Fathom World

Mapping the transformation of shipping and the oceans

Marine Environment & Fuels

ANALYSIS: The global sulphur cap: examining the options for compliance

Following the decision at MEPC 70 in October last year for a global sulphur cap of 0.5% on marine bunker fuels by 2020, the entry into force of the regulation now lies just three years away.

In this week’s spotlight article, Fathom Maritime Intelligence examines five options, coupled with their benefits and limitations, that ship owners and/or operators can embrace in order to remain compliant with the new, stringent global sulphur cap rules.

Low-Sulphur Fuel  

Low-sulphur fuels and their viscosity can have an array of complex interactions upon engine and its components that were built for residual fuel use. The switch to using low sulphur fuels requires planning ahead.

Although some industry dwellers will have become familiar to switching fuels when entering ECAs and using lower sulphur fuel, the implementation of a global sulphur cap will require increased periods of operational time on these fuels (or alternatively the use of a marine scrubber with heavy fuel oil (HFO)).  The full-time use of low sulphur fuels should be approached with some degree of caution due to their distinct behavioural differences when compared with higher more traditionally used fuels of higher sulphur content.   The fuel viscosity of a low-sulphur fuel when heated is very different to a HFO.  The primary problems of using a marine gas oil (MGO) for compliance arises from the low viscosity characteristic it retains when used by machinery designed for traditional HFO.

Furthermore, if the viscosity of the fuel in the pumps is too low, wear and scuffing can be caused by lack of hydrodynamic lubrication of the pump which can lead to increased risk of fuel leaks.  Hence maintenance and cost are exacerbated. Matching engine and component design with fuel type and its viscosity is vital, particularly when using a fuel for longer periods of time, compared with short ECA intervals.  However, one of the advantages is that distillates retain a higher thermal value, minimising engine wear and reducing maintenance, which further contributes to a reduction in fuel consumption.

Distillates have a higher energy content compared with HFO, and because of its more sophisticated quality, less sludge is generated and therefore the task of onshore sludge disposal can be reduced.

LNG Fuel

The use of liquefied natural gas (LNG) would of course eliminate the need for additional emissions reducing technology and minimise the concerns around fuels and incompatibility. Removing virtually all sulphur emissions, LNG is a promising alternative fuel to meeting global sulphur cap requirements.  However, conversion can cost more than USD 20 million, this is an option for newbuildings currently.   Dominating the LNG-conversion quandary is often the sheer size of the LNG tank, which can be detrimental to cargo carrying capacity.  LNG’s low density means that it requires excess storage, however, its higher energy value can sufficiently compensate. The storage and handling issues that surround its adoption are also significant.  Highly flammable in gaseous state, solid training and understanding of LNG behaviour is paramount.

Unable to be stored in traditional hull structural tanks like regular fuels, LNG must be stowed away from the sides and bottom of the ship as any vibrations from collisions may result in explosion as a result of LNG’s highly flammable nature when exposed to the ambient atmosphere outside of its tank.

Furthermore, the evaporation of LNG, also known as its Boil Off Gas results in pressure build-up, which can lead to tank and other component damage if excess LNG is not drained from pipes or hoses.  A Boil Off Gas Plan is therefore essential to minimise such risks, and in the case of a ship conversion, the necessary equipment and procedures must be integrated into ship design modifications.

Methanol Fuel

SOx emissions reduction to the tune of 99% can be achieved using methanol fuel and thereby its use would ensure that a ship met global sulphur cap requirements. While methanol fuels may be cheaper than LNG, they also require ship conversion.  Methanol is particularly toxic and will require additional monitoring and control systems, including overfill alarms, automatic shutdown, and ventilation and gas detection monitoring.

Cylinder Oil Lubrication

As the choice of lubricant is very much dependent on the type of fuel used, it is apparent that a change in fuel will also require a consideration in the change of lubricant.  Although this practise already takes place today when manoeuvring in and out of ECAs, using a lower sulphur fuel for longer periods of time as the global sulphur cap demands will necessitate more thoughtful consideration for the lubricant as some fuels will tolerate certain lubricants for only short periods of time whereas others are more suited to more permanent usage.

Corrosion and engine component wear is a common side-effect of not matching the lubricant to the fuel type.  Operation on low and very low-sulphur fuel doesn’t often generate very much sulphuric acid and therefore the alkaline components in the lubricating oil are not neutralised, generating compounds that are able to harm the engine and its components due to deposition, excessive wear and scuffing. Of course, engine design and operating parameters can also affect the cylinder oil requirements, but matching the type of fuel to the lubricant is an important decision that must not be underestimated.


The use of marine scrubbers in Emission Control Areas (ECAs) is common practise.  With a 2020 global sulphur cap their use could increase to around 3,800 ships, and with this comes higher maintenance and associated costs.  Breakdown potentials must be considered and accounted for to ensure compliance, not just in ECAs but worldwide. The risk of non-compliance will therefore be much higher in case of malfunction as global waters and not just ECAs are more thoroughly regulated.

Additionally, the higher energy consumption that has been calculated when using scrubbers must be accounted for if they are to function for longer periods of time. A seawater scrubber has been estimated consume around 3% more fuel, while a freshwater consumes around 1% more.

Real-Time Ship Tracking

Although not directly related to emissions, installing real-time ship tracking software can help to enable better ship navigation, avoiding bottlenecks in ports and reduce time spent idling, which can contribute to excess emissions, especially while in port. Although this is not a direct method for compliance, it will certainly help reduce unnecessary emissions.

Future Considerations

The development of SOx scrubbing technology is continually evolving and it is inevitable that future all-in-one systems that will be able to abate SOx, nitrogen oxides (NOx) and other greenhouse gases (GHG) will be developed.  The installation of multiple systems for emissions control could become redundant as ship owners drive demand for the development of a multifunctional technology to combat all emissions and comply with the development of future SOx and NOx ECAs for a zero emissions future – a very feasible long-term objective.

Ship Efficiency Review News
To contact the reporter responsible for this article, please email editor@fathom-mi.com

About Author

Comment here