Methanol offers exciting prospects for cruise industry’s green drive

By Kari Reinikainen

Methanol has been suggested as a fuel option for the cruise industry in its efforts to reduce its carbon footprint. Although there are advantages in terms of storage and energy contents, green methanol is very expensive. And there are design issues to consider.

Fincantieri, the Italian passenger ship builder, said there were several alternative fuels suitable for decarbonising the shipping sector, such as ammonia, hydrogen, and methanol. “Each has different pros and cons. There is not a fuel suitable for all ship types and operational profiles,” the company told CruiseTimes.

Using ammonia as fuel ensures a zero-carbon footprint, with no direct CO₂ emission when processed inside a fuel cell accompanied by a sound handling technology. But ammonia is highly toxic and has a pungent odour even in non-hazardous concentration. It also has a low volumetric energy density. The zero-carbon footprint can be achieved only if ammonia is obtained as synthetic fuel. If it is produced from fossil sources, the carbon footprint can be equal to zero only when the tank-to-wake (TTW) approach is applied. Ammonia is used as fuel for solid oxide fuel cells. It can be stored on board as liquefied gas at −33°C to minimise the storage volume.

Hydrogen, like ammonia, offers a very low carbon footprint and enables zero CO₂ emission, but it is a highly flammable fuel even though it is not toxic. It requires a specific cryogenic technology for storage due to its low boiling point of −252.9°C (at atmospheric pressure), and it has the lowest volumetric energy density among alternative fuels. It is also normally stored on board as liquefied gas to minimise the storage volume, especially on big vessels that require high volumes of hydrogen.

Methanol, unlike ammonia and hydrogen, is not a liquefied gas but a liquid at atmospheric temperature and pressure. So its method of storage and handling is similar to the current system used for marine gas oil (MGO). The presence of the carbon atom in the CH₃OH molecule means that the target of net-zero CO₂ emission cannot be reached, but it can be truly carbon neutral only if obtained as synthetic fuel.

Methanol, too, is flammable, although its flammability and toxicity are lower than those of hydrogen and ammonia. Its volumetric energy density is higher than those of ammonia and hydrogen, but lower than that of MGO, so it requires a bigger tank volume to store the equivalent energy content of MGO. The volume required for storing methanol on board must be calculated also by taking into account the need to have cofferdam surrounding the fuel tank to act as a secondary barrier in case of leakage.

Alternative marine fuels energy density index

Source: Fincantieri

Based on the considerations above, methanol is deemed to be the most viable option as an alternative fuel for powering passenger vessels in the short term. It only requires minor specific handling and operating skills from crew members. Ammonia and hydrogen, apart from having a lower volumetric energy density than methanol, set different challenges when used as fuel on board cruise ships.

“Methanol will for sure play a role as one of the future fuels for cruise ships,” said Andreas Ullrich, global market leader of passenger ships and ferries at the Paris-based classification society Bureau Veritas. “Methanol, if produced from renewable energy sources, will reduce greenhouse gas emissions such as CO₂ significantly and thus will contribute to becoming rule compliant. As methanol is a widely traded commodity under the IBC Code, there exists already a strong network of ports and infrastructure. Methanol is a liquid at ambient temperature, [which] means there is no need for cryogenic or high-pressure containment systems. Methanol handling technology is mature, with main (primarily two-stroke) and auxiliary (four-stroke) engines already commercially available.”

Exorbitant cost

Like hydrogen and ammonia, methanol obtained from fossil sources already has a sound supply chain to meet current industrial needs. There has been increased investment in new plants involved in producing methanol from non-fossil-fuels in order to provide the necessary amounts of fuels for the ships ordered by shipowners. There has also been an increase in available chemical tankers which can also operate as bunker vessels.

Prices of alternative fuels vary widely, and they change significantly depending on whether the fuels are produced from fossil or non-fossil sources. Based on production from fossil sources, hydrogen is the most expensive, ammonia is in the middle range, and methanol is the least expensive. When producing them from non-fossil sources, the most expensive option is green hydrogen, followed by e-methanol, then e-ammonia, and finally bio-methanol.

Another important aspect is that there is no reference market for alternative fuels made from non-fossil sources due to the small volume traded. Therefore, the price is not listed on a reference market in the same way as MGO. Instead, it is set bilaterally by the producer and the consumer, thus creating a wide price variability.

The price of green methanol is quite a challenge for its use as marine fuel, according to British shipping economist Dr Martin Stopford.

A calculation has shown that a large container vessel of 23,000-teu capacity – which has an installed power of around 100,000 BHP, equivalent to that of a large cruise ship – would require 400 tonnes of methanol fuel per day to operate at its designated cruising speed of 22 knots. This is a higher speed than what cruise ships maintain for most of their sea days, Stopford told us.

To produce the required amount of methanol fuel by green electricity, the generating capacity of 36 wind turbines of 10 MW each would be needed. Assuming a 25-year lifespan of the wind turbine installation, its lifetime cost would amount to $1.2 billion; that is six times the cost of the container ship at current newbuilding prices and equal to the price tag of a very large cruise ship.

All new fuels cost thousands of dollars per tonne, making them far more expensive than oil fuel. The transitions to greener energy sources will significantly increase the operating costs of cruise ships, and indeed those of all segments of shipping.

“Initially we would expect methanol pricing to be significantly higher than traditional marine fuels, although prices should become more competitive as long as the supply chain develops and production of green methanol increases,” said Linden Coppell, vice president of sustainability and ESG at MSC Cruises.

Lead choice

Despite the cost issue, methanol has resolutely emerged as a leading choice among alternative fuel options. “Considering the current status of supply chain, prices, and the physicochemical properties of the product, methanol can be identified as the most viable option as alternative fuel for the shipping market,” Fincantieri stated.

Tom Strang, senior vice president of maritime affairs, Carnival Corporation & plc, said that the world’s biggest cruise shipping group supported alternative-fuel development and was testing new technologies as they became available. “This includes closely monitoring and participating in technology developments in the application of alternative fuels at scale, including biofuels, synthetic hydrogen-derived fuels, fuel cells, and battery systems – and their associated supply chains – to determine if and when such alternative fuels and technologies will be available to provide the energy required for our business,” he told CruiseTimes.

The biggest challenge with alternative fuels today is availability and logistics. There are also technical challenges to overcome. “Given the barriers, it is most likely that, like the rest of the shipping industry, we will need to look at alternative hydrogen carriers, such as bio-derived methanol and ammonia or bio-LNG, as well as their synthetic versions,” Strang said.

Of the non-traditional fuels, methanol – produced from either sustainable biomass or synthetic sources – is a promising solution. “In fact, we are trialling its use in a fuel cell on board one of our LNG ships, AIDAnova, from our German brand AIDA Cruises,” Strang said. “Although small, the project will demonstrate the use of polymer electrolyte membrane (PEM) technology and reforming methanol into hydrogen. It is key to note, we must keep in mind, that the critical aspect of any fuel of the future will be its availability and scalability. In the case of methanol, for example, the high cost and low availability of renewable (bio- and e-) methanol will be a significant hurdle to overcome for it to become a commercially viable marine fuel.”

Methanol is a possible solution and would probably be the easiest of the new fuels to adopt from a technical standpoint, as it would require relatively few changes to the power plant, onboard tanks, and fuel systems, according to Coppell.

It also has enough energy content to make it a reasonable alternative to fossil fuels, although more storage capacity might be required on board. Coppell also pointed out that most methanol produced today is from using liquefied natural gas, the so-called grey methanol, and therefore it would bring no significant benefits in term of eliminating CO₂ emissions from the well-to-wake perspective. So the challenge is to produce sufficient bio- or e-methanol.

“If you could get e-methanol from green hydrogen or from biomass, it would be among the easiest solutions for shipping, including for those vessels that need to be retrofitted, provided that some safety issues are properly addressed,” said Coppell.

The major challenge for the shipping industry to adopt methanol on a large scale is that there will also be a large demand for this type of fuel from other sectors, such as aviation, and production may not be sufficient.

Other considerations

Although a switch to using methanol as fuel might not require major technical changes as far as the engine designs are concerned, providing more space on board for this or any other future fuel type could be a significant challenge, according to Anders Ørgård, chief commercial officer at OSK-ShipTech in Denmark. A key reason for this is the fact that ships are optimised for stability in accordance with the latest SOLAS rules.

Many designs are consequently sub-optimal when it comes to the space and weight involved for future fuels. Lengthening these ships can also be difficult, given the stability-focused foundation of their designs.

“The technical challenges that many cruise ships may face in the future when it comes to the adaptation for a new fuel has a financial consequence as well. Operating such vessels may not be very profitable over their entire lifespan,” Ørgård said.

While methanol may not have made a significant footprint in the cruise industry, the Swedish ferry company Stena Line has operated a 240-metre ro-pax ferry, Stena Germanica, on methanol on the overnight Gothenburg–Kiel route since 2015. In June 2021, the company took the next step by refuelling the ship with recycled methanol from residual steel gases.

The ferry industry is ideally placed to act as a testbed of new technologies, because ferries often serve just two ports that are rarely more than 24 hours of travelling distance apart, which means that the shore-based infrastructure for supplying new fuels is relatively easier to set up and would be used at a high frequency. The short distances also mean that there is no need to store huge volumes of fuel on board, as bunkering can be done at high frequency.

Cruise ships that operate from one port for all or most of the year are more likely to have access to new fuels than, say, expedition vessels that roam around the world. Because scaling up volumes is one of the challenges shared by methanol and all other green fuels, linking the cruise industry with green corridors that are being planned in various parts of the world could ease these challenges.