When can a steel plant report one combined CBAM figure for sinter, iron, steel and rolled products?
Only when every precursor you make on site is wholly used to make your own finished iron or steel products. The Commission's Guidance 5d calls this one joint production process, or bubble. If part of your crude steel or slabs is sold, the bubble is not allowed and each process needs its own figure.
The test in the Commission's words
Guidance Document 5d (iron and steel, 14 August 2026) says installations producing complex goods from their own precursors, such as sintered ore, pig iron, direct reduced iron (DRI), crude steel and iron or steel products, are permitted to monitor and report embedded emissions by defining one joint production process, or bubble, for all the iron and steel aggregated goods categories covered, provided that the precursors produced are wholly used to make the finished iron or steel products.
For the blast furnace route the guidance adds a narrower case. If all the liquid pig iron is used by the oxygen steelmaking process, the methodology allows a joint production process that includes crude steel, subject to the rules of Article 4, rather than pig iron as a separate process.
What the bubble saves you
In the guidance's first example, an integrated works has a sinter plant, blast furnace, converter, hot rolling, cold rolling, a rail mill and its own power plant, with one boundary drawn around the lot.
- Interim products (sintered ore, pig iron, crude steel) do not have to be monitored.
- Fuels used in more than one process do not have to be split by process.
- The one exception in that example is the electricity used to make sintered ore, which has to be singled out because indirect emissions matter only for that product.
- The carbon in and out of the whole installation is balanced with the mass balance method.
When the bubble is closed
In the second example, a plant makes stainless steel from scrap in an electric arc furnace. Some of its crude steel slabs are sold and the rest go on to its own rolling and forming. The guidance states that, because of the sale of the precursor, the bubble approach is not allowed.
That plant must derive specific embedded emissions separately for each production process: crude steel as process 1, and the finished tubes, bars and sheets as process 2, with the crude steel and its embedded emissions entering process 2 as an input.
Check your own plant
- List every intermediate your site makes: sinter, pig iron, DRI, billets, slabs.
- For each, ask whether any of it is sold or sent to another company's works instead of your own rolling and forming.
- If any does, treat the bubble as closed and set up separate production processes.
- If none does, say so in your monitoring plan, so the verifier can see why you chose one process.
Example: crude steel from a plant with slabs for sale (example figures)
- Crude steel made in the year: 500,000 t
- Rolled in your own mills: 480,000 t. Sold as slabs: 20,000 t (4%)
- Test: the precursors are not wholly used in your own finished products, so the bubble is not allowed
- Result: a figure for crude steel, a figure for finished products, and the crude steel's figure carried into the finished products as a precursor
Example numbers. The guidance says 'wholly used' and gives no percentage tolerance, so even a small sale closes the bubble.
What Senseible does here
Senseible's CBAM suite reads fuel, electricity and production documents into installation records. It does not decide your production process boundary; that is set in your monitoring plan and checked by the verifier.
Last reviewed 2026-11-04. Guidance 5d is not legally binding; re-check when the Commission updates it.