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Landfill Gas Management and Energy Recovery Flashcards

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  1. What is the typical methane concentration range found in landfill gas collected from a well-managed MSW landfill?

    Answer: 35–60% methane by volume

    Typical MSW landfill gas contains approximately 45–60% methane by volume, with most of the remainder being carbon dioxide and small concentrations of trace gases.

  2. What minimum operating temperature must an enclosed combustion device maintain when treating landfill gas under EPA 40 CFR Part 60 Subpart Cf?

    Answer: 1,500°F (815°C)

    EPA regulations require enclosed combustion devices treating MSW landfill gas to operate at a minimum temperature of 1,500°F (815°C) with at least 0.5 seconds of residence time to ensure effective destruction of NMOCs.

  3. Which LFG collection well configuration is most commonly used in completed waste cells at an active landfill?

    Answer: Vertical extraction wells drilled down through the waste mass and connected by header pipes

    Vertical extraction wells drilled through completed waste cells are the primary collection method; they are equipped with perforated casing and connected via sloped header pipes to a central blower/flare station.

  4. What is the primary function of condensate management components (drip legs and collection sumps) in an LFG collection network?

    Answer: To remove liquid water condensate from collection pipes that would otherwise block gas flow

    LFG is saturated with water vapor that condenses in collection pipes as temperatures drop; drip legs and sumps collect and remove this condensate to prevent flow blockages and corrosion.

  5. Which financial instruments generated by LFG-to-energy projects can provide additional revenue through environmental commodity markets?

    Answer: Renewable Energy Credits (RECs) and verified carbon offset credits

    LFG-to-energy projects can generate Renewable Energy Credits (RECs) for electricity production and verified carbon offsets (e.g., under California ARB or voluntary markets) by displacing fossil fuels and reducing methane emissions.

  6. In an LFG collection system, what does a negative wellhead pressure (vacuum) measurement indicate?

    Answer: The blower system is actively drawing gas from the waste mass toward the collection system

    Negative (vacuum) wellhead pressure confirms that the blower is successfully applying suction to pull LFG from the waste mass into the collection system; pressure levels are adjusted to balance collection efficiency against air infiltration.

  7. Which trace compound found in landfill gas is classified as a hazardous air pollutant (HAP) and a known human carcinogen?

    Answer: Vinyl chloride

    Vinyl chloride is a hazardous air pollutant (HAP) present in trace amounts in LFG, formed from the anaerobic degradation of chlorinated compounds in waste; it is classified by EPA as a known human carcinogen.