Emission Factors

EmWise uses emission factors from Schedule 1 of the NGER (Measurement) Determination. Factors are stored per vehicle class per reporting year and are never modified retroactively.

How the factor schedule works

Each emission factor row in EmWise defines:

• Energy content (GJ/kL) — how much energy is released per kilolitre of fuel burned
• CO₂ factor (kg CO₂-e/GJ) — combustion CO₂ emissions per GJ
• CH₄ factor (kg CO₂-e/GJ) — methane emissions per GJ (expressed as CO₂-equivalent using GWP)
• N₂O factor (kg CO₂-e/GJ) — nitrous oxide emissions per GJ (expressed as CO₂-equivalent)
• Scope 3 factor (kg CO₂-e/GJ) — upstream fuel cycle emissions per GJ

The combined Scope 1 factor is CO₂ + CH₄ + N₂O. This relationship is enforced by a database constraint — any seed or migration that violates it is rejected.

Division structure

Division 4.1 — General (unspecified vehicles, rail, aviation, sea)

The baseline division. Used for vehicles where the emission standard cannot be established, and for all non-road modes. The CH₄ factors for road vehicles in this division are the highest of the three divisions.

Division 4.2 — Post-2004 light vehicles

Light vehicles (≤ 3.5 t GVM) manufactured after 2004 emit less methane and nitrous oxide per GJ than older equivalents. Division 4.2 captures this with lower CH₄ and N₂O factors.

Division 4.3 — Heavy vehicles by Euro standard

Heavy vehicles (> 3.5 t GVM) are assigned factors by Euro emission standard. Euro IV+ vehicles produce significantly less CH₄ than Euro I vehicles (0.07 vs 0.20 kg CO₂-e/GJ), reflecting cleaner combustion in modern engines.

Factor values (reporting years 2023–2026)

Factors are identical across reporting years 2023–2026 for all currently seeded vehicle classes.

Road — Division 4.3 (heavy vehicles, diesel)

Vehicle class	EC (GJ/kL)	CO₂	CH₄	N₂O	Scope 1	Scope 3
heavy_vehicle_euro4	38.6	69.9	0.07	0.4	70.37	2.1
heavy_vehicle_euro3	38.6	69.9	0.10	0.4	70.40	2.1
heavy_vehicle_euro1	38.6	69.9	0.20	0.4	70.50	2.1

All factors in kg CO₂-e/GJ. EC = energy content.

Road — Division 4.2 (post-2004 light vehicles)

Vehicle class	Fuel	EC (GJ/kL)	CO₂	CH₄	N₂O	Scope 1	Scope 3
light_vehicle_post2004_diesel	Diesel	38.6	69.9	0.01	0.5	70.41	2.1
light_vehicle_post2004_petrol	Petrol	34.2	67.4	0.02	0.2	67.62	1.8
light_vehicle_post2004_lpg	LPG	26.2	60.2	0.50	0.3	61.00	1.5

Road — Division 4.1 (unspecified / pre-2004)

Vehicle class	Fuel	EC (GJ/kL)	CO₂	CH₄	N₂O	Scope 1	Scope 3
road_vehicle_unspecified_diesel	Diesel	38.6	69.9	0.10	0.4	70.40	2.1
road_vehicle_unspecified_petrol	Petrol	34.2	67.4	0.60	1.6	69.60	1.8

Rail — Division 4.1

Vehicle class	Fuel	EC (GJ/kL)	CO₂	CH₄	N₂O	Scope 1	Scope 3
diesel_locomotive	Diesel (rail)	38.6	69.9	0.10	0.4	70.40	2.1

Aviation — Division 4.1

Vehicle class	Fuel	EC (GJ/kL)	CO₂	CH₄	N₂O	Scope 1	Scope 3
jet_aircraft	Jet A-1	36.8	69.6	0.01	0.6	70.21	2.0
turboprop	Avgas	33.1	67.0	0.06	0.6	67.66	2.0

Sea — Division 4.1

Vehicle class	Fuel	EC (GJ/kL)	CO₂	CH₄	N₂O	Scope 1	Scope 3
vessel_fuel_oil	Heavy fuel oil	39.7	73.6	0.08	0.5	74.18	2.3
vessel_diesel	Marine diesel oil	38.6	69.9	0.10	0.4	70.40	2.1

Factor versioning and immutability

Each factor row in the database includes a reporting_year column. Once a factor row is created for a given year, it is never updated — historical calculations are always reproducible using the same factor.

If the NGER Determination is amended, EmWise adds new factor rows for the affected reporting years going forward. Existing rows for completed reporting years are not touched.

Annual update process

New factor values are typically published by the Clean Energy Regulator before each 1 July period start. When an update is available:

1. New factor rows are inserted for the upcoming reporting year via a database migration
2. The seed file is updated to include the new year
3. Existing factor rows for prior years remain unchanged

The platform is currently seeded with factors for 2023, 2024, 2025, and 2026.