Big polluters: one massive container ship equals 50 million cars

The Guardian has reported on new research showing that in one year, a single large container ship can emit cancer and asthma-causing pollutants equivalent to that of 50 million cars. The low grade bunker fuel used by the worlds 90,000 cargo ships contains up to 2,000 times the amount of sulfur compared to diesel fuel used in automobiles. The recent boom in the global trade of manufactured goods has also resulted in a new breed of super sized container ship which consume fuel not by the gallons, but by tons per hour, and shipping now accounts for 90% of global trade by volume.

The title of world’s largest container ship is actually held by eight identical ships owned by Danish shipping line Mærsk. All eight ships are 1300ft (397.7m) long and can carry 15,200 shipping containers around the globe at a steady 25.5 knots (47.2 km/h, 29.3 mph) . The only thing limiting the size of these ships is the Suezmax standard, which is the term used to define the the largest ships capable of transiting the Suez Canal fully loaded. These ships far surpass the Panamax standard (ships that can fit through the Panama Canal), which is limited to ships capable of carrying 5,000 shipping containers.

Not only are shipbuilders resetting the world record for size on a regular basis but so are the diesel engines that propel them. One of the eight longest container ships in the world, the 1,300 ft Emma Mærsk also has the world's largest reciprocating engine. At five storeys tall and weighing 2300 tonnes, this 14 cylinder turbocharged two-stroke monster puts out 84.4 MW (114,800 hp) - up to 90MW when the motor's waste heat recovery system is taken into account. These mammoth engines consume approx 16 tons of fuel per hour or 380 tons per day while at sea.

Unregulated emissions

In international waters ship emissions remains one of the least regulated parts of our global transportation system. The fuel used in ships is waste oil, basically what is left over after the crude oil refining process. It is the same as asphalt and is so thick that when cold it can be walked upon . It's the cheapest and most polluting fuel available and the world's 90,000 ships chew through an astonishing 7.29 million barrels of it each day. That's equivalent to more than 84% of all exported oil production from Saudi Arabia, the worlds largest oil exporter.

Shipping is by far the biggest transport polluter in the world. There are 760 million cars in the world today emitting approx 78,599 tons of Sulphur Oxides (SOx) annually. The world's 90,000 vessels burn approx 370 million tons of fuel per year emitting 20 million tons of Sulphur Oxides. That equates to 260 times more Sulphur Oxides being emitted by ships than the worlds entire car fleet. One large ship alone can generate approx 5,200 tonnes of sulphur oxide pollution in a year, meaning that 15 of the largest ships now emit as much SOx as the worlds 760 million cars.

South Korea's STX shipyard says it has designed a ship to carry 22,000 shipping containers that would be 450 meters long and there are already 3,693 new ship builds on the books for ocean going vessels over 150 meters in length due over the next three years. The amount of air pollution just these new ships will put out when launched is equal to having another 29 billion cars on the roads.

The UN's International Maritime Organisation (IMO) released a report in 2007 saying a 10% reduction in fuel burning was possible on existing ships and 30-40% possible for new ships but the technology is largely unused, as the regulations are largely voluntary.

Nuclear future?

Oddly enough there is never any mention of alternative power sources such as nuclear power. Nuclear marine propulsion has been in widespread naval use for over 50 years starting in 1955. There are 150 ships in operation that use nuclear propulsion with most being submarines, although they range from ice breakers to aircraft carriers. A Nimitz class supercarrier has more than twice as much power (240,000 hp, 208 MW) as the largest container ship diesel engines ever built and is capable of continuously operating for 20 years without refueling (some French Rubis-class submarines can go 30 years between refueling). The U.S. Navy has accumulated over 5,400 "reactor years" of accident-free experience, and operates more than 80 nuclear-powered ships.

Airborne pollution from these giant diesel engines has been linked to sickness in coastal residents near busy shipping lanes. Up to 60,000 premature deaths a year worldwide are said to be as a result of particulate matter emissions from ocean-going ship engines. The IMO, which regulates shipping for 168 member nations, last October enacted new mandatory standards for phasing in cleaner engine fuel. By 2020, sulphur in marine fuel must be reduced by 90% although this new distilled fuel may be double the price of current low grade fuels.

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BBC