Container / cargo ships, oil tankers and large cruise ships burn some of the grungiest stuff on the earth, bunker fuel. Inexpensive and untaxed, bunker fuel is a very low-grade oil that is as viscous as hot tar. This cheap ocean passage fuel is a type of liquid fuel, which is fractionally distilled from crude oil. From around the world, bunker fuel comes in a number of different classifications. These classifications break down bunker fuel into different categories based upon their chemical composition, intended purpose and boiling temperature. In comparison with other petroleum products, bunker fuel is extremely crude and highly polluting.
To better clarify, after crude oil is extracted from the ground and brought into a refinery, it goes through a process called fractional distillation where the oil is heated, causing different types of oil within the crude to separate as they have different boiling points. Small chained oils like those in propane gas, naphtha, gasoline for cars and jet fuel have relatively low boiling points and are quickly removed at the beginning of the fractional distillation process. Heavier petroleum products like those in diesel and lubricating oil precipitate out more slowly, leaving bunker oil literally at the bottom of the barrel. The only thing denser than bunker fuel is the residue, which is mixed with tar for paving roads and sealing roofs.
The hydrocarbon chains in bunker fuel are very long, and make this fuel highly viscous as a result. Bunker fuel is also highly contaminated with various noxious substances, which cannot be removed from such a thick substance, so when it is burned, it pollutes heavily. This thick bunker fuel is difficult for most engines to burn, since it must be heated before it will combust, therefore it tends to be used in larger engines like those on board giant container / cargo ships, oil tanker and cruise ships.
The dirtiest variety of bunker fuel contains 4.5 percent sulfur, by weight. Sulfur, of course, is that nasty element that forms sulfur dioxide, and contributes to acid rain, cancer, respiratory ailments and heart disease. In contrast, diesel sold in the U.S. is just 0.0015 percent sulfur. According to United States academic research, bunker fuel currently leads to the premature deaths of an estimated 90,000 people a year, world-wide.
To the rescue, this March (2010) the Marine Environment Protection Committee of the International Maritime Organization (IMO) began to tighten controls on what was previously the world’s least-regulated liquid fuel. In the first phase, the 1.5 percent cap on the sulfur content of bunker fuel burned close to shore (in the so-called ‘sulfur emission control areas,’ such as the coast of Florida) will drop to one percent. By the year 2020 the IMO will require that all bunker fuel have a sulfur content of less than 0.5 percent – a change that United States Environmental Protection Agency (EPA) Administrator Lisa Jackson says could result in cleaner air whereby nearly five million people will experience relief from acute respiratory symptoms and as many as 14,000 lives will be saved each year.
These sulfur regulations are an important start, but they do not address the larger and potentially more important problem with bunker fuel – its carbon dioxide emissions contribute to global warming. The Scientific American says “If the international shipping fleet were a country, it would be the world’s sixth-highest greenhouse gas emitter, right behind Japan and just ahead of Germany.”
Likewise, many oil spills have involved bunker fuel, leading some environmental organizations to call for a total ban on the substance. Bunker fuel is extremely difficult to clean up and it coats birds and shorelines very effectively, because it’s so dense. Because bunker fuel also carries a range of contaminants, it represents a serious environmental hazard when it spills. However, because bunker fuel is so cheap, many shipping companies continue to lobby against any proposed ban, out of concern for a sudden jump in shipping costs.