One of the biggest challenges in carbon accounting is that Scope 3 emissions are often estimated using industry averages. While averages are useful when no other data exists, they don’t reflect the real emissions of your value chain or the progress your suppliers are making on decarbonisation.
According to the GHG Protocol, the North Star for carbon accounting is using primary emissions data - information reported directly by your suppliers about the goods and services you purchase. This is also known as a supplier-specific emission factor.
Until now, using supplier-specific data meant finding sustainability reports (if they existed), calculating factors yourself, and then adding them as custom emission factors in your carbon accounting.
Sumday makes this easier with the Supplier-Specific Emission Factor dataset, which is:
Compiled and standardised from publicly available supplier disclosures
Traceable back to the original supplier reports
Automated for use in the Carbon Ledger of your assessments
This enables you to use actuals over averages, creating more accurate and credible reporting.
See Sumday's co-founder Lindsay give and overview and introduction on the value of Supplier Specific emission factors in carbon accounting here.
Add the Supplier-Specific Emission Factors to Your Assessment
You can add the dataset when creating a new assessment, or update the settings of an existing one.
Go to Assessment Settings
Under Scope 3 spend databases, select Add +
Choose Sumday Supplier Specific from the list
Save your changes
Viewing Supplier-Specific Factors in the Carbon Ledger
When supplier-specific factors are available for a supplier or transaction:
A purple tick appears next to the supplier in your Carbon Ledger
Hovering on the tick shows “Emission factor available”
Selecting a transaction opens the right-hand panel where the supplier-specific factors are displayed
In the Scope / Emission Source dropdown, Sumday will suggest the most relevant supplier-specific factor. If multiple options exist (such as market-based and location-based Scope 2 data, or other years), they will also appear in the list.
Overview of a Supplier-Specific Emission Factor
When you select a supplier-specific factor in the dropdown, an overview box shows a summary of key details:
Supplier name
Reporting year
Supplier headquarters country
Boundary (reported / not reported)
Emission factor (kg CO₂e per $ spent)
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You will also see whether the factor is higher or lower than the spend based industry average emission factor for the product or service the supplier sells.
Clicking “higher/lower than spend average” switches back to the industry average factor
When using the industry average, you will also see if it is higher or lower than the supplier’s factor — and you can switch back from there
This makes it easy to compare both sources and apply your professional judgement.
Viewing Detailed Information
Sumday calculates supplier-specific factors by dividing the supplier’s total reported emissions by their operating revenue for the same reporting period. This provides a kg CO₂e per $ spent with that supplier.
To see a full breakdown on what's included in the emission factor, click View Details from the summary screen. You’ll see:
The emission factor value
The reporting year and boundary
The level of assurance over the GHG inventory and who the auditor was
Which scopes (1, 2, 3 Upstream/Downstream) are included
Reporting Currency
Operation Revenue
A link to the source where the emission data was disclosed and which page if relevant
Troubleshooting: Rules vs Supplier-Specific Factors
If a Rule has been set to apply to a supplier, the supplier-specific factor will override the rule
You can back to the industry average option by clicking the 'Higher/Lower than spend average' grey box on the emission factor summary screen, and the emission source set by the rules will be applied
A note on interpretation
While supplier-specific data provides a powerful improvement over averages, it’s not always more accurate by default. Corporate-level data reflects the supplier’s overall emissions intensity, not necessarily the footprint of each product or service you buy.
Sumday displays the source, assurance, and reporting boundary for each factor so you can assess data quality and apply your professional judgement.
For a deeper look at how these factors are calculated, and how Sumday’s approach aligns with the GHG Protocol, see:
👉 How Sumday Calculates Supplier-Specific Emission Factors
Key Takeaways
Supplier-specific emission factors help replace industry averages with primary data, making your reporting more accurate and reflective of your real value chain. Sumday automates this process while giving you the flexibility to switch between supplier-specific and industry averages, with full transparency on data sources.