We burn for LNG in maritime shipping

Maritime transportation contributes significantly to air pollution. Compared to conventional fuels, the use of LNG drastically reduces the emission of air pollutants. In particular, sulphur dioxides, which are harmful to health and responsible for 'acid rain', are almost completely reduced and nitrogen oxides are reduced by 90%. Almost no soot particles can be measured. The effect of LNG is sustainable and already clearly meets all existing and upcoming emission limits (IMO 2020).


less sulphur dioxide


fewer soot particles


less nitrogen oxide


less carbon dioxide

LNG stands for "Liquified Natural Gas". As a fossil energy carrier, natural gas is a mixture of substances that was formed long ago from organic materials.

LNG is an odourless, colourless, non-corrosive, non-flammable and non-toxic liquid. Compared to petrol and diesel, LNG is as a start less dangerous.

The main component of natural gas is the saturated hydrocarbon methane (CH4) with >85%. Secondary components of natural gas are higher hydrocarbons such as ethane, propane and butane and other incombustible components such as nitrogen, carbon dioxide, oxygen, water, traces of noble gases and sulphur components.

Gaseous natural gas has a significantly lower density than liquids. This is impractical for fuel applications on seagoing vessels. By changing the aggregate state from a gaseous to a liquid state, the density (also energy density) is compressed 600 times. The natural gas is cooled down to -160 degrees. The liquefaction enables the use of LNG as fuel on seagoing vessels.

In Europe, a distinction is made between the two natural gas qualities High Calorific Gas (HCV) and Low Calorific Gas (LCV). HCV gas has a higher methane content and a higher energy content than LCV gas. The LNG used as fuel on ships in Europe, is an HCV gas.

Compared to fuels conventionally used in shipping (heavy oil, gas and diesel oils), LNG significantly reduces pollutant emissions.

A further advantage of LNG is the more engine friendly combustion process, which has a noticeable effect on the maintenance costs of the engine. At the same time, the costs associated with the use of heavy oils for processing the heavy oil (heating, separation/filtering) and disposing of oil residues are eliminated. Another positive side effect is the noticeably reduced odour nuisance in the engine room and in the immediate vicinity of the funnel. Contamination by soot particles is also eliminated.

The lower CO2 emissions of four-stroke engines must be considered and evaluated from the point of view of the ’methane slip’. Put simply, methane slip is the process of methane loss through the exhaust valve during the combustion process in the engine. Engine manufacturers are currently working on solutions to avoid methane leakage. In practice, it has been shown that the CO2 balance of four-stroke engines is still positive when LNG is burned, i.e. even a four-stroke engine produces fewer greenhouse gases when LNG is used than when heavy oil or gas/diesel oil is used.

Today's LNG technology for using LNG as a fuel is still based on fossil LNG. Fossil LNG is CO2 reduced compared to conventional fuels but not CO2 neutral! With the technology used, however, synthetically produced LNG, so-called SNG, can be used. If the SNG is produced from renewable electricity, it is CO2 neutral SNG, which can be added to the fossil LNG in the tank or even replace it. In the latter case, the ship can actually run climate-neutral.>

Power-to-Gas (PtG) is a promising method of SNG production for the future. In this process, hydrogen (H2) is first produced from water (H2O) with the aid of an electrolyser and electricity. The hydrogen can be combined with carbon dioxide or carbon monoxide and converted into a synthetic natural gas with the aid of a catalyst.

Overview of the advantages of LNG as maritime fuel:

  • Sustainable compliance with IMO requirements
  • Significantly reduced pollutant emissions
  • Reduced maintenance costs for the drive system
  • Reduced maintenance effort for the crew
  • Reduced odour nuisance (reduced health burden)
  • Paving the way to climate neutrality

LNG has been transported safely across the oceans for around 50 years. LNG has not been widely used as a fuel so far. Therefore, potential users and the general public are often still unaware of its hazardous properties and its proper treatment. Particularly in ports, the question arises: how safe is LNG? And, what is important for safe handling of LNG?

In order to protect people and the environment from adverse effects when handling chemical substances, all chemicals are subject to classification and labelling requirements before they are placed on the market. According to EU CLP Regulation EG/1272/2008 (Classification, Labelling and Packaging), a distinction is made between physical hazards, health hazards and environmental hazards.

LNG is an odourless, colourless, non-corrosive, non-inflammable and non-toxic liquid. Compared to petrol and diesel, LNG is initially less dangerous.

But LNG is a cryogenic liquefied gas. In the case of unprotected exposure, it can cause cold burns on contact. It can also lead to embrittlement of materials that are not cold-resistant. As a preventive measure, appropriate protective clothing is worn when handling LNG. Equipment and components that come into contact with LNG are designed for cryogenic temperatures.

On the other hand, LNG consists of natural gas or mainly methane. This is flammable only at high temperatures. Evaporation, however, produces a highly flammable and explosive gas. Compared to petrol (1.4 - 7.6 %) and diesel fuel (0.6 - 7.5 %), the ignition limits of methane-air mixtures are about twice as high and range from 4.4 to 16.5 %. However, methane is only flammable at higher mixture concentrations.

To burn methane, an oxidizing agent (air/oxygen) and an ignition source are required. For the safe handling of evaporating LNG it follows: LNG is stored and transported in closed, i.e. sealed systems/tanks without air/oxygen supply. Cryogenic pressure tanks used have high safety reserves and are equipped with relief valves. Potential ignition sources are avoided. Since methane is lighter than air, it quickly escapes upwards. Methane, like all other gases, is therefore stored either outdoors or, if indoors, only with good ventilation. The use of gas sensors increases the safety of applications with and storage of LNG in enclosed spaces.

For the safe handling and storage of LNG, both on land and on ships, there is a variety of international codes and standards, especially ISO standards. Compliance with these standards and safety requirements is ensured by the classification societies. 

Yes, LNG can be bunkered! Depending on the location, either on the water side (ship-to-ship) or from land (truck-to-ship).

Rotterdam is currently the port where most LNG is stored as fuel. In addition to shore-side supply by truck, various water-side bunker facilities are now also used or offered here.

Titan LNG supplies LNG with the FlexFueler I, a non-self-propelled bunker barrage in Rotterdam. Two further bunker barges of this type are already under construction. These will also be used in the ARA range.

Shell uses the Cardissa and the London. The latter is a 3,000m3 LNG bunker barge, which is mainly used for bunkering in Rotterdam.

Nauticor's Kairos and Gasum's Coralius are mainly deployed in the Baltic Sea region, where they also offer bunkering at various locations.

The price per ton of LNG delivered depends, among other things, also on the bunker location. The further away the bunker location is from the LNG site (LNG hub), the more expensive it becomes. One ton of LNG delivered in Rotterdam is significantly cheaper than one ton of LNG delivered in Brunsbüttel.

When LNG is used as maritime fuel, the guarantee of LNG supply must always be analyzed and checked. Here Wessels Marine offers assistance.

Here is the LNG Map 


LNG bunkering is more complex than bunkering oil-based fuels. Control mechanisms and safety equipment as well as special protective clothing for personnel is required (see IGF Code).

Currently, two methods of LNG transfer are in use. The Truck-to-Ship (T-t-S) and the Ship-to-Ship (S-t-S) method. With the former, LNG is delivered to the ship by truck. Delivery by truck is very time-consuming and requires a secure bunker location, preferably a pier, where no other activities are taking place during bunkering. Loading and unloading during the truck-based bunker process is generally not possible.

As with conventional fuel, the Ship-to-Ship method can be carried out independently of the terminal, as the supply is from the water-side. It is also possible to carry out loading movements (SIMOPS = simultaneous operations) during the bunker process, as long as the safety distance to the bunker station and the respective terminal is permitting that.

The price for LNG consists of different components. A purchase price, transfer fees, processing fees, logistics costs and margins.

The retail price for LNG from the Netherlands is based on the TTF (Title Transfer Facility). This is a price index that results from the trade and sales volumes. The TTF is a EUR price per megawatt hour (MWh).

LNG bunker suppliers purchase their LNG from gas storage companies (e.g. Gasuni at the GATE terminal in Rotterdam) and pay the current TTF plus transfer fees. They add processing fees, logistics costs and a profit margin, which ultimately results in the price for a delivered megawatt hour (MWh) of LNG.

What is Boil-Off-Gas (BOG)?

Cryogenic liquid gases must be stored in well insulated tanks in order to keep pressure increases as low as possible. Due to the warmer environment of the tank, part of the liquid evaporates continuously. The vaporised gas content in the tank is called boil-off gas (BOG) and steadily increases the pressure in the gas tank. In practice, the resulting BOG is either fed to a consumer (e.g. combustion engine) and thus degraded, or it is returned to its liquid state by a liquefaction plant and fed back to the tank.

What does energy content mean?

Another important parameter for the energetic and economic value of an energy source is its usable energy content. This is called the lower calorific value for combustion engines. Relative to the gravimetric calorific value (mega-joules per kilogram), natural gas and LNG have a higher energy content than diesel fuel. For pure methane this is 50 MJ/kg and for natural gas (in the EU mix) about 45 MJ/kg, while diesel fuel only reaches 43 MJ/kg. Marine gas oil and distillates are close to diesel; heavy fuel oil with a density of about one kilogram per liter is heavier and only reaches 40.5 MJ/kg (JEC 2014c). Paraffinic EN 15940 diesel from natural gas (gas-to-liquids) is somewhat lighter than diesel fuel and, at 44 MJ/kg, therefore also achieves a slightly higher energy density than diesel fuel.

How is the price calculated for one tonne of LNG?

In shipping, the unit of measurement 'tonne' is traditionally used in connection with bunker consumption or purchasing. The respective products (HFO, LSFO, ULSFO, MGO, MDO etc.) are traded in US dollars.

Due to different gas compositions and thus different energy content per tonne or cubic meter, gas trading is done differently. The quantity of energy actually delivered is traded, the unit of measurement is the mega-watt per hour and the trading currency is EUR or USD. There are various indices for LNG in Europe, the TTF (Title Transfer Facility) is currently the most voluminous. In Europe, LNG is sold in EUR per mega-watt hour (MWh).

With an easy-to-use 'rule of thumb', a tonne-based LNG price can be calculated. First, the LNG supply price per megawatt hour is calculated.

TTF + (margin + handling + logistics) = price for delivered LNG in EUR per MWh

When converting mega-watt hours into tonnes, the price per MWh is multiplied by the HCV ('higher calorific value') for LNG. The energy content (HCV) in one tonne of LNG corresponds to approx. 15.25 mega-watt hours.

(EUR pro mW/h) * HCV

Example:    delivered price:    12,00 € + 10,00 €    = 22,00 € per MWh
    conversion:    22,00 € per MWh * 15,25 MWht per tonne   = 335,50 € per tonne

This is merely a ‘rule of thumb’ for determining a tonne-based LNG supply price.

When comparing the price of LNG with other fuels such as HFO or MGO, the different energy content (kJ/kg) must be taken into account. Because, with one tonne of LNG (approx. 49,700 kJ/kg per tonne), the ship gets further than with one tonne of MGO (42,700 kJ/kg per tonne).

What does the methane number tell us?

To be able to describe the LNG quality, a new parameter was introduced, the methane number. The methane number (MN) is a measure similar to the octane number. It gives information about the knock resistance of different LNG qualities. Pure methane by definition has a methane number of 100, hydrogen a methane number of 0. If the proportion of higher alkanes such as ethane, propane, butane and pentane in natural gas increases, the methane number drops significantly.

Other alternatives to conventional fuels?

Renewable alternatives to fossil natural gas (LNG) are bio-methane, synthetic natural gas from bio-mass (Bio-SNG) or SNG by power-to-gas (PtG-SNG).

Ships are major contributors to the emission of traffic-related air pollutants. Emissions of soot particles from ship engines are also extremely high, as the presence of sulphur causes the formation of large (and therefore massive) particles and there are currently no particulate filters that can be used in this area. However, other air pollutant emissions from shipping are still significantly higher today than in road traffic or stationary applications on land, for technical exhaust gas purification systems such as those used in power plants and road traffic have only been required and implemented in shipping for a few years.

When burning mainly fossil fuels, shipping also generates greenhouse gas emissions (carbon dioxide = CO2). The share of global CO2 emissions caused by international shipping is estimated at 2.8 to 3.1 % (IMO 2015).

Diesel engines are responsible for 80% of nitrogen oxide emissions, with ocean shipping making a significant contribution. For example, almost one third of the nitrogen oxide emissions in Hamburg are caused by the port operations of the port of Hamburg. Nitrogen oxides - especially nitrogen dioxide - irritate and damage the respiratory organs. Increased concentrations in the air we breathe have a negative effect on lung function. Nitrogen oxides act at various points in the atmosphere. They contribute significantly to the depletion of ozone in the stratosphere, play a role in global warming as climate-relevant gases, cause acid rain and promote the formation of smog.

High concentrations of sulphur dioxide emissions damage humans, animals and plants. The oxidation products lead to "acid rain", which endangers sensitive ecosystems such as forests and lakes and attacks buildings and materials. Over the past two decades, however, the SO2 emissions of developed industrial countries have been greatly reduced through the use of low-sulphur or sulphur-free fuels and fuel gas desulphurisation (scrubbers).

Of all modes of transport, international shipping makes the highest contribution to emissions. There, the maximum permissible sulphur content in fuel for ships is currently still 3.5 percent. However, the IMO will reduce the limit value to 0.5% by 01 January 2020. In the Baltic and North Seas there are sulphur emission monitoring areas (SECA) in which the limit value today is 0.1%.

Since the late 1990s, the Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO) has gradually introduced mandatory limit values for emissions from seagoing ships. The first binding guidelines for the limitation of pollutants contained in exhaust gases were laid down in Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL) in 1997; in 2008 the exhaust gas regulations were further tightened. Internationally limited exhaust emissions include nitrogen oxide (NOX), particulate matter (PM) and sulphur oxide (SOX) emissions.

In particular, densely populated coastal areas should be protected with regard to air pollutants. As a result, there are already different global and local emission limits. The so-called Emission Control Areas (ECA) have been designated by the IMO as special zones with stricter environmental guidelines, whereby particularly strict restrictions apply in coastal areas for the emission of sulphur oxides (Sulphur ECA), nitrogen oxides (Nitrous Oxide ECA) and, to a lesser extent, soot particles.

ECA areas currently include the entire North and Baltic Sea region (including the English Channel), the waters of the east and west coasts of North America, including Hawaii and the Great Lakes of Canada, and the coastal waters of Central America.

The respective restrictions show significant differences: While the limit values for sulphur oxides are determined by the content of sulphur in the fuel and apply to all ships within the restricted area, the nitrogen oxide limit values are determined in relation to the energy unit produced and only apply to new builds that are laid on keels after the limit value comes into force and operate within the restricted area. The particulate limit values, in turn, currently only apply within the coastal waters of the United States restricted by the U.S. Environmental Protection Agency (EPA) and apply to all ships in those waters.

While the North Sea and Baltic Sea are currently subject to even stricter limits for sulphur and nitrogen oxide emissions and will be subject to even stricter limits from 2020, the emission of soot particles has not yet been regulated here. One of the reasons for this is the persistent disagreement as to whether the particulate mass or the number of particularly small particles in this emission group should be limited and which measurement methods should be used.

In addition to the IMO requirements under MARPOL Annex VI, the Sulphur Directive 2016/802/EU adopted by the European Commission in 2012 to reduce the sulphur content of marine fuels from 3.5 % to 0.5 % by January 2020 applies to other European coastal waters.

A direct limitation of greenhouse gas emissions from shipping does not yet exist. However, the IMO Regulations on Energy Efficiency of Ships already regulate the energy efficiency of ships, which can also reduce greenhouse gas emissions.

Since 2011, this GHG reduction potential has been measured by the Energy Efficiency Design Index (EEDI) for new ships. In addition to the EEDI, the Energy Efficiency Operational Index (EEOI) as a monitoring tool is intended to simplify the evaluation of fuel efficiency and the management of the fleet and provide clues for efficiency-enhancing measures. Because the EEDI only applies to new builds, however, the effect of this efficiency-enhancing regulation will only become apparent in the long term, and the EEDI only applies to selected ship types.

Based on the greenhouse gas study of 2014 published by the IMO (IMO 2015), a reduction in CO2 emissions of at least 40 % by 2030 and at least 50 % by 2050 compared to 2008 is targeted. Since 1 January 2019, all larger ships (over 5000 GT) have been obliged to document consumption and emission values. The recorded data are evaluated annually by the IMO. A strategy with short, medium and long-term measures, such as the development of low CO2 fuels, is to be published in spring 2023. This is intended to confirm or correct the greenhouse gas targets set for shipping in 2014.

So-called bunker fuels are used in international shipping. Depending on the collection method - top-down approach (IEA 2018c) or bottom-up method (IMO 2015, 2016) - the consumption data for shipping varies. It is assumed, however, that around 300 million tonnes of ship bunkers are currently consumed worldwide each year.

Marine fuels are usually subject to certain requirements such as viscosity, specific gravity, sulphur content, ignition point and others. The most important international standard for marine fuels is ISO 8217, which distinguishes between two categories of marine fuels: Distillates and residual fuels, each of which is divided into six to seven additional fuel qualities.

One product of crude oil distillation - similar to diesel fuel - is marine gas oil (MGO). Apart from the ignition temperature, MGO has product properties comparable to those of heating oil.

One residue from crude oil processing is heavy fuel oil (HFO). Unlike MGO, heavy fuel oil must be heated before it can be used.

In addition, marine diesel oil (MDO) is also available; these are mixtures of HFO and MGO. Sea-going vessels can use both heavy fuel oil and marine gas oil; inland vessels in the EU are only been allowed to use diesel fuel since 2011.

More than three-quarters of bunker fuels are heavy fuel oil. Almost half (46%) of global demand for heavy fuel oil comes from shipping. Nearly a quarter of bunker fuels consist of marine gas oil (MGO).

In order to reduce sulphur oxide emissions, the permitted sulphur content of bunker fuels were continuously reduced by MARPOL Annex VI. From 1997 onwards, the sulphur content of bunker fuels was initially limited to 4.5 %, from 2012 onwards to 3.5 %. Following a review of the global availability of heavy fuel oil (IMO 2016), the IMO decided to reduce the sulphur content of marine fuels worldwide to only 0.5% from 2020. This initiative is generally referred to in the industry as "Sulphur Cap 2020".

This fuel quality requirement can be achieved either by marine gas oil, very low sulphur fuel oil (VLSFO) or corresponding fuel blends of gas and heavy oil.

Alternatively, Exhaust Gas Cleaning Systems (EGCS), also known as scrubbers, can be installed. However, these can only be installed in a small fraction of the ship fleet at short notice. This means that from 2020, only a small proportion of ships will be allowed to continue using heavy fuel oil with sulphur contents in excess of 0.5%; most ships will be required to use VLSFO (IMO 2016).

Shipping must limit sulphur emissions. LNG is therefore an interesting and relevant alternative to marine fuel because it contains only "homeopathic" quantities of sulphur. In 2012, 8 million tonnes of global bunker fuel demand was consumed in the form of LNG, primarily by LNG carriers (LNGCs). This could change as more and more ships are equipped for LNG as fuel. The IMO expects maritime LNG consumption to increase to around 12 million tonnes of LNG in the short term (IMO 2016). However, there are other regulatory developments that favour the use of LNG as marine fuel. In Emission Control Areas (ECA), such as the North and Baltic Seas, only marine fuel with an ultra-low sulphur content of 0.1% (Ultra Low Sulphur Fuel Oil ULSFO) or heavy fuel oil in combination with scrubbers or low-emission LNG may be used since 2015. In ECAs, LNG as marine fuel would be an even more relevant low-emission alternative.