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)

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.