Oil has been the fuel of choice for powering ships for over a century now, supplanting coal as a source for running steam boilers just as diesel engines have largely replaced steam engines. The grade used is commonly called bunker fuel and can quite literally be termed bottom of the barrel, since it is the densest form of liquid found in petroleum and tends to sink to the lowest levels during the refining process known as cracking. The term bunker refers to the containers used to store the oil aboard ships. Increasing fuel costs have led to greater attention being given to fuel management systems and advances in technology have permitted greater oversight to be possible. Bunkers are now equipped with sensors that continually monitor fuel use and allow the crew to make decisions on engine speed and course corrections that will impact fuel usage rates. These instruments also allow authorities to closely monitor any spillage that might occur. The system has greatly reduced loss and pollution that used to result from overfilling tanks and has also cut down on pilferage. Ship exhausts constitute a significant source of global totals for emission of both nitrogen oxides and sulfur oxides, two…
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