# We make our own billets and roll them in the same plant. Do we count the billets as a precursor?

Canonical: https://senseible.earth/answers/cbam-own-precursor-made-in-same-installation

You can either treat billet making and rolling as one production process, or keep them separate and pass the billets' figure into rolling as a precursor. Either works if each tonne of CO2 is counted once. The usual error is adding the billet emissions twice: once as direct emissions and again as a precursor.

## Two ways to set it up

1. Combined: one production process covering melting and rolling; direct emissions of both, divided by tonnes of rolled product.
2. Separate: billets get their own figure; rolling adds its fuel plus billets consumed times that figure.

## When separate is better

If you also sell billets, you need their own figure anyway, and separating keeps rolled products from carrying melting emissions for billets that were sold.

## Check for double counting

Total CO2 attributed across all products should not exceed the installation's direct emissions plus bought precursors. If it does, something is counted twice.

## What Senseible does here

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

- [CBAM boundary with two units](https://senseible.earth/answers/cbam-installation-boundary-two-units)
- [Specific embedded emissions](https://senseible.earth/answers/cbam-specific-embedded-emissions-explained)
- [Mandi Gobindgarh rerolling mill](https://senseible.earth/answers/mandi-gobindgarh-rerolling-mill-cbam-figure)

Sources: [Implementing Regulation (EU) 2023/1773, monitoring rules](https://eur-lex.europa.eu/eli/reg_impl/2023/1773/oj/eng), [CBAM Regulation (EU) 2023/956, consolidated](https://eur-lex.europa.eu/eli/reg/2023/956/2025-10-20), [European Commission, CBAM legislation and guidance](https://taxation-customs.ec.europa.eu/carbon-border-adjustment-mechanism/cbam-legislation-and-guidance_en)

Last reviewed 2026-10-22.