Can shipping get greener?

A look at what we can do to improve the environmental impact of shipping.
26 April 2016

Interview with 

Professor Sandy Day, Strathclyde University


What about the environmental impact of the shipping industry? Well, it's pretty significant. Global shipping currently has the same size carbon footprint as Germany, and the International Maritime Organisation (or IMO) has predicted that this figure will rise by up to 250% by 2050. At a recent meeting of their Marine Environment Protection Committee in London, the IMO failed to reach agreement on a plan to kerb future emissions. All the same, what can we do to make boats greener? Professor Sandy Day is Professor of Marine Hydrodynamics in the Naval Architecture Ocean and Marine Engineering Dept. at Strathclyde University is here to take Kat Arney through it...

Sandy - Well, as Rose already said, ships are already very, very efficient. They're a very, very efficient way of moving large amounts of material around the world, relatively slowly. So, if you want to make ships better, most likely you're not going to get a 50% improvement, but what you can hope to do is to get a few 5%, maybe 6, 7% improvements and maybe add a few of these together and, with that, you may be able to make some substantial inroads.

Kat - It's the sort of 'every little helps' approach to it?

Sandy - Aggregation of marginal gains as some of the sporting people call it.

Kat - So how can we do this? How are some of the ways that you and other people looking at to make ships more efficient?

Sandy - The most obvious thing you can do is try and reduce the drag of the ship - how much force you have to apply to it to push through the water, and there are a number of ways that you can do that. One of the things you can do is try and reduce the friction between the hull and the water. And you can try and do that by making the ship surface smoother, particularly by stopping marine fouling.

If you get heavy growth of something like barnacles on the boat that can add 10%, certainly 12% to the drag and that can grow quite quickly, especially if you're in warm waters. So, improving paint coatings so that the barnacles build up more slowly can make a significant difference to the environment impact of the ship, and the energy efficiency.

Kat - What about when we see things like olympic swimmers; they have these special suits that enable them to move through the water that are based on shark skin. Could a boat be built like that?

Sandy - Well, in principle, yes it could. And if you look at the very highest levels of competition. If you look at things like the America's Cup yacht races, people have explored some of these textured surfaces, nano surfaces, some of these things but, on a ship, the problem is first of all the environments pretty harsh. You've got to be out at sea for extended periods between cleaning and a ships just very, very big - 300 metres long maybe, I don't know, 40 metres on the beam, maybe 10 metres on the draught. You're talking about thousands of square metres and these hi-tech coatings are generally expensive and generally quite sensitive to dirt so it's not something you're expecting to see on a large ship.

Kat - And what about thing like the engines, the propellers, even the fuel that's being used. Is there anything that can be done to make that more efficient?

Sandy - For the propulsion systems, yes, there's lot you can do with the propellers. You can improve the flow into the propeller. You can try and extract some of the wasted energy in the flow behind the propellor. Try and improve the interaction between the propellor and the rudder, so there's lots of the things you can do with the hydrodynamics (the flow of water) around the propellor. Again, most of these things you'd be expecting single digit improvements, of course, it depends where you start.  If you've got a very old ship with an propeller, you'd expect to get a better improvement.

Kat - So given that there are all these ways that we could make shipping more efficient, what is the motivation, what's the encouragement for the people that own ships, the people that run ships to actually do any of it?

Sandy - Well, of course, the main motivation is to save money because, if you make ships more efficient, you spend less money on fuel and big shipping companies can spend a billion dollars or more a year on fuel so, even a relatively small percentage change can make a big difference. But one of the problems is that people don't typically own a ship for 25 years and then scrap it at the end. People generally operate ships for fairly limited times and that means that if you want to invest some money in energy saving, you have to pay that money back quite quickly which means, typically, you're looking for quite big gains and that can be difficult.

Kat - Are there things that people can do, maybe re-routing shipping routes to make them more efficient?

Sandy - Absolutely. There's a number of operational things you can do. There's a lot of work going on with people trying to improve weather routing so that you can try and avoid storms. You could avoid adverse winds, for example, and bigs waves because that tends to use up a lot more energy in the ship.

Kat - It sounds like there's quite a lot of complexity in this. You've got to get your ship working as efficiently as possible, you've got to get shipping as a business working as effectively as possible and then what about the role of legislation? We've talked about the International Maritime Organisation - is there anything that the law can do to try and improve efficiency?

Sandy - As Rose mentioned earlier, that shipping's governed by the I.M.O or the International Maritime Organisation which is essentially a U.N. agency, and it's difficult to make a change for existing ships.  But what they've done is they've legislated for new ships and they've used an energy efficiency standard, which is called the EEDI or the Energy Efficiency Design Index. And what that does is it's a formula that estimates in a bit of simple way how much CO2 is generated by a ship to carry any given ton of cargo one mile. The idea of this is that there are prescribed target values for different types ships and different ship sizes which you have to meet when you design a new ship and those target values are going to get more challenging over time. And the intention is that by 2025 that any given ship will have 30% less CO2 emissions, compared to a typical ship that existed between 2000 and 2010, so there is some legislative push ther.

Kat - This all seems like quite long term, slow moving stuff. Is there hope that there can be any immediate or quick efficiency changes to be made because we've had the Paris agreement; climate change is something people are very concerned about and if feels like now, now, now is the time?

Sandy - Yes. It's very difficult with ships because first of all you've got this huge stock of existing ships and even if somebody invented some fantastic new ship, which did have some enormous improvement, it would take many, many years to replace the existing ship stock. But the other problem is, basically, a political problem. It's very difficult to get agreement between the 171 member of the I.M.O., so there's quite a lot of inertia in the system and things tend to, unfortunately, happen rather more slowly than  you might like.


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