Cashewnussschalenöl (CNSL) — Frequently Asked Questions

No. Although it comes from a plant, CNSL is a mixture of phenolic lipids, mainly cardanol, cardol and anacardic acid with a long C15 side chain, rather than a triglyceride oil. That is why it cannot be made into FAME, and why its specification uses cardanol, cardol and polymer content instead of FFA.

Technical CNSL is released by heating or roasting the shells, which decarboxylates most of the anacardic acid, so cardanol predominates. Solvent-extracted, or natural, CNSL is recovered without that heat treatment and is rich in anacardic acid. The two behave differently in resins and in fuel applications, so state which type you need.

CNSL is burned as an industrial fuel oil in suitable burners and boilers, and it has been studied for pyrolysis, hydrotreating and blending into heating or marine fuels. It is not a feedstock for conventional FAME, HVO or HEFA units. Run trials on your own equipment, as its viscosity and polymerisation behaviour differ from those of fatty oils.

Buyers typically specify cardanol and cardol content, polymerised material, viscosity, specific gravity, moisture, ash, matter insoluble in toluene and loss on heating. For fuel use, sulphur, metals and calorific value are added. Ask which test methods are used, as chromatographic and titration-based results are not directly comparable.

Annex IX Part A lists nut shells, but whether a liquid extracted from cashew shells falls under that entry depends on the national authority and the scheme. Do not assume the status; confirm the classification and certificate scope with your certification body before contracting.

CNSL irritates and can sensitise the skin, so follow the safety data sheet and use gloves and eye protection. Keep it in closed containers away from strong oxidising agents, avoid prolonged heating, which promotes polymerisation, and warm it only enough to pump in cold weather.