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Attachment A-2: Methane Emissions Input Parameters and Emissions Calculations <br />Total LFG Derived Methane Emissions over 50 years post project (2026 - 2076) <br />Fugitive Emissions Flare Emissions Total <br />Baseline 635,191 121,311 5,004 126,315 2,864,788 2,526 57,296 <br />Project 742,112 123,649 6,047 129,696 2,941,459 2,594 58,829 <br />Notes <br />Baseline Condition <br />Project Condition <br />Assumptions <br />Project year 2026 <br />Landfill closure year (current)2059 <br />Landfill closure year (project )2043 <br />Landfill gas collection system collection <br />efficiently E_col <br />E_col (2026 to 2029)0.65 <br />E_col (2030 to closure year)0.75 Assume 50% final cover and 50% intermediate cover on average. <br />E_col (after closure year)0.85 Assume all modules will have final cover by the closure year. <br />Inventory end year 2076 50-year period used to represent the overall impacts. <br />Methane oxidation in landfill soil cover <br />E_oxi 10%EPA default. <br />Flare methane destruction efficiency <br />E_fla 99%Title V Permit minimum requirement. <br />Metric tons per short ton 0.907 <br />Global Warming Potential 25 CARB 2022. GHG Global Warming Potentials. Available at https://ww2.arb.ca.gov/ghg-gwps. Accessed on September 9, 2024. <br />Abbreviations <br />CH4 =methane; CO2e = carbon dioxide equivalents; LFG = landfill gas <br />Equations: <br />Emissions [short ton/yr] = total uncontrolled emissions [short tons/year] × (1-Ecol [%]) × (1 - E_oxi [%]) + total uncontrolled emissions [short tons/year] × (1-Efla [%]) <br />Emission Scenario <br />Total CO2e <br />Emissions <br />(2026-2076) <br />(metric tons) <br />CFR Part 98 Table HH-3. According to the North County Landfill Status Impact Report dated Feb 14, 2023, final cover placement phase 1 would occur on 2029 under the <br />baseline condition. Assumed final cover placement phase 1 would occur on the same year for project condition. <br />Total LFG emissions were calculated using LandGem. Fugitive emissions were estimated using parameters from the U.S. Environmental Protection Agency's Compilation of Air Pollutant Emissions Factors (AP-42), <br />Section 2.4 Municipal Solid Waste Landfills. <br />Provided by applicant. Assumptions: increase waste acceptance rates from 250,000 tons in 2024 to 660,000 tons in 2026, then assume 3% increase annually thereafter. <br />Predicted based on the baseline operation condition (250,000 tons in 2024) and assume 3% increase annually thereafter. <br />Assume most of the filled area covered by intermediate cover. <br />Total Uncontrolled <br />CH4 Emissions (2026- <br />2076) <br />(short tons) <br />Total CH4 (2026-2076) (short tons)Annual Average <br />CH4 Emissions <br />(short tons) <br />Annual Average <br />CO2e Emissions <br />(metric tons) <br />Net Difference <br />CO2e Emissions <br />(metric tons) <br />1,533 <br />Page 2 of 25