There are several fuel choices that can contribute to carbon reduction, according to Andreas Ullrich, global commercial director for passenger ships and ferries at RINA.

“First is LNG,” he said, “which is the fuel of choice for most newbuildings today, and with drop-in fuels could reach IMO’s 2030 and 2040 targets. Other alternatives are methanol, biofuels and hydrogen.

“The most practical solution today, however, is LNG,” he continued, “and then use drop-in fuels for the next five to 10 years. That makes more sense than fuel cells and hydrogen or methanol.”

Added Maria Garbarini, head of passenger ship excellence: “Based on the orderbook, we know that the majority of new ships will be using LNG; in addition, existing ships will have to be retrofitted to biofuels, synthetic fuels or methanol, unless they are scrapped.”

Ships can also operate even more efficiently than they already are, according to Garbarini, who said that digitalization is the key to an even more efficient future, using the thousands of data points available and optimizing and managing the electric equipment onboard better.

The next step would be to have green LNG, e-LNG or bio-LNG, and there is development in this direction in North America and Europe, Ullrich said.

But there are challenges, including carbon content, availability and price.

Green methanol also requires unique tank construction with specific materials or coatings, and it needs pilot fuel as well.

Another option is hydrogen, but it has low energy density, and its storage onboard requires a lot of energy.

Biofuels also face challenges because there is no uniform standard for the time being, according to Ullrich. And while biofuels can be blended with other fuels, they will require trial periods to test the viability onboard and the impact on powerplants.

There is also a lack of clarity on the documentation trail required in terms of the sustainability of biofuels, Garbarini said.

She added: “We not only support cruise operators in terms of implementing new technology onboard, we are also in contact with governments regarding their commitment to investing in new fuels such as hydrogen. The first task would be to solve the logistics and production of hydrogen which would then open doors for different technologies. But that would come at the end of a very long chain with many different stakeholders involved.”

Once that is overcome, there is also the issue of the amount of sustainable electric power that would be required to produce green fuels, Ullrich said. “Globally, we may never have enough electricity to produce the fuels in the quantities that would be needed.”

It may lead back to nuclear power, according to Garbarini, but not necessarily to power ships, but to make sustainable electricity. But that again would depend on the political landscape, she said.

“The challenges are a bit like the chicken-or-the-egg concept; nobody wants to invest unless there is sufficient demand, and cruise lines are naturally hesitant to build ships with technologies that require new fuels unless there is fuel available at an acceptable cost,” Ullrich said.

Images: Andreas Ullrich, global commercial director for passenger ships and ferries; Maria Garbarini, head of passenger ship excellence