Is FAS actually cheaper than Sodium Hydrosulfite?

This is perhaps the most important purchasing question.

The comparison should never be:

USD/MT of FAS vs. USD/MT of Sodium Hydrosulfite

Instead, calculate:

Cost per ADT of pulp

Sodium Hydrosulfite Process

Dosage × Price = Chemical Cost / ADT

FAS Process

FAS Dosage × FAS Price

NaOH

Chelant, if required

Other incremental chemical costs

= Total Chemical Cost / ADT

Then compare the two processes at the same target brightness.

Example

If:

DIP production = 100,000 ADT/year

Existing Sodium Hydrosulfite dosage = 9 kg/ADT

Sodium Hydrosulfite price = USD 1,000/MT

Annual Sodium Hydrosulfite cost:

100,000 × 9 kg × USD 1/kg

= USD 900,000/year

If the optimized FAS process requires 3 kg/ADT at USD 2,050/MT:

100,000 × 3 kg × USD 2.05/kg

= USD 615,000/year

In this hypothetical example, FAS is cheaper on chemical purchase cost alone: about USD 615,000/year versus USD 900,000/year for Sodium Hydrosulfite, a saving of roughly USD 285,000/year.

However, the final comparison must also consider:

Actual dosage

Brightness achieved

Chemical stability

Wastewater treatment

Safety/handling

Storage losses

Process efficiency

Other chemical savings

The final decision should therefore be based on total cost per ton of acceptable pulp, not product price alone.