Several ships in Singapore and Rotterdam reported operational problems in recent months after using marine fuel blended with cashew nutshell liquid biofuel, fuel testing agency CTI-Maritec said in an advisory on Thursday.

Singapore-based CTI-Maritec said it tested samples from the affected ships and found the marine fuel was blended with cashew nutshell liquid that came from undeclared source materials or production processes.

The ships had reported operational problems including fuel sludging, injector failure, filter clogging, system deposits and corrosion of turbocharger nozzle rings, the agency said.

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CTI-Maritec did not name the vessels or shipping lines involved, and it was not immediately clear how many ships were affected.

The Maritime and Port Authority of Singapore and the Port of Rotterdam did not immediately respond to a request for comment.
CTI-Maritec advised ship-owners not to use 100% cashew nut liquid as a marine fuel or as a blending component, or unestablished bio-products in marine diesel engines.

It said their use would contravene guidance from the International Maritime Organization on the supply of fuel oil to ships.

Cashew nut liquid is a non-FAME (fatty acid methyl ester) biofuel, which is a byproduct of the cashew nut industry. While it has been touted as an alternative renewable fuel, it also has high acid values and is corrosive.

Ship-owners have been exploring various marine biofuel blends as an alternative to dirtier bunker fuels in order to cut emissions.

The latest version of the ISO 8217 marine fuel specification specifies the use of accepted biofuels including FAME-based biofuels and hydrotreated vegetable oil.

There is no marine fuel specification available for cashew nut liquid from any authorized body, CTI-Maritec said.