How do you report Carbon Border Adjustment Mechanism (CBAM) emissions when batches of liquid fertiliser from different plants are blended in one tank?
Report one weighted average. Where batches of liquid fertiliser of the same Combined Nomenclature (CN) code from different installations are blended in one tank, they form a single functional unit, and emissions are reported as a weighted average of it. The mass balance chain of custody model cannot be used as proof of traceability.
What the Commission says
The Questions and Answers (Q&A) 4.13 start from the functional unit. Under Article 4 of Implementing Regulation (EU) 2025/2547 the default functional unit is the quantities of goods produced in tonnes classified under the same CN code. For fertilisers, the functional unit is the kilograms of nitrogen contained in the goods produced under a CN code. In the blended-tank case a functional unit consists of two different batches of the same CN code product, so emissions are reported as a weighted average of emissions of a functional unit.
What is not allowed
The mass balance chain of custody model cannot be used as proof of traceability in the CBAM. Our reading: you cannot say the low-carbon batch was the one that left the tank, and blended product carries the blended figure.
How to weight it
The Q&A does not say what the weights are. Our reading: because the functional unit for fertilisers is kilograms of nitrogen, weight each batch by the nitrogen it contributes, not by the mass of liquid. Confirm the weighting with your verifier before you fix it in the monitoring plan.
Two batches in one tank, example numbers
- Batch A: 180 tonnes of nitrogen at 2.4 tonnes of carbon dioxide equivalent (CO2e) per tonne of nitrogen = 432 tonnes CO2e
- Batch B: 120 tonnes of nitrogen at 3.6 tonnes CO2e per tonne of nitrogen = 432 tonnes CO2e
- Blend: (432 + 432) / (180 + 120) = 864 / 300 = 2.88 tonnes CO2e per tonne of nitrogen
Example numbers only. The Q&A's functional unit is kilograms of nitrogen, and 1 tonne = 1,000 kilograms, so the example uses tonnes. The weighting by nitrogen is our reading, not a figure from the Q&A.
What Senseible does here
Senseible does not trace batches in a tank or set the weighting. It reads fuel and electricity bills into dated, fingerprinted installation records for each plant.
- Fertiliser figure per tonne of product or nitrogen
- Urea ammonium nitrate and its precursors
- Mass balance for green steel is not accepted
- Senseible for CBAM
Sources: European Commission, CBAM Questions and Answers, last updated 15 October 2026, question 4.13
Last reviewed 2026-11-05. The weighting basis is our own reading, as are the sentences marked Our reading.