Compressed Natural Gas (CNG)
Reviewed by Afonso Firmo, Co-Founder & Director · Updated 7 July 2026
Compressed natural gas has a Scope 1 emission factor of 51.53 kg CO₂-e/GJ (NGA Factors 2025). Worked examples, transport factors and a CNG calculator.
Emission Factor Value
51.53 kg CO₂-e/GJ
Try it with your own numbers
Estimated emissions
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CNG combustion is reported under Scope 1 at 51.53 kg CO₂-e/GJ (NGA Factors 2025, Table 5, standard conditions). Cubic metres are converted at 0.0393 GJ/m³. For road transport use, apply the Table 9 factors (59.0 light duty, 54.5 heavy duty) instead.
Official Source & Citation
This emission factor is sourced from the Australian National Greenhouse Accounts Factors 2025 , Table 5 — Gaseous fuels including liquefied natural gas, published by the Department of Climate Change, Energy, the Environment and Water (DCCEEW).
Citation: DCCEEW (2025). Australian National Greenhouse Accounts Factors 2025. Commonwealth of Australia. Available at: https://www.dcceew.gov.au/climate-change/publications/national-greenhouse-accounts-factors-2025
Notes
Combined Scope 1 factor of 51.53 kg CO₂-e/GJ = CO₂ 51.4 + CH₄ 0.1 + N₂O 0.03 (NGA Factors 2025, Table 5, standard conditions). Energy content 0.0393 GJ/m³. 1 GJ of CNG combusted = 51.53 kg CO₂-e. For CNG used in transport, Table 9 factors apply instead: 59.0 kg CO₂-e/GJ for light duty vehicles and 54.5 for heavy duty.
Calculation Example
If your CNG bus fleet consumed 2,400 GJ of fuel during the year:
| Working | Result |
|---|---|
| 2,400 GJ × 51.53 kg CO₂-e/GJ = 123,672 kg CO₂-e | 123.67 tonnes CO₂-e (Scope 1) |
Compressed natural gas keeps a lower profile than diesel in Australian fleet accounting, but for bus operators, waste contractors and warehouse forklift fleets it can be the largest fuel line in the Scope 1 inventory. The good news: CNG is chemically the same product as pipeline gas, so the stationary emission factor is identical and the calculation is just as simple.
The catch is that transport use gets its own factors. This entry covers both, with worked examples you can lift straight into your workpapers.
Quick Verdict
Compressed natural gas at standard conditions carries a combined Scope 1 emission factor of 51.53 kg CO₂-e per gigajoule under the NGA Factors 2025 (Table 5) — the same as pipeline natural gas, because compression changes pressure, not chemistry. Organisations combusting CNG in equipment they own or control report under Scope 1. For road transport, Table 9 substitutes higher factors of 59.0 kg CO₂-e/GJ (light duty vehicles) and 54.5 (heavy duty), reflecting methane slip from gas engines. Fleet operators, depot managers and industrial users should apply the factor that matches the end use, and can model both in a Scope 1 and 2 calculator.
How to Calculate CNG Emissions
Emissions (kg CO₂-e) = Energy consumed (GJ) × 51.53 kg CO₂-e/GJ
Convert cubic metres at 0.0393 GJ/m³ and megajoules at 1,000 MJ per GJ.
Worked Example 1: CNG bus fleet (stationary factor shown for comparability)
A council bus depot dispenses 2,400 GJ of CNG over the year.
2,400 GJ × 51.53 = 123,672 kg CO₂-e
123.67 tonnes CO₂-e (Scope 1)
(Under Table 9 heavy duty transport factors this fleet would report 2,400 × 54.5 = 130,800 kg = 130.80 tonnes CO₂-e.)
Worked Example 2: Warehouse forklift fleet
CNG forklifts consume 60,000 MJ across the year.
60,000 MJ ÷ 1,000 = 60 GJ
60 GJ × 51.53 = 3,091.8 kg CO₂-e
3.09 tonnes CO₂-e (Scope 1)
Worked Example 3: Depot metering in cubic metres
A refuelling station meters 5,000 m³ of gas at standard conditions.
5,000 m³ × 0.0393 GJ/m³ = 196.5 GJ
196.5 GJ × 51.53 = 10,125.645 kg CO₂-e
10.13 tonnes CO₂-e (Scope 1)
How CNG compares with other gaseous fuels
| Gaseous fuel | Combined Scope 1 factor (kg CO₂-e/GJ) |
|---|---|
| Hydrogen | 0.05 |
| Biomethane | 0.13 |
| Landfill biogas | 6.43 |
| Compressed natural gas (stationary) | 51.53 |
| Natural gas (pipeline) | 51.53 |
| Coal seam methane | 51.63 |
| Town gas | 60.27 |
NGER and AASB S2 Reporting
CNG combustion counts towards facility and corporate thresholds under the NGER scheme and is reported as Scope 1 using NGA factors — stationary or Table 9 transport factors depending on end use. The same split carries into your AASB S2 disclosures, where CNG sits inside your Scope 1 inventory and upstream fuel production is disclosed under Scope 3.
Related Emission Factors
Frequently Asked Questions
Disclaimer
This page is provided for general information, not professional or compliance advice. The factor shown is reproduced from the official publication cited above, and while we work to keep it current, government factors change — the publication is always the authoritative source.
- Before using this value in any formal reporting — including under the National Greenhouse and Energy Reporting Act 2007 — confirm it against the current official publication and the methods specified by the Clean Energy Regulator.
- NetNada is independent of the Australian Government, DCCEEW, and the Clean Energy Regulator. Government data is Crown copyright, Commonwealth of Australia.