Coal Seam Methane (Captured for Combustion)

Coal seam methane is one of the few fuels where burning it is a climate win. Left to vent, methane carries a global warming potential 28 times that of CO₂; captured and combusted in gas engines or boilers, the same gas reports at just 51.63 kg CO₂-e per gigajoule in your Scope 1 inventory. That arithmetic drives every drainage-and-use project in the Bowen and Sydney basins.

Here is the NGA Factors 2025 combustion factor, how to apply it, and how it differs from the closely related coal mine waste gas factor.

Quick Verdict

Coal seam methane captured for combustion has a combined Scope 1 emission factor of 51.63 kg CO₂-e per gigajoule under the NGA Factors 2025 (Table 5) — CO₂ 51.4 plus CH₄ 0.2 and N₂O 0.03 — at an energy content of 0.0377 GJ/m³. The factor applies to the organisation combusting the gas, typically mine operators or gas producers running engines, boilers or power generation from drained seam gas. It sits within a whisker of pipeline natural gas (51.53) and well below coal mine waste gas (56.8). Combusting captured methane instead of venting it avoids reporting the methane at its GWP of 28, making capture-and-use one of the highest-impact abatement levers in carbon accounting for the coal sector.

How to Calculate Coal Seam Methane Emissions

Emissions (kg CO₂-e) = Energy consumed (GJ) × 51.63 kg CO₂-e/GJ

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

Worked Example 1: Mine-site gas engines

Gas engines generating on-site power combust 5,000 GJ of captured seam gas.

5,000 GJ × 51.63 = 258,150 kg CO₂-e

258.15 tonnes CO₂-e (Scope 1)

Worked Example 2: Site boilers billed in megajoules

Site boilers consume 900,000 MJ of seam gas over the year.

900,000 MJ ÷ 1,000 = 900 GJ

900 GJ × 51.63 = 46,467 kg CO₂-e

46.47 tonnes CO₂-e (Scope 1)

Worked Example 3: Drainage plant metered in cubic metres

A drainage plant supplies 250,000 m³ of coal seam methane to combustion equipment.

250,000 m³ × 0.0377 GJ/m³ = 9,425 GJ

9,425 GJ × 51.63 = 486,612.75 kg CO₂-e

486.61 tonnes CO₂-e (Scope 1)

How coal seam methane compares with other gaseous fuels

NGER and AASB S2 Reporting

Combustion of captured coal seam methane is reported as Scope 1 under the NGER scheme, while fugitive methane from coal mining is a separate NGER source category with its own methods. Both feed the Scope 1 inventory you disclose under AASB S2 — itemise combustion and fugitives separately so the abatement benefit of your capture programme is visible to reviewers.