When building a greenhouse gas (GHG) inventory, the emission factor (EF) database you choose directly impacts the accuracy, credibility, and comparability of your results.
Good factor selection ensures that your footprint:
Stands up to audit and compliance checks (CSRD, GHG Protocol, CDP).
Reflects real-world emissions hotspots for effective reduction planning.
Remains transparent and credible with stakeholders.
The hierarchy of preference
Not all emission factors are created equal. To maximise accuracy, use this hierarchy when selecting factors:
Supplier-specific data - Best source, when available (e.g., your electricity supplier’s own emission factor or supplier-provided product footprints).
Activity- or process-specific factors - Close match to your actual activity (e.g., litres of diesel combusted in a specific vehicle type).
Geographically specific national/regional factors - Government or regional databases (e.g., AUS DCCEEW for Australia, DEFRA for the UK, NZ ME for NZ, EPA for the US)
Industry-average factors - Sector-wide averages published by governments, industry associations, or research bodies.
Generic or proxy factors - Global averages or spend-based models (e.g., EXIOBASE). Useful as a fallback but less precise.
Key criteria for selecting an emission factor database
When comparing databases, ask:
Geographic specificity – Does it reflect where the activity happened (country or region)?
Industry relevance – Does it cover your sector (e.g., aviation, aluminium, retail supply chains)?
Activity detail – Does it match the process (e.g., natural gas for heating vs. gas for electricity generation)?
Time relevance – Is the factor valid for your reporting year? Grids and processes change over time.
Reliability – Is it published by a recognised authority (government, IPCC, respected LCI database)?
Transparency – Does it provide documentation on sources, methods, and uncertainty?
Common emission factor database types
Governmental databases
Free, region-specific, often used for compliance.
Examples: DEFRA (UK), EPA (US), NGA (Australia), CO₂emissiefactoren (NL).International organisations
Provide global consistency and broad coverage.
Example: IPCC guidelines.Commercial Life Cycle Inventory (LCI) databases
Subscription-based, very detailed, strong for Scope 3.
Examples: ecoinvent, GaBi.Academic & research models
Useful for spend-based or global supply chain analysis.
Examples: EXIOBASE, GTAP.Industry-specific databases
Tailored to certain sectors, highly relevant but limited in scope.
Examples: ICAO (aviation), IAI (aluminium).
Example: applying the hierarchy
Imagine you’re reporting electricity use in the UK:
Best option → Supplier-specific factor from your provider.
Next best → DEFRA’s UK grid factor.
Fallback → IPCC global electricity average.
This ensures your footprint reflects your actual purchasing decisions and grid mix, not just a global proxy.
How Sumday helps
Selecting factors can be complex, but Sumday automates this process:
Curated mix of local, international, and industry publicly available databases on offer in our platform
Default database selection depending on the region you set for your assessment as a starting point.
Customisation, so you can import your own emission factor databases where you find more relevant options for use in an assessment
Full transparency, so you can see exactly which factor was applied and why.
This way, your results are always accurate, auditable, and trusted.
✅ Tip: Start as specific as possible (supplier or activity), then step down the hierarchy only when more detailed data isn’t available. Always document which database you used.