7.6

• Reducing emissions = reducing air pollutants

  • drive less, walk/bike/bus more
  • conserve electricity
  • eat more plants, less meat
  • renewable, non-pollution emitting energy (solar, hydro, wind)
• What is the purpose of the Clean Air Act?

  To reduce air pollution levels
• What does the Clean Air Act allow the EPA to do?

  Set acceptable levels for criteria air pollutants
• How does the EPA monitor emission levels?

  By monitoring emissions from power plants
• What actions can the EPA take against corporations that exceed emission levels?

  Tax, sue, or fine them
• What are pollution credits?

  Credits earned by companies reducing emissions
• How do companies earn pollution credits?

  By reducing emissions above EPA-set levels
• What happens to companies that do not use pollution credits?

  They can sell their credits to others
• What do CAFE vehicle standards stand for?

  Corporate Average Fuel Economy
• What do CAFE vehicle standards require?

  US vehicle fleet to meet average fuel efficiency
• What is the goal of vehicle manufacturers under CAFE standards?

  To make more efficient vehicles
• What is a benefit of more efficient vehicles?

  They burn less gasoline and release less emissions
• Which pollutants are reduced by more efficient vehicles?

  NOx, PM, CO, and CO2
• Vapor recovery nozzle: captures hydrocarbon VOCs released from gasoline fumes

  • Separate tube inside nozzle captures vapors and returns them to underground storage tank beneath the gas station
  • Reduces VOCs, which contribute to smog & irritate respiratory tracts
  • Also reduces benzene (carcinogen) released from gasoline vapors
• Catalytic converter:

  • Required on all vehicles after 1974
  • contains metals (platinum and palladium) that bind to NOx and CO
  • CC converts NOx , CO, and other hydrocarbons into CO2, N2, O2, and H2O
• Crushed limestone:

  • reduces SO2 from coal powered plants
  • crushed coal mixed with limestone before being burned in boiler
  • calcium carbonate in limestone combines with SO2 to produce calcium sulfate, reducing SO2 being emitted
• Fluidized bed combustion:

  • Reduces NOx by pumping fluidized jets of air into combustion bed
  • Jets of air bring more O2 into reaction, making combustion more efficient and bring So2 into more contact with limestone
  • Allows coal to be combusted at a lower temperature, emitting less Nox
• dry scrubbers (NOx, SOx, VOCs):

  • large column/tube/pipe filled with chemicals that absorb or neutralize oxides (NOx, SOx, VOCs) from exhaust streams (emissions)
  • Calcium oxide is a common dry scrubber additive which reacts with SO2 to form calcium sulfite
• wet scrubbers (Nox, SOx, VOCs, PM):

  • May involve chemical agents that absorb or neutralize NOx, SOx, VOcs but also includes mist nozzles that trap PM in water droplets as well
  • Mist droplets with pollutants and PM trapped in them fall to bottom of scrubber or get trapped at top by mist eliminator
  • Sludge collection system traps polluted water for disposal
• electrostatic precipitation:

  • removes PM
  • power plant/ factory emissions passed through devices with a negatively charged electrode giving particles a negative charge
  • negatively charged particles stick to positively charged collection plates, trapping them
  • plates discharged occasionally, so particles fall into collection hopper for disposal in landfills
• baghouse filter:

  • large fabric bag filters that trap PM as air from combustion/industrial process passes through
  • shaker device knocks trapped particles loose into collection hopper below
  • PM collected and taken to landfill