Controls on landfill gas collection efficiency: instantaneous and lifetime performance

Area of Science:

• Environmental Engineering
• Waste Management Science
• Atmospheric Science

Background:

• Accurate estimation of landfill gas (LFG) collection efficiency is vital for quantifying methane emissions and evaluating landfill environmental performance.
• LFG collection efficiency is dynamic, influenced by landfill design, operation, and regulatory practices.
• Existing literature indicates instantaneous collection efficiencies ranging from 50% to nearly 100%, depending on cover type and collection system coverage.

Purpose of the Study:

• To propose and calculate the temporally weighted gas collection efficiency as a more appropriate metric for reporting landfill performance.
• To determine temporally weighted gas collection efficiencies under various decay rates and landfill operational scenarios.

Main Methods:

• Calculated temporally weighted gas collection efficiency considering total gas production and collection over the landfill's operational life.
• Modeled efficiencies for refuse decay rates representative of arid and wet climates.
• Assessed efficiencies for bioreactor landfill conditions with aggressive gas collection.

Main Results:

• Temporally weighted collection efficiencies were calculated: 67–91% (0.02 yr⁻¹), 62–86% (0.04 yr⁻¹), and 55–78% (0.07 yr⁻¹).
• For bioreactor landfills, efficiencies ranged from 84% (0.04 yr⁻¹) to 67% (0.15 yr⁻¹).

Conclusions:

• Temporally weighted gas collection efficiency provides a more comprehensive measure of landfill performance over time.
• Results highlight the significant impact of decay rates and operational strategies (e.g., bioreactor conditions) on LFG collection efficiency.