Menu

Methodology Overview

General

Global Warming Potentials

Where applicable, Carbonzero uses Global Warming Potentials (GWPs) from the Fifth Assessment Report of the IPCCC to generate CO2-equivalent emissions calculations.

Natural Gas Emissions

Natural gas emission factors are sourced from Canada’s National Inventory Report submission to the UNFCCC. Provincial factors are used in specific cases, whereas the average of all provinces is used in more generic calculators.

Other Stationary Fuel Combustion

Other stationary fuel emission factors, such as for Fuel Oil, are sourced from Canada’s National Inventory Report submission to the UNFCCC.

Vehicle Fuel Emissions

Greenhouse gas emissions from fuel use specific to vehicle types are calculated using Canada’s National Inventory Report submission to the UNFCCC.

Greenhouse gas emissions measured from kilometres traveled by general vehicle class are calculated using United States Environmental Protection Agency “Emission Factors for Greenhouse Gas Inventories”, EPA Centre for Corporate Climate Leadership.

Specific vehicle emission factors are sourced from the Canadian Federal Government’s Fuel Consumption Ratings database.

Electricity Emissions

Electricity emission factors are sourced from Canada’s National Inventory Report submission to the UNFCCC. United States emission factors are sourced from E-Grid.

Business Travel Emissions (Ground Travel)

Business travel emission factors for ground travel are sourced from the United States Environmental Protection Agency “Emission Factors for Greenhouse Gas Inventories”, EPA Centre for Corporate Climate Leadership.

Business Travel Emissions (Flights)

Business travel emission factors for flights are sourced from the United Kingdom’s Department of Environment, Food, and Rural Affairs Carbon Conversion Factors. Emission factors include radiative forcing as well as an uplift factor to account for sub-optimal routing.

Product Freight Emissions

Product freight emission factors are sourced from the United Kingdom’s Department of Environment, Food, and Rural Affairs Carbon Conversion Factors.

Paper Life Cycle Emissions

Environmental impact estimates were made using the Environmental Paper Network Paper Calculator Version 4.0. For more information visit www.papercalculator.org.

Westjet

Carbonzero has partnered with WestJet to effectively determine the greenhouse gas (GHG) emissions associated with the air travel of their valued guests. Each guest has the ability to calculate and offset the GHGs from their particular flight, specific to the WestJet fleet. This process has been made possible through analyzing the amount of fuel that is consumed per journey (see the Emissions model summary for the three different flight categories) over a 12-month period and creating an average emissions factor that is applied to each flight.

An average emissions factor has been identified to be the most appropriate mode of calculation of fuel consumed for individual flights. This emissions factor incorporates the time of year, emergency routing changes, the number of guests on board, and/or the amount of cargo traveling to a particular destination.

The following outlines the process and details pertinent to determining the GHG emissions of a particular flight.

Emissions model summary

The methodology for the WestJet flight carbon calculator is based on emissions factors that have been determined through the analysis of actual fuel consumption and distances travelled for the three models of planes that make up the WestJet fleet. The greenhouse gas emissions are calculated by multiplying the emissions factors by the actual distances of the three flight categories, which are as follows:

  • Short haul (less than 1200 km)
  • Medium haul (1200 – 3700 km) and
  • Long haul (> 3700 km).

In scenarios where multiple guests and/or journeys (i.e. lay overs) are applicable to a particular flight, the emissions are obtained simply by multiplying the appropriate number of guests and journeys respectively.

Model data

There are a number of models of planes that make up the WestJet fleet: the Boeing 737-600, 737-700, 737-800 and 787 Dreamliner. For a 12-month period, the actual fuel consumption, number of guests and weight of cargo per flight were analyzed to determine the amount of GHGs produced per passenger- kilometer (pkm) travelled. The emissions factors are expressed in terms of the grams of GHGs produced, or gCO2e / pkm). This data was gathered from WestJet’s internal monitoring programs. These programs are:

  • Aerodata load sheets – identify the number of guests and freight cargo weight on each individual flight.
  • Movement Manager (dispatch software) – identify the distance of each flight and the amount of fuel consumed by each series (or model of plane).

Determining the emissions factors for each flight category

Over the 12-month period, the actual fuel consumed per flight event was determined and then averaged for the three flight categories mentioned above. The steps taken to determine the gCO2e / pkm are outlined below:

  1. Identify the actual litres of aviation turbo fuel consumed per flight event.
  2. Determine the average fuel burn per pound of take-off weight (TOW) by taking the litres of fuel consumed and dividing it by the total TOW (including freight).
  3. Determine the fuel consumed by an average guest. The following equation identifies the calculation:During the sample 12-month period, an average of 78% of available seats were sold to customers.
    Screenshot from 2020 01 23 12 39 50
  4. The average litres of fuel burned per passenger on a particular flight (less fuel burned for freight) was divided by the number of kilometers travelled. The distance of each flight is based on the great-circle distance, or the shortest distance between the departure / destination airports. The result is the fuel burned per pkm.
    Screenshot from 2020 01 23 12 40 40
  5. Once the amount of fuel (litres) was determined for each flight category, the emissions were determined for CO2, CH4, and N2O.

    Flight Category Grams CO2e per Passenger Km
    Short Haul 122.87
    Medium Haul 80.83
    Long Haul 73.46