There are only about 65,000 large ocean-going ships of the world when navy, fishing, tug, offshore, yacht, and small coastal ships under 400 feet are not included. They do present an air quality problem because they can be 7,000 to 70,000 kW diesel engines that essentially run 24 hours a day except when in the shipyard - if not running, smaller auxiliary engines and a boiler are used in port when this ship is stopped. There are absolutely no emission controls, catalytic converters, electrostatic precipitators, scrubbers (except some tankership boilers) although cleaner fuels are often used within the port areas.

The new IMO air emissions rules only apply to special control areas that nations may petition for, such as the one in the Baltic Sea and Sweden - the only one I know about now. There was some thought given to making offshore California such a special area but that was killed by the EPA Administrator and the White House.

Slowing ships might sound like a good deal but think about it, the slower you travel the longer it takes. So while it can be demonstrated the most air pollutants go down when you slow before entering a port, but over the entire ocean trip fuel and resulting CO2 emissions remain fairly much the same because they are linear, not exponential. In simple terms, a 1,300 mile trip will use a very similar amount of fuel if you go 12 knots or twice that much.

This leads one to think that to reduce the global warming potential from ships, one must simply reduce ship trips! The recent economic slow-down appears to be doing that very well ... although shipping companies do spend a lot of money on routing schedules, fastest path, avoiding storms (a horrendous waste of energy), and increasing efficiency. One must be careful because if cleaner fuels and more ozone and particulate related reductions are imposed, CO2 emissions will have to go up - there is no way around this logic.

-sammie

Onward through the fog

"In simple terms, a 1,300 mile trip will use a very similar amount of fuel if you go 12 knots or twice that much."

No!  You misunderstand hull design.  There is a theoretical maximum speed a ship of a given geometry can travel - this is called the "hull speed".  The only way to travel faster than this is to hydroplane (something no cargo ship will be able to do).  So what happens as you approach hull speed?  Your energy goes into making bigger waves.  In fact, a ship can be putting much more energy than required to go hull speed but not even know it.