How is your carbon footprint calculated ?

 

Your carbon footprint refers to the amount of greenhouse gases that you generate in the form of carbon dioxide. The amount of carbon dioxide generated is is typically expressed in metric tonnes (tCO2).

The vast majority of carbon dioxide emissions generated by individuals are generated through transportation or heating (and cooling) of homes. More specifically, the burning of gas, oil or other fossil fuels results in the release of carbon dioxide. In the case of cars or airplanes, this occurs directly in the combustion chamber of the engines and the associated emissions are known as direct emissions since they occur at the point of consumption. When we consume electricity, the emissions are indirect since they occurs at the generation plant and not at the point of consumption.

The amount of carbon dioxide generated by direct emissions can be calculated through the use of emission factors. An emission factors is the ratio of carbon dioxide generated for a given quantity of fuel. It varies from fuel to fuel but is dependant only on the fuel type . Indirect emissions from electrical power consumption are estimated through the use of electrical emission coefficients. This number varies by region and location. For example, areas that depend on coal for power generation have higher coefficients than areas using oil. Hydroelectric power has the lowest coefficient since it does not rely on combustion for power generation. 

Here are some more details on each of the components of the carbon footprint calculations:

Calculating carbon emissions from your home

• Emission factors for the various fuel types are based on factors published by the US Energy Information Administration (EIA).
• Electrical emission coefficients for Canada and Europe are based on data published by the International Energy Agency (IEA). US electrical emission coefficients are based on data published by the US Energy Information Administration (EIA).
• There are very large variations in electrical emission coefficients from region to region due to the various sources of power generation.
•  In Canada, Quebec which draws almost all of  its electrical energy from Hydroelectric power, has the lowest coefficients. Ontario also has a relatively low electrical emission coefficient due to some reliance on nuclear energy. Alberta, with a very heavy reliance on fossil fuels, has the highest coefficient.
• In the US, the median coefficient is higher than in Canada due to a heavier reliance on fossil fuels and particularly due to the use of coal. Amongst the states with the lowest coefficients are Vermont, Oregon and Idaho with the highest coefficients occurring in North Dakota, Indiana and Wyoming.
• In Europe, countries that rely on hydroelectric and nuclear power such as Norway and France have low electrical emission coefficients. Germany, Italy, Spain and Greece are amongst the highest. 

Calculating carbon emissions from your cars

• Car emissions are directly related to the quantity of fuel burned which is in turn related to the fuel efficiency of your car.
• Fuel efficiencies vary from model to model but also depend on driving conditions (eg. highway versus city driving). Be sure to use a fuel efficiency factor that reasonably reflects your driving patterns.
• Your carbon footprint is calculated using an assumption of 19.6 lbs/gal of gasoline and 22.4 lbs/gal of diesel
• Although the combustion of 1 lb of  diesel results in the release of more emissions that 1 lb of gasoline, a pound of diesel typically translates into a larger travel distance . Overall emissions effectiveness thus depends on fuel efficiency.

Calculating carbon emissions from air travel

• Air travel definitions and factors are from the GHG Protocol Mobile Combustion Tool. The emissions factors for short and long haul flights are originally from the UK Department for Environment, Food and Rural Affairs (DEFRA).
• Aircrafts consume more fuel during takeoffs and landings and thus short haul flights have a higher per unit distance consumptions that longer flights.
• A higher portion of the overall consumption is assigned to business class flyers since these seats occupy mores space (a factor of 1.3 is used versus economy class).
• Charter flights are typically operated at higher occupancy rates and this results in lower per person contributions than regular flights (a factor of 0.8 is used versus regular economy flights).

Calculating the carbon footprint of business or corporations is significantly more complex and involves a thorough evaluation of all operations. Please contact  ZeroGHG for help with calculating your corporate footprint.

ZeroGHG can also provide you with assistance in calculating the carbon footprint of your for conferences and events.