CPWM Landfill Gas Management and Energy Recovery 1 — Questions and Answers
Question 1: What are the two primary components of landfill gas (LFG)?
- Nitrogen and oxygen
- Methane and carbon dioxide (Correct answer)
- Hydrogen sulfide and ammonia
- Carbon monoxide and water vapor
Correct answer: Methane and carbon dioxide
LFG is composed primarily of approximately 50% methane and 50% carbon dioxide by volume, produced through anaerobic decomposition of organic waste.
Question 2: Under the Clean Air Act, which regulatory standard specifically governs MSW landfill air emissions requiring gas collection and control systems?
- RCRA Subtitle D regulations
- New Source Performance Standards (NSPS) under 40 CFR Part 60 (Correct answer)
- National Emission Standards for Hazardous Air Pollutants under 40 CFR Part 61
- Clean Water Act Section 402 permits
Correct answer: New Source Performance Standards (NSPS) under 40 CFR Part 60
MSW landfill air emissions are regulated under NSPS in 40 CFR Part 60, which sets emission thresholds that trigger gas collection and control system installation requirements.
Question 3: At what volume concentration of methane in ambient air does the lower explosive limit (LEL) become a safety concern?
- 1% methane by volume
- 5% methane by volume (Correct answer)
- 15% methane by volume
- 25% methane by volume
Correct answer: 5% methane by volume
The lower explosive limit (LEL) for methane is approximately 5% by volume in air, below which the gas-air mixture is too lean to ignite.
Question 4: What biological process is primarily responsible for landfill gas production in a sanitary landfill?
- Aerobic biodegradation of organic waste
- Anaerobic biodegradation of organic waste (Correct answer)
- Chemical oxidation of inorganic materials
- Photodegradation of plastic waste
Correct answer: Anaerobic biodegradation of organic waste
LFG is generated when anaerobic microorganisms decompose organic waste in the oxygen-depleted environment deep within the landfill, producing methane and carbon dioxide.
Question 5: Which type of landfill gas combustion device most effectively controls trace organic compound emissions?
- Open candlestick flare
- Pipe stack flare
- Enclosed ground flare (Correct answer)
- Portable thermal oxidizer
Correct answer: Enclosed ground flare
Enclosed ground flares achieve destruction efficiencies of 99%+ for trace organics by providing controlled residence time, high temperature, and turbulent mixing in a sealed combustion chamber.
Question 6: What is the approximate energy content (BTU/scf) of typical landfill gas containing approximately 50% methane?
- 100–200 BTU/scf
- 250–350 BTU/scf
- 450–550 BTU/scf (Correct answer)
- 700–800 BTU/scf
Correct answer: 450–550 BTU/scf
LFG with approximately 50% methane content has an energy value of roughly 450–550 BTU/scf, about half the energy content of pipeline-quality natural gas.
Question 7: Which voluntary EPA program specifically promotes the development of landfill gas energy recovery projects?
- ENERGY STAR Program
- Landfill Methane Outreach Program (LMOP) (Correct answer)
- Green Power Partnership
- WasteWise Program
Correct answer: Landfill Methane Outreach Program (LMOP)
EPA's Landfill Methane Outreach Program (LMOP) is a voluntary assistance and partnership program that facilitates the development of LFG-to-energy projects at landfills across the United States.
CPWM Landfill Gas Management and Energy Recovery 1
What are the two primary components of landfill gas (LFG)?