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Cruise ship pollution exaggerated

The following letter was sent to the Post and Courier some weeks ago and and never published. We thought viewers might find it interesting.

Sir,

The cruise ship foes have been short of facts. Now they are indulging in fantasy. Ms. Agnew of the Charleston Communities for Cruise Control cites (November 8) a study that says Carnival Fantasy when in port will emit as much sulfur dioxide as 34,000 idling tractor-trailers even though the ship will be burning low sulfur fuel. She even states that the EPA has “vetted” the study. Recently, another letter writer made the same assertion. Something is very wrong.

First the facts! The sulfur content of diesel used by tractor-trailers cannot exceed the EPA standard of 15 parts per million (ppm) The sulfur content of diesel used by cruise ships in-shore in 2015 and beyond cannot exceed the Marpol Annex 4 standard of 1000 ppm. Yes, there is no doubt that cruise ship emissions will be more polluting than tractor-trailers’, even with the new fuel standards. But let’s look at the potential pollution in absolute terms and do some arithmetic.

I calculate that 34,000 idling tractor-trailers would consume 1,214 tons of # 2 diesel over the 10-hour period that Ms. Agnew has defined as the time a cruise ship is in port. This estimate is based on assumptions of a consumption rate of 1 gallon an hour for each tractor-trailer, and 280 gallons to the ton.

Cruise ship fuel consumption varies with size and conditions. The big ships can burn 200 tons a day when at sea but a medium sized ship as the Carnival Fantasy probably burns about 100 tons a day. Most of this fuel is used pushing the 70,367-ton vessel through seas. The consumption of fuel used to power lights and air conditioning when the boat is in port would be a fraction of the at-sea rate. I would estimate 2-4 tons over a 10-hour period, but let’s assume 4 tons.

Extrapolating, the 1,214 tons of fuel used by the tractor-trailers would emit over 36 lbs of sulfur as sulfur dioxide (1214 tons X 15 ppm X 2000 lbs). The cruise ship would emit 8 lbs of sulfur as sulfur dioxide (4 tons X 1000 ppm X 2000 lbs). And this assumes it burns only marine fuel. Many cruise ships, and possibly the Carnival Fantasy have generators that power the lights by burning the same fuel as tractor-trailers.

In my opinion, the comparison with the 34,000 tractor-trailers is hyperbole whether “vetted”, as alleged, by the EPA or not. In absolute terms, the emission of cruise ships in port and using low sulfur fuel will be barely damaging. Do you really think that the emission of 8 lb of sulfur as sulfur dioxide over a 10-hour period, twice a week, is going to lead to the disease and deaths suggested by the writers of letters to your paper? The pollution from hundreds of thousands of cars and trucks that ply through Charleston each day is far more significant.

Warwick Jones

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