Primary vs. secondary data: why clients won't settle for an estimate
Two companies can report the exact same CO2 emissions, and yet an auditor will value those figures very differently. The difference lies in where the data comes from: is it an actual measurement, or an estimate based on an industry average? Under ESRS E1, this is the distinction between primary and secondary data, and disclosing which one you use is mandatory.
What is secondary data?
Secondary data arises when a company doesn't have actual figures from a value-chain partner and instead uses a generic emission factor — for example, "average CO2 emissions per euro spent in the construction sector". That's a reasonable assumption, but it says nothing about how sustainably your specific business actually operates. Two suppliers with very different footprints end up assigned the same number.
What is primary data?
Primary data comes directly from the value-chain partner itself — in this case, from you as the supplier. Your own energy use, your own emission factors, your own fuel consumption. This is the highest quality tier under ESRS E1, because it reflects the actual situation instead of an industry average.
Why this distinction matters to the auditor
CSRD-obligated companies must disclose what percentage of their scope 3 data is primary versus secondary, and that percentage is expected to improve year over year. A buyer who can only show estimates therefore scores worse with their own auditor than one who can demonstrate that X% of their suppliers provide their own, verified figures. That's the direct, financial reason clients are increasingly reaching out to you: every supplier that switches from an estimate to their own data improves their quality percentage.
How this shows up in your VSME profile
In the verified.supply wizard, you mark each data point as either measured or estimated (`is_estimated`) and record where the data comes from (`source`). That classification then appears explicitly in the Supplier Evidence PDF and the machine-readable export your client receives — including the emission factor, its source, and the year. Nobody has to guess: the data you supply is demonstrably primary data.
Frequently asked questions
- What is the difference between primary and secondary data?
- Primary data comes directly from the value-chain partner itself (e.g. your own energy use); secondary data is an estimate based on a generic industry average. Primary data counts as the highest quality tier under ESRS E1.
- Why does my client specifically ask for my own figures?
- Because they're required to disclose what percentage of their scope 3 data is primary, and that percentage needs to improve. Your own data directly raises that percentage; an industry average does not help them.
- Is an estimate allowed if I don't have exact figures?
- Yes, a well-substantiated estimate is allowed, but it must be explicitly flagged as such (`is_estimated`). Where possible, a measured or invoiced figure is always preferable to an estimate.
- How does verified.supply make sure my data counts as primary?
- Every data point in your profile gets a source and estimation label, and the Supplier Evidence PDF and export show that classification alongside the emission factor and year — so the origin of your figures is fully traceable for your client's auditor.
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