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)

VOLUME Uncertainty
Emblematic example
Reliability
Completeness
Temporal rep.
Geographical rep.
Technological rep.

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.

Activity Category
Volume Uncertainty smart default

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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