When Celebrity Cruises’ 3,260-passenger Celebrity Xcel debuts in November, it will be the first purpose-built tri-fuel cruise ship designed to operate on LNG (liquified natural gas), methanol, and conventional fuel. It’s a means to test, and be ready to adopt, future fuels such as bioLNG and green methanol—as supply scales up.
“As Xcel enters service, we will closely monitor how to refine and advance this new technology, as we continue our journey to becoming more energy efficient,” says a spokesperson for parent company Royal Caribbean Group.
Celebrity is not alone in advancing and testing new technology onboard.
As cruise lines pursue net-zero emissions cruising by 2050 they are building ships today that will be around well past that date. So, beyond new shipboard attractions such as rollercoasters and waterslides, cruise lines are working behind the scenes to conduct a wide range of tests and trialing innovations to make ships eco-friendlier both now, and in the years to come.
These eco-labs range from fuel-testing centers to complex wastewater treatment plants and include developing AI and software solutions, to reduce fuel consumption and food waste, and even using robots for better energy efficiency and waste management.
And the cruise lines aren’t just accessing off-the-shelf solutions. It’s not unusual to have experts from technology and engine companies onboard cruise ships joint-testing new ideas and products.
“Cruise lines are early adopters and innovators and are spending tens of billions of dollars to build the fleet of the future,” says Bud Darr, president and CEO of the Cruise Lines International Association (CLIA). “They are proceeding, not even knowing what sustainable fuels may be available in ports around the world in the future.”
Benefiting, he adds, will be the entire maritime industry and beyond.
Using cooking oil to fuel ships
Major cruise lines are, like Celebrity, building ships with fuel flexible propulsion designed to incorporate non-fossil, zero- and near-zero emission fuels when they become more readily available.
Meanwhile, cruise lines are turning to low-emission fuels that are currently attainable such as LNG, a cleaner burning fossil fuel. Cruise line AIDA introduced the first LNG ship in 2018 and others have followed.
Fuel flexibility is increasing as new ships are ordered, and by the end of this year, according to CLIA’s latest Environmental Technologies and Practices (ETP) report, there will be 23 ships specifically built with multi-fuel capabilities—that are able to use LNG and/or are methanol-ready. Projects underway also include using hydrogen for supplementary power (rather than as primary propulsion for large, ocean-going cruise ships).
At the same time, cruise companies such as Carnival Corporation, Royal Caribbean Group, Norwegian Cruise Line Holdings, MSC Group and others are conducting pilot tests including using biofuels derived from used cooking oil and other renewable biostocks (including non-food biomass). These trials have demonstrated feasible pathways toward lower-carbon operation.
Four ships—German line AIDA’s AIDAprima, Holland America Line’s Volendam and Rotterdam, and Carnival’s Carnival Magic—currently sail using biofuels, when available, as a supplemental energy source. In Juneau, Alaska, Holland America works with a local biofuel refiner to turn cooking oil into fuel, not only shipboard but for some of its tour buses.
“The good news with biofuels, though expensive, is it’s already been shown you can blend it in with traditional fuels,” says Darr. Supply, however, is another matter. The availability of biofuels has not yet caught up with industry innovation, and even in the future availability may vary by region. Cruise lines will also be competing for these fuels with much larger fuel users, such as road transport, and the steel, cement, and agriculture industries, Darr notes.
Carnival’s 6,654-passenger AIDAnova cruise ship has tested using biofuel as an alternative fuel source.
Photo by Juanjo Martinez
Microscopic air bubbles are helping to reduce drag
While they are waiting for sustainable fuel supplies to catch up with demand, cruise lines have been busy with technology focused on reducing fuel usage and improving energy efficiency.
Onshore Power Supply (OPS) allows cruise ships to plug into local power grids and turn off their engines in ports—reducing emissions while docked by up to 98 percent. Currently, about 166 cruise ships, or 58 percent of the CLIA member fleet, have OPS capability, according to the organization. By 2036, that number will rise to 273 ships, or 85 percent of the member fleet.
Cruise lines are also increasingly using AI and software programs to track and reduce fuel consumption. Royal Caribbean, for instance, has deployed a new AI-driven Marine Insights and Analytics Platform to pinpoint and reduce energy inefficiencies fleetwide.
Innovations have also focused on how ships can better move through the water. For instance, 33 ships, including some in the fleets of Carnival, Norwegian, and Royal Caribbean, have air lubrication systems which allow them to float on a bed of millions of microscopic air bubbles to reduce drag and fuel consumption.
Other innovations include waste heat recovery systems that transfer surplus heat from machinery to heat water for showers and pools. Waste-to-energy gasification systems, such as on new ships from Royal Caribbean and Silversea, repurpose solid waste (including food waste), into energy—both decreasing a ship’s energy demand and minimizing what goes to landfill.
Using image recognition to scan what guests eat
In fact, cruise lines are completely changing how they deal with waste overall. Some ships are now able to recycle or repurpose nearly all waste that is generated onboard.
With thousands of guests and crew on large ocean ships, reducing food waste is a big focus area. State-of-the art systems include microbial digestors (also known as biodigestors)—currently in use on 128 ships—that process tons of food waste much like a human stomach, the byproduct a harmless slurry that can be responsibly disposed, either at an authorized facility onshore or far from shore under strict international environmental regulations.
Cruise lines are also looking at the source, including using AI in the kitchen to help reduce waste. Carnival Corp. has been working with Dutch company Orbisk to better align food prep and passenger demand with a fully automated system that uses advanced image recognition to scan what goes out to guests, and what comes back, and then acts as a command center for the kitchen crew.
Carnival Corp. has also been testing a robotic tool to sort through food waste to remove plastics and glass before the food is treated by biodigesters.
Drones searching for barnacles and robots doing maintenance
Drones and robots are being used as behind-the-scenes players on cruise ships. Underwater drones can be deployed to inspect cruise ship hulls looking for anything that may create drag such as barnacles and chipped paint, while robots are being tested to do the actual hull maintenance, all to improve fuel efficiency.
Want to know more? You can book an eco-tour
For those who want to learn more about environmental efforts above and below the waterline, many ships now offer small-group tours run by the ship’s environmental officer, that may even include a look at the engine room. These tours sell out quickly, so interested guests may want to reserve this option well before their cruise.
Some ships also host scientists onboard who are doing fieldwork and testing emerging technologies, and who may offer lectures on their research. French luxury line Ponant, for instance, announced this month a partnership with the Woods Hole Oceanographic Institution, with scientists joining select expeditions to conduct experiments ranging from looking into the behavior of sea life and ocean conditions to gathering information on weather.
For years, large cruise ships have drawn attention for their size and environmental impact, often attracting unfavorable scrutiny from NGOs and environmental advocates. Yet beneath their decks, innovation runs deep. Advanced technologies are quietly transforming how these vessels move through the water—reducing emissions, improving efficiency, and charting a more sustainable course for the future of ocean travel. It’s a transformation worth watching.
