Future Maritime Fuels - Part 1

The need for the marine industry to reduce its Green House Gas emissions and the role which different fuels will play in this is all the talk of the town. The results of MEPC 76 may be disappointing, but the trend remains clear.

The Energy Efficiency Index for Existing vessels (EEXI) and the Carbon Intensity Indicator (CII) will have a dramatic effect on shipping over time. We, as an association of independent suppliers, manufacturers and service providers, need to keep updated on these critical developments.

Even though shipping is, from a Green House Gas point of view, by far the most efficient means of transporting cargo, each industry must find ways to become fully sustainable in the long term. There are short term measures, medium-term measures and long term measures. In the short term, shipowners can operate their vessels more efficiently, for example by polishing their propellers, scrubbing their hulls, route planning, reducing speed, optimising the usage of ancillary equipment, fitting energy saving devices such as the Mewis Duct, etc. Taken together, these measures can achieve a reduction of emissions, but the ships will still be burning fossil fuels. So how can shipping become carbon neutral? In part 1 of this article series, we will look at LNG, Hydrogen and Ammonia. In part 2 we will look at Methanol, explore biofuels, the use of hybrid systems and examine the likely time scales of future development.


Liquified Natural Gas (LNG)
The vast majority of vessels built today are fitted with Dual Fuel engines, i.e. engines capable of burning either traditional fuels or LNG.

The reason why Dual Fuel engines are more popular than pure gas engines is the lack of LNG infrastructure. LNG as a fuel has two significant advantages. As a fuel, it generates hardly any NOx or SOx. it is also readily available today at a commercially acceptable price, subject, of course, to there being sufficient infrastructure to allow for bunkering on a global basis. However, LNG can only be considered an interim solution at best. It is still a fossil fuel generating significant quantities of Green House Gases. When the potential GHG impact of methane slip is taken into account, LNG may have a greater negative impact on global warming than traditional fuels. For this reason, several environmental lobbying groups have argued that instead of investing huge sums of money into new LNG infrastructure, it would make more sense to spend that money on developing the new technologies required to produce true carbon-neutral fuels, such as hydrogen, ammonia or methanol. Nevertheless, it seems that the die is cast, and LNG will enter general use during the next few years.


From a technical point of view, the use of hydrogen as a fuel is already well established. It can be used in reciprocating engines, turbines and fuel cells. It produces no carbon emissions, NOx or SOx. However, this does not make it carbon neutral. It is how hydrogen is produced that is critical. It can be generated from coal (“brown” hydrogen), fossil fuels/LNG (“grey” hydrogen or “blue” hydrogen if the CO2 from production is captured and stored), or by splitting water into hydrogen and oxygen by electrolysis using sustainable electricity (“green” hydrogen). Right now, the cost of producing either “blue” or ”green” hydrogen is many times that of traditional fuels or LNG.

Hydrogen has other disadvantages in addition to the cost. Even when stored in liquid form, the space required is so considerable that it can only be used for vessels operating on fixed short voyages. In addition, hydrogen is explosive, leading to safety issues onboard the vessel and problems with bunkering. Finally, in addition to the production costs, there remains the problem of transporting the hydrogen from its place of production to the relevant ports. Whilst liquid hydrogen is being used experimentally on some ferries and inland vessels, it is likely to remain a niche fuel due to the present challenges.

The solution to liquid hydrogen’s problems may lie in utilising other hydrogen-rich substances with a higher energy density that are easier to handle.


Ammonia is currently gaining traction as one of the possible fuels of the future for maritime applications. Recently, a group of 23 companies and organisations, such as ABS, DNV, MAN ES, Mitsui E&S and Trafigura, came together for a joint study on ammonia production, availability, storage and emissions. Currently, companies around the world already produce $60 billion worth of ammonia every year, for use primarily as fertilizer. Ammonia is known for its foul smell and toxicity. The chemical is also commonly used in household cleaners.

The most popular production method uses the Haber-Bosch process, which generates huge quantities of CO2. But much like hydrogen, it can be produced through electrolysis and, depending on the source of the electricity, ammonia can become a carbon-neutral fuel. As its energy density by volume is nearly double that of liquid hydrogen, this could give it a significant advantage. Ammonia can either be used as a fuel itself or be split into nitrogen and hydrogen.

Ammonia has been transported as cargo for many years, which means that the problems relating to handling and storage should generally not be an issue. The risk of explosion is much lower than with hydrogen. On top of that, even though it is toxic for humans, it is easily detectable in case a leak occurs, in part because of its smell. Ammonia is highly reactive when it comes in contact with other substances and is potentially highly corrosive to the components in an engine or the fuel storage tanks unless suitable materials are used. Both Wartsila and MAN ES are already working on ammonia fuelled internal combustion engines to see if these problems can be overcome. In the meanwhile, ammonia is also being considered for use with fuel cells. Industry forecasts state that by 2050 more than 30% of all fuel used in maritime applications might be ammonia.


To sum up, hydrogen, ammonia and LNG are three of the current options for future maritime fuels in the context of the industry’s path towards decarbonisation. LNG is readily available. The technology is there, but it is an interim step, at best. The space requirement of liquid hydrogen is such that it can only be a niche player, whilst ammonia needs to develop new cost-effective carbon-neutral production methods.
Stay tuned for Part 2 of this article series, where we will explore biofuels, methanol and hybrid systems and conclude our research into the maritime fuels of the future.