Two pulps at $780 and $830 per tonne look like an easy decision until the cheaper one needs 6% more fibre to hit the same absorption target. At that point the expensive pulp is the cheaper pulp.
The calculation
Cost per absorbed gram normalises price against performance:
Cost per absorbed gram = price per tonne ÷ (absorption capacity in g/g × yield factor)
Where the yield factor accounts for fibre lost as dust and rejects in your specific line, typically 0.93–0.97 for a well-run converting operation.
A worked example
- Pulp A: $780/t, absorption 9.8 g/g, yield 0.95 → $83.8 per absorbed gram unit
- Pulp B: $830/t, absorption 11.2 g/g, yield 0.96 → $77.2 per absorbed gram unit
Pulp B is 6% more expensive per tonne and 8% cheaper per unit of performance delivered. On 2,000 tonnes a year that difference is worth more than the entire negotiation over unit price.
What to include and what to leave out
Include absorption capacity measured by the same method for both pulps. Do not mix supplier data with your own — method differences can exceed the real performance gap.
Include yield. Dust is real money, and a pulp that generates 3% more dust is 3% more expensive than its invoice suggests.
Leave out brightness unless the product requires it. Paying for brightness you cover up with a printed top sheet is the most common waste in pulp procurement.
Why this rarely happens
Procurement is usually measured on unit price, and quality is usually measured separately by the technical team. The two numbers never meet, so the cheaper-looking pulp keeps winning contracts it should lose.
Running the calculation once, on your own line data, changes the conversation permanently. It is also the fastest way to justify a specification change to a finance team that only sees the invoice.