How do I work out precursor emissions when I buy the same steel from several suppliers?

Take each supplier's embedded emissions per tonne and weight it by the tonnes you consumed from them in the period. Where a supplier gives no figure, use the default value for that share. Keep the purchase register that shows tonnes by supplier, because the verifier will check the weights.

Steps

1. List tonnes consumed from each supplier in the reporting period.
2. Collect each supplier's figure and installation details.
3. Multiply and add, then divide by total tonnes used.

Stock

Use tonnes consumed, not bought. Opening and closing stock shift the weights when purchases are lumpy.

Worked example

• Mill A: 600 t at 2.0 t CO2 per t = 1,200 t CO2
• Mill B: 400 t at 2.5 t CO2 per t = 1,000 t CO2
• Weighted precursor figure: 2,200 / 1,000 t = 2.2 t CO2 per t

What Senseible does here

Senseible reads fuel, power and production records into dated, fingerprinted installation records, the starting point for the actual emissions your EU importer asks for.

• Where to find default values
• Fuel stock: bought or burned

Sources: Implementing Regulation (EU) 2023/1773, monitoring rules, Implementing Regulation (EU) 2025/2621, CBAM default values, European Commission, CBAM legislation and guidance

Last reviewed 2026-10-22.