Cutting emissions at sea


FOR most people, unless they live near a port, seeing an ocean-going vessel is a rarity. Around 90 percent of world trade is carried by merchant vessels which spend the greater part of their time operating far out to sea. But when a ship is close to shore, it is not unusual to watch a plume of black smoke rising from its funnel.

The burning of heavy fuel oil by ships’ engines clearly causes pollution though not as much as that created by the less efficient coal-fired ships boilers of late nineteenth and early twentieth century. But there are now far more merchants ships at sea and the clouds of oil smoke they emit is therefore greater than the combined output from coal-fired merchantmen.

Environmentalists have produced the striking calculation that combined, world shipping now produces as much pollution as Germany, taking into account all that country’s power production, exhaust emissions and heating boilers. On that basis, they say, if the world’s merchant fleet was regarded as a country, it would be the state with the six largest emissions.

The drive to cut carbon gases is now general. Until last week, shipping along with aircraft had enjoyed an exemption. But the International Maritime Organization has just agreed emissions will be reduced by a half from 2008 levels. The Kingdom, backed in particular by the United States and Brazil, had questioned the need for cuts. Modern trading vessels, not least very large crude carriers (VLCCs) and the huge container ships that carry most finished products around the world, now have computerized engine systems. Most ports are extremely busy and schedule the arrival and unloading of ships almost to the minute, where necessary, taking into account tidal movements. Using sea-state forecasts, a ship’s master will tap in his destination and thereafter the voyage is worked out by the computer. In particular, this will calculate the optimum speed and therefore consumption of heavy fuel oil. From the point of view of a ship’s operator, there is no point burning more fuel by going full steam ahead only to arrive at a port and having wait offshore until a berth becomes available. It costs tens of thousands of dollars to have a vessel doing nothing while it waits to be unloaded and is unable to sail off to pick up a fresh cargo.

While ships undoubtedly pollute, as fleets are renewed with modern, more efficient vessels, their emissions are set to come down. The IMO has accepted the 50 percent cut will not have to be met until 2050. In the next 32 years, ocean-going ships are likely to be very different in their engineering design.

It is perhaps ironic that the IMO’s move was triggered by Marshall Islands, the world’s second largest flag-of-convenience register. It is easy to see why this country, along other Pacific island states, should be concerned in the light of the accepted wisdom that carbon emissions are bringing about global warming and sea-level rises which threaten the existence of low-lying areas al around the globe. But it might be wondered why the Marshall Islands has not been more selective in its registration of vessels. Clearly until now the income from its shipping register has outweighed its concern about rising sea levels.