Carbon Calculator Emission Factors

CN has made every effort to provide you with the best estimates of the carbon emissions throughout a supply chain. After examining various logistics activities, we developed a set of emission factors used to estimate the carbon emissions for each transportation segment of the shipment.

Marine vessel shipping

Marine emission factors were estimated for both bulk and container shipments to account for differing emissions between the two. Based on three technical studies*, it was determined that the emission factors for larger bulk ships (Handymax to Post-Panamex size classifications) are in the range of 2.5-6 g CO2e/tonne-km. For our GHG Calculator, we are using an emission factor from within this range, specifically, 4 g CO2e/tonne-km. The emission factor for container shipping was derived from the August 2014 Clean Cargo Working Group study “Global Maritime Trade Lane Emission Factors”**.  An average of dry and reefer emissions factors over all trade lanes for 2013 was used for our GHG calculator, giving a factor of 8.3 g CO2e/tonne-km (based on an average load weight 10 tons in each container/TEU).

Rail transportation

The rail emission factor was calculated using the 2020 average rail fuel consumption (liters diesel / revenue tonne -km) as disclosed in CN’s 2020 Annual Report. This rail fuel consumption factor is multiplied by the rail diesel and biomass-based diesel combustion emissions factors from Canada's National GHG Inventory Report 1990-2019, accounting for CN’s average biomass-based diesel blend percentage in 2020. The overall rail emissions factor we are using in our GHG Calculator is 12.1 g CO2e/tonne-km.

Truck transportation

The truck emission factor was calculated based on an average truck fuel consumption of 7 miles per gallon, following an industry standard range of between 6 and 7 mpg, and in line with the results of the National Resources Canada study “Fuel Efficiency Benchmarking in Canada’s Trucking Industry”***.   This truck fuel consumption factor is multiplied by the heavy-duty diesel vehicle combustion emission factor from Canada's National GHG Inventory Report 1990-2019.  In our GHG calculator, an average shipment weight of 16 tons (14.5 tonnes) was used to develop an emission factor of 63.4 g CO2e/tonne-km.  This can be adjusted to reflect other shipment weights by using the “Average shipment weight” field in the calculator.  


Sources:

* (1) Incorporating lifecycle elements into the energy efficiency design index, C. Walsh and A. Bows, Sustainable Consumption Institute (UK);  (2) National Technical University of Athens Laboratory for Maritime Transport, Ship Emissions Study (May 2008); (3) Transport and Environment Database System (TRENDS): Maritime air pollutant emission modelling. Atmospheric Environment 39 (2005) 2357–2365, by Georgakaki, Aliki et al.

** Global Maritime Trade Lane Emissions Factors
*** Fuel Efficiency Benchmarking in Canada’s Trucking Industry, National Resources Canada