Several ships in Singapore and Rotterdam have recently reported issues after using cashew nutshell marine biofuel.
Reported operational problems included fuel sludging, injector failure, filter clogging, system deposits and corrosion of turbocharger nozzle rings. CTI-Maritec carried out extended gas chromatography mass spectrometry testing for very low sulphur fuel oil samples from the vessels. The results showed the fuel was blended with Cashew Nutshell Liquid (CNSL) from undeclared source materials or production processes.
CNSL, a non-FAME biofuel, is a naturally occurring byproduct of the cashew nut industry and acts as a low-cost alternative renewable fuel.
It has high acid values and is therefore highly corrosive as well. High potassium found in CNSL blend fuels cause serious post-combustion deposits and corrosion of turbocharger nozzle rings.
The latest version of ISO:8217 specifies the accepted biofuels such as FAME-based biofuels, hydrotreated vegetable oil, defined by the specifications of EN 14214, ASTM D6751 and EN 15940 respectively. These fuels are now established and acknowledged by equipment manufacturers, classification societies and flag administrations as ‘drop-in’ fuels. There is no specification available for CNSL from any authorised body like above.
CTI-Maritec has recommended shipowners should not use 100% CNSL as a marine fuel or use CNSL as a blending component in marine fuel, which is contrary to the guidance by IMO on best practices for suppliers on the quality of fuel oil delivered to ships.