Carnival’s AIDA Cruises launched its first liquefied natural gas (LNG) cruise ship in 2018, providing confirmation that the company was taking its CO2 emissions output very seriously. This was underscored when Carnival’s Italian-branded Costa Cruises took delivery of its first LNG-powered ship, the Costa Smeralda, in 2019. And in December 2021, its second LNG ship, the Costa Toscana, followed.

Tom Strang, senior vice-president of maritime affairs at Carnival Corporation, is also taking the CO2 emission issue seriously as he oversees the company’s long-term objective to reduce its carbon footprint.

For example, its 2030 goal, aligned with that of the International Maritime Organisation, is to reduce carbon emissions by 40%. Carnival also intends on achieving net carbon-neutral ship operations by 2050.

Meeting key objectives

Central to realising these objectives has been an expansion of the company’s alternative fuel strategy across its LNG programme. As well as battery, fuel cell and biofuel capabilities, the aim is to deliver a 50% reduction in absolute air emissions (of particulate matter) by 2030, relative to a 2015 baseline. And this is despite a more than 10% increase in capacity since 2015, as well as the factoring in of an additional 19% capacity currently on order.

An odourless, colourless, non-toxic gas, LNG is the cleanest burning fossil fuel available. Indeed, when compared with traditional ship fuel (marine diesel), the reduction in CO2 and nitrogen oxide emissions is significant.

LNG also eliminates nearly all particulate emissions (like soot) and sulphur oxide emissions, benefiting the environment and the sea air that passengers breathe while on board, according to Strang.

With four LNG-powered cruise ships currently in operation, Carnival intends on having a grand total of 11 next-generation cruise ships across its fleet through 2025, which will represent nearly 20% of its total capacity.

For Strang, availability of LNG is certainly not an issue; indeed, it is improving all the time. “We’ve now taken LNG from 12 ports worldwide, with permission for more, and that number continues to expand. By working with partners like Shell, for example, we’ve managed to ensure we have the LNG supply we need, and when and where we need it,” he says.

Similarly, he pushes back regarding the question of space, given LNG takes up approximately 1.8 times the space of conventional fuels, especially when stored in C-type tanks. “If we weren’t careful in the planning and design of our next-generation LNG ships, we could have potentially lost revenue-generation space. However, given that a number of other systems are no longer needed when using LNG, such as fuel treatment, by utilising clever design, that has not been the case.”

A plan for the future

Strang has previously described LNG as both a short-term and long-term solution, and, currently, the most future-proof technology available – in major part due to ongoing incremental improvements.

“We are continuously improving the plans on each of our ships, both from a design and operational perspective. However, any changes are relatively minor, as we spent a considerable amount of time in the design of our LNG ships to ensure we had a safe and reliable platform,” says Strang.

He adds: “In the first of our LNG ships, we have three standard cylindrical LNG tanks, whereas our next-generation LNG ships have two bi-lobe tanks that will help space utilisation. We have also spent a lot of time on the operational aspects and have seen bunker times drop by around 25% through careful analysis of the system and training of our personnel.”

The key consideration, however, is choice. Strang argues that, as you transition to a net-zero future, you can either wait for a potentially perfect fuel to come along or act now by making use of the most sustainable fuels that are commercially available at scale currently.

“In our view it’s better to take action now, and the significant increase in the number of ships that are LNG-powered demonstrates that more and more ship owners and operators recognise this option,” he says, adding: “The beauty of LNG is that all parts of the system – fuel supply chain, tanks on board ships, bunker vessels, etcetera – are fully compatible with both bioLNG and synthetic LNG.

“BioLNG from sustainable biomass resources is increasing in availability and, as hydrogen feedstock grows on the back of renewable or net-zero electricity, then synthetic LNG can become competitive.”

Carbon savings reaped will self-evidently be determined by the type of technology used, for example, from internal combustion engines of different types through to gas turbines or even fuel cells.

As Strang puts it: “We need to use dual fuel engines, we can expect savings of around 12% with LNG, when compared to using compliant, very low-sulphur fuel oils. With the advancements that are expected in the reduction of methane slip within this decade, we expect to see this increase to around 22% in carbon savings.”

Stay ahead of the game

Of similar importance has been the training of crew and shore staff, with Carnival opting to train current teams to the required standard rather than going out into the LNG market. “One significant training advantage for [Carnival] and our brands has been the development of our state-of-the-art crew training, professional development and research facility in the Netherlands – the Arison Maritime Center, home of the Center for Simulator Maritime Training Academy, or CSMART Academy,” Strang notes. “[This] has enabled us to stay ahead of the game and continually improve our training processes and content, including top-notch instructors, immersive courses and leading simulation technologies.”

Similarly, the company has had to develop the designs, technologies and the supply chain, alongside processes with ports and authorities, that other cruise and shipping companies are ultimately able to benefit from. “Collaboration is extremely important, and we are happy to share our experiences and learn from others. As an example, we have joined various member work groups and organisations, such as SGMF and SEA-LNG, to do just that,” says Strang

“Collaboration is extremely important, and we are happy to share our experiences and learn from others.”

LNG is not the only game in town when thinking long term though, given the potential benefits of hydrogen fuel cell technology, as well as the ongoing debate over marine gasoil (MGO) versus LNG.

However, hydrogen fuel cell technology is yet to be economic at scale. Not least because while hydrogen fuel has a clean combustion process, the creation of hydrogen for use in a vessel as large as a cruise ship still requires massive amounts of energy, therefore, the costs are prohibitively high.

“We’ve looked at hydrogen as another possible low-carbon fuel solution and while there are certainly advantages to its use, there are significant barriers as well,” says Strang. “Even in its liquid form (at -283°C), it will require at least four to six times as much volume as conventional fuels when filling limits are taken into account,” he adds.

Strang also points out the technical challenges to overcome when considering its flammability, such as including codes and standards for fuel storage in marine use, as there is currently no approval in place to store hydrogen below deck for cruise ship types. “Given those barriers, it’s most likely we’ll need to look at alternative hydrogen carriers such as methanol, ammonia or synthetic LNG.”

The strongest substitute

Synthetic LNG is regarded as the most efficient alternative, since the molecule is the same as LNG. This being the case, according to Strang, there are no changes needed; however, the production facilities and prices are two aspects that must be taken into consideration as well.

“For ammonia, I am confident our engineers and designers would be able to find appropriate solutions for handling it safely, but I am not convinced the cruise sector will be [the] first to use ammonia.

“Methanol – from either sustainable biomass or synthetic sources – is another promising solution and we are investigating its use in a fuel cell on board one of our LNG ships: the AIDAnova. Although small, the project will demonstrate the use of polymer electrolyte membrane technology and reforming methanol into hydrogen,” Strang adds.

Up for debate

In the meantime, debate continues regarding MGO versus LNG; proponents of the former arguing LNG is only a short-term solution. Moreover, it gives off methane, which is a worse greenhouse gas to emit than CO2. Yet, as Strang argues: “Even when methane slip is taken into account, LNG has lower greenhouse gas emissions than MGO and solves the issue of local pollutants, such as nitrogen oxide, sulphur dioxide and particulate matter.

“At the same time, liquefied natural gas facilitates a very clear pathway for the decarbonisation of the global maritime industry, allowing for the introduction and use of other possible low-carbon fuels through bio to synthetic fuels. Its use also helps us prepare for the application of other potential challenging fuels such as ammonia, methanol or hydrogen,” he adds.

Improving efficiency through the use of technology is one thing, yet as history has shown, the best laid plans can quickly unravel due to circumstances beyond one’s control, such as the geopolitical instability currently giving rise to gas prices. It is an issue with no obvious solution, in the short term at least.