Kostik Soda (NaOH) — Frequently Asked Questions

For well-pretreated oil with low FFA, catalyst dosing is typically in the region of 0.5–1 % NaOH on oil mass, adjusted by trial. Any FFA left in the oil consumes extra caustic as soap, roughly 0.14 kg of NaOH per kg of FFA as oleic acid, so the quality of pretreatment has a direct effect on consumption.

Pearls dissolve quickly and evenly and flow well through dosing equipment, which suits continuous methoxide preparation. Flakes are widely used for batch dissolution in stirred tanks. Chemically they are the same product; the choice depends on your handling and dissolving system and on how much dust your operators can tolerate.

Sodium hydroxide absorbs carbon dioxide from air and forms sodium carbonate, which contributes little catalytic activity, so a high carbonate content reduces the effective catalyst dose. Store bags sealed, use opened stock quickly and specify a carbonate maximum, commonly around 0.8 % for solid technical grades.

Both work. NaOH is cheaper per mole and widely used. KOH costs more but dissolves faster in methanol and gives a glycerine phase containing potassium salts, which some plants value for fertiliser outlets. The choice is a process and by-product decision rather than a quality one.

Caustic soda is a process chemical, not a feedstock, so it has no Annex IX status. Where actual greenhouse-gas values are calculated under RED III or a voluntary scheme, the emissions from chemicals used in processing are included, so record consumption per tonne of product and use the emission factor your scheme specifies.

It is corrosive (UN 1823, Class 8) and dissolves with strong heat release. Wear chemical-resistant gloves and eye and face protection, add the solid slowly to liquid rather than the reverse, and keep bags closed, dry and off the floor, away from acids and aluminium. Follow the safety data sheet.