The shipping industry is constantly looking for alternative fuels to achieve decarbonization and mitigate its environmental impact. Yet, Alvin Foster, North Club, states that the new fuels introduced to the bunker market have been found to be diverse.Specifically, it is noted tha one particular feature of these new fuels can prove troublesome if the vessel is carrying a heat-sensitive cargo.
Very-low-sulphur-fuel oils (VLSFO) is the umbrella term for marine fuels (other than marine gas oil) having a maximum sulphur content of 0.50%. Their popularity rose since the introduction of the IMO global sulphur cap earlier this year.
Alvin Foster comments that
Early experience shows that most VLSFOs are blended products and can vary quite remarkably. Some are very low viscosity, similar to distillate fuels whereas some closely resemble traditional high-viscosity heavy fuel oil products, with most somewhere in between.
The molecular structure of the new fuels also impacts its storage and use.
It is added that wax is a challenge, as if it begins to form in the ship’s fuel storage tanks it will be very difficult to pump. Transfer pump filters and pipelines are likely to become choked. If the wax formation is extensive, the vessel’s tank heating systems may struggle to re-liquefy the fuel. Manual digging of wax out from the tank might then be required, which is a costly and time-consuming exercise.
The key, quite simply, is to keep the fuel at a temperature above at which wax starts to form,
... Foster stated.
Whatever the test method, the fuel analysis report provided to a vessel could recommend a relatively high fuel storage and transfer temperature to prevent waxing and solidification.
In such cases, there is a risk that the temperature of the fuel in tanks located adjacent to cargo holds could damage a heat-sensitive cargo. For example, according to BMT’s Cargo Handbook, a bulk cargo of raw sugar is at risk of caking at temperatures as low as 25°C. If loaded into a hold which is above a hot double-bottom fuel tank, there is a real risk of cargo damage.
Despite the challenges each fuel may experience, Mr. Foster advises that it is important to find the right temperature and "know your fuel."