Greenhouse gas emissions from fuel use

This page provides general information about the greenhouse gas emissions we create when we use fossil fuels.

Important note: If you’re required to monitor and report your emissions, you’ll need more specific information. Please see Participating in the Emissions Trading Scheme.

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How fossil fuels cause emissions

The carbon in fossil fuel is the main thing that causes emissions. When fossil fuels are burnt, the carbon within fuel is oxidised by oxygen in the air. This process forms carbon dioxide (CO2), methane and nitrous oxide, which are emitted into the atmosphere. CO2 is the principal greenhouse gas emission from burning fossil fuels.

In some cases a tonne of fossil fuel (eg, coal) can produce more than a tonne of CO2. When carbon is oxidised, two oxygen atoms are added to every carbon atom in the fuel to create CO2. The weight of a CO2 molecule (containing three atoms) is greater that the weight of a carbon atom on its own.

Calorific values and their impact on emissions

The calorific value (CV) determines the amount of energy you get from the combustion of your fuel source. If the fuel has a lower CV then you may need to use a larger quantity to reach your required level of energy. For example, bituminous coal has a higher CV than lignite.

It’s not just a matter of simply switching to the lowest emissions fuel source. You might need to use a greater quantity to generate the same level of energy and this could in fact create more emissions.

Units of energy

Fuels and electricity are often sold on an energy basis. Energy and electricity are often expressed in different units, such as kilowatt hours (kWh) of electricity and gigajoules (GJ) of gas.

Large quantities of fuel are often sold in larger units, such as terajoules (TJ.) One terajoule of gas equals 1,000 gigajoules. The prefixes most commonly used are listed below.

Prefix Symbol Factor Term
kilo k 103 thousand
mega M 106 million
giga G 109 billion
tera T 1012 trillion
peta P 1015 quadrillion

Emissions by fuel type

The amount of carbon dioxide-equivalent (CO2-e) emissions that result from each of fuel varies between fuel types, as set out below.

Transport fuels

Transport fuel Tonnes of CO 2 e produced per litre
Petrol 0.0023
Diesel 0.0027
Aviation fuel 0.0022
Fuel Oil 0.0029

Source: Climate Change (Liquid Fossil Fuels) Regulations 2008

Coal

We’ve used average calorific values in these examples to provide an estimate. This won’t be suitable if you’re preparing a formal calculation.

Coal by type

Coal type Tonnes of CO 2 e produced per tonne of coal
Bituminous 2.47
Sub-bituminous 2.08
Lignite 1.52

Source: Climate Change (Stationary Energy and Industrial Processes) Regulations 2009

Coal by location

If you don’t know what type of coal you use, you can make a reasonable guess by location. To be sure, ask your supplier what type of coal you use and its energy content.

Location Tonnes of CO 2 e produced per tonne of coal
Waikato-Taranaki 2.08
West Coast 2.08-2.47
Canterbury 2.08
Otago-Southland 1.52-2.08

Source: Climate Change (Stationary Energy and Industrial Processes) Regulations 2009

Gas

Natural gas

Emissions from natural gas vary between fields. If you don’t know which specific field your gas comes from you can use the figures below to estimate emissions. Natural gas is normally purchased on the basis of terajoules (TJ). A small scale activity may buy it in gigajoules (GJ).

Type of gas Tonnes of CO 2 e produced per terajoule
Natural gas 53.64

Source: Climate Change (Stationary Energy and Industrial Processes) Regulations 2009

LPG

Type of gas Tonnes of CO 2 e produced per tonne
LPG 3.00

Source: Climate Change (Stationary Energy and Industrial Processes) Regulations 2009

Electricity

New Zealand has a high level of renewable electricity generation. This makes determining emissions from electricity use more complex.

When you reduce your electricity use you may be reducing production from a coal based power station, a gas-fired combined plant, or a renewable source. As all electricity is sold into the national grid –where it’s mixed together – it’s difficult to know exactly where your electricity comes from. However, the more we reduce electricity use the less fossil-fuel generated energy is needed across the country.

 

Last update: 15 October 2010