APES unit 6

5.9 - Mining

Mining Basics

• Ore: commercially valuable deposits of concentrated minerals that can be harvested and used as raw materials

• Metals: elements that conduct electricity, and heat, and have structural properties for building (found within ores)

• Reserve: the known amount of a resource left that can be mined usually measured in years left of extraction

• Overburden: soil, vegetation, and rocks that are removed to get an ore deposit below

• Tailings and slag: leftover waste material separated from the valuable metal or mineral with ore (often stored in ponds at the mine site)

Surface Mining

• have to remove overburden to access ore near the surface

• different types: open pit, strip, mountaintop removal, placer

  • Mountaintop removal= most damaging to landscape and habitats, streams nearby

  • removal of veg. and soil (gunna be found in most surface mining)

    • topsoil erosion

    • habitat loss

    • increased turbidity

    • increased particle matter (PM) in the air

  • As ore near the surface becomes more scarce, mining moves deeper into the ground to subsurface mining (more dangerous and expensive$$)

Subsurface Mining

• More expensive due to higher insurance/care cost for workers

• Risk: poor ventilation → toxic gas forms → mine shaft collapse → injury from falling rocks → lung cancer → asbestos → fires → explosions

• Vertical “shaft” drilled down into the ground

  • elevator to carry down workers/transport out resources

  • often used for coal

• Increasingly used as surface coal deposits are depleted since they have to dig deeper because there are less coal closer to the surface

Environmental Impacts of Mining

• Acid Mine Drainage: rainwater leaks into abandoned mine tunnels and mixes with pyrite, forming sulfuric acid

  → rainwater carries the sulfuric acids to nearby streams or contaminates groundwater

  → Lowers the pH of the water, making toxic metals like mercury and aluminum more soluble in water sources (killing aquatic org.)

• Methane Release: coal mining releases methane gas (CH₄) from the rock around the coal

  • vented out of the mine to prevent explosion and continues seeping out after the mine closes

  • GHG → climate change

• PM Release: coal mining especially, releases lots of soot and other particulates that can irritate human and animal lungs

Mine Reclamation

• process of restoring land to original state after mining has finished

• Includes:

  1. Filling of empty mine shafts/holes

  2. Restoring original contours of land

  3. Returning topsoil (without acids, metals, and tailings)

  4. Replanting the area with native plants to restore community to as close to the original state possible

6.1 - Renewable vs. Nonrenewable Energy Sources

Renewable: can be replenished naturally, at or near of consumption and reused

• Depletable Renewables: can run out if overused

  • Ex. biomass, wood, charcoal, ethanol

• Nondepletable Renewables: do not run out if overused

  • Ex. wind, solar, hydroelectric, geothermal

Nonrenewable: Exist in fixed amounts on earth and can’t easily be replaced or regenerate

• Fossil Fuels: fossilized remains of ancient biomass that take millions of years to form

  • coal, oil, nat. gas

• Nuclear: energy generated from uranium or other radioactive fuels

Key to Renewable Energy

• Rate of Consumption

  • rate of use must be at or below regeneration for renewables

  • fossil fuels will run out because they take far longer to regenerate than the rate we use them

6.2 - Global Energy Consumption

Developed vs. Developing Countries

• Developed: use more energy on a per capita basis,

• Developing: use more energy in total (bc of higher pop.)

  • The average US resident uses 5x as much energy as the world's average

  • Developing nations are still industrializing & pop. is still growing rapidly

    → will also increase on a per/person basis as their economies industrialize and residents achieve higher standards of living

Fossil Fuels: Most Used Energy Source

• most common fuel source globally

  • Oil → Gasoline = main fuel for vehicles

  • Coal = main fuel for electricity generation

  • Natural Gas = secondary fuel for electricity generation and main fuel for heating

• 2nd most common form of energy outside of FF

  • Hydroelectricity Energy (dams used to create electricity) = water spins a turbine which generates electricity

• 3rd most common form of energy outside of FF

  • Nuclear = Uranium fission releases heat to turn water into steam to turn a turbine to generate electricity

Development Increases FF Consumption

• LDC (less developed countries) depend on subsistence fuels - biomass that can easily gather/purchase

  • Ex. wood, charcoal, dried, animal manure

  • Can drive deforestation

• Economies development → affluence (wealth) → higher per capita GDP → energy use

• As developing nations develop, fossil fuel consumption will increase

  • Oil → Gasoline for vehicles

  • Coal and Natural Gas → electricity

    • electricity demand for homes and manufacturing

Factors That Affect Energy Source Use

• Availability: FF use depends on discovered reserves and accessibility of these reserves

  • use of FFs varies heavily with availability

• Price: FF price goes down with discovery of new reserves or goes up with the depletion of existing ones

  • Fracking opens new NG reserves, increasing availability, decreasing price, increasing uses

• Government Regulations: can mandate certain energy source mixes (25% renewable by 2025)

  • Gov. cannot directly raise or lower prices of energy sources (ex. raise gas to $10/gallon)

  • Gov. can use:

    • taxes increase or discourage companies from building FF power plants

    • Rebates, or tax credits to encourage companies building renewable energy power plants

6.3 - Fuel Types and Uses

Subsistence Fuels

• Biomass fuel sources that are easily accessible (can be found and gathered by hand); often used in developing countries as a home heating or cooking fuel

  • Wood and charcoal are two most common fuel sources in developing nations

    • wood is free and cheap → but can cause deforestation and habitat loss

    • charcoal is made by heating wood under low oxygen conditions for a long time

  • Peat is partially decomposed organic matter (often fern or other plants) found in wet, acidic ecosystems like bog and moors

    • can be dried and used as biomass fuel

Coal Formation

• Pressure from overlying rock and sediment layers compacts peat into coal over time

  → In order of energy density and quality: Lignite → Bituminous → Anthracite

• The deeper a coal reserve is buried, the more pressure from overlying rock layers and the more energy-dense

  → Because higher energy density means more energy released when a fuel source is burned anthracite is the more valuable form of coal (Highest Quality)

  • Coal is burned to heat water into steam, to turn a turbine that generates electricity

    • more dense coal = hotter/longer fire = more steam = more electricity

  • Also cleaner/less impurities because its been squeezed out

Natural Gas

• Decaying remains of plants and animals(mostly marine life) are buried under layers of rock and converted by pressure into oil (petroleum) and nat. gas overtime

  → Natural gas is mostly methane (CH₄) and is found on top of trapped oil (petroleum) deposits

• Forms when oil is trapped in a porous, sedimentary rock, underneath a harder, impermeable rock layber that doesn’t let the gas escape

  → Considered the “cleanest” FF (produces the fewest air pollutants and least CO₂ when burned)

• Produces about ½ as much CO₂ as coal when burned to generate electricity

• Produces virtually no PM (ash/soot)

  • Produces far less SO₂, NO₂ than coal or oil, and NO MERCURY

Crude Oil (petroleum)

• Decay organic matter trapped under rock layers is compressed into oil over time

  → Extracted by drilling a well through the overlying rock layers to reach the underground deposit and then pumping liquid oil out under pressure

  → Can also be recovered from Tar sand (oil sand) (a combination of clay, water, sand, and bitumen)

  • Bitumen: a thick, sticky, semi-solid form of petroleum (not liquid)

  • Extracting and using oil from tar sands is extremely energy and water-intensive

    • Lots of water needs to be heated (requiring energy) to create steam that’s piped down into the tar sand to melt the bitumen into a liquid that can flow up a pipe

    • Lots more water is used to separate the oil from all of the impurities (sand, clay) at the refinery

    • Overall more environmentally consequential

Fossil Fuel Products

→ Crude oil (petroleum) is converted into lots of different products through the process of fractional distillation

• Crude oil is burned in a furnace, and vapor passes into a column where different hydrocarbons are separated based on their boiling points

• Hydrocarbons w/lower boiling points gather at the top of the column, higher boiling points gather at bottom

• Different hydrocarbons within petroleum are used for differemt products

  • Petroleum gas

  • Gasoline (fuel for cars)

  • Naphtha (used to make plastic)

  • Jet Fuel

  • Diesel Fuel

  • Motor Oil

  • Bitumen (asphalt for roads)