Landfill Biogas (Captured for Combustion)

Landfills are methane factories: buried organics decompose anaerobically and vent a gas with 28 times the warming power of CO₂. Capturing that gas and burning it in engines or flares flips the equation, converting high-GWP methane into biogenic CO₂ that carries no charge in your greenhouse gas inventory. The residual factor for the combustion itself is tiny.

This entry covers the NGA Factors 2025 landfill biogas factor, the biogenic CO₂ logic behind it, and three worked examples.

Quick Verdict

Landfill biogas captured for combustion has a combined Scope 1 emission factor of 6.43 kg CO₂-e per gigajoule under the NGA Factors 2025 (Table 5). The CO₂ component is zero because the carbon is biogenic — it is reported separately, not in your CO₂-e total — leaving only residual methane (6.4) and nitrous oxide (0.03). The factor applies to landfill operators and power generators combusting captured gas, reported under Scope 1, at an energy content of 0.0377 GJ per cubic metre of methane. Per gigajoule, combusted landfill gas emits about 87% less than natural gas, and combustion versus venting is the difference between 6.43 kg CO₂-e and methane at a GWP of 28.

How to Calculate Landfill Biogas Emissions

Emissions (kg CO₂-e) = Energy consumed (GJ) × 6.43 kg CO₂-e/GJ

Convert cubic metres of methane at 0.0377 GJ/m³ and megajoules at 1,000 MJ per GJ.

Worked Example 1: Landfill gas power station

Gas engines generating electricity combust 10,000 GJ of captured biogas.

10,000 GJ × 6.43 = 64,300 kg CO₂-e

64.30 tonnes CO₂-e (Scope 1)

Worked Example 2: Flare-only site

A smaller landfill flares 2,500 GJ of captured gas.

2,500 GJ × 6.43 = 16,075 kg CO₂-e

16.08 tonnes CO₂-e (Scope 1)

Worked Example 3: Capture system metered in cubic metres

A gas collection system delivers 300,000 m³ of methane to combustion.

300,000 m³ × 0.0377 GJ/m³ = 11,310 GJ

11,310 GJ × 6.43 = 72,723.3 kg CO₂-e

72.72 tonnes CO₂-e (Scope 1)

How landfill biogas compares with other gaseous fuels

NGER and AASB S2 Reporting

Combustion of captured landfill gas is reported as Scope 1 under the NGER scheme, while fugitive methane from the landfill body is calculated separately under waste-sector methods. Under AASB S2, the combustion figure sits in your Scope 1 inventory, with biogenic CO₂ disclosed separately where material — a distinction assurance providers increasingly check.