Calculating scope 3 category 1: from supplier data to ESRS E1 disclosure

Scope 3 category 1 — purchased goods and services — is for most companies the largest and hardest to calculate scope 3 category. The data sits with your suppliers, not with you.

Two methods under the GHG Protocol

The GHG Protocol Scope 3 Standard recognises two calculation methods for category 1. The primary method uses actual emissions data from the supplier itself. The spend-based method estimates emissions from the purchase amount and sector emission factors.

Both are permitted. The difference is not in the arithmetic but in the quality of the answer: a spend-based estimate moves with your purchasing volume, not with your supplier's actual performance. If your supplier gets cleaner, a spend-based calculation will not show it.

Primary data: the preferred method for ESRS E1

Under ESRS E1-6, companies must report the percentage of scope 3 covered by primary data. A supplier who has recorded their scope 1 and 2 in a VS profile delivers primary data. That data is qualitatively superior to a spend-based estimate.

That percentage is not a cosmetic figure. It is exactly where an auditor starts asking questions: which part of your largest emission category rests on actual measurements, and which part on an average?

How verified.supply aggregates this

For every supplier with a VS profile, verified.supply calculates the scope 3 cat. 1 contribution using the spend-attribution method: (supplier scope 1 + scope 2) × (your purchase amount / supplier revenue). For suppliers without a profile, the spend-based method is used automatically, with EXIOBASE 2023 emission factors.

Both outcomes appear side by side in the same overview, with the method used on every line. So you can see at a glance which part of your category 1 rests on supplier data and which part on an estimate.

The export

You download a single CSV with all suppliers, their scope 3 contribution, the method used and the calculation documentation. That CSV imports directly into Greenly, Normative or Coolset.

The calculation documentation is not a side note: it is the part your auditor wants to see. Without a traceable calculation, a figure in a CSRD report is no more than an assertion.