CN’s Carbon Calculator Emission Factors

CN’s Carbon Calculator was created to provide an estimate of Scope 1 carbon emissions resulting from three transportation modes: vessel, rail, and trucking.

Marine vessel shipping

The marine emission factor was estimated using CN’s 2021 shipping vessel fuel consumption and associated combustion emissions and the total ton miles of the vessel fleet. The resulting factor of 10.43 g CO2e/tonne-km was crosschecked with the Fourth IMO Greenhouse Gas Study 2020. The average emission factor for the global fleet, based on 2018 data, was 6.30 g CO2e/tonne-km, with a wide range depending on ship type. For example, the average emission factor for bulk carriers was 3.94 g CO2e/tonne-km, 8.26 g CO2e/tonne-km for average container ships, and 12.74 g CO2e/tonne-km for general cargo. CN’s emission factor falls within this range, toward the more conservative end.

Rail transportation

The rail emission factor was calculated using the 2021 total locomotive fuel consumption (liters fuel/revenue tonne-km) as disclosed in CN’s 2021 Annual Report. This fuel consumption factor is multiplied by the rail diesel and biomass-based rail diesel combustion emissions factors from Canada's National GHG Inventory Report 1990-2020, accounting for CN’s average biomass-based diesel blend percentage in 2021. The overall rail emissions factor we are using in our Carbon Calculator is 13.05 g CO2e/tonne-km.

Truck transportation

The truck emission factor was calculated using average loaded truck fuel consumption of 5.34 miles per gallon based on the fuel efficiency of CN’s 2021 trucking fleet including CNTL and TransX. This fuel consumption was crosschecked with several sources for reasonableness. The ATRI 2021 study reports an average fuel economy of 6.535 mpg based on 138,930 truck-tractors operating in the US in 2020 and travelling over 12 billion vehicle miles combined. The US Department of Transportation reports an average of 6 mpg in 2019 for combination trucks. An older Canadian study was also reviewed, which reported a range from 4.51 mpg (in BC) to 5.81 mpg (in NS), based on total fuel use and distance travelled of 31,170 Class 7 and 8 trucks operating in Canada from June 2016 to July 2017. CN’s average truck fuel consumption falls within the range of the Canadian study and is a more conservative estimate compared to the two US sources. This truck fuel consumption factor is multiplied by the heavy-duty diesel vehicle (advanced control) combustion emission factor from Canada's National GHG Inventory Report 1990-2020. In our Carbon Calculator, an average shipment weight of 16.3 tons (14.8 tonnes) is used to develop an emission factor of 81.14 g CO2e/tonne-km. This can be adjusted to reflect other shipment weights by using the “Average shipment weight” field in the calculator.

The results from CN’s Carbon Calculator are meant for informative purposes only. CN cannot guarantee the accuracy and completeness of a user’s resulting greenhouse gas (GHG) emissions and net savings from its supply chain transportation activities generated by this calculator.