Unit 6.5 - Fossil Fuels

Question 1

Fossil Fuel COmbution

Answer 1

• Reaction between oxygen and fossil fuels (hyrocarbons) that releasesenergy as heat and produces CO2 and H2O as products
• Remember: combustion is a step in the carbon cycle: hydrocarbons (fossil fuels) are burned to release energy and the carbon stores in them reacts with O2 in the air to form CO2
• Methane (natural gas), gasoline, propane, butane, and coal are all fossil fuels (hydrocarbons) that release energy in the same way
• wood and biomass work the same, carbon is burned and reacts with O2 to fors the CO2 and give off energy

Question 2

Fossil Fuelsto Generate Electricity

Answer 2

• the #1 source of electricity production globally, coal, is followed by naturala gas
• These steps of electricity generation are the same no matter what youre burning to produce the inital heat:
  1. Heat
  2. Water into steam
  3. Steam turns a turbine
  4. Turbine powers generator
  5. Geenrator produces eelctricity
• Coal, oil, natural gas, biomass, and trash can all be burned to drive this same process and create energy. Even nuclear energy works similarly with nuclear fission producing the initial heat

Question 3

Environmental Consequences: Coal

Answer 3

• Habitat deconstruction to clear land for mining
• Prodcues pollutants and releases CO2 (GHG -> global warming)
  - releases more CO2 than any other Fossil Fuel when burned for electricity generation
  - releases PM (soot/ash) which can irritate respiratory tracts of humans/animals
  - produces toxic ash contaminated with lead, mercury, and arsenic
  - taken to landfills or stored in ash ponds: both can leak into ground/surface water, or into soil
  - releaes SOx and NOx (sulfur and nitrogen oxides) which irritate respiratory systems, and contribute to smog and acid precipitation

Question 4

Generating Electricity: Coal

Answer 4

• Coal is around 30% efficient as a fuel source for generating electricity (30% of energy from the bons in the hydrocarbons are converted to electricity)
  - natural gas is around 60% efficient wen its burned to generate electricity
• Much of the energy lost or ot converted into electricity escapes as heat
• Cogeneration: whenthe heat produced from electricity generation is used to provide heat (air and hot water) to a building
• CHP (combined heat and power) systems are close to 90% efficient (much better thann coal/NG alone)

Question 5

Oil/Petroleum Extraction

Answer 5

• Extracted by drilling a well through the overlying rock layers to reach the undergrounf deposit and then pumping liquid oil out under pressure
• Can also be recovered from tar sands (combination of clay, sand, water, and bitumen)
  - Bitumen is a thick, sticky, semi-soil form of petroleum (not liquid)
  - Extracting and using oil from tar sands is extremely energy and water intensive
  - lots of water needs tobe heated (requiring energy) to create steam that’s piped down into the tar snad to melt the bitumen into 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

Question 6

Environmental Consequences: Tar Sands

Answer 6

• Habitat deconstruction to clear landfor: roads, drilling equiptment, digging through ground surface to reach deposits (biodiversity loss)
• Ground or nearby surface water depletion (H2O needed for steam and for washingimpurities from bitumen at refinery)
  - Water ocntamination: tailing pons (holes dug for storm waterwaste) can overflow and run into nearby surface waters or leach into ground
  - Bensene (carcinogen) salts, acids, hydrocarbons, bitumen
  - All toxic to plants and animals
• CO2 released by machinery during extraction, transport, and refinement

Question 7

Environmental Consequences: Crude Oil/Petroleum

Answer 7

• Possibolity ofspill (either from ranker hiprs or pipelines breaking)
  - spills into water = crude oil covering sun, clogging fish gills, suffocatinf many ocean animals, sticking to bird feathers
  - sills on land = toxic to plant roots, surface or groundwater contamination (with hydrocarbons/crude oil)
• Habitat loss or fragmentation when land is cleared for roads, drilling equiptment, pipelines

Question 8

Fracking (Hydraulic Fracturing)

Answer 8

• Used to extract natural gas froms edimentary rock
• Vertical well is drilled fown to sedimentary rock layer, then turns horizontally into the rock layer
  -perforating gun cracks (fractures) the rock layer around horizontal well, making it more permeable
• Fracking fluid (water, salt, detergents, ect) is pumped into well at a very high pressure to crack the rock even more and allow natural gas to flow out
• Natural gas is collected at the surface and shipped for processing/use
• Flowback water (used fracking fluid) flows back out well and is collected and stored in containers fo ponds nearby

Question 9

Environmental consequences: Fracking

Answer 9

• Possibility of well leaking and contaminating groundwater with fracking fluid (salt, detergents, acids) or hydrocarbons
• ponds can overflow r leach into grounf and contaminate surface or ground waters with fracking fluid
  - can be toxic to plants and animals that rely on these water sources
• Depletion of ground or surface waters nearby (as theyre drawn from for fracking fluid)
• Increased seismic activity (earthquakes) linked with wastewater injection wells (storing fracking fluid deep underground)