Cashew nut biofuel blends present major operational challenges for vessels

As the maritime industry seeks renewable and environmentally friendly fuels to meet stringent emissions regulations, Cashew Nutshell Liquid (CNSL) is emerging as a potential feedstock for biofuel production.  Derived as a byproduct of the cashew nut industry, CNSL can be processed and blended with conventional fuels, offering a renewable option for reducing greenhouse gas emissions.

According to David Browbank, Fuel Chemist at Brookes Bell, CNSL has gained attention as a potential component in marine fuel blends for several reasons.  “As a byproduct of the cashew nut industry, CNSL is a renewable and readily available feedstock that can be extracted efficiently.  It is also more environmentally friendly than traditional fossil fuels, making it a suitable option for meeting carbon emission targets.  Additionally, a strong cashew nut harvest can result in an abundant and cost-effective supply of material for biofuel production.”

Despite its potential benefits, early reports suggest that use of CNSL as a marine fuel blend component may have contributed to operational issues.  These include fuel sludging, filter clogging, system deposits, and corrosion of fuel pumps, injectors and turbocharger nozzle rings, leading to significant maintenance requirements and operational disruptions.

David noted that part of the reason why these issues are occurring is due to CNSL still being in the early stages of development.  “There is still not a lot of literature or field trial data to support CNSL as an established bunker fuel blend component in its raw, unprocessed form.  Already we are seeing that some engines cannot handle this blend component.  To date there has been one notable trial with successful results, this however was highly processed and blended with a high percentage of Marine Gas Oil (MGO). “Some engines have used it without any problems, but some engines have had major issues.  This suggests there may be different percentages and/or grades of CSNL being blended into different bunker fuels.  There just isn’t enough data out there to understand how CNSL will interact with the engines.  Ship owners looking to use CSNL should be aware of the operational issues caused by this product before using it,” he added.

Brookes Bell’s team of marine engineers and fuel chemists have identified several other potential operational challenges that could come from using CSNL as a marine fuel.  These challenges include corrosion of the fuel pumps, increased risk of sludging due to the potential for high polymerisation of cashew nut-derived compounds and seizure of fuel injectors or filter blockages caused by the high oxidation rates of CNSL.

“The problem we have as fuel chemists is that you can have one engine that works perfectly well but you put the exact same fuel into another engine, and you end up with a whole host of damage or problems.  Perhaps the temperatures were slightly higher, or the pressures were slightly different.  It is also possible that different grades of CNSL are being used by different Suppliers although this is very difficult to establish and only the Supplier can really comment on what they have used to prepare the overall fuel blend. 

“Every fuel has a unique chemical fingerprint so it is unknown how the blend components will react.  This is where the added value of expert fuel chemists, marine engineers and metallurgists comes into play.  This uncertainty is creating challenges in the maritime industry as CSNL and other biofuel blend components become more readily available options for vessels looking to meet environmental targets,” David added.   

Whilst bio blends are permitted in the latest edition of ISO 8217, these are FAME blends with clearly defined characteristics and limits and do not include CNSL or any alternate bio- derived product.  With any fuel, testing is the first line of defense before it is put into use.  As CNSL gains attention as a biofuel blend component, it is believed that this biofuel and its testing will become more regular and more routine amongst testing houses.  This will enable more data to be available to be able to pinpoint any issues that may arise before the fuel is used commercially.

As more biofuel blends are introduced to the market, the risk of operational issues and potential damage to vessels may increase.  Owing to the complexities and challenges of fuel transportation, all of this have the potential to lead to fuel quality disputes between ship owners and partners.  Brookes Bell’s fuel and fuel cargo expertise, alongside our dedicated experts, regularly advise and support clients all over the globe to help mitigate their issues, undergoing vital testing and helping resolve any fuel-related disputes.