SWANA Landfill Gas Management 1 — Questions and Answers
Question 1: What is the primary component of landfill gas (LFG) produced during anaerobic decomposition?
- Carbon dioxide
- Nitrogen
- Methane (Correct answer)
- Hydrogen sulfide
Correct answer: Methane
Methane (CH4) is the primary component of LFG, typically comprising 45–60% of the gas mixture produced by anaerobic microbial decomposition of organic waste.
Question 2: What does NSPS stand for in the context of EPA landfill gas regulations?
- National Site Pollution Standards
- New Source Performance Standards (Correct answer)
- National Solid Permit System
- Non-point Source Prevention Standards
Correct answer: New Source Performance Standards
NSPS stands for New Source Performance Standards, established under the Clean Air Act (40 CFR Part 60, Subpart XXX) to regulate emissions from new MSW landfills.
Question 3: Under EPA regulations, MSW landfills above what design capacity threshold must install a gas collection and control system (GCCS) if NMOC emissions exceed 34 Mg/yr?
- 1 million Mg
- 5 million Mg
- 10 million Mg
- 2.5 million Mg (Correct answer)
Correct answer: 2.5 million Mg
EPA requires MSW landfills with a design capacity of 2.5 million Mg or more that emit at least 34 Mg/yr of NMOC to install and operate a GCCS.
Question 4: What is the typical methane concentration range found in landfill gas?
- 10–20%
- 40–60% (Correct answer)
- 25–35%
- 70–90%
Correct answer: 40–60%
Landfill gas typically contains 40–60% methane by volume, with most of the remainder being carbon dioxide and trace amounts of other gases.
Question 5: In an active LFG collection system, what is the primary function of the blower/vacuum pump unit?
- Heat the gas to prevent condensation
- Filter trace volatile organic compounds
- Create negative pressure to draw gas from extraction wells (Correct answer)
- Monitor gas composition in real time
Correct answer: Create negative pressure to draw gas from extraction wells
The blower creates a negative pressure (vacuum) in the collection pipes that draws landfill gas from the extraction wells toward the header system for control or utilization.
Question 6: What is the primary purpose of a knockout pot (condensate trap) installed in an LFG collection system?
- Measure the volumetric gas flow rate
- Add odorant for leak detection
- Remove moisture and liquid condensate from the gas stream (Correct answer)
- Compress the gas for pipeline injection
Correct answer: Remove moisture and liquid condensate from the gas stream
A knockout pot separates and collects liquid condensate (water and leachate) that accumulates in collection pipes, preventing liquids from entering blowers or control equipment.
Question 7: Which trace gas in landfill gas is primarily responsible for odor complaints at and near landfill facilities?
- Methane
- Nitrogen
- Carbon dioxide
- Hydrogen sulfide (Correct answer)
Correct answer: Hydrogen sulfide
Hydrogen sulfide (H2S), though present in trace concentrations, has a very low odor threshold (detectable at <1 ppb) and is the main cause of rotten-egg odor complaints near landfills.
SWANA Landfill Gas Management 1
What is the primary component of landfill gas (LFG) produced during anaerobic decomposition?