Oil spills

With so much oil being transported around the world, it’s little wonder that some of it gets spilt – sometimes with tragic consequences.

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The number of oil spills taking place each year has been declining sharply over the last forty years but any oil spill can be a disaster in the locality where it occurs.

We think of oil spills as accidents but of the largest oil spills to occur over the last hundred years, the biggest was the 1991 Gulf War oil disaster caused by the deliberate discharge of 240-460 million gallons of Kuwaiti crude oil into the Persian Gulf. Find a brief account of major oil spill disasters here.

Why do they happen?
Oil spills are avoidable. The value of learning about them is in ensuring they don’t happen again. Determining their cause, however, can be difficult especially when they occur in volatile regions where limited access by outsiders can reduce the accuracy and credibility of information.

Most spills are ‘small-scale’ (less than 7,000 tonnes) and occur for reasons ranging from leaking pipes, valves and storage facilities to the cleaning of ships tanks and bunkering (loading fuel onto ships).

Larger spills (over 7,000 tones) result from serious equipment failure such as wellhead blow-outs (e.g. Ixtoc in the Gulf of Mexico) or malfunctions on oil tankers. Shipping disasters such as collisions, on-board fires and running aground and are often associated with human error or difficult weather conditions.

Pollution is more likely where unlawful activity is taking place. In Nigeria, illegal bunkering (stealing oil directly from pipelines to waiting ships) is a major cause of oil spillage in the Niger Delta. The links between illegal bunkering, lack of opportunity among marginalized groups and related conflict are the subject of extensive debates; a useful starting point can be found in the Special Report on ‘blood oil’ in Nigeria here.

What happens to the spilt oil?

When oil is discharged into the environment, up to half may evaporate especially in warm climates. On land, oil can contaminate plants and animals for decades as it disintegrates or seeps into the ground. Oil at sea floats on the surface and can drift onto coasts or be broken up by currents, tides and waves, eventually dispersing through the water column and onto the sea floor. Certain microbes digest hydrocarbons so some oil will ‘disappear’ in this way.

Cleaning up oil spills often involves the use of dispersants that can be more toxic than the oil. These act like soap on water and allow the oil to sink. Surface oil can be captured by booms (floating barriers) and skimmed off the water or sucked up using vacuums. The oil can also be burnt off, which creates local air pollution.

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