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Getting the Right Fit for the Cap: Assessing the Options

17 Jul 2018

The following article is written by Alvin Forster, Deputy Director (Loss Prevention) at North P&I:

The reduction of the IMO MARPOL Annex VI global fuel sulphur cap to 0.5% will come into force on 1 January 2020. Shipowners have some very difficult and important decisions to make on how to comply with these stringent requirements.

Changes have long been driven by a combination of economics and environmental compliance. This is likely to remain true when considering the 2020 global sulphur cap. There are several options open to shipowners, with the majority currently opting for distillates, perhaps keeping one eye on the development of cheaper hybrid fuels, blends or compliant residual fuels. The choice will be driven by what is right for the vessel and what is economically viable. 

There are several options available to a shipowner that will allow compliance with the 2020 global sulphur cap. There are pros and cons with each, mostly concerning fuel availability, on-board fuel management, capital and operational expenditure as well as maintenance requirements. It is not a simple choice and the decision on what method of compliance is best depends on a number of factors, such as vessel type, trading area and remaining service life. The proportion of time spent within emission control areas (ECA) should be considered as well as the impact of changing over fuels when entering/leaving these areas. The 0.1% sulphur cap currently in operation within the ECAs will remain in force and it is possible that new ECAs may emerge in coming years. For some vessels, the best solution might be multi-fuel, such as having the ability to burn LNG or distillates, depending on the availability of each. Another method may be to install an EGCS but also use hydrogen fuel cells where appropriate. 

Compliance option 1: Burn distillates
Marine fuels are categorised as being either a distillate or a residual. Distillates are the lighter grade fuels from the refining process, the most common being marine gas oil (MGO/DMA) and marine diesel oil (MDO/DMB).


  • No major modifications or capex (capital expenditure) needed – usually limited to minor system modification and tank cleaning
  • Relatively simple changeover process between 0.5% and 0.1% fuels when transiting ECAs
  • Reduced engine maintenance demands and reduced risk of engine failure


  • Forecasted high cost – the difference in price between high sulphur residuals and compliant MGO is expected to increase significantly post-2020
  • Concerns about refineries’ abilities to meet demand in 2020
  • Potential problems with low temperature flow characteristics of some distillates
  • Over-rating of vessel steam generation capacity as there will be no longer any need to heat fuel – possibly leading to vessels having to dump steam due to no heat sink

Compliance option 2: Burn hybrids or blends
A number of producers have developed or are developing compliant products which are heavier than MGO and MDO but lighter than the residual fuel oils that are currently used. Some are specially-produced products and are commonly referred to as ‘hybrid’ fuels. Other products are the result of blending, producing a heavy distillate or light residual blend.

It may be possible that a 0.5%S residual fuel (e.g. 380cst) could be produced from either refining sweet crudes or from sour crudes undergoing a desulphurisation process. But there are currently no plans to make this widely available as a marine fuel.


  • No major modifications or capex needed – usually limited to minor system modification and tank cleaning
  • Expected to be cheaper than distillate fuels


  • Concerns about refineries’ abilities to meet demand in 2020
  • Uncertain supply can lead to price volatility
  • Heavier fuels may contain cat fines
  • Some fuels may require onboard treatment, such as centrifugal separation, viscosity control and heating
  • Some products fall outside the specified grades in ISO 8217
  • Higher risk of incompatibility if using different blends or hybrids

Compliance option 3: Install EGCS
Exhaust Gas Cleaning Systems (EGCS) are commonly referred to as scrubbers. These systems effectively wash the exhaust gas to remove sulphur dioxides and particulate matter. Post-2020, vessels operating an EGCS can continue to legally burn fuels with a sulphur content of greater than 0.5%. 

Systems are categorised as open loop, closed loop or hybrid. 

Open loop systems: Water is taken from the sea and pumped into the scrubber wash tower. The natural alkalinity of seawater neutralises the acids in the wastewater effluent. 

Closed loop systems: Recirculated seawater or freshwater is treated with an alkaline chemical before entering the wash tower to scrub the exhaust gases. A small amount of the wash water is bled-off to a treatment plant before discharge to sea, or they can be run in ‘zero discharge’ mode where the effluent is held in a tank. 

Hybrid systems: Hybrid systems can operate in either open or closed loop mode. Depending on design, they may operate with either freshwater or seawater when in closed loop mode. 


  • Capex typically US$3-5m with payback period expected to be reasonably short
  • Expected low fuel costs – some market analysts have forecasted high sulphur fuels to plummet in 2020
  • The lower fuel costs may make the vessel more attractive to time charterers


  • Systems and equipment require lot of space
  • High power demands resulting in around a 3-5% increase in fuel consumption
  • Concerns about maintenance demands and reliability which could result in periods of non-compliance
  • The long term viability of EGCS could be impacted by any future legislation on wastewater effluent discharge standards
  • The availability of high sulphur fuels post-2020 is unknown and some refineries could divert streams elsewhere if not profitable
  • The time required to retrofit EGCS on an existing vessel could take several weeks and require the vessel to be out of service

Compliance option 4: Burn LNG
One of the main drivers for shipowners to turn to LNG as a marine fuel is that it emits zero SOx and virtually zero particulate matter.

LNG is natural gas – predominantly methane (CH4) – in liquid form. Exact composition depends on source and generally contains a mix of heavier hydrocarbons (such as butane and ethane) with some contaminants such as CO2, water and nitrogen.

To make storage and handling manageable, it is condensed into a liquid at close to atmospheric pressure by cooling it to approx. -162°C.


  • Generally regarded as a very clean fuel and may be more resilient to any future changes in environmental legislation than the alternatives. 
  • Lower fuel costs
  • Green credentials


  • Relatively high capex (upgrade to gas or dual-fuel engines and storage and handling system) with expected long payback period
  • Limited infrastructure of LNG supply therefore restricting worldwide trading
  • Bunkering challenges – higher risk operation and strictly controlled
  • High delivery costs push up the real cost of fuel
  • Lower energy density compared with traditional marine fuels – therefore more volume needed
  • The global warming potential (GWP) of methane is significantly higher than CO2
  • Large tanks and restrictions on their position can result in loss of cargo carrying capacity
  • Crew will require additional training in bunkering, storing and managing LNG

Compliance option 5: Use other alternative energy sources
There are a number of alternative fuels or energy sources that are either available or currently in development. It is understood the take-up of these options is low and where they have been adopted, they are one of several modes used on board – pieces of the multi-fuel jigsaw. 

These include: 
Methanol (CH3OH): Easy to manage and store but main challenges are its low flash point and relatively poor energy density.

Hydrogen fuel cells: Fuel cell systems use an electro-chemical reaction to generate electricity. Strong green credentials but there are concerns on their high cost, size and weight and expected life. 

Liquefied Petroleum Gas (LPG): Composition can vary but consists mainly of propane, butane and propylene. Similar positives and challenges to that of LNG as a marine fuel. 

Batteries: A low-maintenance (and arguably low-carbon) solution is battery power but the current technology does not meet the needs of an oceangoing vessel. When the technological breakthrough on batteries happens, could this be the game-changer? 

Published: 17 July, 2018

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