Scope 5’s TCR Resource Library includes emission factors published by The Climate Registry. TCR is "the broadest based GHG initiative in North America", with the goal of developing and managing "the premier voluntary GHG emissions registry in North America".
As such, TCR conversion factors are broadly recognized and the library is general enough to support most most Greenhouse Gas emissions reporting protocols.
The Scope 5 TCR resource library includes emission factors published by TCR from 2011 through the present. Scope 5 maintains our TCR library by incorporating annual TCR updates.
TCR offers conversion factors for many activity sectors (including such specialized sectors as the Oil and Gas Production sector and the Geothermal Energy Production sector). Scope 5's standard implementation of TCR's library includes the following subsets of emissions factors that we consider broadly applicable:
- Stationary Combustion
- Mobile Combustion
The full TCR library includes emissions factors for domestic and international electricity (sourced from the EPA and the IEA, respectively). Both sets are available to Scope 5 users as part of the Scope 5 WRI Resource Library and International Electricity Library.
If there are specialized sectors or emissions factor sets that your organization would like to see added to the Scope 5 TCR library, please contact us to discuss them.
Where the Numbers Come From
TCR sources their emission factors from other authorities, such as the Environmental Protection Agency (EPA) and the Intergovernmental Panel on Climate Change (IPCC). The emissions factors are available from TCR in this downloadable PDF.
Scope 5's implementation of the TCR library is organized into resources by resource type under the headings Biogenic, Stationary Combustion and Mobile Combustion.
Resources under the Biogenic and Stationary Combustion resource types come from TCR tables 1.1, 1.9 and 1.10 and indicate the following information parenthetically in the resource name:
- Sector - Industrial (ind), Energy (nrg), Commercial (com) or Residential (res)
- Type of input activity units (volume, weight or energy)
- Sub headings from TCR tables (gaseous, liquid, etc.)
Resources under the Mobile Combustion resource types come from TCR tables 2.1 - 2.9 (except 2.2, 2.3 and 2.8) and indicate the following information parenthetically in the resource name:
- Source table - such as Alternative Fuel or Model Year
- Type of activity units - distance (driven) or volume (of fuels)
To identify the source of a specific set of emissions factors in Scope 5, please refer to the ‘Source’ for the specific conversion factor set, as illustrated in the following example:
In most cases, TCR provides emissions factors for CO2 in one set of tables and for CH4 and N2O in a separate set of tables. Where possible, the Scope 5 implementation combines these into a single set of emissions factors for the user's convenience.
For Biomass and Stationary Combustion, TCR provides emissions factors for CO2 in Table 1.1 and emissions factors for CH4 and N2O in Tables 1.9 and 1.10. While emissions factors for CO2 are expressed both as a function of fuel mass (or volume) and heat content (energy), those for CH4 and N2O are expressed only as a function of energy.
In Scope 5's implementation of the Biomass and Stationary Combustion resources, we use each fuel's Heat Content from Table 1.1 to combine the separate emissions factors into a single table with each expressed as a function of mass (or volume). This is illustrated in the following example for the resource Fossil Fuel-derived Fuels (gaseous) - Propane (Gas) (ind) (volume).
For this resource, the 2019 Scope 5 emissions factor for CO2 (0.15463 kg/standard cubic foot) is taken directly from TCR's Table 1.1. The emissions factors for CH4 (0.003 kg/MMBtu) and N2O (0.0006 kg/MMBtu) are taken from TCR's Table 1.9, under the sub-heading for Petroleum Products. However, since these emissions factors are expressed as a function of energy, we use the Heat Content for Propane (Gas) from TCR's Table 1.1 (0.002516 MMBtu/standard cubic foot) to convert the two emissions factors such that they are expressed as a function of volume. As a result, we get 0.00000755 kg/standard cubic foot (for CH4) and 0.00000151 kg/standard cubic foot (for N2O). These are the values provided in the Scope 5 table for the resource's conversion factor sets, an excerpt of which is illustrated below.
For Mobile Combustion, TCR also provides emissions factors for CO2 in tables separate from CH4 and N2O. While CO2 emissions factors are expressed in units of emissions/fuel volume, CH4 and N2O emissions factors are expressed in units of emissions/distance driven. In this case, it isn't possible to combine the two sets of emissions factors - doing so would require assuming a certain fuel efficiency (in units of distance/volume or mpg).
An exception to the above rule derives from TCR's SEMS Table 2.9 which expresses CH4 and N2O emissions for gasoline and diesel vehicles as a proportion of CO2 emissions. These proportions are used to generate the CH4 and N2O emissions factors for the resources under the SEMS sub-heading in the Scope 5 implementation.
Users wishing to use a single set of mobile combustion resources to calculate CO2, CH4 and N2O emissions are advised to use the SEMS resources from Scope 5's TCR library or to use mobile combustion resources from Scope 5's implementation of the WRI resource library (which combines emissions factors for CO2 with those for CH4 and N2O by assuming certain fuel-efficiencies).
A Note on Date Ranges in Mobile Combustion resources
TCR provides mobile combustion emission factors for each model year of vehicle as well as an aggregate emission factor that spans a range of model years. The aggregate factor applies to all vehicles from 1983 through the latest date for which TCR has published numbers. One year is added with each release. For example, the mobile combustion date range in the 2016 Default Emission Factors was 1983 to 2013; the 2017 factor ranges from 1983 to 2014.
Starting with TCR's 2017 release, Scope 5 will not be adding new aggregate resources for each release. Instead, Scope 5's TCR resource library will combine the incremental aggregate sets for each vehicle type from each release into a single resource for each vehicle type. The resource will be named with the suffix Model Years 1983 or Newer. Scope 5 will accommodate TCR's subsequent updates to the aggregate resources by adding a new conversion factor set with the appropriate effective date for each update.
TCR periodically incorporates emissions factor updates from the EPA and other sources. TCR releases their yearly emission factor updates typically in the January/May timeframe. Scope 5 will update our TCR Resource Library soon after the TCR release. At times, TCR releases an emissions factor update later in the year to reflect updates from EPA’s eGrid and potentially other resources. Scope 5 will evaluate the mid-year update to determine if any resources in the Scope 5 library should be updated.
The emission factors released by TCR vary from time to time due to rounding. As such, users may find relatively small variations that are not attributable to actual changes in activity so much as to changes in the rounding of TCR's emission factors on certain years.
A Note on Heating Values
For all values by energy - for which the denominator is in mmBtu (or any energy unit) - Scope 5 has chosen to use the Higher Heat Value (HHV), as opposed to the Low Heating Value (LHV), to calculate the emissions factor. In GHG reporting the HHV is the more conservative value as it is always slightly higher or equivalent to the LHV, resulting is a slightly higher (or equivalent) emissions factor than would be calculated by using the LHV.
Global Warming Potentials (GWPs)
Following the Greenhouse Gas Protocol recommendation, all Scope 5 standard resource libraries use global warming potentials from the IPCC's Fifth Assessment Report (AR5) as of February 13, 2017.
Scope 5 cannot guarantee that by using the Scope 5 TCR Resource Library users will produce a report that is fully compliant with The Climate Registry. We recommend working with your verifier and/or with a sustainability consultant well versed in GHG emissions reporting to be sure that your report will be fully compliant with the protocol under which you are reporting. Scope 5 can provide customized resource libraries on a case-by-case basis.
Wolf Lichtenstein is the Principal of Lightstone Consulting, LLC and of Evergreen Carbon, an organization dedicated to promoting sustainable development through carbon offsets. With many years of auditing Greenhouse Gas inventories and carbon offset projects, Wolf has been a technical adviser to Scope 5 since 2010. Wolf can be reached at firstname.lastname@example.org or at email@example.com.