About 90% of international trade in goods is via shipping, involving over 100,000 commercial ships. The propulsion units rank among the world’s most powerful machines (the Wartsila Sulzer RT-Flex 96 C has an output of approximately 80,000 KW or 108,900 BHP) yet few alternatives to fossil fuel burning have been widely introduced. On top of this the bunker fuel they use is basically refinery dregs, close to a solid gunge until heated. Thus some 3% of global CO2 emissions are from this source.
This pointed to shipping as a significant contributor to global warming, except that this is not the case. The high sulphur content of bunker fuel results in emissions of sulphates which do not just just scatter sunlight but also help form and thicken clouds which reflect solar radiation away from earth. The net effect of these emissions is said to have reduced global warming by 7% in the 20th century.
The International Maritime Organisation is a UN body responsible for the world’s shipping but not known for its openness or representative membership. It is not just that seats are allocated according to size of merchant fleets (Panama and Liberia come out well) but the countries sometimes assign their voting rights to private companies or even a foreign individual in one case. Nor are they averse to inducements. At one meeting last year there were so many of these loaded onto delegates’ desks that 137 sets of headphones were broken.
Nevertheless the IMO has acted on the issue of sulphur in bunker fuel by requiring the amount to be reduced from 3.5% to 0.5%. It has been estimated that will reduce premature deaths by between 139,000 and 396,000 pa. This reduction, which is imminent and legally enforceable, will thus contribute to global warming. In contrast action to restrict CO2 emissions is restricted to a requirement for a global reduction of 50% by 2050 which apart from not being legally enforecable is a long way from carbon neutral.
How then can shipping emissions be reduced. A number of ways have been tried with many only making small savings on fossil fuel powered vessels. Some suggestions:
- Reduce drag
- redesign propellers with tip fins not unlike the turbulence reducing upturned winglets on planes. Also polish the propeller. A 3% reduction in fuel consumption is possible.
- Smooth the hull by antifouling paints or similar (not toxic ones, copper works well), or mechanically or hydraulically clean the hull, but to avoid fouling the water with scrapings or foreign species it should be combined with a suction device (Ja, ja, just like our South African Kreepy Krauly swimming pool cleaner). You can pay $25,000 for this at Southampton.
- Alternatively save up to 10% on costs (depending on the hull profile) by spraying compressed air through nozzles in the hull. This apparently is a salesman’s dream as switching it on causes the ship to accelerate (besides the free cruise). Three ships have been retrofitted and 12 newbuilds are incorporating it.
- Diesel electric propulsion. At first glance this might seem a non-starter but it has the advantage that the diesel engine can be run at a constant efficient speed to drive a generator for propulsion or to charge batteries. This can be 30% more efficient than conventional ship drives. [A mechanically challenged writer thus queries how diesel electrics are common on the railways but yet to be so at sea where images of long distance steady speed voyages spring to mind.]
- Performance management software. Inputs include data from sensors, past voyages and weather reports.
- Admit defeat and go back to sails.
- Five ships were fitted with kites but not too successfully.
- Fit revolving vertical cylinders (Flettnor rotors) to provide thrust via the Magnus effect, the same principle used by whats-his-name to bend it like Beckham. Not in common use but being tested by Maersk.
- Battery powered. Some Dutch barges are being built with 8% increased cargo capacity by savings on fuel and engine space. Norwegian ferries similarly, but all well and good depending on how those additional units of electricity to recharge the batteries are generated. For the Netherlands this doesn’t sound too good currently – over 90% of electricity is generated from fossil fuels. Hydroelectricity in Norway currently fits the bill. Not currently economical though.
- Fuel cells. Given that the hydrogen fuel is most commonly made by steam reformation of natural gas, a process involving a lot of heat with CO2 as a byproduct, this seems another non starter. The only advantage over batteries seems to be that hydrogen storage can provide a greater range than equivalent battery weight/space.
In my mind, and from a bystander’s point of view, this seems to cry out for nuclear. It is easy to despair on this score when the Fukushima accident seemed to cause panic in Germany even though a few sites in that country spring to mind where there is a low probability of badly sited back-up generators being rendered inoperative by a 15m tsunami. Various submarines, warships and ice-breakers already are nuclear powered so the technology is there. Most have either one or two reactors but the USS Enterprise has eight, presumably so it can boldly go where no man has gone before. The first experimental nuclear powered civil merchant ship was actually completed in 1962 but in 2012 there was only such ship in service – on Russia’s Northern Sea Route. The military / civilian discrepancy appears accounted for by cost considerations. The need to reduce emissions could lead to large scale adoption and lower unit costs.
Sources and references: Wikipedia; marineinsight.com; The Economist; Nature Communications; Finnish Meteorological Institute
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