This paper provides an overview of the possible alternative fuels for the shipping industry for the propulsion purpose. A whopping 80% of world trade (by volume) is handled by the maritime transport, it also approximately produces 3% of the world’s greenhouse gas emissions, while also contributing to air pollution around coastal areas and ports. In order to reduce to the impact maritime transport has on the climate and on environment, various fuel efficiency measures can be taken into consideration to immediately collapse the SOx, NOx and particulate matter percentages. And depending on what type of alternate fuel to be used, greenhouse gas reductions will also be possible.

This introduction of alternative fuels will surely have a good environmental impact, but their introduction and implementing them will add more layers of complexity to the maritime trade. To start with, infrastructure needs to be upgraded, new safety rules, new equipment on board, from engine to the bunker for fuel. Some factors also include the availability of the fuel, and new roles for officers and the crew in order to ensure safe handling of the fuel.

Keywords: alternative fuels, maritime transport.


Regulatory bodies, like the International Maritime Organization (IMO) and national environmental agencies have strict laws that direct ships to drastically reduce their emissions. These rules impact ships that engage in international and coastal trade, cruise industry and ship owners. The ships operating in Emission Control Areas (ECA) are expected to run on low sulphur fuels and/or add the SOx exhaust scrubber. In the near future, high traffic maritime areas, for eg. Singapore, Shanghai, will have more stringent laws to control the SOx, Nox and particulate matter emissions, and not to forget greenhouse gases.

Many ships currently sailing the seas cannot meet the new regulations without equipment like the exhaust scrubbers, have to switch to the more expensive low sulphur fuel, or to fuels with reduced exhaust emissions. Bottom-line, this impacts the profits made. And now the need for clean alternative fuels is dramatically rising, ranging from both liquefied to gaseous alternates. These alternative fuels have the advantages, but the disadvantages can also be a deal breaker from the shipping perspective.

Current Situation:

The current marine fuel oil consumption is of low-quality, low-cost residual fuel oil which is known as Heavy Fuel Oil (HFO). HFO usually has a high sulphur content and is almost entirely used by large cargo ships. The maximum allowed sulphur content is 0.5% (from MARPOL Annex VI fuel content limits) and HFO used in marine diesel engines typically contains around 2.7% of sulphur. And alternative fuels is the only way to have a clean and sustainable source of energy. Right now, the most practical solution to SOx Nox content is the use of low-sulphur diesel and the implementation of scrubbers to the exhaust of the engine.

Below are the MARPOL Annex VI regulation caps on sulphur content for both, ECA and globally. (Table 1)

Source: Internet

Below given picture depicts the Primary sources of the fuel. (Fig. 1)

Sources of Fuel
Source: Internet

Below given diagram indicates which fuel gives maximum Torque and Speed. (Fig. 2)

Source: Internet

Below given diagram depicts the process of conversion of fuel into energy (Fig. 3)

Source: Internet

Below are the NOx regulation caps for diesel engines with respect to the maximum engine speed. (Table 2):-

Source: Internet


There are a number of incentives for stopping the usage of heavy diesel oil and start using alternatives instead.

  • SOx and NOx regulations as discussed above (MARPOL Annex VI)
  • Pricing volatility of fossil fuels.
  • Diesel shortages around the world.
  • Possible scarcity of low-sulphur fuel.
  • More strict regulations of ECAs and SOx NOx emissions.
  • Possible increase in the number of ECAs, ranging from Mediterranean Sea, Mexico and Singapore.
  • The Renewable Fuels Standards (RFS) by the USA, which requires a certain amount of renewable fuel in the available fuel inventory.
  • The addition of Energy Efficiency Design Index (EEDI) by IMO to MARPOL Annex VI. New alternate fuels will also improve the efficiency of new ships. It is calculated as the rate of CO2 emissions from the ship.


Alternative fuels must have some characteristics and/or requirements to be satisfied in order to be used in marine engines. These characteristics ideally should outweigh the cons of using the fuel, after which the fuel will be considered good to go.

  • To start with, the fuel should have a much lower SOx NOx emission than standard fuel oil.
  • It should not have an adverse effect in the engine or any other equipment on board.
  • Engine performance when run on the alternative fuel should not be low.
  • Engine and the fuel should be compatible.
  • The fuel should be reasonably priced. For reference, current Heavy Residual Fuel Oil is priced at around 750 USD.
  • Fuel should be available in sufficient quantities around the world.
  • Can be mixed with standard traditional fuels.
  • Fuel is safe to use and should not have any environmental impact.

A fuel satisfying these conditions is called a ‘drop in fuel’.

A drop in fuel is a synthetic and interchangeable substitute for conventional hydrocarbons (diesel, petroleum, gasoline, fuel oil). It does not require changing of the engine, fuel network or fuel systems.

The Trans-European Transport Network (TEN-T) has a maritime pillar named Motorways of the Seas (MOS). It consists of short-sea routes, ports, associated maritime infrastructures, equipment, facilities and relevant administrative formalities. MOS aims to introduce new inter-modal maritime-based logistics chains to bring about structural change to door-to-door integrated transport systems.

To this end, MOS has:

  • Helped implement policy initiatives on the European maritime space without barriers and the maritime transport strategy for 2018.
  • Positively contributed to greenhouse gas (CO2) reductions, which is of paramount importance in the context of climate change.
  • Introduced new intermodal maritime based logistics chains contributing to door-to-door integrated transport systems.
  • Turned LNG as marine fuel into reality in the North Sea-Baltic region.
  • Developed LNG infrastructure facility deployment in the Baltic Sea region.
  • Adopted LNG as marine fuel in the East-Mediterranean Sea.
Bottlenecks and missing links faced by MOS:
  • Compliance with 2015 MARPOL Annex VI (Regulations for the Prevention of Air Pollution from Ships) across fleets operating in Sulphur Emission Control Areas (SECAs).
  • Establishment of viable network for alternative fuels, including development of relevant technologies, infrastructures, safety provisions, and regulatory frameworks for alternative fuels.
  • Development of technologies to tackle operational pollution such as exhaust gas cleaning systems and on-board water treatment systems.
  • Implementation of critical port infrastructures and inter-modal links, both sea side and land side.


Studies and research conducted by organizations around the world have found some fuels which could be potentially used in the future of shipping.

  • Liquefied Natural Gas (LNG)
  • Liquefied Petroleum Gas (LPG)
  • Bio-fuel (Methanol, Ethanol, DME, Biogas, Pyrolysis Oil,
  • Electricity
  • Hydrogen
  • Synthetic fuels (Fischer-Tropsch)

Important information to be collected for the fuel for a better understanding and future enhancements:

  • Chemical and physical characteristics
  • Production, availability, cost
  • Applications and current status
  • Safety considerations
  • Emissions and environmental impacts

Solar energy is not listed as an alternative fuel, although it has the potential of negating carbon emissions. Solar is not seen as a reliable source of energy for an entire, huge ship. Sure, a ship equipped with solar panels can provide energy to a fraction of equipment on board, for eg. galley, laundry systems and lighting, solar won’t provide it all the time. Solar is also ill-suited for deep sea transport and for operations in some places where sunlight is scarce, or in places which have seasonal weather conditions.

Similarly, nuclear fuel also is problematic. Although it is proven that nuclear fuel does not liberate any greenhouse gases or other harmful gases, usage of nuclear fuel will have risks too high for its value. Furthermore, the storage of nuclear waste and its disposal will put additional risks and safety issues on the table.


Over the next couple of decades, it is highly likely that energy mix will be characterized. LNG has great potential the best choice as a fuel in all shipping segments, given that the infrastructure is in place.

Using LNG as fuel offers a lot on the table. To start with, it has clear environmental benefits, from the elimination of SOx, NOx and particulate matter to massive reduction in greenhouse gases (except CO2).

There are right now a little less than 400 ships out of a total 80,000 registered ships which run on LNG as fuel source. And by the end of 2030, the fleet of LNG run ships should increase to 1,000 vessels. LNG bunkering currently is not possible all over the port. As of now, only 93 ports worldwide offer LNG bunkering and an estimate of 54 ports are in the process of facilitating LNG bunkering investments and processes, according to reports.

In 2020, The Maritime Port Authority (MPA) of Singapore expects the first of its two LNG bunker tankers to facilitate ship-to-ship LNG bunkering for ocean going vessels from the second half of 2020 onwards. DNG Energy will provide LNG bunkers in Algoa Bay, South Africa’s largest bunkering port, from the second quarter of 2020. Later that year, Shell will charter an articulated tug barge (ATB) to help it carry out its pledge to deliver LNG to various ports in Florida and southeast US.

Barriers: Relatively high cost for system installation. Requirement of numerous large fuel tanks. Which in turn decreases the payload capacity of the ship. LNG is not compatible with existing fuel systems and requires modifications.

Engine requirements: Engine concepts include gas-only engines with both dual duel 4-stroke and dual fuel 2-stroke engines. Methane emissions are practically eliminated in 2-stroke engines and reduction in 4-stroke engines are possible. With further research and development, 4-stroke engines will also eliminate the methane liberation.

LNG uptake is subjected to grow rapidly in the next 5 to 8 years, effect starting from small ships operating in areas which support LNG bunkering. As LNG prices are competitive to HFO, large ocean-going cargo ships will also follow and LNG bunkering operations will be sooner or later available around the whole world.


Electricity is a promising source of energy, for the shipping industry and for land transport. While electricity has already been implemented to an extensive collection of road legal vehicles with sound infrastructure in its place, shipping does not entirely depend on electricity.

Recent developments in ship electrification hold significant promise for more efficient use of energy. Renewable power production can be exploited to produce electricity, in order to power ships at berth (cold ironing), and to charge batteries for fully electric and hybrid ships. Enhancing the role of electricity on ships will contribute towards improved energy management and fuel efficiency on larger vessels. For example, shifting from AC to on board DC grids would allow engines to operate at variable speeds, helping to reduce energy losses. Additional benefits include power redundancy and noise and vibration reduction.

China has the first fully electric container ship only used for inland water transport, along the Pearl River in Southern China. Using 1,000 Li-Ion batteries which weigh about 26 tons and achieve 26,000 kilowatt-hours of power, they can only propel the ship for only about 80 km before coming to a halt. Norway is working on electric ships to transport chemicals and fertilizers. Traditionally trucks do the job by having around 50,000 trips per year, but a small power efficient ship will significantly reduce the transport time.

Future developments: There are several energy storage devices available and battery powered propulsion systems are already ready for small ships. On the other hand, for larger vessels, engine manufacturers are keen on the hybrid solutions.

Barriers: Safety, availability of materials, the life of the battery, reliability. All these points will be considered to remain competitive to traditional fuels.


Biofuels can be obtained from vegetable oils, animal fats and algae. Liquid biofuels available for marine use are biodiesel, FAME, algae fuels, methanol, hydrogenation‐derived renewable diesel (HDRD), which is also known as second generation biodiesel, and pyrolysis oil.

The most promising source is algae, which can be grow on water in large quantities without competing with food production. Further, biofuels can greatly reduce the overall greenhouse gas emissions. Also, biofuels produced from plants, algae or organisms have rapid biodegradable properties. This means that clean after an unfortunate oil spill will be easy, without posing any risk to the environment. Biofuels also have the flexibility of being mixed with conventional fuels, meaning traditional engines can also be run using biofuels.

Future developments: Algae-based biofuels seem to be the most efficient and the process has the added benefit of consuming significant quantities of CO2, but more work needs to be done to identify alga strains that would be suitable for efficient large-scale production. Experimentation with biofuels has already started on large vessels, and preliminary results are encouraging. However, advances in the development of biofuels derived from waste or algae will depend on the price of oil and gas. As a result, biofuels will have only limited penetration in the marine fuels market in the next decade. However, by 2030, biofuels are set to play a larger role, provided that significant quantities can be produced sustainably, and at an attractive price.

Barriers: Long-term storage stability, biofuels can cause corrosion, biofuels will have limited penetration in the market, significant quantities cannot be produced in the current scenario.


Propane or Liquefied Petroleum Gas  is mentioned from time to time as a potential marine fuels candidate. However, there seems to be very limited material available on LPG’s viability as a marine fuel. The general view around the globe seems to be that LPG is a premium product and, as such, is priced accordingly and is too expensive compared to other alternative fuel options. So, although the supply is there, its current markets are in automotive transportation and domestic heating and cooking, markets that have a different price reference than shipping.

Barriers: In terms of safety, propane is heavier than air and thus presents an explosive safety hazard if it were to accumulate in the bilges or low sections of a ship’s engine room in the event of a leak in the fuel system; thus, it is not considered safe for shipboard use.


Renewable electricity can be employed to produce hydrogen, which can be utilized to power fuel cells on board ships. This solution will also help to deal with the challenges associated with the intermittent nature of many renewable energy sources. Hydrogen is the smallest and lightest of all gas molecules, thus offering the best energy-to-weight storage ratio of all fuels.

Fuel cells are the most commonly used devices to convert the chemical energy of hydrogen into electricity. When a fuel reformer is available, other fuels, such as natural gas or methanol can be used to power a fuel cell. Although operational experiences have shown that fuel cell technology can perform well in a maritime environment.

Barriers: Compressed hydrogen requires x6 to x7 more space than HFO. Liquid hydrogen on the other hand, can be stored in less space, but requires cryogenic conditions at temperatures of just 20K (-253 oC), along with highly insulated tanks. Hydrogen has high investment costs; weight of fuel cells is high. Increased safety considerations on board ship.

Future development: Cost reductions, weight and size of fuel cells should decrease.


The implementation of alternative fuels will take place, but initially at a slow rate. This is due to the “chicken and egg” dilemma. Meaning, until the infrastructure is not in place, ship owners may not commit to alternative fuels. And until ships don’t have provisions for alternative fuels, the infrastructure won’t be developed. As technology matures, necessary developments take place and users start to grow, every new alternative fuel will carve a path into the market. Eventually, from small inland transport vessels to large ocean-going cargo ships. Provided that global infrastructure becomes available.

For the present scenario, the use of fossil fuels will continue worldwide. Low-sulphur fuel will be dominant in the 1% ECAs. Other options are low-sulphur residual fuel, or to have a dual fuel system, where the operator can switch between different fuels when needed.

Considering an alternative fuel, LNG is the foremost and the best option available to replace HFO. The adoption of LNG will be driven by fuel price developments, technology, regulation, increased availability of gas and the development of the appropriate infrastructure. LNG should remain cost competitive with marine fossil fuels for the foreseeable future and provides a strong incentive for newbuilds to have gas engines and LNG fuel systems. The higher initial cost of constructing a gas‐fueled ship can be recovered over the lifetime from the lower fuel costs. In addition, LNG fueled ships that spend a large part of their time operating in ECAs will be able to comply with the low‐sulfur and NOx Tier 3 requirements for gas engines without having to switch fuels or add exhaust aftertreatment emissions devices for SOx and NOx reduction.

The pace of development for other alternative fuels, particularly biofuels produced from locally available waste biomass, will accelerate, and may soon compliment LNG and oil-based fuels. Indeed, it is likely that a number of different biofuels could become available in different parts of the world after 2030. However, acceptance of biofuels in deep-sea transportation can only take place if these fuels can be produced in large volumes and at a competitive price around the world.

There are numerous solutions to problems created by shipping, to have our skies clean and our oceans clear. But the barriers in technology limit us from obtaining such feats. It is very likely that the future will have various fuels to use, from LNG, biofuels, electricity to hydrogen. Who knows that maybe nuclear propulsion is what the world will be running on? We don’t what the future holds, but sure it is a bright one.


Authored By:- Cdt. Shubham Shivne and Cdt. Nikhil Choudhary, TMI

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