So I understand that cruise ships are not environmentally friendly. Link.Link.Link. In particular, cruising generates over twice as much CO2 as flying.
But it’s also my understanding that ocean shipping is the most efficient and environmentally-friendly method of shipping goods, even with the issue of some ships burning sludge-like fuel oil. Link.
So would it be feasible to run an ocean liner (link) – not an oversized lumbering cruise ship (link) but a sleek liner of the kind built when ships competed for the Blue Riband (link), except now burning cleaner fuel than bunker oil – and have a smaller carbon footprint than flying? Or does burning the fuel needed to move about 2000 passengers + crew + food and water for a few days inherently outweigh just putting those 2000 people on a bunch of planes that make the crossing in hours?
And a related question: would crossing in, say, a week be better environmentally than in 3-and-a-half days as they got it down to by the 1950s, or would the extra fuel burned carrying the food and water for the extra days outweigh the extra fuel burnt in getting there faster?
The biggest difference between ocean shipping and cruising is that a container ship is almost all cargo and a cruise ship has very few people on it (relative to its size).
Going slow across the Atlantic would probably use less energy per ship, and people might be satisfied with the same amount of space for a week as they are for 3.5 days, but the question is how much space pr passenger you can have and still beat a plane.
An interesting point. The fastest ocean liner “was able to carry 15,000 troops 10,000 miles without refueling” but carried about 3000 passengers and 1000 crew in regular service. Link. On one hand, 10,000 miles without refueling shows great efficiency, but on the other hand I can’t picture paying passengers traveling like the 15,000 troops did, but going back to the first hand I imagine 4000 people in much less cramped conditions were even lighter to move.
Perhaps combining the kite with some Flettner rotors.
Of course, the ship would still have problems with getting enough electrical power. Even coating the entire top surface with solar panels would leave it starved for juice.
It’s annoying that whoever wrote that article apparently knows nothing about sailing (emphasis mine):
Does the ship have to be going the same way as the wind is blowing?
No, the kite can work over a range of angles away from the wind to provide power, just like a sail. In theory a ship can take a course up to 50 degrees skewed from the wind. Salty old sea dogs might recognise that this isn’t far off the capabilities of a yacht.
Wrong. The kite requires some significant component of the wind direction to be behind the boat; the claim is that it can be skewed by up to 50 degrees from the direction of the boat’s movement. Whereas a modern sailboat can sail against the wind, and typically can come as close as about 40 degrees to a headwind.
One of the interesting dynamics of sailing is that this “close” configuration is the one that produces maximum side pressure on the sails. When you see a sailboat that is well heeled over, it’s probably sailing upwind.
I think the answer to the OP’s question is “Yes, but …”.
Yes, you could move people cleanly by ship, but they would need to put a high priority on environmentally friendly transport, to the point where they were happy to endure serious crowding (like those 15,000 troops) and slow progress.
Which is another way of saying that in the real world, this couldn’t work. People who simply want to get there are content with air transport and willing to put up with its shortcomings (e.g. crowding) for the reasonably small time required. People are attracted to passenger ships for various reasons, of which efficient transport is a very minor one.
To compare fuel economy for different modes of passenger transportation, you use passenger-miles per gallon. According to this article, the Oasis of the Seas, one of the more recently made cruise ships, achieves 0.0023 miles per gallon; if it’s filled to max capacity with 6780 passengers (not counting crew here), then it gets 15.6 passenger-miles per gallon. The Boeing 787, one of the more recently made passenger aircraft, achieves about 90 passenger miles per gallon.
As naita pointed out, the population density on a cruise ship is much less than it could be. Look at how much wasted space there is! Passengers can lie down in their own private rooms, walk down hallways without getting near each other, and wander around on deck. There are huge full-service kitchens preparing delicious fresh food from scratch, full size theatres and dance halls, arcades, pools, on and on.
If you got rid of all of that and packed passengers onto cruise ships as densely as they are packed into commercial airliners, I suspect a cruise ship could dramatically exceed flying fuel economy.
You can run the ship on fuel generated from hydrogen produced by electrolysis of water using low-emission electricity sources.
Hydrogen itself is probably too low-density for ships, but people are already looking at ammonia. And you could make hydrocarbon fuels from captured CO2, but that starts getting even more expensive. It’s all a roundabout way of powering the ship with electricity, with lots of losses along the way.
It’s all chemically feasible. The economics are more tenuous.
I think what this shows is that rapid long distance travel just isn’t sustainable. There would probably be a market for crossing the Atlantic in 5-6 days in a small cabin with non-luxurious food if there were no planes, but as long as those of us with the money to do so think it’s fine to use an oversized share of the global carbon budget to jet from here to there, it’s just not going to happen.
And remember, we have to do more than just beat flying. Flying is extremely bad.
Roundtrip JFK-LHR on economy class: 1.8 tons CO2 per passenger according to MyClimate.org
Maximum quota if we’re to stop the current trend: 0.6 tons per person annually.
Then again, the vast majority of the population never takes a plane trip that long, certainly not one every three years. So we could hit per capita annual emission goals even without changing flying at all.
A sensible plan would still make changes in air travel, of course (probably replacing most of it with remote options that take almost no energy). But there probably will still be fossil-fuel-burning airliners, for the foreseeable future.
There are a lot of things we could keep in place and still hit per capita annual emissions if we just did drastic cuts elsewhere. But we’re having real trouble doing those cuts and air travel is 2.65% of emissions and an increasing share of still increasing emissions. There is no actual reason to declare it a “no cuts needed” sector that doesn’t apply to all the others, other than “it’s part of what we like about being in the richest fraction of humanity”.
Ocean liners are transportation, just like air liners. Cruse ships are recreation. Different beasts - but same media.
Cruse ships are about excess, just like the Las Vegas Casinos are about excess and thus so hard to be a Eco-Friendly.
Ocean Liners do follow that somewhat do to having to differentiate themselves from airlines that can do the same thing much quicker. This puts them in a tough situation, as to what they can offer.
I don’t see why it should be. A large ship can support liquid hydrogen storage. The Oasis of the Seas above burns 11,361 gal of diesel every hour. I don’t know what its fuel tank size is, but say it has 14 days worth of fuel at cruise speed. That’s 3.8 million gallons, or about 14,500 cubic meters. A gallon of liquid hydrogen has about 1/4 the energy of a gallon of diesel, so at the same efficiency it would need about 58,000 cubic meters of storage.
But the ship is roughly a 360x60x60 meter block, or 1.3 million cubic meters. So that hydrogen takes <5% of the internal volume. And in reality it would be much better, since fuel cells are going to be more efficient than just burning the hydrogen, and you get some other benefits like free purified water and cooling. The hydrogen is also so lightweight that the ship itself gets more efficient.
It’s an interesting question. I just happen to be coming to the end of a rather utopian Sci-Fi novel based on solving the climate crisis. It basically is exploring different ways of getting down to negative carbon. One of the things that happens is the return of sailing ships that have a top deck full of solar panels. Airplanes are banned, replaced by dirigibles also covered in solar panels. And many other things happen. How much of it is sci and how much fi is not clear. I hope the author has worked out the numbers accurately. The book is almost more polemic than novel.
The book is Ministry for the Future by Kim Stanley Robinson.
