CBAM precursors explained: how upstream emissions carry into your good
Precursor embedded emissions travel through the supply chain. Here's how to identify, request and account for them in a CBAM declaration.
Published 19/10/2026 · Facts checked on 2026-10-18
Answer box
A precursor is an upstream input to a CBAM good that itself has embedded emissions, and those emissions carry through to the good you import. Crude steel is a precursor to flat and long steel; billet is a precursor to seamless tube; unwrought aluminium is a precursor to extrusions; wire rod is a precursor to fasteners. For steel, the sintered-ore precursor carries its indirect emissions.
Common precursors by sector
Iron and steel
- Crude steel (BF-BOF or EAF route) → downstream flat and long.
- Billets, blooms, slabs (CN 7207) → downstream rolled products and seamless tube.
- Sintered ore → carries indirect emissions into BF-BOF steel.
- DRI (direct-reduced iron) → feed to EAF.
- Scrap (recycled steel) → feed to EAF, lower embedded.
- Wire rod (CN 7213) → fasteners (7318), wire (7217), mesh.
- Hot-rolled coil (CN 7208) → welded tube (CN 7306).
- Ferro-alloys → stainless and alloy steel.
Aluminium
- Unwrought aluminium (CN 7601) → everything downstream (extrusions, sheet, wire, foil).
- Alumina → unwrought aluminium.
- Anode material → carried process emissions at smelters.
How to request precursor data
- Ask your supplier to declare their precursor suppliers.
- Where traceable, invite the precursor supplier to the system too.
- Where not traceable, default values plus mark-up apply for the precursor portion only.
What CBAMWorks does
The engine lets a supplier add precursor suppliers in their own workspace and link to their emissions data. If no data is available, defaults apply only to the precursor portion, not the whole good.