Ammonia – a new fuel for marine engines

Currently, ships consume approximately 300 million tons of petroleum products annually and emit 3-4% of the total CO2 emissions caused by human activity. At the same time, commercial fleet plays a fundamental role in the global economy, transporting more than 80% of all cargo.

Comparison of SOx emissions from cruise ships and cars in European ports

In 1973, the IMO (International Maritime Organization) adopted the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78), which was supplemented by the 1978 and 1997 Protocols and is constantly updated by relevant amendments. The MARPOL Convention covers pollution from ships by oil, noxious liquid substances carried in bulk, harmful substances carried by sea in packaged form, sewage, garbage, and the prevention of air pollution from ships. MARPOL has contributed significantly to the reduction of environmental pollution from international shipping and applies to 99% of the world's merchant tonnage.

The first step was to limit atmospheric emissions of sulphur oxide (SOx) and nitrogen oxides (NOx) generated during fuel combustion in marine propulsion systems. The Regulations for the Prevention of Air Pollution from Ships – Annex VI of MARPOL (entered into force on 19 May 2005) establish certain sulphur oxide (SOx) emission control areas with stricter sulphur emission controls and nitrogen oxide (NOx) emission control areas for Tier III NOx emission standards (Emission Control Areas for Sulphur Oxides, Nitrogen Oxides). Emission Control Areas (ECAs) are either sulphur emission control areas (SECAs) or nitrogen oxide emission control areas (NECAs).

In accordance with IMO Regulations under MARPOL Annex VI, all Emission Control Areas (ECAs) currently have SOx emission limits (SECAs) and NOx emission limits (NECAs).

The following ECAs are currently installed:

• Baltic Sea & North Sea (Baltic and North Sea).
• North American Area. Includes coastal areas of the United States, including the Hawaiian Islands, and Canada.
• US Caribbean Sea Area (US Caribbean islands).
• Mediterranean Sea.
• Canadian Arctic & Norwegian Sea.
Entered into force on March 1, 2026.

Furthermore, the IMO considers the Northeast Atlantic Ocean a potential ECA for the foreseeable future. Several countries, including China, South Korea, Australia, and Mexico, have already proposed including their territorial waters in ECAs.

*** Ships constructed on or after 1 January 2016 and operating in these emission control areas shall comply with the NOx Tier III standards set out in regulation 13.5 of MARPOL Annex VI.

**** A ship constructed on or after 1 January 2021 and operating in these emission control areas shall comply with the NOX Tier III standards set out in regulation 13.5 of MARPOL Annex VI.

ECA zones

Within the ECA, the maximum sulfur content in marine fuel must not exceed 0,1%, while outside the ECA, up to 0,5% is permitted. And yet, the author still remembers the "good old days" when he had to work with heavy fuel oil with a sulfur content of as much as 4,5%!

IMO requirements for the sulphur content of marine fuels

Outside SECA, vessels built in 2010 or earlier must meet at least Tier I NOx emissions standards, while those built in 2011 or later must meet Tier II standards. While Tier I and Tier II emissions are achieved through engine design modifications, Tier III emissions can only be achieved through special exhaust gas treatment.

Using scrubbers in ECAs allows for the use of higher-sulfur fuels. In the scrubber, the exhaust gases are sprayed with water (seawater or freshwater), which absorbs sulfur oxides and, to some extent, nitrogen oxides, forming acids, as well as soot, which is collected in a sludge tank. The exhaust water is discharged overboard, if permitted by local regulations (open loop), or, after neutralization with alkali and soot removal, is returned to the process (closed loop), typically using freshwater.

Open-loop scrubber

Closed-loop scrubber

To achieve Tier III NOx compliance, various methods are used, including:

1. Selective catalytic reduction (SCR)
In this system, urea or ammonia is injected into the exhaust gases before they pass through a system consisting of a special catalyst bed, at a temperature of 300 to 400 degrees Celsius. The chemical reaction between the urea/ammonia and the NOx in the exhaust gases reduces NOx emissions (NO and NO2) to N2. The SCR unit is installed between the exhaust manifold and the turbocharger. This method reduces NOx emissions by over 90%.

2. Exhaust gas recirculation (EGR)
This technology returns a portion of the exhaust gases from the turbocharger to the scavenge receiver after passing through a scrubber unit (exhaust gas washing). This reduces NOx by 50-60% compared to Tier I.

NOx reduction occurs by reducing the excess air ratio (oxygen content) used for combustion, the addition of CO2 and water vapor reduces peak temperatures.

The above measures significantly increase operating costs and reduce the economic efficiency of ships. For example, reducing the sulfur content of marine fuel increases its cost by an average of 20%, and installing scrubbers costs over €300 per 1 MW of engine power, excluding subsequent operating costs.

Since 2011, the IMO has been committed to combating greenhouse gas emissions (GHG) by adding Chapter 4 to Annex VI of the MARPOL Convention, "Regulations on energy efficiency for ships." This regulation applies to ships of 400 gross tons or more engaged in international voyages.

The Energy Efficiency Design Index (EEDI) for new ships, the Ship Energy Efficiency Management Plan (SEEMP) and the Fuel Data Collection System (DCS) for ships over 5000 t were introduced.

The EEDI measures the number of grams of CO2 emitted per ton-mile, thereby encouraging the use of more efficient equipment. The lower the EEDI, the more efficient the vessel. The formula takes into account the vessel's technical parameters (engine power, speed, deadweight). The "Achieved EEDI" must be less than the "Required EEDI," which is tightened every five years. It is mandatory for most new ships of 400 gross tonnage or more, for which the construction contract was signed after January 1, 2013.

In 2018 and 2023, the IMO defined its strategy to reduce GHG emissions from global shipping.

IMO's Greenhouse Gas Emissions Strategy

Carbon Intensity Indicators (CII) – requirements for rating ships (from A to E) based on their operational efficiency have been implemented since 2023. The CII is a measure of a ship's operational energy efficiency, calculated annually. It shows how many grams of carbon dioxide (CO2) are emitted per unit of transport work. It uses data from the IMO Data Collection System (IMO DCS), which is already mandatory for ships.

The most effective method for reducing harmful emissions from marine engines, other than nuclear and all-electric propulsion systems, is the use of alternative fuels. These may include:

• Liquefied natural gas (LNG) is readily available and effectively reduces SOx and NOx emissions, but requires cryogenic storage (-162°C) Tanks high pressure. The disadvantage is that the energy content of LNG per unit volume is only 43% of that of high-sulfur fuel oil. Therefore, fuel tanks take up 3-4 times more space compared to ships running on traditional fuel. An example of the use of LNG is the line of two-stroke low-speed diesel engines Everllence B&W ME-GI (formerly MAN B&W ME-GI) with a capacity of 4350-82400 kW at 56-167 rpm. Since 2014, 1000 of these units have already been ordered. According to expert estimates, the share of LNG in the total volume of marine fuel will reach 23% by 2050 (currently it is around 0,3%). Compared to traditional heavy fuel, LNG allows for a reduction in CO2 emissions by 20-30%, SOx by almost 100%, and NOx by 80-90%.

Ships with dual-fuel diesel engines running on LNG (from top to bottom): Coast Guard vessel Turva (Finland), icebreaker Polaris (Finland), cruise liner Costa Smeralda

Everllence B&W ME-GI

Everllence B&W ME-GI Diesel Engine Line

• Liquefied petroleum gas (LPG – Liquefield Petroleum Gas). Easily accessible, no need for high-pressure tanks or ultra-low temperatures for storage. No SOx emissions, reduced CO2 emissions. An example is the Everllence B&W ME-LGIP (formerly MAN B&W ME-LGIP) line of two-stroke, low-speed diesel engines. Since 2018, more than 270 have been ordered.

• Liquefied Ethane Gas (LEG). Readily available, stored at cryogenic temperatures (below -100 °C), but requires thinner tank insulation than LNG due to its higher boiling point. Reduces emissions of sulfur oxides (SOx), nitrogen oxides (NOx) and carbon dioxide (CO2) compared to traditional heavy fuel oil (HFO) and marine diesel fuel (MDO). An example is the Everllence B&W ME-GIE (formerly MAN B&W ME-GIE) range of two-stroke, low-speed diesel engines. Power 8300-29 120 kW at 62-127 rpm.

• Ethanol and methanol. Methanol remains liquid at temperatures from -93 °C to + 65 °C (at atmospheric pressure), which eliminates the need for complex cryogenic storage systems (the cost of a fuel system using methanol is approximately 1/3 of the price of an LNG system for a marine engine). It can be produced from natural gas, coal and renewable sources. There are technologies for producing methanol directly from harmful emissions into the atmosphere, which seems the most promising in terms of reducing COx emissions. NOx emissions depend on the type of engine used. In the case of a two-stroke diesel engine, a 30% reduction in emissions will be observed (compared to high-sulfur fuel oil), while use in a four-stroke engine will reduce emissions by 60%. A serious disadvantage of methanol, in contrast to ethanol, is its high toxicity, but the cost of ethanol is significantly higher than that of methanol. Methanol, as a motor fuel, has a high octane rating and low flammability. Its flash point is +9°C, and its viscosity is 5,9 mM.²/s at 21 °C, elevated autoignition temperature. Ethanol is characterized by a low flash point (13 °C), low viscosity (1,2 m²/s) and an elevated autoignition temperature. Both methanol and ethanol can be used in mixtures with fuel oil in various ratios.

In 2015, the main engines of the cargo-passenger ferry Stena Germanica, converted for methanol use for the first time. The installed fuel system allowed the use of four medium-speed Wärtsilä-Sulzer 8ZAL40S engines in dual-fuel mode. According to measurements, when the main engines ran on methanol, emissions of sulfur oxide (SOx) decreased by 99%, nitrogen oxide (NOx) by 60%, carbon dioxide (CO2) by 25%, and particulate matter by 95%.

Wall Germanica

The world's first two-stroke marine engine powered by methanol was the Everllence B&W ME-LGIM (formerly MAN B&W ME-LGIM). Development began in 2012, and the first vessel with this engine entered service in 2016. In addition to methanol, the engine can run on heavy fuel oil (HFO), marine diesel fuel (MDO), or marine gas oil (MGO). In 2024, Everllence successfully tested the four-stroke 21/31 DF-M engine on ethanol.

Everllence B&W ME-LGIM on a test bench

Everllence B&W ME-LGIM Diesel Engine Line

• Hydrogen. H2 is another alternative marine fuel option currently being considered. For use on ships, hydrogen is either liquefied (the cryogenic liquid has a temperature of -240 °C), placed in compression tanks, or stored as a chemical compound. Produced from renewable energy sources, hydrogen is becoming one of the cleanest fuels with zero greenhouse gas emissions. When burned, it produces only water vapor. Dual-fuel engines (e.g. 85% hydrogen + 15% diesel) are being developed to use hydrogen, and existing marine diesels can be upgraded, which is especially important for coastal vessels. Anglo Belgian Corporation (ABC) produces hydrogen engines with a capacity of 1000-2800 kW. The most efficient method of using hydrogen is fuel cells, which are used to generate electricity. Hydrogen production, like fuel cells, is well developed, but they still remain uncompetitive in price with conventional marine engines. However, hydrogen storage requires significantly larger volumes than traditional fuels.

Comparison of the mass and volume of fossil fuels and liquefied hydrogen

• Ammonia. It is considered one of the most promising types of alternative marine fuel.

Comparison of fuel characteristics

Продолжение следует ...

Comments

[Nemchinov Vl]

I wonder, in the event of an accident and spillage into the water... what harm would be more widespread and devastating to aquatic life?! Fuel oil spreading across the surface and preventing oxygen from entering the water, some kind of chemical reaction from LPG/LNG getting into the water? Alcohol spilling into the sea, or something that might happen when ammonia dissolves in water?!

How much have the dangers of such things been studied? emergency!!, cases, by activists of fuel and energy environmentalists (or if this issue was not considered in detail in advance, then - ecoLOOKERS) ..??!
Here is an emergency spill of ammonia into the sea (instead fuel oil), is it definitely not more dangerous from an environmental point of view?!

[alexoff]

The ammonia will quickly rise upward. Sailors will likely die, as will fish within a few hundred meters. But it will all be over fairly quickly; within an hour, you'll be left with a slightly stinking ghost ship. Unlike fuel oil, which is relatively harmless but won't go away for decades and will ruin the view on the beach.

[Alexander Mitrofanov]

Fuel oil is the most dangerous. Liquefied gas will quickly evaporate and disappear. And ammonia isn't all that dangerous. Thousands of vessels with ammonia refrigeration units (fishing vessels, reefers) have operated, and continue to operate, with fatal accidents being rare. I worked on such vessels for a decade.

[alexoff]

And ammonia isn't that bad.

Much less pleasant than methane, but certainly not mustard gas.

Thousands of vessels with ammonia refrigeration units (fishing vessels, reefers) have worked and are working

The amount of ammonia there is small and it is initially cold and will slowly sizzle, and if your tank of several hundred tons breaks through, then you need to run to another part of the ship.

Fuel oil is the most dangerous.

For marine organisms in the long term, yes. And the beaches in Anapa never opened. But for sailors, it's fine.

[Archon]

Ammonia is undoubtedly toxic due to its high reactivity and will poison many living things around it. However, being a natural active component, it is quickly neutralized into harmless salts. This means that in the event of an accident, fish and mammals will die locally, but there is no need for extensive cleanup; the surrounding environment will effectively absorb all the ammonia, and the neutralization products will dissolve through diffusion in the vast volumes of water.

That is, the problem is not environmental, but that an accidental ammonia leak could occur on the ship, for example, at night while sleeping.

[Nemchinov Vl]

Quote: Archon

So the problem is not ecology.

Come on.
This is humanity with its unpredictable carelessness... to them, and the "peaceful atom" of, for example, Chernobyl, did not seem like a possible problem for the environment before the accident (!). All that remains now is to build several thousand new huge tankers and gas carriers running on ammonia and send them across the seas and oceans. And then, "some huddled together in a flock" (pack / coalition, something like NATO, the US, Israel and the like) degenerates will begin to sink the trade caravans of interest groups, "other profiteering degenerates" (like China, Iran, India or Russia), either with drone attacks, or with unmanned boats or missiles, or something even newer (!). and the first to suffer from each such spill from catastrophes will be the nature of the world's oceans...?!
And there, not a few crucian carp will die, considering the volume of the tanker’s fuel tanks (or container ships) fleet ..!!!

[Alexander Mitrofanov]

There are many gas carriers transporting ammonia. At one time, the Black Sea Shipping Company had some, too, loading ammonia in Yuzhny. And nothing terrible happened.

[Dmitry Eon]

True. And in agriculture, they even use ammonia-water solution as a fertilizer if there's no saltpeter, so the "environmental damage" argument is utter nonsense.

[traveler 63]

The article is interesting and informative! It just triggered a "flash of memory"! Specifically, back in college, during a lecture on turbojet engines, the instructor told us (the cadets): "Work is currently underway to reduce unburned fuel emissions into the atmosphere. Why do you think that's the case?" When we answered, "Economics, etc.", he responded very simply: "We're carrying nuclear weapons, so what the hell is ecology?" The answer turned out to be very simple: reducing the engine's heat signature. But I've remembered that lecture forever!

[Amateur]

Ammonia – a new fuel for marine engines

The fact that ammonia can be used as a fuel sparked genuine interest. I read and read this rambling machine translation of the "IMO Regulations in accordance with MARPOL Annex VI" and became convinced that Avtov had no idea what he was talking about. Then I finally found out in the article that ammonia is indeed used, but as a catalyst (!!!) for cleaning exhaust gases. I barely made it to the end and... voila... Mitrofanov!
Dear VO editors! Once again, I ask, no, I beg, please put the author's name AT THE BEGINNING of the article.

[Old Michael]

So there are two Mitrofanovs here: the one who is a rationalizer and a dreamer is Andrey, and the author of this article is Alexander (sometimes he writes well).

[Alexander Mitrofanov]

I downloaded the IMO rules from the official website of this venerable organization, so I have no complaints about the IMO. I probably understand what I'm writing about. I worked as an engineer for 50 years and was regularly certified. And especially according to MARPOL rules!

[zampolite]

More green hysteria, as if someone is hyping up the ammonia issue. I've already come across more than one article along the lines of "we'll bind nitrogen and make ammonia the "green" way and burn it with ammonia..."
True, it is toxic, burns poorly, and has a calorific value half that of regular fuel oil - but the main thing is to inflate the theme of the uselessness of oil and gas.

[Uncle Sam_2]

Back in my first year, my teacher swore: "Soon, soon, absolutely all FFSEs will be driving, flying, and swimming on hydrogen!" (84 g)
Ehhh ...

[Victor Alien]

Large-capacity vessels and ships need to be converted to nuclear power. Although recent events suggest these troughs will soon be much smaller—production and consumption will simply be confined to the mainland where they are located. Most goods are transported using a completely illogical system. And the ocean is becoming a wild territory—everyone against everyone else. I wonder why insurance is not issued in the vessel's home port?! It was funny once when I saw a vehicle inspection document in the Orenburg region listing an LLC's registration as being located in Petropavlovsk-Kamchatsky... No one questioned the regulatory authorities about this arrangement.

[Grossvater]

A serious disadvantage of methanol, in contrast to ethanol, is its high toxicity,

Enough! Where, exactly, is methanol highly toxic? To cause poisoning, a massive dose—more than 30 grams—is needed, along with a host of other necessary conditions, without which it's no more toxic than regular vodka.

[Alexander Mitrofanov]

We are not talking about drinking methanol by the glass, but about inhaling its HIGHLY TOXIC vapors.

[Grossvater]

Quote: Amateur

Dear VO editors! Once again, I ask, no, I beg, please put the author's name AT THE BEGINNING of the article.

I join the request!

[papas-57]

I wonder where the crew will go if the ammonia tank depressurizes. There's water all around.

[Paragraph]

In full force on the sky.

[mad-max78]

Is anyone seriously considering this kind of fuel after what's happening to tankers and gas carriers? If the ammonia storage tank were damaged, there'd be no escape from this ship. As a child, I dropped a medicine bottle of ammonia from the top shelf onto the floor, it broke, and I almost suffocated. There was a maximum of 100 grams of ammonia in there, and there are thousands of tons of ammonia on this ship.

[Yuri_K_Msk]

When ammonia burns, it produces a mixture of nitrogen oxides, which, when in contact with water, form a mixture of nitrous and nitric acids. These substances are extremely toxic and corrosive. Ammonia itself is classified as a particularly hazardous toxic substance. The maximum permissible concentration is 20 mg/m³. Furthermore, industrial production of NH³ is the main source of atmospheric pollution from carbon dioxide, which is formed during the synthesis process. So, the author was clearly overreacting when it comes to ammonia as a fuel. The environmental damage would be an order of magnitude greater than that from sulfur fuel oil.

[Svetlana]

Ammonia isn't exactly harmful or toxic. It's dangerous. One breath, whether pure or in high concentrations, can cause respiratory arrest. A gas mask—and at ammonia and its derivatives plants, personnel don't walk around without them—won't help.

[cpls22]

I read about a bunch of emission standards, and the idea of ​​segregating ships into "clean" and "dirty" ones came to mind. What if the latter are barred not only from ports but also from their territorial waters? There you have it, a pretext for a naval blockade and other sanctions. Anyone who hasn't committed to sovereign, environmentally friendly engine manufacturing becomes dependent on the non-supply of these engines. In other words, a monopolization of maritime freight transport is possible.

[Tests]

I've long been under the impression—and I admit, it's deeply and widely mistaken—that all the green hysteria from countries designated as NATO allies for many years was designed to make NATO countries even richer and stunt the economic development of "emerging market countries." But the smart guys in Europe and America didn't anticipate China's economic miracle. And so China began to flood Europe with cheap wind turbines, solar panels, and energy storage systems. And South Korea has made a breakthrough in shipbuilding... The "greens," however, for some reason forgot to explain how much "green" energy actually costs and how to utilize all its wealth, and most importantly, that energy is intermittent and almost uncontrollable... True, in recent years, the "greens" have seen a slight awakening: nuclear energy has been recognized as green, and, apparently, hydroelectric power plants have been recognized as almost green power plants...
Despite all the Central Bank of Russia's heroic, systematic attempts to cool the Russian economy, the damn thing is still thrashing! And not all young scientists have yet left Russia for the Promised Land and the blessed West to live permanently.
The respected author is very fond of the West, which is probably why he hasn't written a single line about the experimental pleasure river vessel "Ecobalt," project 00393. The Krylov State Research Center (KSRC) developed a hydrogen power plant; the vessel was built in Zelenodolsk. In the summer of 2025, the Ecobalt successfully tested the system on the Volga. Later, tests were conducted on a system with a PEM battery—a device that generates electricity from hydrogen and oxygen through a chemical reaction, without burning fuel. The only byproduct of the process is water. The power plant is distinguished by high efficiency, environmental friendliness, the ability to flexibly respond to changes in load, and a virtually complete absence of noise. - https://spb.aif.ru/society/v-rossii-odobrili-proizvodstvo-pervogo-passazhirskogo-sudna-na-vodorode. More details here: https://paluba.media/news/53843
Technical characteristics of the vessel project 00393:
length - about 15,4 m;
width - about 3,3 m;
draft - about 0,54 m;
passenger capacity - 10 people;
crew - 2 people;
speed on calm water - up to 12 km/h;
Flight duration is 5 hours.

[AlexisT]

The title talks about ammonia as a fuel, but the text only mentions, in one sentence, that it's promising. Why bother with such a title?!

[Alexander Mitrofanov]

Read the continuation, it is clearly written there.

[Pravodel]

Engines running on methanol, LNG, or something else are interesting. But is this a topic for the website https://topwar.ru???? Or have journalists and newsreaders simply lost their focus and switched to popular science topics?

[Alexander Mitrofanov]

I'm not a journalist or a newsreader, but a marine mechanic. If you're not interested, don't read. It's voluntary.