Volume Uncertainty
Selecting a volume uncertainty
We try to facilitate a quick and reliable assessment of volume uncertainty without causing decision paralysis by the number of individual parameters to tweak.
To that purpose, Carbon+Alt+Delete has summarised the 4-by-5 pedigree matrix presented by GHG Protocol (1024 combinations) into a predefined list of 4 realistic and distinct options.
These four levels are broadly aligned with the terminology commonly used in uncertainty classification (Very Good, Good, Fair, Poor), yet they each represent a specific combination of parameters, to be maximally representative of real-life situations.
For each option, an emblematic example is given to convey the context in which this volume uncertainty option would be applicable. You can find these examples in the table below, together with their individual indicator scores for each of the uncertainty indicators.
Ideal way to approach is to compare the given examples with your application and pick the one that aligns best with your situation.
If your situation really does not align with the predefined levels. You can try “averaging out” by alternating between the two adjacent levels over multiple inventory lines. Also, it is important to consider that the goal of uncertainty estimates is not to be endlessly tweaking parameters, but to get a good high-level overview of the degree of uncertainty across different activity categories. For the source of the uncertainty factors and the definitions of each parameter in the pedigree matrix, please consult the following sources.
GHGP Quantitative Uncertainty Guidance
GHGP Scope 3 Uncertainty Calculation Tool
Section 7.3 of Ecoinvent v2.0 data model methodology (referenced source for pedigree matrix)
Very Good
litres of diesel from invoice
Very Good
Very Good
Very Good
Very Good
Very Good
Good
Waste total in kg when original data is in number of containers
Good
Good
Very Good
Very Good
Very Good
Fair
estimate on km commuted based on employee survey
Fair
Fair
Very Good
Good
Good
Poor
electricity usage estimate for 1000 consumer products based on product info
Poor
Poor
Good
Fair
Fair
Smart Defaults for volume uncertainty
To make your life easier, and with the goal of achieving the most representative uncertainty estimate with a minimum of manual tweaking, each activity category has a predefined smart default volume uncertainty.
Below you can find an overview of the smart default value for each activity category.
Each new and existing entry will be set to the smart default, based on its activity category. It is not possible to deactivate uncertainty.
For more information on the meaning of each the volume uncertainty level, see picking a volume uncertainty.
Stationary Combustion
Very Good
Mobile Combustion
Very Good
Process Emissions
Good
Fugitive Emissions
Very Good
Electricity
Very Good
Steam, Heat, Cooling
Very Good
Goods & Services
Fair
Capital Goods
Good
Transport Upstream
Fair
Waste
Good
Business Travel
Good
Commuting
Fair
Leased Assets as Lessee
Very Good
Transport Downstream
Poor
Processing of Product
Poor
Use of Product
Poor
End-of-life of Product
Poor
Leased Assets as Lessor
Fair
Franchises
Fair
Investments
Fair
Custom
Fair
Unknown
Fair
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