How do you clean up an oil spill?

Oil Field Image Gallery A crew attempts to skim oil from the surface of the waters of Prince William Sound following the 1989 Exxon Valdez wreck. See more oil field pictures.
Courtesy Chris Wilkins/AFP/Getty Images

In 2006, the world consumed more than 3.5 billion gallons of oil each day [source: U.S. Dept. of Energy]. Sixty percent of that oil reached its destination by sea [source: Corn]. Fortunately, due to stricter penalties and better ship design, the number of oil spills has decreased since the oil shipping boom began in the 1960s. Unfortunately, they haven't been eliminated. Between 1990 and 1999, an average of 150,000 tons of oil spilled each year into the world's waterways [source: National Academies]. 2001 was a particularly bad year, with five spills occurring within the same week [source: Marine Group].

In March 1989, the Exxon Valdez catastrophe opened the eyes of the American public to the problem of oil spills. The Valdez ran aground in Prince William Sound in Alaska releasing 11 million gallons of crude oil. As a result, Americans saw countless dead and dying birds and aquatic mammals covered in oil. People began to wonder just how the experts clean up oil spills.

Supertankers aren't the only sources of oil spills. Underwater pipelines, offshore oil drilling rigs, and coastal storage facilities and refineries all have the potential to accidentally release crude oil into the water.

­But how exactly do you undertake the daunting task of cleaning up millions of gallons of oil? Agencies responsible for cleaning up oil spills -- like the Coast Guard and the Environmental Protection Agency -- have some clever and relatively simple methods.

It's fortun­ate that oil and water mix like, well, oil and water. When an oil spill occurs, the oil forms a millimeter-thick slick that floats on the water. The oil eventually spreads out, thinning as it does, until it becomes a widespread sheen on the water. How fast a cleanup crew can reach a spill -- along with other factors, like waves, currents and weather -- determines what method a team uses to clean a spill.

If a crew can reach a spill within an hour or two, it may choose containment and skimming to clean up the slick. Long, buoyant booms which float on the water and a skirt that hangs below the water contain the slick and keep the oil from spreading out. T­his makes it easier to skim oil from the surface, using boats that suck or scoop the oil from the water and into containment tanks.

A slick like this may also call for sorbents -- large sponges that absorb the oil from the water. Cleanup crews may set the oil on fire in a process called in situ burning, but this produces toxic smoke, and probably wouldn't be used in a spill near coastal settlements.

An oil spill reached relatively quickly and located away from towns is the easiest to clean up by one of these methods. But rarely do things work out so easily. Oil spills are generally very messy, hazardous and environmentally threatening. Spills may reach shorelines, have time to spread and affect wildlife. In these cases cleanup crews use other measures. Read the next page to learn about other methods of cleaning oil spills.