Our plant makes many nitrogen, phosphorus and potassium (NPK) grades on one line. How do we work out the Carbon Border Adjustment Mechanism (CBAM) figure for each grade?
Add up the year's precursors, fuel and electricity for the whole line, divide by the total kilograms of nitrogen in all the NPK grades you made to get one figure per kilogram of nitrogen, then multiply by each grade's nitrogen content. The Commission's fertiliser guide describes this route for plants that make many grades.
Why not one calculation per grade (our explanation)
A line that swaps from one grade to the next all year would need a separate set of books for each grade. CBAM is the European Union's (EU) charge on the carbon built into imported goods. For fertiliser it counts per kilogram of nitrogen, which lets one figure serve every grade, like pricing all your cloth by the metre instead of by each pattern.
The steps the guide gives
- For each component, record the total tonnes used in the year, not kilograms per tonne.
- Take as the activity level the total nitrogen in all the NPK products made, in kilograms of nitrogen. Do not split it between ammonia and urea inputs.
- Divide the total embedded emissions of the year (precursors, direct and indirect) by that nitrogen to get an average in tonnes of carbon dioxide equivalent (CO2e) per kilogram of nitrogen.
- For each grade, multiply that figure by the kilograms of nitrogen in a tonne of the grade.
What the guide assumes
It assumes granulation and drying are similar for all grades, so the plant's direct and indirect emissions can be monitored over the whole year and divided by all the fertiliser made. It also lists what must be monitored: the mass of each precursor used in the period, the recipe of each grade or an analysis of the final product, and the embedded emissions of the precursors.
What this averaging does
Our reading: because the nitrogen is averaged across all grades without separating ammonia from urea, a grade that happens to use more of the higher-emission precursor is not charged more, and a grade that uses less is not charged less. The guide describes this as the way to handle a many-grade plant.
Ask your verifier about the ranges
Earlier, the guide says emissions are averaged by composition across nitrogen-content ranges, with ranges not exceeding 10%. It does not say 10% of what here. Read Annex III, section B of the Methodology Act with your verifier before you fix your ranges.
Two grades on one line (example)
- NPK 15-15-15: 6,000 tonnes, 150 kilograms of nitrogen a tonne = 900,000 kilograms
- Grade 20-20-0 (nitrogen and phosphorus only, so not a full NPK): 4,000 tonnes, 200 kilograms of nitrogen a tonne = 800,000 kilograms. Total nitrogen 1,700,000 kilograms
- Embedded emissions of the year: precursors 4,700 + direct 160 + indirect 110 = 4,970 tonnes of CO2e
- Per kilogram of nitrogen: 4,970 / 1,700,000 = 0.0029235 tonnes (we keep the unrounded figure)
- 15-15-15: 0.0029235 x 150 = 0.4385 tonnes per tonne. 20-20-0: 0.0029235 x 200 = 0.5847
- Check: 6,000 x 0.4385 + 4,000 x 0.5847 = 4,970 tonnes, the same 4,970
Every number is an example, including the precursor total. The method is the guide's.
What Senseible does here
Senseible reads fuel invoices and electricity bills into monthly records. Reading your recipes or working out nitrogen content is custom, on request. Senseible builds the verifier-ready file and checks every figure in-house; an accredited verifier Senseible partners with signs it off, or the client sends it to their own.
- Build your fertiliser CBAM file
- NPK 15-15-15 worked example
- Nitrogen content ranges for mixed fertilisers
- Blended liquid fertiliser batches
- Verifier checks at a fertiliser plant
Sources: European Commission, CBAM Guidance No. 5c, fertilisers (14 August 2026)
Last reviewed 2026-11-07. Check the multi-grade route in section 4 of the guide, and the nitrogen-range rule in Annex III, section B of Implementing Regulation (EU) 2025/2547, before you fix your method. The guide says it is not legally binding.