Lecture Notes: Reduction of Air Pollutants

Objective

• Explain how air pollutants can be reduced at the source.
• Practice using data to justify a solution to an environmental problem.

Key Methods of Reducing Air Pollution

Reducing Emissions

• Personal Actions:
  • Use bikes, walk, or take public transit instead of driving.
  • Conserve electricity by using smart appliances and turning off lights.
  • Eat less meat to reduce energy and agriculture-related emissions.
  • Shift to renewable energy sources like hydroelectric, solar, and wind power.

Laws and Regulations

• Clean Air Act

  • Empowers the EPA to set acceptable levels for six criteria air pollutants.
  • Allows for monitoring and penalizing entities exceeding pollution limits.

• CAFE Vehicle Standards

  • Corporate Average Fuel Economy Standards.
  • Raising fuel economy standards reduces air pollution from transportation by burning less gasoline.

• Pollution Credits

  • Incentivize companies to reduce emissions by earning credits.
  • Companies exceeding emission limits buy credits from low-emission companies.
  • Example: Tesla profits from selling pollution credits.

Technologies to Reduce Vehicle Emissions

Vapor Recovery Nozzle

• Captures volatile organic compounds (VOCs) at gas stations.
• Reduces photochemical smog and respiratory irritants.
• Captures fumes and returns them to underground tanks.

Catalytic Converter

• Mandated for vehicles post-1975.
• Filters exhaust, converting harmful gases to less harmful substances:
  • Converts carbon monoxide to carbon dioxide.
  • Reduces nitrogen oxides (NOx) emissions.

Technologies for Reducing Power Plant Emissions

Limestone in Coal Combustion

• Crushed limestone mixed with coal before combustion.
• Traps sulfur dioxide (SO2) as calcium sulfate.
• Calcium sulfate can be used to make gypsum wallboards.

Fluidized Bed Combustion

• Jets of air create a bubbling fluid bed.
• Improves combustion efficiency and reduces temperature, lowering NOx emissions.

Scrubbers to Clean Emissions

Dry Scrubbers

• Use chemical agents like calcium oxide to react with pollutants.
• Convert pollutants like SO2 into solid forms (e.g., calcium sulfite).

Wet Scrubbers

• Similar to dry scrubbers but more effective at trapping particulate matter.
• Use mist to capture and bind pollutants, forming sludge for disposal.

Particulate Matter Reduction

Electrostatic Precipitator

• Charges particles negatively, attracting them to positively charged plates.
• Particles collected in hoppers for disposal.

Bag House Filters

• Use bags to trap particles from emission streams.
• Shaker mechanism collects particles in hoppers for disposal.

Practice Task

• Analyze a graph showing potential CAFE standards.
• Make a claim about the effectiveness of Obama CAFE standards to reduce NOx.
• Justify the claim with data from the graph.