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In need of a sea change

Published by , Senior Editor
Hydrocarbon Engineering,

The maritime industry is undergoing a historic period of adjustment. The road to full economic recovery following the economic downturn of 2008 has been hampered by COVID-19 pandemic-related challenges, while at the same time environmental legislation is being tightened globally. It is a tough twosome to combat and an operational re-think is essential if the industry is to flourish again.

It is becoming increasingly clear that something has to change if ship owners and operators are to successfully overcome the operational cost and environmental regulatory hurdles that they are now encountering. Efficiency levels need to be raised, the latest smart technologies need to be introduced, and environmental performance needs to be improved. These are the fundamentals of the transition currently taking place throughout the sector.

This is not to suggest that the maritime industry has been standing still. Some significant changes have been taking place during recent years, but the pace needs to be upped and more needs to be done if real change is to be accomplished. Wärtsilä has focused heavily on developing products, systems, and integrated solutions that can achieve this change. For example, for the past 40 years the company has been working on developing dual-fuel engine technology.

Dual-fuel engines have made possible a global acceptance of LNG as a viable marine fuel, since conventional fuels can still be used where LNG is not available or where the regulations are not so strict. Today, LNG is viewed as being an important ‘transitional’ fuel, bridging the gap between conventional exhaust gas-emitting diesel fuels and a new generation of yet-to-be-adopted carbon-free fuels. LNG eliminates sulfur oxide (SOX) emissions, since natural gas contains no sulfur. Similarly, particle production is practically non-existent, due to the efficient combustion of natural gas (a fuel with almost no residuals), while nitrogen oxide (NOX) emissions are reduced by some 85%. With LNG, CO2 emissions are lessened by up to 25% compared to heavy fuel oil (HFO), making the fuel a realistic step in the right direction for meeting the industry’s goal of reducing greenhouse gas emissions by 50% from 2008 levels by the year 2050.

The situation today

In 2005, the International Maritime Organization (IMO), the United Nations agency responsible for the “safety and security of shipping and the prevention of marine pollution by ships”, established a series of Emission Control Areas (ECAs) and in some areas Sulphur Emission Control Areas (SECAs). From 2015, ships sailing in SECAs have been restricted from using fuel with a sulfur content of more than 0.1%, while in all other areas the sulfur content limit has been lowered to 0.5%, effective from January 2020.

These restrictions are being met through three basic means: switching to LNG fuel; continuing with conventional fuels but with exhaust scrubbers installed; and by the use of low sulfur fuels. The preferred option, to use fuels with low-content sulfur, has so far been the easiest of the three. This is because of the narrowing price differential between conventional and low sulfur fuel oils, which reflects the sharp decline in oil prices generally, and the improved availability of low sulfur fuel.

However, oil prices fluctuate constantly and the low fuel costs of today may become nothing more than a pleasant memory at some point in the future. With this in mind it should be remembered that high fuel oil prices were at the heart of the shipping industry crisis that began in 2008. On the other hand, while LNG-fuelled propulsion is rapidly gaining favour for certain types of newbuild vessels, it is a somewhat costly conversion project for existing ships.

Hybrid propulsion, using a combination of marine engines and battery storage, is also emerging as an additional option for short journey vessels, such as ferries and harbour tugs, as well as offshore platform service vessels. With these vessel types, zero-emission operation is possible when using only batteries. However, for deep-sea sailing over long distances, limited battery life restricts the viability of hybrids – with the possible exception of cruise ships that can switch to battery propulsion when visiting ports or sailing in protected pristine waters.

Looking to the future

Central to making ship operations cost-effective and compliant with the regulations will be the continued use of combustion engines for propulsion power. No energy converter is more flexible than the internal combustion engine. It only requires a limited exchange of components for the marine engines used today to be able to operate with any of the clean fuels expected to become available during the coming years. Although related requirements, such as the fact that storage, handling, and fuel supply systems will need to be addressed, given the properties of the emerging fuels these are manageable challenges. Building ships with future conversions in mind will also help overcome any problems in these areas. Flexibility of the power production solution will be an essential element in new-build vessels from this point on, and ships with the built-in flexibility to convert to new fuels will have an important hedge against possible risks associated with newly introduced fuels.

Wärtsilä believes that the role of LNG as a transitional fuel is extremely important, since the next logical step is the production of bio- and synthetic LNG. These could be used initially as drop-in fuels alongside conventional LNG to reduce its fossil carbon content and later, as supply increases, to replace it entirely. Again, the flexibility of the internal combustion engine allows this next step to become entirely viable, since engines and fuel systems operating with LNG require no changes to be made in order to operate with bio- or synthetic LNG. Furthermore, the same bunkering infrastructure that is already established can be used, which means that these fuels have a significant head-start over other emerging fuels that will need to have an infrastructure built from scratch.

On the downside, the production, supply, and incomplete combustion of LNG creates emissions of methane, a potent greenhouse gas. However, modern engine technology has notably reduced the level of methane slip and further developments over the coming few years will reduce this even further. At the same time, the largest source of methane emissions – the production, storage, and transport of fossil LNG – will be significantly abated with the introduction of biomass and synthetic sourced versions.

The likely alternative future fuels

The research and testing of alternative carbon-neutral marine fuels has been going on for some years already, and much is known of their benefits and drawbacks. In addition to LNG, the supply, storage, and control systems developed by Wärtsilä are capable of handling, for instance, LPG, bio-diesel, methanol, and volatile organic compounds. There are already ships in operation fuelled with these alternatives.

Nevertheless, the IMO’s greenhouse gas reduction targets have given new impetus to this work. The company is investing heavily in development work in order to speed the transition to decarbonised shipping. Combustion trials using ammonia have already been initiated and these tests will be continued with both dual-fuel and spark-ignited gas engines. The world’s first long-term, full-scale testing of ammonia in a marine 4-stroke engine is set to commence in Norway with support from the Norwegian Research Council through its DEMO 2000 programme. Field tests in collaboration with ship owners are expected to commence in 2022 or earlier.

Ammonia is a promising, carbon-free fuel that, although currently derived mainly from fossil sources, will likely be able to be produced in the future using electricity from renewable sources. This will virtually eliminate ammonia’s greenhouse gas footprint. In comparison with hydrogen, another fuel that is often mentioned as a future clean alternative, ammonia has several advantages. Notably, it has a greater energy density than hydrogen, and it does not need to be stored under compression or at very low temperatures.

The disadvantages of ammonia are that it is toxic and highly corrosive, making it difficult to handle. However, Wärtsilä has already been designing cargo-handling systems capable of being used with ammonia for several years. These are installed on LPG carrier vessels and the technology is clearly well-established. The other negatives are that it ignites and burns poorly compared to many other fuels, and combustion could lead to higher emissions of NOX unless controlled by after-treatment systems or by optimising the engine process. Nevertheless, Wärtsilä believes that in combination with clean energy production from renewable energy sources, ammonia could become an important carbon-free fuel for shipping. Furthermore, the company’s involvement in the development of systems that will supply ammonia to fuel cells will provide valuable data on the viability of long-range, zero-emissions shipping with high power utilisation.

Another interesting candidate for future fuel adoption is methanol. Methanol is an easily and inexpensively produced industrial alcohol that is made predominantly from natural gas. By using hydrogen from renewably-sourced electricity and recaptured carbon, carbon-neutral green methanol could be produced. Methanol is easier and safer to handle and store than ammonia, and it has better combustion properties. A Swedish ferry has been operating on methanol fuel since 2015, and the company is seriously studying its potential for expanded use with marine engines. As mentioned earlier, hydrogen is often cited as being a likely future alternative fuel but its potential is somewhat limited for marine applications. Hydrogen has a low volumetric energy density, meaning that large storage tanks would be needed on board ships. For example, liquefied hydrogen has around a third of the energy of LNG per cubic metre, and it is corrosive and explosive. There may be some niche maritime applications in short-voyage vessels, but hydrogen’s main attribute will probably be as a building block for other fuels.

Availability and price will be the deciders

Biofuels in various forms represent a relatively simple path towards decarbonised shipping. They can be used in both diesel and gas engines, and with existing storage and supply systems. The question is, however, whether sufficient supplies can be scaled up to meet the needs of the global fleet and whether or not this can be done at a competitive price. Wärtsilä’s work with developing advanced combustion techniques for efficient use of biofuels has continued for some years, and the engine performance is now at a point where particle emissions and sulfur content are significantly reduced. In other words, the technology exists but the lack of a realistic supply infrastructure remains a hurdle yet to be overcome.

The willingness of the maritime industry as a whole to create clean and green operations is not in question. The IMO has set the targets and shipping, by and large, is willing to do its best to achieve them. Efficiency upgrades to lower fuel consumption are an established means for lowering operating costs, and this will also naturally reduce exhaust emission levels. But the long-term key to sustainability for the industry will be the adoption of carbon-neutral fuels, and although development work is well under way, full acceptance by owners and operators of switching from their known and trusted fuels may be a harder nut to crack.

Written by Mikael Wideskog and Kaj Portin, Wärtsilä Marine Power, Finland.

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