The rising demand for low to zero carbon fuels has led to increased interest in alternative sources, particularly in the transport sector, to meet environmental regulations. While Fatty Acid Methyl Esters (FAME) are widely used for biofuels, their high demand often outpaces supply.
This has turned attention towards Cashew Nut Shell Liquid (CNSL), a byproduct of the cashew industry, as a potential alternative biofuel. CNSL is a cost-effective renewable fuel distinct from traditional FAME biofuels.
It is a substituted phenol characterized by high reactivity and lower stability due to its elevated iodine value. Apart from its fuel applications, CNSL is also utilized for producing plastics, resins, adhesives, laminates, and surface coatings.
Its high acid value (> 3mgKOH/g) makes it highly corrosive and problematic, contributing to the formation of gums and deposits. Despite the advantages of CNSL, such as enhanced lubricity and energy content, it can cause significant operational issues, including fuel sludging, injector failures, and corrosion of engine parts.
Reports from 2022 suggest widespread contamination of conventional fuels with CNSL in the ARA region, leading to these complications. There have been instances where no operational problems were reported, even with CNSL blended fuels, indicating variability in performance.
Recent testing conducted by VPS indicated mixed results for CNSL blends with different marine fuels, with high sulphur fuel oil blends performing poorly due to negative interactions. It was emphasized that CNSL is not classified as a permissible component under the ISO 8217 standard, potentially categorizing it as a contaminant.
Recommendations for owners and charterers include confirming with suppliers the presence of CNSL in fuel and conducting advanced testing. For biofuels, further testing and verification of sources are essential, as CNSL biofuels do not conform to the ISO 8217 standard, necessitating cautious approaches to handling and usage.