Our paper on the carbon footprint of cruise holidays continues to attract a good deal of interest (link to paper and slides), and that’s satisfying to see. Still, it only tells part of the story. The paper described our work to calculate the carbon footprint of a cruise holiday, but that’s a partial job, for two key reasons.
Firstly, there are other forms of environmental hazard: sustainability doesn’t begin and end with climate change. For this reason, Christine and I are working on a follow-up study. Secondly, though… it’s ever so easy to criticise something without having a workable alternative to propose, isn’t it? We showed that a cruise holiday involved somewhat over four times the contribution to climate change of a hotel-based holiday, but we didn’t actually say how to make cruise holidays ‘greener’.
We have to keep in mind that a $36bn industry isn’t going to change overnight, and particularly not if the changes mean that you have to stop using expensive assets that have a design life measured in decades… but there are some things that a cruise operator could do. Not tomorrow: that would be unrealistic, but perhaps next season. Here’s seven things that could make a cruise holiday ‘greener’ – and that passengers could look for when choosing their next cruise.
1. Travel Less, Visit More.
As you might expect, persuading up to 100,000 tonnes of metal to move through the sea requires a lot of energy. Cruise ships get through much more fuel when sailing than when in port or at anchor. Cruise itineraries often include ‘sea days’, where passengers don’t get to go ashore because the ship is travelling non-stop towards some distant destination. For some passengers, sea days are alluring: days when you’re guaranteed to be out of reach of e-mails from your boss, or phone calls from your relatives. Lazy days meant for working on your suntan, getting blind drunk or whatever. Other passengers, though, prefer a more varied and cultural experience.
Baker  reported that sunburn was the most commonly treated ailment on cruises… although sexually transmitted diseases came in at number 2. Lovely.
A typical cruise ship, while underway, will be burning through multiple tonnes of Heavy Fuel Oil per hour. Consumption of around 125 tonnes per day can be considered normal, and DEFRA  report emissions from HFO consumption to be 3766.5 kg CO2e per tonne, so that’s 470 tonnes of CO2e a day. Naturally, emissions are higher on days of non-stop cruising, and lower on a day spent in-port when the ship is essentially a floating hotel. Thus, the itinerary is a major determinant of the carbon footprint – and a quick way to slash the contribution to climate change. The environmental benefits of an overnight stay in port (two days in one place) should already be obvious – and it also means a reduced spend on HFO for the operator and more opportunities for the host community to do business with the passengers, so extended visits are win-win.
On the other hand, perhaps you believe that in a port city like Genoa or Piraeus there are only enough entertainment possibilities to keep visitors amused for around six or eight hours… which is a little bit rude to the passengers and the host community alike!
2. Higher Occupancy is (Somewhat) Greener
Whether it’s half-full or crammed with passengers, the energy used by a cruise ship won’t vary significantly. When moving up to a hundred thousand tonnes of boat, a few tonnes of passengers and luggage isn’t going to make a measurable difference, so it makes good sense to offer attractive deals that fill unoccupied cabins. The costs associated with the boat and its crew are largely fixed, so the incremental cost of an extra passenger is almost zero – and even a deeply discounted cruise sees the typical passenger shopping on board, buying drinks, and losing money in the casino…
Thus, there is a good business case for discounting to fill up a cruise ship. It’s arguably greener as well, given the fuel usage discussed in point one. (The no-frills airline that everyone loves to hate, Ryanair, used to claim their sustainability performance was better than that of other airlines because their load factor was better.) Of course, a ‘deep green’ would argue that low prices encourage increased consumption… but that’s another story.
It remains true that it would be better to have 200 cruise ships at full occupancy than 300 operating with moderate occupancy. The trick, of course, is avoiding the worst aspects of a price war. It’s more profitable to use a cruise ship than to leave it mothballed, and information from statistica.com suggests there are 296 cruise ships in use… but if we could avoid building any more for a while, it might actually improve the profitability of the industry, by reducing oversupply.
3. Go a Little Slower
A cruise ship isn’t built like a Type 23 frigate, and it shouldn’t be manoeuvred like one. Forcing that big hull through the water demands a great deal of energy: give the water more time to move aside and your fuel bill will be slashed.
A ten percent speed reduction could mean a twenty percent fuel saving… with a corresponding reduction in the vessel’s carbon footprint, and perhaps less wear and tear in the engine room. It’s really just a matter of marketing a realistic itinerary. The industry doesn’t need to compete on speed: a good, modern boat with lots of amenities is a destination in itself, and a passenger who really cares about getting places fast is going to fly instead of cruise, so why not take time to smell the roses along the way?
4. Scrub that Sulphur
The emissions from ships’ engines can be very bad for public health and the natural world. Heavy Fuel Oil may contain as much as 4.5% sulphur by weight, and combustion results in emissions of sulphur dioxide. That’s bad news for people with asthma or chronic lung or heart disease, and it’s a major source of acid rain as well.
‘Sweeter’ fuels are available, at a price, but Kalli et al  suggest that an exhaust scrubber is the way to go. Particulates will also be trapped by this relatively simple retrofit, and it’s a cheaper way to cut sulphur dioxide emissions than buying low-sulphur fuel. With the expansion of sulphur emission control areas, cruise operators might be forced to abandon some of their traditional itineraries if they can’t clean up their act, so addressing the problem makes a lot of sense.
Current and anticipated Emission Control Areas
5. Watch that Whale!
One can only imagine how upsetting it was for passengers of Princess Cruises’ Sapphire Princess in July 2010, when a female humpback was found dead, pinned in place on the bow of their boat. This might seem like a freak accident… except that a finback whale was caught and killed on the same ship’s bow in the same way, one year earlier. In all, Princess Cruises were involved in three such cases in a decade [Gordon, 2010], the most recent two occurring after a legal case in which Princess Cruises pleaded guilty to “failing to operate at a slow, safe speed while near humpback whales”, and paid fines and restitution totalling $755,000 [Hunter, 2007].
Obviously, nobody in the cruise industry sets out to harm endangered species (and as Laist et al  shows, ships of virtually all types have been involved in whale strikes) but whale-watching is marketed as one of the attractions of some cruise itineraries, and thus cruise ships deliberately sail in waters where whales are to be found. Smaller vessels that take people out to view whales for a few hours generally adhere to better guidelines: they approach whales only slowly, and from a direction that doesn’t cause stress. They keep noise to a minimum (shutting down the engines) and they don’t dump anything in the water. They typically limit access to a third of the total daylight hours: all very different to whale watching on a cruise ship.
Dead whale, pinned to the bow of a cruise ship [Reuters / Daily Mail]
It may be possible to turn whale-watching into a paid excursion, transferring passengers that want to see whales up close into tenders. Thus, the cruise line stands to get some more money while keeping the big boats away from our large mammalian friends.
6. Plug in
Although the biggest requirement for energy comes from moving the boat, a great deal of electricity is required for other purposes on-board, such as air conditioning, lighting and entertainment. Even if the boat is moored, one or more engines will still be running in order to supply the boat with electricity. Typically, vessels in port use marine distillate in place of HFO because it burns a lot more cleanly… but it also costs twice as much.
“Cold Ironing” is the industry term for obtaining electricity from a shore-based source. Using a land-based supply greatly reduces air pollution from ships, and could substantially reduce the carbon footprint as well (if generated by a nuclear or renewable source). It requires that the port has infrastructure that allows visiting vessels to ‘plug in’, but this is becoming more common, and it has the potential to reduce a ship’s energy bill considerably [Sisson and McBride, 2010].
Hurtigruten have taken things a step further, and are exploring the potential for battery-powered propulsion. “I will be disappointed if we don’t have a vessel with battery propulsion within 10 years,” said CEO Daniel Skjeldam [Nilsen, 2016]. Even if it has to be a ‘plug-in hybrid’… imagine that!
7. Promote Local Food
Part of the appeal of cruising is the idea that everything is taken care of. The full cost of the holiday is known in advance, and there’s no need to obtain five different kinds of currency… we get that. But can you imagine how disheartening it is for host communities is to see a swarm of tourists heading back to the boat to have their lunch? What’s wrong with sampling the local food? So many cruise tourists leave the boat (carrying a bottle of water), have a look around a market or something… and then stampede back to the boat because it’s lunchtime!
The more adventurous souls who have lunch ashore get a far better holiday: they spend more time at each destination, meet local people and sample more varied cuisine. Their holiday is a more memorable one, perhaps leading to repeat business… and critically it gives something back to the host community, who have put up with increased congestion and so on.
The cruise line that champions local food might actually save a little money, too.
And Finally… A Pinch of (Sea) Salt
In their ‘Ten Signs of Greenwash’, Futerra warned that being the cleanest in a dirty industry doesn’t indicate sustainability. There are no bragging rights to be had for being the greenest Formula 1 team, or the most sustainable cigarette manufacturer. With the cruise industry, we have something similar. In our research, Christine and I have already established that a cruise holiday is far from ‘green’… but I wanted to show that there are some things that can be done, in the near-term, that would lead to measurable improvements. It all comes down to what the informed customer wants. And for that… we will have to wait and see.
Baker, D. (2013) Cruise passengers’ perceptions of safety and security while Cruising the Western Caribbean, Revista Rosa dos Ventos, Vol. 5, No. 1, pp. 140–154
DEFRA (2012) 2012 Greenhouse Gas Conversion Factors for Company Reporting, online available: https://www.gov.uk/government/publications/2012-greenhouse-gas-conversion-factors-for-company-reporting [date accessed: 7/4/13]
Gordon, S. (2010) Whale found pinned to Princess liner is the third in a decade, Daily Mail, 20th July 2010, online available: http://www.dailymail.co.uk/travel/article-1298928/Dead-whale-pinned-Princess-cruise-ship-iin-Alaska.html [date accessed: 25/11/2013]
Hunter, D. (2007) Cruise line agrees to fine over whale death, Anchorage Daily News (Alaska), January 24, 2007, pp B1
Kalli, J., Karvonen, T. and Makkonen, T. (2009) Sulphur content in ships bunker fuel in 2015–A study on the impacts of the new IMO regulations and transportations costs, Centre for Maritime Studies, University of Turku. Helsinki: Ministry of Transport and Communications
Laist D.W., Knowlton A.R., Mead J.G., Collet A.S. and Podesta M. (2001) Collisions between ships and whales, Marine Mammal Science, 17, 35–75.
Nilsen, T. (2016) Hurtigruten of the future will operate on battery power, Barents Observer, online available: http://thebarentsobserver.com/industry/2016/01/hurtigruten-future-will-operate-battery-power [date accessed: 05/02/16]
Sisson, M. and McBride, K. (2010) The economics of cold ironing, online available: https://www.broward.org/Port/MasterPlan/Documents/PTI Cold Ironing Economics.pdf [date accessed: 02/02/16]