Scope 5 WRI Library - Explanation of Mobile Combustion Resources

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There are several groups of Mobile Combustion Resources defined for the Scope 5 WRI library. While these are all derived from the WRI data (which in turn is often derived from other data), they may not all be directly listed in the WRI tools. These notes describe the manner in which the resources and their conversion factors are derived.

Note that the intent in deriving resources/emissions factors in this manner is to simplify Scope 5’s customer’s emissions calculations while remaining faithful to the WRI numbers. For example, the derivation of Scope 5’s Transport by Fuel Use resources amounts to combining WRI tables 10 and 11 (as described below).

Sub-Type: Transport by Fuel Use

Resources of this sub-type are intended to be used when activity data is available in the form of fuel volume. Resources are named according to the type of vehicle used (and possibly the vehicle year), the type of fuel used and the region in which the vehicle is used (US or UK). Conversion factors for these are all taken directly from tables 10 and 11 on the WRI’s Transport Fuel Use tab of the Emission-Factors-from-Cross-Sector-Tools-(April 2014) spreadsheet.

Resources in this sub-type are defined for each of the activities defined in the Transport and Fuel column of table 11 (CH4 and N2O Emission Factors by Fuel), except for activities with Fuel Unknown and activities named Other. For each resource, the CH4 and N2O conversion factors are taken directly from the corresponding activity row in table 11. The CO2 conversion factors are taken from the best match for the corresponding fuel type in table 10.

Sub-Type: Transport by Distance

Resources of this sub-type are intended to be used when activity data is available in distance traveled. Resources are named according to the type of vehicle used (and possibly the vehicle year), the type of fuel used and the region in which the vehicle is used (US or other, UK to be added in the future). Conversion factors for these are all taken directly from table 12 on the WRI’s Transport Vehicle Distance tab of the Emission-Factors-from-Cross-Sector-Tools-(April 2014) spreadsheet.

Resources in this sub-type are defined for each of the activities defined in the Vehicle and Fuel and Vehicle Year column of table 12 (CO2, CH4 and N2O Emission Factors for US and other regions by Vehicle Distance), except for activities with Fuel Unknown. Conversion factors for the Scope 5 resources are derived from the WRI tables according to the following rules:

CO2 (or biogenic) factors are taken from column ‘N’, CO2 (or column ‘O’, CO2 – Biomass Fuel) where available. Note that conversion factors for CO2 are not available for activities with fuel type CNG. For these, the CO2 conversion factor is calculated using the WRI’s Transport_Tool_v2_5-1_0 spreadsheet, Activity Data tab. Specifically, the spreadsheet is used to produce the weight of CO2 generated per gallon (US) of CNG fuel burned. Then, the result is divided by the mileage assumed for the corresponding vehicle type (from table 12), to get CO2 emissions per mile.

CH4 and N2O conversion factors are not included for Scope 5 resources that are defined for the region Other. This is because the emissions of these component gases depend largely on the specifics of the engine type, which are assumed by WRI for US and UK regions, but not for other regions.

For the US region, the conversion factors for CH4 and N2O are taken from columns ‘D’ and ‘G’ of table 12, respectively, for the corresponding activity.

Sub-Type: Public Transport by Distance

Resources of this sub-type are intended to be used when activity data is available in distance traveled. Resources are named according to the type of vehicle and the region in which the vehicle is used (US, UK or other). Conversion factors for these are all taken directly from table 16 on the WRI’s Reference – EF Public tab of the Emission-Factors-from-Cross-Sector-Tools-(April 2014) spreadsheet.

Resources in this sub-type are defined for each of the activities defined in the Vehicle and Type column of table 16 (CO2, CH4 and N2O Emission Factors by Passenger Distance). Conversion factors are taken directly from the corresponding activity row in table 16.

General Notes

  • All resources are configured to use AR5 when calculating the GWP totals (either CO2e or ‘biogenic’).
  • Passenger vehicles might be the best choice for commute tracking when personal or rental cars are used. Resources for these are found under the Transport by Fuel Use and/or the Transport by Distance sub-types.
  • The Transport by Distance sub-type resources use conversion factors that assume a certain average mileage for the vehicle (in order to estimate volume of fuel actually consumed based on distance activity units – these are available in the referenced table 16).
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