and minerals
Mineral Leasing Act of 1920 • Public lands must be leased for mining, and royalties on profits are to be paid • Amounts depend on the resource being mined • Covers fossil fuels, sodium, sulfur, and phosphates
Surface Mining Control and Reclamation Act of 1977 • Regulates the surface effects of coal mining • Mandates reclamation of mined areas
Minerals are Nonrenewable • Minerals regenerate slowly • Many mineral deposits are being mined very quickly • As they become scarce, they will become more expensive • Environmentally friendly alternatives are being sought, including recycling
Sustainable Mineral Use • Recycling is the best way to sustainably use many minerals • Uses less energy in production of goods • Reduces the amount of mining • Recycling e-waste is especially important • Reducing the use of products that contain minerals also helps
Waste • Anything not useful or consumable • Is the product of a system • Inputs are raw materials and/or energy • Outputs are useful products, recyclable products, and waste
A Culture of Waste • In the 1950s it became culturally acceptable to throw things away • Labor-saving, disposable consumer goods were developed • Planned obsolescence became a part of life • Products designed to be replaced
Municipal Solid Waste • Is waste from non-industrial, non-agricultural, non-mining sources • Includes residences and businesses • 60% is from residences • Average is 2.8 (4.5 lbs) kg/person/day
E-Waste • Is only 2% of the waste stream, but is increasing • Has an environmental impact greater than its small percentage implies • Contain metals and acids that are harmful • Poor disposal can release these pollutants to the environment • Recycling of this material must be done carefully
Decreasing the Impact of Waste • Includes implementing the three R’s • Reduce, reuse, recycle • Includes composting
Landfills • Are the most common waste disposal method • Basically just a hole in the ground filled with trash • Are a better option than open dumps • There is some control over what goes in a landfill • Can generate leachate • Water runs through the landfill and picks up chemicals from waste
Sanitary Landfills • Are designed to minimize impact on surrounding areas • Are lined in plastic, often with a layer of clay beneath • Have pipes that are used to collect and remove leachate • Also have methane collection pipes • Methane can be burned to generate electricity or to power vehicles
Sanitary Landfills • Are filled with materials that are: • Unlikely to create methane or toxic leachate • Difficult to recycle • Are closed once they are full • Capped with plastic • Covered in a layer of concrete or soil • Can be reclaimed for construction or parks