Alternative fuels and technologies in maritime applications

Alternative fuels and technologies in maritime applications

LNG, LPG, methanol, biofuel and hydrogen have been highlighted by DNV GL as the most promising alternative fuels to meet present and future environmental regulations, lower fuel consumption and emissions, and drive sustainable shipping. In a new White Paper, the classification society considers these fuels alongside wind-assisted propulsion, batteries, and fuel cell systems to have reasonable potential for ship applications in the future. VPO Global takes a look at some of the factors of alternative technologies and fuels in maritime applications.



Liquefied natural gas (LNG) is made up largely of methane (CH4 ), the hydrocarbon fuel with the lowest carbon content.

According to DNV GL, LNG has the potential to reduce CO2 by 26% compared with heavy fuel oil (HFO) and today it has reached the most cost competitive feedstock price level among alternative fuels.

Teekay’s LNG-powered Creole Spirit. Courtesty of Teekay

The main component of LNG is methane, which is subject to release when producing, transporting, and storing the gas. Methane has 25 to 30 times the greenhouse gas effaced compared with CO2. While its SOx contents is low, the resulting methane slip could eliminate the benefits it has over HFO or marine gas oil (MGO). This is an industry concern, but Peter Keller, executive vice president of TOTE Maritime and chairman of SEA\LNG, confirmed to VPO Global that while there are always going to be issues with new technologies or fuels, the industry, including OEMs, are working hard to eradicate these problems. There will never be one solution applicable to all ships, and while batteries or biofuels (see below) are suited to small vessels and short sea shipping, larger international ships have to rely on tried and tested applications for now, including LNG.

According to DNV GL, as of 1 March 2018, there are 121 LNG-fuelled ships in operation with 127 newbuilding orders confirmed.


Liquefied petroleum gas (LPG) is a mixture of propane and butane in liquid form. LPG combustion results in CO2 emissions that are approximately 16 per cent lower than those of HFO.

Most LPG is an oil refinery product and so LPG prices tend to align with the oil price. Global production of LPG was 284m tonnes in 2015, higher than the global demand for marine fuel, which means it has the potential to cover the energy needs of the global fleet. However, LPG is subject to the International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code) and is not currently included or on the agenda for the near future. The main safety concern is the density of LPG vapours, which are heavier than air.


Methanol has the lowest carbon content and highest hydrogen content of any liquid fuel. It is typically produced from natural gas and therefore is more costly than the gas price. However, it is simple to transport and store as the fuel is liquid at room temperature.

The methanol-powered Stena Germanica. Courtesy of Stena Line

Methanol has the potential to be produced from biomass, which means it can be used as a renewable energy for ship propulsion. Stena Line’s Stena Germanica, which bunkers in Gothenburg, is the only present example of a ship bunkering methanol at the present time. There are, however, seven 50,000 tonne deadweight vessels being built with the first-of-its-kind MAN B&W ME-LGI two-stroke dual-fuel engine that can run on methanol, fuel oil, marine diesel oil, or gas oil.

The IMO is continuing to work on the IGF Code for methanol (as well as low-flashpoint diesel). According to DNV GL, this should be taken into consideration by owners contemplating hydrogen applications in the near future as they will need to demonstrate compliance with the Code through alternative design.


Biofuels are derived from primary biomass or biomass residues that are converted into liquid or gaseous fuels. Biofuels include sugar, starch or lipid from plants, woody crops, or aquatic autotrophic organisms. Greenhouse gas emissions are lower than conventional marine fuels and because they are used as drop-in fuels substituting conventional fossil fuels, they are compatible with existing infrastructure and can be used in existing engines, subject to approval by the manufacturer.

Advanced biofuels are likely to be higher in price than fossil fuels and lack of global infrastructure means that it is not globally available. Biofuel is available in certain ports, for example in the Netherlands or Norway. At the current time, global production is around 32m tonnes of biodiesel and 170m tonnes of straight vegetable oil (SVO) per year. Algae-based fuel production could occur close to ports and coastal areas in future, according to DNV GL.

Biofuels may eventually be covered by the IGF Code’s new chapter on low-flashpoint diesel fuels, which is on the current agenda.


Hydrogen is a non-toxic gas and can be stored as a cryogenic liquid, as compressed gas, or chemically bound for use on ships. it is produced largely from natural gas and according to DNV GL’s research, it can be used along with CO2 to produce methane, which can be used in a similar way to LNG or synthetic liquid fuels as a substitute for diesel or gasoline.

Hydrogen has the possibility to create zero emissions ships if generated using entirely renewable energy, nuclear power, or natural gas.

Cost depends on the price of electricity or natural gas. More than 50m tonnes of hydrogen is produced per year globally. This is equal to the energy content of 150 m tonnes of ship fuel. According to DNV GL, as hydrogen can be produced from water using electrolysis, there are no principal limitations to production capacity that could restrict the amount of available hydrogen to the shipping industry. However, as there is currently no demand for it, there is no distribution or bunkering infrastructure for ships.

Hydrogen is also subject to the IGF Code as it is a low flashpoint fuel. However, it is not currently covered by it.


Wind-assisted propulsion

Viking Grace fitted with the Norsepower Rotor Sail solution for wind-assisted propulsion. Courtesy of Viking Line

Wind-assisted propulsion is an option to reduce energy consumption and save fuel. Wind assisted power has the potential to help meet the decarbonisation goals of the Paris Agreement, but implementation of alternative technologies, including wind power, will depend largely on the will of the industry to trial and implement these methods.

There is no specific infrastructure required as wind power is an unlimited resource, only technologies that are able to harness its power to use in ship propulsion. One method is by using Flettner rotors, which operate on the Magnus effect, producing a force perpendicular to the direction of the air flow.

The SOLAS Convention permits the use of wind propulsion, as long as a ship does not solely rely on it. Using wind alone for international shipping would not be feasible but ships that install Flettner rotors, sail systems, or kites can significantly reduce all types of air emissions.


The uptake of lithium-ion batteries on small ships and ferries has increased over the last few years and due to global interest, batteries have reduced in price by around 50% since 2016, finds DNV GL.

During operation, batteries produce zero emissions. In a Norwegian study, the environmental payback for a hybrid platform supply vessel for global warming potential and NOx was found to be 1.5 and 0.3 months, respectively. This was calculated using the Norwegian electricity mix.

Norwegian ferry, Vision of the Fjords, operating on ABB’s battery hybrid system. Courtesy of ABB

Batteries are highly efficient. DNV GL’s research confirms that efficiency of battery systems ranges from 85-95 per cent round trip. In comparison, diesel propulsion systems rarely have an efficiency exceeding 50 per cent, especially during low loading.

Individual classification societies, including DNV GL, have developed their own rules for batteries on board ships, but nothing has been developed at the IMO level. In 2016, there was an increase in testing and approval of battery systems, increasing safety levels. Shore connections at ports for re-charging batteries are governed by regulations and requirements established for the electrical grid.

According to DNV GL, the automotive and maritime industries are rapidly developing the infrastructure for batteries and the increasing number of companies focussing on developing batteries specifically for the maritime sector points to more than adequate manufacturing infrastructure. While batteries do not yet contain the energy to power ships trading globally, they have proven very successful where they have been used on board smaller ships and with continuous investment and development, it is possible that they will contribute significantly to reducing fuel consumption and emissions from international shipping in the future.

Fuel cells

According to DNV GL, fuel cells offer electrical efficiencies of up to 60 per cent and low noise and vibration emissions compared with conventional engines. Fuel cells typically eliminate NOx, SOx, and particulate matter, with CO2 reductions of 30 per cent possible. At the present time, small maritime fuel cell applications with an electrical power output of up to 100 kW are in operation.

Different fuel cell types exist, including alkaline fuel cells (AFC), proton exchange membrane fuel cells (PEMFC), high-temperature PEMFCs (HT-PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC).

E4 ships is aiming for a market launch of fuel cells in 2022. It is expected that infrastructure development will take off from here, while at the moment development of fuel cells is largely focussed on by fuel cell manufacturers.

It is expected that the requirements for fuel cell installations will be integrated into the IGF Code when it is revised in 2020.

To find out more about these fuels and technologies, read DNV GL’s White Paper here.