Continue to Operate Gas Collection System and Flare

When a landfill is required or otherwise decides to continue collecting and destroying landfill gas (LFG) but recovering energy is not feasible or desired, the site can continue to operate the collection system and flare all the collected LFG. This option will generally achieve the largest methane emission reductions and also reduces odors. For landfills with declining gas production, the flare system may need to be retrofitted or replaced to accommodate a lower flow rate. The collection system will also require adjustments and maintenance to ensure that it operates as designed and can accommodate declining gas flows. Additionally, wells in unproductive areas of the landfill may be capped and decommissioned to prevent these wells from introducing ambient air into the collection system and degrading the quality of the collected LFG.

Greenhouse Gas (GHG) Mitigation Potential:

  • Methane destruction in flares is typically greater than 99 percent.1 A flare operates routinely except during periodic maintenance or malfunctions.
  • Methane collection efficiency will vary depending on wellfield coverage, condition of the infrastructure and landfill cover type. For well-designed and well-operated systems, collection efficiencies of 60 percent are achievable in areas with daily soil cover. This increases to 75 percent for areas with intermediate soil cover or final cover not meeting certain criteria, and up to 95 percent for areas with final cover meeting certain criteria.2
  • In addition to collected methane, some methane may be oxidized depending on cover type. For landfills with an active gas collection system, methane oxidation rates range from 20 percent in areas without final cover to 35 percent in areas with final cover.3

Example

Worcester County Central Landfill, Maryland 5, 6, 7

Worcester County’s Central Landfill near Newark, Maryland, was home to a privately owned 2-megawatt reciprocating engine project from 2008 through mid-2013. The project developer/owner, Worcester County Renewable Energy, paid an annual $25,000 gas rights fee to the county to use the LFG to generate the green power for sale to Old Dominion Electric Cooperative.

A major drop in waste disposal at the site caused an LFG shortage as compared to the original projections, which in turn led to a loss of investors in the project. The county decided in May 2013 to end the project instead of purchasing it from the owner.

The landfill’s 1,500-cfm flare was installed in 2008, the same year as the energy project. The county recirculates leachate, the first landfill in Maryland to do so, and uses dual-purpose gas wells for leachate recharge and gas extraction.

The county has voluntarily flared the site’s declining LFG since the energy project ended in 2013.

Criteria:

  • Landfill still has sufficient methane content to be able to support combustion and maintain flame stability at the flare.
  • Landfill has concerns about gas odor and/or migration.

Pros:

  • Minimizes fugitive LFG releases to the atmosphere, reducing GHG impacts and odor issues.

Cons:

  • Ongoing cost to operate the gas collection system and flare.

Economic Considerations:

  • Recurring annual operation and maintenance costs, e.g., $2,600 per well and $5,100 per flare.4
  • Electricity consumption costs from active blower system, e.g., $74,000 per year for a typical landfill at 800 cubic feet per minute (cfm) of LFG.4
  • Costs to maintain pumps to remove moisture from system for landfills with leachate recirculation or high quantities of gas condensate.
  • Possible cost to retrofit or replace flare if LFG quantity and/or quality has declined significantly, depending on the turndown capabilities of existing equipment.
  • Supplemental fuel costs for propane to maintain combustion may be required at sites with lower gas quality.
  • Some sites may qualify for carbon credits through voluntary carbon markets if not required to collect and combust LFG.

More Information:

  • For landfills seeking to monetize GHG reduction credits from voluntary methane reduction actions, protocols such as the Climate Action Reserve’s U.S. Landfill Project Protocol outline monitoring, recordkeeping and reporting requirements.

References

1 U.S. EPA. Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from Municipal Solid Waste Landfills. June 2011. https://www.epa.gov/sites/default/files/2015-12/documents/landfills.pdf.

2 U.S. EPA. Greenhouse Gas Reporting Program. Subpart HH – Municipal Solid Waste Landfills. Table HH-3 to Subpart HH of Part 98 – Landfill Gas Collection Efficiencies. As amended December 9, 2016. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-98/subpart-HH#ap40.23.98_1348.3.

3 U.S. EPA. Documentation For Greenhouse Gas Emission and Energy Factors Used in the Waste Reduction Model (WARM). Management Practices Chapters. November 2020. https://www.epa.gov/sites/default/files/2020-12/documents/warm_management_practices_v15_10-29-2020.pdf.

4 U.S. EPA. Landfill Gas Energy Cost Model (LFGcost-Web), Version 3.4. October 2020. https://www.epa.gov/lmop/lfgcost-web-landfill-gas-energy-cost-model.

5 U.S. EPA. LMOP Landfill and Landfill Gas Energy Project Database. July 2021. https://www.epa.gov/lmop/lmop-landfill-and-project-database.

6 The Dispatch. County to Close Landfill’s Renewable Energy Facility. May 9, 2013. https://mdcoastdispatch.com/2013/05/09/county-to-close-landfills-renewable-energy-facility/.

7 Godlove, Chris. Making Carbon Credits Work for Your Landfill. November 1, 2009. https://www.mswmanagement.com/collection/article/13004939/making-carbon-credits-work-for-your-landfill.

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Last updated on July 1, 2024