Alternative power ahoy: New fuel solutions for the shipping industry

The impact of heavy fuel oil and marine diesel used in shipping on our climate

By the end of 2021, the Uthörn II, the new research vessel of the Alfred Wegener Institute in Bremerhaven, was nearing completion. The Uthörn II will soon become the first German ocean-going vessel to use the more climate-friendly fuel methanol as it sails the world's oceans, especially in the Arctic and Antarctic. This new research vessel will replace the Uthörn I, which was launched in 1982. For good reason: Every year, the diesel engines of the Uthörn I emit around 250 tonnes of CO₂ into the atmosphere – equivalent to the annual emissions caused by around 26 people in Germany. This will soon come to an end.

The Uthörn II symbolises the dawn of a new era, considering that the global shipping industry currently faces the challenge of drastically reducing its pollutant emissions to play its part in the fight against climate change. And it is not a moment too soon: There are currently around 90,000 freighters and passenger ships on the world's oceans, which together burn around 370 million tonnes of fuel a year. The burning of fossil fuels such as heavy fuel oil or marine diesel results in a great many harmful emissions of sulphur oxides, nitrogen oxides, carbon dioxide, soot particles or fine particulate matter into the atmosphere. In addition, ship exhaust gases also contain heavy metals, ash and sediment. 

Globally, shipping is responsible for the emission of around 1 billion tonnes of carbon dioxide annually, equivalent to approximately 3 percent of all man-made CO₂ emissions. Or to put it another way: If shipping were a nation state, it would rank 7th in the global carbon footprint ranking. It was for this reason that, in 2018, the International Maritime Organization (IMO) stipulated that, by 2050, CO₂ emissions generated by the shipping industry must be reduced by at least 50 percent compared to 2008. For the International Chamber of Shipping, this target is not ambitious enough: The association, which represents 80 percent of the industry, has called for the shipping industry to be completely climate neutral by 2050. 

Alternative fuels for shipping

Alternative and carbon-free fuels represent attractive solutions for the decarbonisation of the shipping industry, but there remain a number of challenges. This is because each type of fuel has advantages and disadvantages in terms of the fuel's properties, the availability of technologies, and rules for the storage and use of the various fuels on board ships. Below we present the main sources of alternative energy that are currently being discussed.

Natural gas (LNG)

Natural gas (or methane, CH₄) is mainly used in industry in liquefied form, where it is referred to as liquefied natural gas (LNG). The use of liquefied gas can almost entirely avoid ship-generated emissions of sulphur oxide and fine particulate matter. Another advantage of LNG is that liquefying the gas at a temperature of -162 °C reduces the volume of the gas by 600 times, simplifying transport and storage. LNG also has disadvantages, however. Not only because of the high expense for the technology on board and the fact that special personnel are required to handle it. Because of the complex tank design, among other things, LNG ships are around 20 percent more expensive than conventionally powered ones. And if the LNG escapes (due to a leak, for instance), the escaping methane is about 25 times worse for the environment than CO₂. 

Furthermore, doubt has recently been cast on the CO₂friendliness of natural gas by the International Council of Clean Transportation (ICCT). Contrary to the long-standing assumption that CO₂ emissions from LNG are 20 to 25 percent lower than diesel, ICCT data show that LNG as a marine fuel actually generates higher greenhouse gas emissions than the previously used fuel from crude oil. Nevertheless, LNG could become more than purely a transitional technology because the gas can also be produced from biological waste or synthetically. 

LPG

LPG is a variable mix consisting mainly of propane and butane. Due to its poorer carbon-to-hydrogen ratio, LPG causes higher CO₂ emissions than natural gas. LPG is stored in liquid form, either under a pressure of 8 to 10 bar or at cryogenic temperatures when stored at ambient pressure, with the boiling point depending on the mixing ratio of the butane with the propane. The calorific value of the LPG also depends on this mixing ratio: The calorific value of propane is 12.9 kWh/kg and that of butane is 12.7 kWh/kg. 

The biggest advantages of LPG are its climate friendliness and ease of storage. However, since the energy input for the synthetic production of LPG is higher than for methane, LPG is unlikely to be a long-term or comprehensive alternative to diesel fuel. 

Methanol

Methanol (CH₃OH) is a source of energy that is comparatively easy to produce synthetically. Methanol can even be produced and used without harming the climate using electrical energy from renewable sources (such as wind power). Another advantage of methanol as an alternative fuel is that it is liquid at normal temperature, and therefore does not have to be pressurised or stored at cryogenic temperatures. Also, methanol is easy to handle both on board and on land because the alcohol is easy to transport and store at atmospheric pressure and ambient temperature. And engine combustion does not pose a problem although it only works using electric ignition or pilot injection. 

The biggest disadvantage of methanol compared to diesel fuel lies in its significantly lower calorific value, meaning that methanol is only able to cover around half the distance of diesel fuel. This is why methanol ships are designed with some special features due to the significant amount of space required for the tanks and for safety reasons. At 15 metres, the vent mast of the Alfred Wegener Institute's Uthörn II, for instance, which ventilates and vents the engine room and other areas of the ship, is significantly higher than usual. In the event of an unexpected methanol leak, this height prevents the methanol from starting to combust too close to the ship. Such extras can mean that a methanol ship can cost around € 1.5 million more than a comparable ship with diesel propulsion. 

Hydrogen

On Earth, hydrogen (H₂) is found only in bound form, the majority of it in water (H2O). In order to obtain H2 and use it as a source of energy, it must be separated from chemical compounds, such as hydrocarbons or water. If renewable energy sources such as wind power, hydropower or solar energy are used for electrolysis (the splitting of water into oxygen and hydrogen), this is referred to as 'green' hydrogen because it is produced CO₂-neutrally. 

According to the short study "Maritime Fuels" by the German Aerospace Center (DLR), hydrogen may be a practical solution for shipping due to its efficiency (water being the only by-product of its use). It would also permit the use of existing technologies (from fuel cell vehicles for example). Hydrogen also has a number of disadvantages, however. It is highly flammable, heavy and occupies a substantial volume. And handling liquid hydrogen, in particular, requires specialist expertise. 

Despite the drawbacks, hydrogen fuel cells could be an alternative to today's internal combustion engines, bearing in mind that hydrogen is only actually an emission-free option if made using renewable energy sources.

Liquid Organic Hydrogen Carriers (LOHC)

Liquid Organic Hydrogen Carriers (LOHC) are oil-based liquids that are able to store hydrogen through a chemical reaction with the oil. They can be handled like normal diesel oil using the existing infrastructure. The chemical binding of the hydrogen to the carrier liquid mitigates most of the risks.

LOHC for ships consists of an organic oil enriched with hydrogen (LOHC+). This is done in a facility on land. LOHC behaves similarly to diesel fuel in terms of storage, transport and handling and has about the same risk level as normal diesel fuel in terms of fire hazard and toxicity. It can also be bunkered in the same way. On board the ship, the hydrogen is released from the LOHC+, then used in a fuel cell or internal combustion engine, while the used LOHC (LOHC-) is stored in another tank on board. At the next bunkering of LOHC+, the LOHC- is unloaded from the ship. This LOHC is then enriched with hydrogen again at the production facility to be used again.

Currently, there are several projects (including a cooperation project between H₂-Industries and Lloyd's Register) aimed at obtaining approval for use of LOHC technology on ships that also deal with the refuelling of ships, the storage of LOHC on board and the generation of electricity on board. 

Ammonia

The only advantage that ammonia has over the aforementioned energy sources is the fact that it does not contain carbon. Neither carbon dioxide nor carbon monoxide are produced during its combustion. Ammonia is a highly toxic gas even in the smallest quantities, and therefore requires special precautions during transport and storage. The boiling point of ammonia is -33 °C, meaning that it has to be stored in special pressure vessels. Another disadvantage is that the calorific value of ammonia is less than half of methane.

Important note: The technologies and regulations for the transport, supply, storage and use of alternative fuels on board inland and ocean-going vessels are currently still in development. 

For specialist knowledge about all fuel issues, ask KSB!

The rules for reducing emissions in shipping are becoming increasingly strict. Given the 2050 target set by the IMO, ships will have to switch to alternative fuels in the very near future. Many aspects relating to the production, transport, storage and bunkering of the new fuels are currently being carefully investigated and developed. 

As an active participant in the alternative fuels sector, KSB is helping to shape developments in this area and is a reliable partner to ship builders, engine builders, equipment suppliers and component suppliers alike. KSB has long been a reliable partner to the shipping industry in the supply of pumps, valves, automation solutions and accompanying services. 

Shipping companies, shipyards and engineers alike have benefited from the high quality of KSB products, their wide range of possible applications, in-depth KSB expertise and the best service for many years. As a single-source supplier, KSB is well versed in chemical production processes and has detailed knowledge of the production, transport and storage of new alternative fuels and alternative energy sources. 

Do you have any questions on this topic or about our products? We look forward to hearing from you. Please contact us.