Hydrogen (Combustion)

Burn hydrogen and you get water, not CO₂ — the fuel has no carbon atom to release. That is why its Scope 1 combustion factor is the lowest in the Australian tables. But the number comes with a warning label: 0.05 kg CO₂-e/GJ describes only what happens at the burner, and hydrogen’s real climate story is written upstream, in how the gas was made. Getting that distinction right matters for every greenhouse gas inventory that includes hydrogen.

This entry covers the NGA Factors 2025 hydrogen combustion factor, the grey-versus-green production caveat, and three worked examples.

Quick Verdict

Hydrogen has a combined Scope 1 combustion emission factor of just 0.05 kg CO₂-e per gigajoule under the NGA Factors 2025 (Table 5). Because hydrogen contains no carbon, combustion emits no CO₂ and no methane — the factor is trace nitrous oxide only. It applies to organisations burning hydrogen directly, reported under Scope 1, at an energy content of 0.0122 GJ per cubic metre. Crucially, this is a combustion factor only: it excludes the emissions of producing the hydrogen, which for grey hydrogen made from natural gas can be very large and for green hydrogen from renewable electrolysis is near-zero. Treat the combustion factor as one piece of a full life-cycle picture, not the whole answer.

How to Calculate Hydrogen Emissions

Emissions (kg CO₂-e) = Energy consumed (GJ) × 0.05 kg CO₂-e/GJ

Convert cubic metres at 0.0122 GJ/m³ and megajoules at 1,000 MJ per GJ. Remember this covers combustion only.

Worked Example 1: Industrial burner

A manufacturer combusts 20,000 GJ of hydrogen in a process burner over the year.

20,000 GJ × 0.05 = 1,000 kg CO₂-e

1.00 tonne CO₂-e (Scope 1, combustion only)

Worked Example 2: Smaller load

A pilot facility burns 5,000 GJ of hydrogen.

5,000 GJ × 0.05 = 250 kg CO₂-e

0.25 tonnes CO₂-e (Scope 1, combustion only)

Worked Example 3: Supply metered in cubic metres

A hydrogen supply is metered at 2,000,000 m³ over the year, all combusted on site.

2,000,000 m³ × 0.0122 GJ/m³ = 24,400 GJ

24,400 GJ × 0.05 = 1,220 kg CO₂-e

1.22 tonnes CO₂-e (Scope 1, combustion only)

How hydrogen compares with other gaseous fuels

The combustion factor makes hydrogen look untouchable, but the comparison is only fair once production is included: grey hydrogen’s upstream footprint can rival or exceed simply burning the natural gas it was made from.

NGER and AASB S2 Reporting

Direct combustion of hydrogen is reported as Scope 1 under the NGER scheme using this factor. Under AASB S2, combustion emissions sit in your Scope 1 inventory, while the upstream emissions of purchased hydrogen belong in Scope 3. Disclosing hydrogen as a low-carbon fuel without documenting its production pathway — grey, blue, or green — is precisely the kind of claim assurance providers now test.