Emergence of new shipping fuels: biodiesels and heavy fuel oil blends

ISO 8217 is the international standard that sets out the technical specifications of marine fuels. It defines the general requirements, test methods and specifications applicable to fuels used in ship engines and boilers, prior to onboard fuel handling (storage, settling, centrifuging, filtration, heating) before use. This standard specifies the grades and categories of fuels, their physicochemical properties, as well as test methods. It defines the acceptable levels for physicochemical parameters such as density, viscosity, sulphur content, flash point, pour point and carbon residue.

The 2024 edition of this standard includes biofuels, allowing blends of conventional fossil fuels and biodiesels (Fatty Acid Methyl Esters – FAME) up to a 100% biofuel content (B100). This development comes as a direct upshot of policies aimed at transitioning the shipping industry towards lower-carbon and more renewable energy sources. The ISO 8217:2024 specifications ensure that these blends of biodiesel and conventional marine fuel comply with strict performance standards in terms of engine efficiency and reliability. The different grades of marine fuels are classified in accordance with ISO 8216-1:2024, which defines two categories of marine fuel: residual marine fuels and petroleum distillate/bio-distillate marine fuels.

The first category conventionally includes heavy fuel oils regardless of their sulphur content and, since 2024, it has included blends of heavy fuel oil and biodiesel. Under this standard, fuel suppliers and shipowners are free to determine the proportion of biodiesel used in the blend. In practice, the first trials have mainly involved B24 FAME/VLSFO blends (blends of 24% FAME with VLSFO). Over the coming years, it is likely that we will see blends containing increasing proportions of biodiesel.

The second category of marine fuels includes, in addition to marine diesels (such as MDO and MGO), blends of these conventional fuels with up to 100% FAME. B30 FAME/MGO is currently the blend most commonly in use by shipping companies. Just as with residual marine fuels, the proportion of biodiesel in marine distillates is likely to gradually increase as energy transition policies evolve.

With the emergence of these alternative fuels, CEDRE is currently conducting studies designed to provide insights into their behaviour when spilled at sea and to define the most appropriate response strategies.