Most approaches to cutting CO2 emissions have focused on reducing consumption and achieving efficiency gains. However, alternative fuel could have a role to play. With Wärtsilä publishing a concept LNG liner, the company's Fred Danska and Royal Caribbean's Richard Pruitt talk to Ian Duncan about the technical and operational issues that need to be ironed out.
Attempts to curb CO2 emissions from cruise ships have traditionally focused on improving the energy efficiency of liners to reduce absolute fuel consumption in addition to more recent experiments such as using solar panels to provide auxiliary power. While these methods have proven successful, using liquefied natural gas (LNG) as a primary fuel could deliver a significant boost to environmental performance in a single step.
Many operators are cautious about alternatives to marine fuel oil after biodiesel proved to be less sustainable than it first appeared. But LNG is being touted as a clean, readily available source of energy for the future. The market for the fuel is relatively young but is developing quickly. Seizing on the trend is Finnish engine manufacturer Wärtsilä, which has worked with Aker Shipyard to publish a concept design for a large cruise liner powered solely using the gas.
Concept LNG cruise ship
LNG-powered ships afloat today number only in the hundreds. Many of these are the huge tankers used to ship the gas around the world, which feed off their cargo, but ferry operators and oil and gas producers are also starting to deploy the technology.
The concept liner would accommodate 2,780 guests in 1,390 cabins and could travel at a maximum speed of 21k, powered by the same dual-fuel engines that Wärtsilä supplies to LNG tankers.
Fred Danska, Wärtsilä's director of cruise business, is excited about the possibility presented by the fuel, seeing it as a way for the industry to keep a few steps ahead of formal emissions regulations.
"When people get together at conferences, everyone discusses legislation and anticipates that it will only get more stringent," he says. "There will definitely be environmental benefits for operators in LNG and that was the primary reason for us to develop this concept."
Wärtsilä's estimate is that the LNG vessel will have 30% lower CO2 emissions than if it was powered by marine fuel oil; NOx output will be cut by 85% and SOx by almost 100%. Those figures mean the ship would comply with even the strictest International Maritime Organization (IMO) standards when they come in to force in 2016.
The main design challenge for the liner is storing the fuel, which is twice the volume of oil and has to be stored at -162°C, creating a need for bulky insulation. Overall, the storage requirements are four times greater than for traditional fuel, running the risk of eating into valuable revenue generating space.
Danska explains that the company had to take an innovative approach when developing the concept to make LNG viable and decided to raise the tanks above the passenger decks and just below the ship's exhaust stacks.
"We had to have a novel location for the fuel, putting it in the centre-line casing," he says. "It provides free ventilation to the open air and does not disrupt the aesthetics of the interior."
Although LNG is generally stable, it can become combustible, so ventilation is an important safety feature in allowing any excess gas to safely evaporate. Danska admits that building the vessel from scratch would be more expensive than a similar liner powered by traditional fuel, largely because of the storage requirements, but that over the lifetime of the ship the operator would realise cost savings.
Prices of LNG are currently low as demand is weak. This will likely change over time but Wärtsilä accounted for the introduction of carbon pricing over the course of the next decade, which would keep the fuel competitive.
Fuel supply and demand
Despite Danksa's optimism, Rich Pruitt, Royal Caribbean International's director of environmental services, identifies a number of significant obstacles that need to be removed before an LNG cruise ship becomes a realistic commercial prospect. The main difficulty is guaranteeing the fuel supply.
"We visit over 400 ports around the world and although you do not need LNG at every one, it would still require a large investment," he explains. "There's no place in North America where you can get the fuel onto a ship; it's one thing having it available in general, it's quite another to get it on board. Right now, with the exception of parts of Scandinavia, I don't know that the availability is really there."
He notes that whenever Boston harbour received an LNG tanker in February, all other shipping was brought to a halt. While import hubs on the Gulf of Mexico take a more relaxed attitude, the example demonstrates the hurdles the new fuel faces.
Despite these concerns Pruitt acknowledges that seeking out alternatives to marine fuel oil remains attractive. Royal Caribbean is also working on the assumption that some form of carbon pricing will be introduced in the near future and IMO limits on the sulphur content of fuel could help to drive change.
The company has committed to cutting CO2 emissions by 30% by 2015 through energy efficiency and design measures rather than using alternative fuels. The combination of this approach with LNG could see dramatic reductions in pollution and greenhouse gases emitted by its liners.
LNG is trapped in a catch-22 situation: there are too few ships using it to spur the growth distribution networks, but ship operators are reluctant to invest without guaranteed availability. In the face of this, Pruitt sees two main routes to the development of a fully functioning LNG infrastructure. The first would be for it to be adopted by commercial shipping, which accounts for the majority of fuel consumption in the sector.
"Our industry makes up a tiny fraction of the tonnage in the global market, so it's difficult for us to drive any change," he explains. "We get targeted a lot, but when you look at the facts we're a small proportion. It's a little bit easier to focus on an industry that's discretionary rather than going after ships bringing in oil, food or clothing."
The second, and arguably more likely, prospect would be for governments to implement a regional strategy promoting LNG.
"We could see the EU looking at this and working out how to establish fuelling hubs," Pruitt explains. "It's something that would require significant government intervention and incentives to get companies to take the first step."
Given that these programmes remain largely theoretical, Pruitt is reluctant to put a timeline on when he envisages Royal Caribbean making an investment and says that instead of a date, it would have to be event driven.
When the time is right, though, he signals that the company would look seriously at the role the fuel could play in its operations. While Danska sees the main opportunities being for newbuilds, Pruitt would be keen to consider retrofit opportunities as well.
Equipping some vessels to burn gas as shore power could be a first step, followed by installing small LNG tanks for operations in IMO-designated environmental control areas.
Older, less efficient designs could benefit in particular, boosting the performance of the fleet as a whole.
LNG presents some exciting opportunities from financial and environmental perspectives but how its potential will be realised remains unclear. Although the technology is proven, the rather more taxing question of infrastructure development remains to be conclusively answered. For that reason, the prospect of LNG-powered liners cruising remains years on the horizon.