Footprint methodology
How your carbon footprint is calculated

Version 6 - 8 February 2010

Introduction
What is and isn’t included
Offsets
Emission factors
Carbon dioxide equivalent
Staying up to date

Section A. Transport
Personal and business travel
Petrol, gas and LPG vehicles
Air Travel

Section B. Energy
Standard electricity
Green power (accredited renewable electricity) 
Natural gas 

Section C. Waste
Non-recyclable waste
Recyclable waste
Useful websites for further information

Introduction

'Carbon footprint' is a shorthand term to describe the total amount of greenhouse gas (GHG) emissions for which an organisation, household or individual is responsible.  Footprints can also be calculated for events or products.

A carbon footprint takes into account all types of greenhouse gases – not just carbon, but it is usually expressed as a carbon dioxide equivalent (CO2-e) which is a simple unit for adding up and comparing the amount of global warming caused by different greenhouse gases.

Measuring your carbon footprint can help you understand how much you are contributing to the problem of climate change, and what actions you can take to reduce your emissions.

There are many different ways of calculating a carbon footprint, ranging from a quick estimate to a comprehensive audit done by qualified experts. The degree of accuracy depends on the methodology and assumptions involved, and how much time and effort is put into collecting quality information.

The results shown by the Zero Carbon Moreland (ZCM) carbon footprint calculator should only be used for estimating the greenhouse gas emissions of your activities. The calculator should be used as a guide only and not as a substitute for formal professional advice.

What is and isn’t included

To calculate a carbon footprint, you must first define the scope of what is being measured i.e. what is and isn’t included. For example, should emissions attributable to the products you buy be included when measuring a household’s carbon footprint? Decisions about the scope of a carbon footprint will depend on the purpose for doing the footprint, the information you have available, and other considerations.

The scope of the ZCM carbon footprint calculator covers emissions related to energy use, transport and waste.  Several other sources of emissions, like those related to food production, are not included in the scope of the ZCM footprint calculator.

Offsets

A carbon offset is a way to compensate for GHG emissions from your own activities by investing in another project or activity that reduces greenhouse gas emissions or remove carbon from the atmosphere.  There are many companies now offering an array of carbon offset products.

We have chosen not to include the use of offsets in the ZCM carbon footprint calculator because as a first step, it’s important to know what all your emissions add up to, so that you can identify ways to reduce those emissions, and calculate what quantity of offsets you might decide to purchase.

Therefore we recommend that you include all your energy use, waste, and travel when using the ZCM carbon footprint calculator - even if you have purchased an offset for some of your activities.

Emission factors

An ‘emissions factor’ is a multiplier based on the standard rate of greenhouse gas emissions for a given activity. Emissions factors are used to calculate the amount of greenhouse gas emissions produced per unit of activity (e.g. grams of carbon dioxide emitted per barrel of fossil fuel consumed). They are sometimes also called ‘conversion factors’.

The emission factor chosen will depend on whether you want to include only the direct point-of-use emissions (eg. the CO2 that comes out of your car exhaust pipe) or also include indirect emissions associated with that product or activity (eg. from mining the crude oil, refining it into petrol, transporting and selling it).

Governments and international bodies such as the International Panel on Climate Change agree on standard emission factors for calculating the emissions from different activities. Emission factors are regularly being reviewed and updated based on new scientific research, changes in the way energy is produced, or amendments to the agreed way of measuring emissions.

The emission factors used in this calculator are taken from a number of sources, mainly:

2009 National Greenhouse Accounts (NGA) Factors, Department of Climate Change.  View this online here.

2008 Guidelines to DEFRA’s GHG Conversion Factors: Methodology Paper for Transport Emission Factors, Department for Environment, Food and Rural Affairs, UK www.defra.gov.uk/environment/business/reporting/pdf/passenger-transport.pdf

Carbon dioxide equivalent

Carbon dioxide equivalent (CO2-e) is a simple unit for adding up and comparing the amount of global warming caused by different greenhouse gases like methane, halocarbons or nitrous oxide.

The carbon dioxide equivalent for a gas is calculated by multiplying the actual mass of emissions by the Global Warming Potential (GWP) factor appropriate for that gas. For example, the GWP for methane (over 100 years) is 25 which means that emitting of 1 million tonnes of methane is equivalent to 25 million tonnes of carbon dioxide.

Staying up to date

Our scientific understanding of climate change and greenhouse gas emissions is rapidly evolving and improving. As new scientific evidence becomes available the methods for measuring GHG emissions and their impact need to be constantly updated and amended.

The methodology and assumptions used in this calculator will be reviewed and updated at least twice a year, to take into account policy changes, new information and the latest science.

Section A. Transport

Personal and business travel

If you are calculating your household carbon footprint include only your personal travel (ie. trips you pay for yourself) plus travel to and from your normal place of work, for each person in the household. Public transport emissions are not included, but if you are a regular taxi user you may choose to estimate how many litres of fuel are used for that travel.

If you are calculating the carbon footprint of a business or organisation, include all travel paid for by the business or organisation.

Petrol, gas and LPG vehicles

The table below shows the emission factors used to estimate the greenhouse gas emissions from 1 litre of fuel. This includes both direct emissions from burning the fuel, plus indirect emissions attributable to the extraction, production and transport of those fuels (Scope 1 & 3).

 Fuel
Volume
Emissions (CO2-e)
 Petrol 1 litre
 2.56 kg
 LPG 1 litre
 1.71 kg
 Diesel 1 litre
 2.90 kg

 

 

 





Source: 2009 National Greenhouse Accounts (NGA) Factors, June 2009

Note that our online calculator takes litres of fuel per week and converts them into emissions of CO2-e per year.  Therefore, the emissions that result by applying the above emission factors to litres of fuel per week are multiplied by 52 to get an annual figure for transport emissions.

Air Travel

Calculating greenhouse gas emissions from air travel is a tricky business! There are many factors to take into account such as: distance, type of aircraft, length of time in the air, altitude and much more. Whichever way you look at it, flying is one of the most polluting forms of travel.

The Zero Carbon Moreland carbon footprint calculator aims to give you a simple estimate of the emissions from your flights, so that you can see how flying compares to other activities like driving or running your heater. 

The emission factor used in the ZCM calculator is 0.22kg CO2-e per passenger for each kilometre flown. 
Short flights generally use more energy per kilometre than long flights, because of the extra fuel burnt during take-off and landing. This emission factor takes an average of short-haul and long-haul emission factors, plus 9% to allow for delays and indirect routes (as recommended in the DEFRA 2008 Guidelines to DEFRA’s GHG Conversion Factors: Methodology Paper for Transport Emission Factors ). 

Greenhouse gases emitted at high altitudes have a greater influence on climate change (more radiative forcing) than the same gases emitted at ground level.  The emission factor used in this calculator includes an altitude multiplier of 1.9, as recommended by the DEFRA guidelines.
 

B. Energy

Standard electricity

The emissions factor used for regular electricity is 1.35kg CO2-e per kilowatt hour (kWh). This is the “full fuel cycle factor – scope 2 & 3” which takes into account:
  • direct emissions from burning fuel  at the power plant
  • indirect emissions from the extraction, production and transport of the fuel
  • indirect emissions attributable to the electricity lost during transmission from the power station to the point of use
This emissions factor is for Victoria, which uses mainly brown coal – a highly polluting power source.
Source:  2009 National Greenhouse Accounts (NGA) Factors, Department of Climate Change.

Green power (accredited renewable electricity) 

An emissions factor of 0 is applied to Government-accredited GreenPower green electricity as participants who purchase accredited GreenPower are obtaining their electricity from emissions free renewable energy sources. For more information about the GreenPower accreditation system visit: www.greenpower.gov.au.

Natural gas

The emissions factor used for natural gas is 0.05583kg of CO2-e per mega-joule (MJ).
This factor is taken from the June 2009 NGA Factors full fuel cycle (scopes 1&3) factor and includes indirect emissions attributable to the extraction, production and transport of the gas.
Source:  2009 National Greenhouse Accounts (NGA) Factors, Department of Climate Change.

Section C. Waste

Non-recyclable waste

Litres of waste are converted to kg of waste using the 2006 AGO factors conversion from volume to waste for co-mingled waste, which assumes that 1 litre of waste weighs 120 grams.

One kilogram of non-recyclable waste is calculated to produce 1.0 kg carbon dioxide equivalent. So putting out one 120 litre bin per week (52 bins per year) emits 749kg CO2-e per year, and putting out one 80 litre bin per week (52 bins per year) emits 499kg CO2-e per year.
 
These emissions factors are based on the June 2009 NGA factors emissions factor for municipal solid waste.
Source:  2009 National Greenhouse Accounts (NGA) Factors, Department of Climate Change.
2006 Australian Greenhouse Office (AGO) Factors, Department of Climate Change.

Recyclable waste

Recycled waste is not included in the ZCM Carbon Footprint calculator because currently there is no official emission factor for co-mingled municipal recyclable waste. The Department of Climate Change reasons that where waste material is diverted from landfill to recycling, the household (or organisation) will have fewer emissions attributed to its activities because less waste is going to landfill.

Useful websites for further information

The UK Carbon Trust ‘Guide to Calculating your Carbon Footprint’ is available at:   www.carbontrust.co.uk/solutions/CarbonFootprinting
Australian Government ‘National Greenhouse Accounts Factors’ is available at: www.climatechange.gov.au/publications/greenhouse-acctg/national-greenhouse-factors.aspx