No single alternative fuel will be universally optimal (to meet emissions reduction targets) for global shipping, according to Wee Meng Tan, chief projects officer at the Global Centre for Maritime Decarbonization (GCMD) in Singapore.
“The GCMD approaches the future with a tech- and fuel-agnostic stance, focusing on solutions with viable decarbonization pathways,” Meng Tan told Cruise Industry News.
“Fossil fuels are likely to remain in the mix in the near- to medium-term,” he added, “given the long asset lifespan of ships, and the time it will take for alternative fuels to ramp up.
“We also anticipate wider adoption of energy-efficient technologies and carbon capture and storage as it becomes increasingly essential to plan for fuel transition pathways rather than fuel end-states.”
Under the IMO’s net-zero framework, fossil LNG will only allow shipowners to avoid penalties until 2035, at the latest, according to Meng Tan, who said that bio-LNG may be the key to moving the needle on reducing emissions.
“It is also cheaper to produce than most biofuels but producing at scale for shipping would mean direct competition with powerplants using the same feedstock for greener grid electricity, creating a supply constraint,” he said.
Meng Tan explained that sustainable fuels like bio-LNG may also not be readily available at every port. To overcome this challenge, one solution being explored is the book-and-claim model, in which the physical LNG molecule is delivered to a vessel that does not have bio-LNG. Instead, the certified bio-LNG is injected into the wider gas grid or supply chain and issues certificates representing the green attributes of the fuel. A shipowner can thus purchase these certificates, he said, claiming their emission benefits and meet regulatory IMO targets without being restricted to the limited locations where bio-LNG is available for bunkering.
Meng Tan said that while biofuels are appealing for existing fleets as a drop-in fuels requiring minimal retrofitting, their adoption is limited by feedstock availability, which is further constrained by competing demand from other consumers.
To expand feedstock availability, he said that the GCMD is exploring crude algae oil, animal tallow-derived biodiesel and cashew nutshell liquid as promising third-generation biofuels.
Methanol is also in the picture, according to Meng Tan, who noted that the new Disney Adventure set to launch service from Singapore later this year will be methanol ready.
Fuel cells are currently limited in scale, making them suitable for auxiliary or hotel loads rather than main propulsion, Meng Tan said.
He pointed to what he called a lesser-known approach, combined gas turbine electric and steam (COGES) plants, similar to those used by national electric grids. However, COGES is hampered by its limited load flexibility as the fuel efficiency is low when the load is below 50 percent.
“In the end,” he said, “cruise lines must weigh fuel cost and availability, engine modification expenses, and the potential risk that the chosen fuel may offer a shorter period of viability than a ship’s operational lifespan.”
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