WestJet methodology and standards

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 (1):

  • 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 three models of planes that make up the WestJet fleet: the Boeing 737-600, 737-700 and 737-800. For a 12-month period (September 2010 through August 2011) 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:

It has been determined that for each flight over the 12-month period, an average of 78% of available seats were sold to customers.

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.

5. Once the amount of fuel (litres) was determined for each flight category, the emissions were determined for each of the following greenhouse gases:

The values for each of the emissions listed above were determined by identifying the emissions from aviation turbo fuel in Canada’s National Inventory Report (2011) submission to the UNFCCC (2). The Global Warming Potentials (GWP) for each GHG was sourced from the fourth assessment of the IPCC (3).


1. UK DEFRA (2010): Guidelines to Defra/DECC’s GHG Conversion Factors for Company Reporting: Methodology Paper for Emissions Factors. Section VII.

2. National Inventory Report Canada (2010): Part 2, Table A8-11.

3. IPCC - Climate Change 2007, The Physical Science Basis – The working Group 1 contribution to the IPCC Fourth Assessment Report. Table 2.14. 100 year values taken.

Carbonzero offset cost distribution

The proportion and distribution of your investment varies according to the project type and standard associated with each offset project. Additional costs to consider when purchasing carbon offsets are advertising, broker fees, outreach, staff salaries and operating costs, among others. Please see the chart below for our average offset cost distribution:

Carbonzero offset portfolio

Carbonzero’s Signature Offset Portfolio is sourced from projects which reduce greenhouse gas emissions and support the local communities in which they are originated. All Carbonzero offsets are additional, quantified, verified by independent third parties and registered on the Canadian Standards Association CleanProjects registry or similar.

Carbonzero provides clients with a variety of projects which are governed by various standards. Carbonzero’s Signature Portfolio includes high-quality, ISO-based offsets in addition to CCBA, VER+ and VCS projects, and can build a customized carbon offset portfolio to meet your needs.

The VER+ is a carbon offset standard and closely follows the Kyoto Protocol’s project-based mechanisms (CDM and JI). The VER+ standard was developed by TÜV SÜD, a designated operational entity (DOE) for the validation and verification of CDM projects. It was designed for project developers who have projects that cannot be implemented under CDM, yet who want to use procedures similar to the CDM. The VER+ was launched in mid-2007. The revised version two of the VER+ Standard was launched in My 2008. Any DOE/AIE accredited for corresponding scopes under UNFCCC may carry out validations and verifications for VER+ projects.

The Climate, Community and Biodiversity Standard (CCB) is a partnership between leading companies, NGOs and research institutes seeking to promote integrated solutions to land management around the world. With this goal in mind, the CCB has developed voluntary standards to help design and identify land management activities that simultaneously minimize climate change, support sustainable development and conserve biodiversity.

ISO 14064-2 specifies principles and requirements and provides guidance at the project level for quantification, monitoring and reporting of activities intended to cause greenhouse gas (GHG) emission reductions or removal enhancements. It includes requirements for planning a GHG project, identifying and selecting GHG sources, sinks and reservoirs relevant to the project and baseline scenario, monitoring, quantifying, documenting and reporting GHG project performance and managing data quality.

Carbonzero’s projects adhere to the following tenets of an offset:

  • REAL — Emissions reduction or removal must be created by a specific project. The benefit must be real and reliably ascribed to a project activity — not theoretical
  • QUANTIFIABLE — Must be able to precisely account for the tonnes of CO2 equivalent reduced or removed by the project.
  • VERIFIABLE — Because of the value being placed on an intangible asset (one tonne of CO2 equivalent that is NOT in the atmosphere), one must be able to prove the reduction has occurred, and that it was the result of the project activity. All tenets of an offset must be audited before that offset is ready for use. Depending on the nature of the project, we select offsets verified to different standards, with priority currently given to ISO-14064-2 project origination standards, ISO-14064-3 project verification standards, VER+, and CCBA.
  • AUDITABLE — Verification/Validation reports delivered by accredited 3rd party verifiers.
  • REGISTERED — When possible, all projects are registered, serialized and retired publicly with the Canadian Standards Association (CSA) CleanProjects, Markit, BlueRegistry or similar reputable project registries in order to avoid double-counting or the sale of offsets to more than one entity.
  • CONSERVATIVE — In a similar vein to the requirement for verifiability, using conservative approaches to estimation, measurement and monitoring ensures that an offset is sound. One must always choose the path that does not lead to overestimation.
  • PERMANENT — The beneficial action of an offset to the atmosphere must be durable and lasting. Offsets that result from reduced use of fossil fuels are often considered permanent by default. Because protection and restoration of forests and natural systems are also critical to stopping climate change, a variety of methods have been established to show permanence. Along with smart project design, the creation of a buffer pool of unsold offsets and/or the purchase of re-emission insurance can be utilized for this purpose.
  • ADDITIONAL — The reduction or removal of greenhouse gasses by a project must be shown to be dependent on the expectation of revenues or removal of barriers caused by the fact that the project is being undertaken for offsets. This is to ensure that the offset really equals a true “-1” counterbalance to the pollution it is offsetting, rather than an emissions reduction that would have happened anyway. Projects must go beyond “business as usual” to generate offsets. The Additionality of all of Carbonzero’s projects is assessed using the CDM Additionality Tool.
  • LOCAL — Climate change is a global problem but many wish to make their solutions local. Carbonzero has built capacity to source projects in the sectors and regions that suit our clients best. We supply ‘made-in-Canada’ offsets to our home-country clients, and are processing country-specific offsets for clients worldwide.
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  • ACCESSIBLE — Proponents must allow for annual visits to project sites, and spot check audits on available and sold offset volumes.

Methodology and Emissions Factors last updated: October 14, 2011