What are the key principles of carbon accounting?
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The GHG Protocol sets 5 principles for a fair GHG inventory: relevance, completeness, consistency, transparency and accuracy. They guide every choice that the standards leave open. When you are unsure how to handle a source or a gap, pick the option that best meets these principles and write down why.
Relevance
The inventory must show the emissions of your business in a way that helps its users make decisions. In practice, this means choosing a boundary that matches how your business works and including the sources that matter most.
Example: a logistics company includes its subcontracted transport in Scope 3, because transport is its main business.
Completeness
Account for every source inside your chosen boundary. If you leave anything out, say what and why. A missing small office is a minor gap. A missing factory is not.
Example: a company includes the diesel generators at its remote sites, even though the data is harder to collect.
Consistency
Use the same methods over time, so that you can compare years. If you change the boundary, the method or the data, explain the change and its effect.
Example: a company that changes from an average grid factor to a newer published factor notes the change and, if the effect is large, recalculates its base year.
Transparency
Write down your methods, data sources and assumptions clearly enough that someone else can follow them. Keep an audit trail from each number back to its source.
Example: a report states which emission factor database and which GWP values it used, with their year.
Accuracy
Make sure that your numbers are neither systematically too high nor too low, and reduce uncertainty as far as you practically can. Accuracy must be good enough for users to rely on the results.
Example: a company replaces a spend-based estimate for its largest supplier with the supplier's own emissions figure.
When principles pull in different directions
Sometimes the principles conflict. For example, better data for one source (accuracy) can break the comparison with last year (consistency). The usual answer is to use the better data and explain the change. If the effect is large, recalculate earlier years too.
The GHG Protocol and the 3 scopes explains the standards that these principles come from.
Sources
- GHG Protocol Corporate Standard, chapter 1
- GHG Protocol Corporate Value Chain (Scope 3) Standard, chapter 4
