Appendix A — Derivation of fuel emission factors

A.1 The importance of calorific value

The energy content of fuels may vary within and between fuel types. Emission factors are therefore commonly expressed in terms of energy units (eg, tonnes CO2-e/TJ) rather than mass or volume. This generally provides more accurate emissions estimates. Converting to emission factors expressed in terms of mass or volume (eg, kg CO2-e/litre) requires an assumption around which default calorific value should be used.

It is therefore useful to show how we derived the per-activity unit (eg, kg CO2-e/litre) emission factors, and which calorific values we used. It is important to note that if you can obtain fuel use information in energy units, or know the specific calorific value of the fuel you are using, you can calculate your emissions more accurately.

Note that we have used gross calorific values.

A.2 Methane and nitrous oxide emission factors used in this guide

Although carbon dioxide emissions remain constant regardless of how a fuel is combusted, methane and nitrous oxide emissions depend on the precise nature of the activity in which the fuel is being combusted. The emission factors for methane and nitrous oxide therefore vary depending on the combustion process. Table A2 shows the default methane and nitrous oxide emission factors (expressed in energy units) used in this guide. The calculation in Emission factor derivation methodology shows how we converted these to a per activity unit (eg, kg CO2-e/kg) emission factors.

Note that we have used gross emission factors.

A.3 Oxidation factors used in this guide

We sourced all oxidation factors from MBIE and the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Oxidation factors have only been applied to the carbon dioxide emission factors and have not been applied to the methane and nitrous oxide emission factors.

A.4 Sector classification

Emission factors for stationary fuels are provided for the residential, commercial and industrial sectors. Consumption statistics for these sectors are based on Australian and New Zealand Standard Industrial Classification (ANZSIC) codes, with the mappings shown in table A1 used for industrial and commercial sectors.

Table A.1: Mappings used for industrial and commercial sectors
Sector ANZSIC codes
Agriculture, Forestry, and Fishing A
Mineral and Petroleum Extraction B
Food Processing C11, C12
Textiles and Leather C13
Wood, Pulp, Paper and Printing C14, C15, C16
Chemicals C17, C18, C19
Non-metallic minerals C20
Basic Metals C21, C22
Mechanical/Electrical Equipment C23, C24
Industry unallocated C25, D26, D27, D28, D29
Building and Construction E
Commercial F-G, H, I, J, K-N, O, P, Q, R-S

Table sourced from MBIE Energy Statistics Sources and Methods, November 2021 v1.2

For more information on ANZSIC 2006, see Stats NZ’s Ariā system: www.aria.stats.govt.nz/aria/

The gross GHG emission factors for fuels are taken from Annex 4 of New Zealand’s Greenhouse Gas Inventory 1990–2023.

A.5 Reference data

Table A.2: Underlying data used to calculate fuel emission factors
Emission source User Unit Calorific Value (MJ/unit) T CO2/TJ (After Oxidation) T CH4/TJ T N2O/TJ
Biofuel and Biomass
Wood - Chips Manufacturing kg 15.15 89.466667 0.024 0.0032
Wood - Pellets Manufacturing kg 18.988 89.466667 0.024 0.0032
Wood - Green Manufacturing kg 8.888 89.466667 0.024 0.0032
Wood - Chips Commercial kg 15.15 89.466667 0.24 0.0032
Wood - Pellets Commercial kg 18.988 89.466667 0.24 0.0032
Stationary Combustion of Fuels
Coal - Bituminous Residential kg 29.590041 89.13 0.285 0.001425
Coal - Sub-Bituminous Residential kg 21.64376 91.99 0.285 0.001425
Coal - Lignite Residential kg 15.255589 93.11 0.285 0.001425
Coal - Bituminous Commercial kg 29.590041 89.13 0.0095 0.001425
Coal - Sub-Bituminous Commercial kg 21.64376 91.99 0.0095 0.001425
Coal - Lignite Commercial kg 15.255589 93.11 0.0095 0.001425
Coal - Bituminous Industry kg 29.590041 89.13 0.0095 0.001425
Coal - Sub-Bituminous Industry kg 21.64376 91.99 0.0095 0.001425
Coal - Lignite Industry kg 15.255589 93.11 0.0095 0.001425
Diesel Commercial litre 38.492092 69.203964 0.0095 0.00057
LPG Commercial kg 50 59.274527 0.00475 0.000095
Heavy Fuel Oil Commercial litre 40.739295 74.537407 0.0095 0.00057
Light Fuel Oil Commercial litre 40.454041 73.021372 0.0095 0.00057
Diesel Industry litre 38.492092 69.203964 0.00285 0.00057
LPG Industry kg 50 59.274527 0.00095 0.000095
Heavy Fuel Oil Industry litre 40.739295 74.537407 0.00285 0.00057
Light Fuel Oil Industry litre 40.454041 73.021372 0.00285 0.00057
Distributed natural gas Industry GJ 54.057909 0.0009 0.00009
Distributed natural gas Commercial GJ 54.057909 0.0045 0.00009
Distributed natural gas Industry kWh 0.194608 0.000003 0
Distributed natural gas Commercial kWh 0.194608 0.000016 0
Transport Fuel
Regular Petrol Mobile Use litre 34.582233 66.020087 0.03135 0.0076
Premium Petrol Mobile Use litre 35.052833 66.223793 0.03135 0.0076
Diesel Mobile Use litre 38.137695 69.203964 0.003705 0.003705
LPG Mobile Use litre 26.54 59.274527 0.0589 0.00019
Heavy Fuel Oil Mobile Use litre 40.739295 74.537407 0.00665 0.0019
Light Fuel Oil Mobile Use litre 40.454041 73.021372 0.00665 0.0019
Aviation fuel - Kerosene Mobile Use litre 36.799907 67.934018 0.000475 0.0019
Aviation gas Mobile Use litre 33.866778 65.891495 0.000475 0.0019

Note1: The total of each gas contribution is expressed in tonnes of gas (not CO2-e as presented elsewhere in this guidance).

Note2: The solid and gaseous fuel calorific values remain unchanged from last year. Liquid fuel calorific values were updated using the MBIE energy statistics for oil, available at www.mbie.govt.nz/building-and-energy/energy-and-natural-resources/energy-statistics-and-modelling/energy-statistics/oil-statistics/.

Note3: The gross GHG emission factors for fuels are taken from Annex 4 of New Zealand’s Greenhouse Gas Inventory 1990–2023.

Note4: The assumed moisture content for wood chips, pellets and green is 25%, 6% and 56% respectively.