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Cruises pollute because it’s cheaper; so is electricity

5 May 2020

It’s been over a month since the Ruby Princess cruise ship released 2700 corona-ridden passengers on an unsuspecting Sydney, and the investigation is still making headlines. Around the world, cruise companies are taking flak as they’re blamed for outbreaks, maligned for tax avoidance, and reprimanded for their treatment of passengers and crew. It seems that corona has laid bare the many flaws of this imperfect industry.

Most of them, at least. Even if corporations’ bailout requests are denied and cruise demand remains stalled, there will presumably come a point when these ships rise back from the murky depths to pick up where they left off. And they’ll be bringing their enormous diesel engines with them.

How polluting are cruise ships, anyway?

The physical size of cruise ships can be hard to grasp. In March 2018 the Symphony of the Seas left Barcelona and became officially the largest cruise ship on Earth. It’s more than 50 metres longer than the Sydney Tower is tall; it’s passenger and crew capacity would comfortably drain more than 1700 of Australia’s small towns. It also pollutes the particulate equivalent of a million combustion cars.

Cruise ships are propelled by enormous diesel engines, up to four storeys high, that burn fuel significantly more toxic than what’s used by regular vehicles. Sulphur alone is emitted at 3500x the rate of regular diesel.  Studies have found that the largest cruise corporation, Carnival, accounts for 10x the sulphur emissions of all of Europe

In response to public outcry, some ships including the Symphony of the Seas have installed sulphur scrubbers which reduce the pollutants in the exhaust smoke by converting it to a liquid sludge — which is then sprayed straight into the sea.

Ships don’t have to use sulphur-laden fuels, either. The same diesel fuels and emissions-reduction tech used by cars would absolutely work for their engines, they just choose not to use it because the high-polluting fuel is cheaper. New regulations are forcing some to switch to LNG or low-sulphur fuel, but many have warned this won’t significantly reduce emissions. 

So in the absence of a well-placed iceberg or some corporate responsibility, how might we reduce the emissions of these diesel behemoths?

Meet Yara

This February a beacon of hope left port in Norway: the world’s first all-electric cargo ship, the Yara Birkeland, began ferrying fertilizer between a handful of Norwegian ports. 

the Yara Birkeland

Compared to the average cruiser, Yara is tiny at only 80 metres in length with a 3200 tonne deadweight capacity. That’s tiny by international standards — the Yara’s 120 container maximum barely registers against the 20,000+ of the world’s largest container ships.

Yet, despite its size, the Yara is expected to replace 40,000 diesel truck journeys every year as it travels between the ports of Herøya, Brevik, and Larvik in Norway. It’s longest route clocks in at around 30 nautical miles (~56 km). It’s a small but significant step away from combustion fuels in shipping. 

And it’s not alone. We wrote last year about the Port of Auckland’s first all-electric tugboat, and in 2018 two ferries were successfully converted to electricity for operation between Sweden and Denmark. The Tycho Brache and Aurora are both 100 metres in length, originally constructed as combustion-fuelled ferries in 1991.

EV tech is coming to an industry near you

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Batteries not included

And that’s the problem — at least for now. Boats of all kinds require enormous amounts of power to complete their work and current battery technology is just too heavy for most applications. 

The Yara Birkeland requires 7MWh of battery capacity to operate, 70x more than the largest EVs sold today. Even with the latest lithium-ion technology that doesn’t come cheap, and the shipping industry’s ongoing reliance on toxic fuels and tax havens has already shown what they’ll do to avoid any rise in costs. Even the ForSea ferries on their 4km route still need 4160 kWh of batteries to make it.

Batteries onboard the Tycho Brache

As vessels get larger, loads get heavier and routes get longer, the feasibility of electric power gets weaker. Electrifying commercial-scale cargo ships and cruise liners will require a strictly economic argument with the technology to back it up. Realistically, that means solid state batteries.

Chasing the perfect electric vehicle battery

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Lithium ion batteries are improving every year, but the chemistry itself has an expiration date. Solid state batteries promise to replace li-ion and have been a focus of research for years — if a commercially viable design emerges, they have the potential to double batteries’ energy-, weight- and space-efficiency for all forms of electric mobility.

Suddenly, with that kind of improvement, there’s a strong economic case to be made for shipping to move past combustion fuels. It wouldn’t just be cleaner, it would be cheaper. The same goes for other sectors that have struggled with electrification including airlines and heavy industry.

In the meantime there are still alternatives to the ultra-high-polluting fuels used routinely by the cruise industry.