Oil and Water

What’s going to happen to all that oil in the Gulf of Mexico?

Oil rig explosion. Click image to expand.
Oil rig explosion

A deep-sea oil well has been leaking 42,000 gallons per day since the massive rig explosion last week off the Louisiana coast. Remote-controlled submarines are trying to plug the leak, and cleanup crews have collected 48,000 gallons of oily water from the area. Is there any use for the recovered oil?

Yes. Even the black gold that comes straight from deep-sea wells is mixed with water. So the purest oil from a spill—the stuff skimmed right off the top of the open seas—is just a more diluted version of the original. Once it has been separated from the water, refineries can process it for use in cars, furnaces, and the manufacture of milk jugs. And if the recovered oil is too salty, or too contaminated with small solids for all but the most technologically advanced refineries, it can still be used to power incinerators or brick kilns.

Recovering spilled oil is fairly straightforward. A floating skimmer, lined with a chemical that attracts oil, sucks the fuel from the ocean surface, and then a pump forces the collected liquid—which is still 30 percent to 50 percent water—into a tanker. (Modern skimmers process more than 500 gallons of fluid per minute.) Almost immediately, the water begins to drop to the bottom of the tank. The water is sucked out from the bottom, and the remaining oil gets pumped into a second tank to repeat the process. After three or four rounds, what’s left is almost 100 percent oil. In certain instances (and contrary to popular wisdom) the oil and water mix, which complicates the process. This viscous emulsion, known as “chocolate mousse,” must be broken down with chemicals before going through the multistage separation process.

If the oil reaches shore, it likely can’t be used to power your car, but it can still serve a purpose. Oil recovery specialists combine oiled beach sand with quicklime and turn the muck into pavement. (The little tarballs [PDF] you sometimes see on the beach are actually just bits of sand that got mixed up with the remnants of oil spills.) If the oil gets mixed up with other flotsam or jetsam, it will likely end up as landfill. Processors put the greasy debris into a heated tank or cement mixer and use a solvent to extract the oil. The solvent-oil compound is then combined with another chemical to solidify it, and placed into lined pits to prevent it from leaking into the groundwater.

Researchers are now experimenting with bioremediation—the use of living cells to break down environmental pollutants and accelerate the slow natural process by which fossil fuels decompose. In a typical experiment, they spread the oil over a patch of low-value farmland far from watersheds, then mix it with micro-organisms that eat hydrocarbons. While mushrooms are showing some real promise—researchers inoculate the oily mess with mushroom mycelia, the mushrooms eat the oil, and the oil field turns into a big mushroom patch—bioremediation is still a somewhat minor player in large-scale cleanups.

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Explainer thanks Doug Helton of NOAA and Michael O’Brien of the International Tanker Owners Pollution Federation Limited. Thanks also to reader Christopher Chang for asking the question.

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