Ship engines develop allergy to cashew nut fuel

Shipowners have been told to avoid selecting fuel made from cashew nutshells, a niche fuel that has been found to cause problems in engine rooms. 

Bunker fuel tester CTI-Maritec has reported that several ships fuelling up in Singapore and Rotterdam have reported operational problems including fuel sludging, injector failure, filter clogging, system deposits and corrosion of turbocharger nozzle rings.

CTI-Maritec carried out gas chromatography mass spectrometry testing for very low sulphur fuel oil (VLSFO) samples from these vessels and found the fuel had been blended with cashew nutshell liquid (CNSL) from undeclared source materials or production processes.

CNSL is a low-cost alternative renewable fuel. It’s a substituted phenol, which is highly reactive and less stable owing to its high iodine value. CNSL has high acid values and is therefore highly corrosive as well. High potassium found in CNSL blend fuels causes serious post-combustion deposits and corrosion of turbocharger nozzle rings.

Fuel made from cashew nuts is not one of the drop-in biofuels approved by equipment manufacturers, classification societies, and flag administrations.