Geologic Resources Chapter 15

General Mining Law 1872 Encouraged mineral exploration Help 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, aluminum Nonmetallic – salt, gypsum, clay, soil Energy – coal, oil, natural gas, uranium Ore – rock containing a metallic mineral Reserve – 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

Black smoker White smoker Sulfide deposit Magma Tube worms White crab White clam Fig. 14.3, p. 322

Removing mineral resources Shallow deposits are removed through surface mining Open-pit mining Dredging Area strip mining Contour 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

Room-and-pillar Fig. 14.5b, p. 325

Underground Coal Mine Fig. 14.5a, p. 325

Longwall Mining of Coal Fig. 14.5c, p. 325

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 surface Collapse and subsiding of land Wind and water caused toxin-laced mining wastes Acid mine drainage Sulfuric acid from rain water combination Run-off to streams Destroys aquatic life Toxic chemical emission into air

Percolation to groundwater Leaching of toxic metals Subsurface Mine Opening Surface Mine Runoff of sediment Acid drainage from reaction of mineral or ore with water Spoil banks Percolation to groundwater Leaching of toxic metals and other compounds from mine spoil Leaching may carry acids into soil and ground water supplies Fig. 14.7, p. 326

Environmental Effects Steps Environmental Effects Disturbed land; mining accidents; health hazards; mine waste dumping; oil spills and blowouts; noise; ugliness; heat Mining exploration, extraction Processing Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat transportation, purification, manufacturing Use Noise; ugliness thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat transportation or transmission to individual user, eventual use, and discarding 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

Recycle; increase reserves by improved mining Mine, use, throw away; no new discoveries; rising prices Recycle; increase reserves by improved mining technology, higher prices, and new discoveries B Production Recycle, reuse, reduce consumption; increase reserves by improved mining technology, higher prices, and new discoveries C Present Depletion time A Depletion time B Depletion time C Fig. 14.9, p. 329 Time

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

Oil and Natural Gas Coal Geothermal Energy Contour strip mining Hot water storage Floating oil drilling platform Oil storage Geothermal power plant Oil drilling platform on legs Pipeline Area strip mining Oil well Pipeline Mined coal Drilling tower Gas well Valves Pump Water penetrates down through the rock Underground coal mine Water is heated and brought up as dry steam or wet steam Impervious rock Natural gas Coal seam Oil Hot rock Water Water Magma 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 consumer We 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 energy 91% of the U.S.’s energy in nonrenewable

Energy Net 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

Gases Gasoline Aviation fuel Heating oil Heated crude oil Diesel oil Naphtha Grease and wax Furnace Fig. 14.16, p. 337 Asphalt

Advantages Disadvantages Ample supply for 42–93 years Need to find substitute 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 Moderate water pollution Fig. 14.21, p. 340

Oil continued Oil 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 material Both are more expensive than crude recovery

Advantages Disadvantages Moderate existing supplies High costs Low net energy yield Large potential supplies Large amount of water needed to process Severe land disruption from surface mining Water pollution from mining residues Air pollution when burned CO2 emissions when 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 Ample supplies (125 years) Releases CO2 when burned High net energy yield Methane (a greenhouse gas) can leak from pipelines Low cost (with huge subsidies) Shipped across ocean as highly explosive LNG Less air pollution than other fossil fuels Sometimes burned off and wasted at wells because of low price Lower CO2 emissions than other fossil fuels Moderate environ- mental impact Easily transported by pipeline Low land use Good fuel for fuel cells and gas turbines 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 ago Peat – 1st, low heat content Lignite – 2nd, low heat and low sulfur Bituminous Coal – 3rd, high heat and abundant supply, high sulfur Anthracite – 4th, high heat, low sulfur, limited supply

Increasing heat and carbon content Increasing moisture content Peat (not a coal) Lignite (brown coal) Bituminous Coal (soft coal) Anthracite (hard coal) Heat Heat Heat Pressure Pressure Pressure Partially decayed plant matter in swamps and bogs; low heat content Low heat content; low sulfur content; limited supplies in most areas Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in 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 electricity 75% of the worlds steel China is the largest user followed by US US creates 52% of energy with coal

Advantages Disadvantages Ample supplies (225–900 years) Very high environmental impact High net energy yield Severe land disturbance, air pollution, and water pollution Low cost (with huge subsidies) High land use (including mining) Severe threat to human health High CO2 emissions when burned Releases radioactive particles and mercury into air Fig. 14.28, p. 344

The cost of coal Land disturbance Air pollution (especially sulfur dioxide) Co2 emissions Water 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 disease Cost 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 burnt This removes most sulfur dioxide, reduces Nox and burns the coal more efficiently and cheaply

Flue gases Coal Limestone Steam Fluidized bed Water Air nozzles Air Calcium sulfate and ash 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 Remove dust, tar, water, sulfur Recover sulfur Air or oxygen Steam Raw gases Clean Methane gas 2C Coal + O2 2CO Pulverizer Recycle unreacted carbon (char) CO + 3H2 CH4 + H2O Methane (natural gas) Slag removal Pulverized coal Fig. 14.30, p. 345

Advantages Disadvantages Large potential supply Low to moderate net energy yield Higher cost than coal Vehicle fuel High environmental impact Increased surface mining 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 energy The reaction rate is controlled The energy heats water and turns it to steam Steam spins turbines connected to generators which create electricity

LWR light water reactors All US reactors are of this type, so know it

Small amounts of Radioactive gases Uranium fuel input (reactor core) Containment shell Waste heat Electrical power Emergency core Cooling system Steam Control rods Useful energy 25 to 30% Turbine Generator Heat exchanger Hot coolant Hot water output Condenser Pump Pump Coolant Coolant passage Moderator Cool water input Black Pump Waste heat Pressure vessel Water Shielding Waste heat Water source (river, lake, ocean) Periodic removal and storage of radioactive wastes and spent fuel assemblies Periodic removal and storage of radioactive liquid wastes Fig. 14.32, p. 346

Nuclear is out of favor The US has not ordered a new nuclear facility since 1978, and 120 ordered since 1973 were cancelled Most 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 construction Strict govt. safety regulations High operating costs More malfunctions than expected Poor management Public concern after Chernobyl, and Three Mile Island Investor concern about economic feasibility

Advantages Disadvantages Large fuel supply High cost (even with large subsidies) Low environmental impact (without accidents) Low net energy yield High environmental impact (with major accidents) Emits 1/6 as much CO2 as coal Moderate land disruption and water pollution (without accidents) Catastrophic accidents can happen (Chernobyl) Moderate land use No acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants Low risk of accidents because of multiple safety systems (except in 35 poorly designed and run reactors in former Soviet Union and Eastern Europe) Spreads knowledge and technology for building nuclear weapons Fig. 14.35, p. 349

Coal Nuclear Ample supply Ample supply of uranium High net energy yield Low net energy yield Low air pollution (mostly from fuel reprocessing) Very high air pollution High CO2 emissions Low CO2 emissions (mostly from fuel reprocessing) 65,000 to 200,000 deaths per year in U.S. About 6,000 deaths per year in U.S. High land disruption from surface mining Much lower land disruption from surface mining High land use Moderate land use Low cost (with huge subsidies) High cost (with huge subsidies) Fig. 14.36, p. 349

Chernobyl In the former Soviet Union, April 26, 1986 the reactor core went out of control and exploded sending a cloud of radioactive dust into the atmosphere 3,576 – 32,000 people died 400,000 forced to evacuate 62,000 square miles still contaminated More than 500,000 people exposed to high level radiation Cost the govt. $385 billion

Three Mile Island March 29, 1979 in Harrisburg, Penn. Coolant failed and core melted Radioactive material escaped into air 50,000 people evacuated Luckily the radiation release was believed to be too low to cause death or cancer Cleanup 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 ocean Today some countries (US) stores the waste at govt. run landfills, but no one wants to live anywhere near them

Waste container 2 meters wide 2–5 meters high Several steel drums holding waste Steel wall Steel wall Lead shielding Fig. 14.38a, p. 351

Up to 60 deep trenches dug into clay. As many as 20 flatbed trucks deliver waste containers daily. Barrels are stacked and surrounded with sand. Covering is mounded to aid rain runoff. Clay bottom 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 level Currently 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 currently Shoot it into space/Sun Bury it deep in the Antarctic ice sheet Dump it into descending subduction zones Bury in deep mud deposits on ocean floor Convert into less harmful isotopes (currently we do not have the technology)

Fig. 14.39a, 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 years More than 144 highly contaminated weapons construction sites will never be completely cleaned