This photograph shows windrows of emulsified oil (bright orange) sprayed w/dispersant. The photo taken on April 26, 2010 as part of an aerial observation overflight. Credit NOAA.
BP is attacking the oil spill in the Gulf of Mexico on all fronts, from the traditional skimmers and booms to more advanced technologies. But history and science suggest this clean-up effort probably won't end in a spotless environment.
BP Chief Executive Tony Hayward said the company would do "everything in our power to contain this oil spill and resolve the situation as rapidly, safely and effectively as possible," according to news reports. The company, which was leasing the Transocean oil rig that exploded and sank on April 22 in the Gulf, is responsible for the clean-up.
And yes, all hands are on deck – skimmers, booms, domes, controlled burning and chemical dispersants – to try to clean up the 1,000 to 5,000 barrels a day estimated to be leaking out of the well.
However, for an oil spill at sea, typically only 10 to 15 percent of the oil is recovered, Gerald Graham, president of Worldocean Consulting, a marine oil spill prevention and response planning firm based in British Columbia, told LiveScience.
So far, BP claims it has recovered 685,062 gallons (more than 2.5 million liters) of an oil-and-water mix. That mix is almost entirely water, with oil stirred in like vinaigrette. Until the entire recovery process finishes, it will be impossible to tell how much crude oil BP has recovered, Graham said.
The rest of the oil that doesn't get cleaned up evaporates, breaks up and floats on the surface, or sinks to the bottom, Graham said.
"It's kind of overwhelming," U.S. Coast Guard Petty Officer 3rd Class Cory Mendenhall said of the cleanup effort.
"A lot of it cannot be collected," Mendenhall said. "95 percent [of the oil] is a rainbow-y sheen. It's too thin to scoop up. Most of that breaks up naturally, so about 3 percent of the oil is what people think of as big globs of oil that you can skim off the water. Now, how much of that 3 percent has been collected is still unsure."
History attests to the lingering problem of oil spills. Exxon Valdez, one of the worst oil spills ever, dumped more than 10 million gallons of crude into Prince William Sound, Alaska, on March 24, 1989. And there's still a lot of oil that didn't get cleaned up, which has continued to impact wildlife in the area for the past 20 years, experts say.
"Despite spending $2 billion dollars and using every known clean-up method there was, they recovered 8 percent of the spilled Exxon Valdez oil," said Jeffrey Short, Pacific science director for Oceana, a Washington, D.C.–based ocean conservation organization. "That is typical of these exercises when you have a large marine oil spill. You're doing really great if you [get] 20 percent."
Cleanup under way
So far, the most effective method has been chemical dispersants. Least effective: booms, according to Mendenhall. Here's what's being done to capture the oil:
Chemical dispersants: About 100,000 gallons of chemical dispersant has been dropped from the air into the Gulf, where it breaks up the oil slick into smaller droplets. The droplets then get mixed into the water, where they are subjected to ocean currents and natural degradation processes, according to the Minerals Management Service (MMS). "This potentially exposes the water column and near shore shallow bottom-dwelling organisms to oil," according to MMS.
Skimmers: Once broken up, skimming vessels come in and collect what's left. The droplets are collected in drums and some of that material gets cleaned and recycled. The rest is "properly disposed," Mendenhall said. But skimmers can only capture about 10 percent of the volume of spilled oil, according to Charlie Henry of the National Oceanic and Atmospheric Administration (NOAA).
Controlled burn: On Wednesday, BP and the Coast Guard, along with other agencies, conducted an in-situ burn in which they used a fireproof boom to corral dense parts of the oil spill, moving it to another location and then burning it.
In general, burning is probably the most effective method for cleaning up heavy oil like that leaking in the Gulf, according to said Edward Overton, a professor emeritus of environmental sciences at Louisiana State University. But it has drawbacks. When you burn near the coast, you have to destroy wildlife, and offshore burning is harder to do.
"I have no idea what we're going to do, this is trial and error to see what works and what doesn’t work," Overton said. And news reports suggest since the oil is really an oil-water mix, burning actually might not do the trick.
Collection domes: BP has also started to put together a subsea oil collection system, and when used will be the first time this shallow-water technology has been adapted for the deep water. The oil leaks in the Gulf are nearly a mile down. It is expected to be ready for deployment within the next four weeks, according to BP.
When ready, here's how the oil-spill technology would work: The dome would be placed on the seabed to capture the leaking oil. This oil would then be pumped up to surface vessels that could collect the oil and take it away. Similar systems have been used in shallow water, but never at depth of 5,000 feet. The Coast Guard has said the construction could take two to four weeks.
New method: However, Thursday afternoon officials said they might try an experimental oil-dispersal method that would involve releasing chemicals from under the water. "We were notified that this technique might be more effective in spreading the dispersant at the source on the riser than by using aircraft to spread it on the sea," said Doug Suttles, BP's Chief Operating Officer.
As for what happens to the "dispersed oil," that doesn't get skimmed off or burned off or otherwise collected, "We're told it disperses naturally. It eventually breaks up and evaporates. There are different ways, but we're told it just kind of goes away," U.S. Coast Guard's Mendenhall said.
Bacteria can also help degrade most components of oil.
But not all oils are created equally. At first, reports suggested the oil leaking into the Gulf was standard Louisiana crude oil, a type of oil that biodegrades pretty well, Overton said. But sample testing revealed that the leaking oil was a different type, one that contains a very high concentration of components that don't degrade easily, called asphaltenes, according to Overton. He estimates that the concentration of these asphaltic components could be as high as 50 percent in this oil spill, while in other types of crude oil it might be as low as 1 or 2 percent.
"That is bad, bad news, because this oil is going to be very slow to degrade," Overton said today.
Some of the oil sinks to the sea bottom, where it can get buried into an anaerobic zone where there's no oxygen. Oil in these zones stays in a chemically reduced form and doesn't degrade as much, Overton said. But, he added, there's not much life down there to be contaminated.
The oil slick could reach the Mississippi Delta coast as early as Friday, so at least some oil will hit shore. A satellite image of the slick taken Thursday showed it was almost touching the delta.
History as a guide
The 1989 Exxon Valdez spill that fouled over 1,200 miles (1,900 kilometers) of shoreline in Alaska in 1989 has shown that once an oil slick makes landfall and soaks into the beach, it can take decades for the pollution to break down and disappear. About 40 percent of the 10.8 million gallons spilled reached shore in Prince William Sound, according to Short.
"There's still a lot of oil that didn't get cleaned up," from the area around Prince William Sound where the spill occurred, said Daniel Esler, a University Research Associate, based at the Centre for Wildlife Ecology at the Simon Fraser University in British Columbia, Canada.
Some beaches didn't get cleaned up as much as others, and certain coastal environments (with particular types of sediments and patterns of water flow) tend to hold on to the oil for longer than others. While it can't be seen if you walk along the beach, digging down into the sediments at certain spots can lead to pools of oil that remain in much the same condition as when they first spilled.
For instance, in 2001, 2003 and 2007, researchers dug over 12,000 pits at dozens of beach sites that had been covered in oil back in 1989. The team found black, oily liquid in over half of the holes dug in 2001.
This subsurface oil was "fingerprinted" back to the Exxon Valdez as the ultimate source (the star-crossed region also had an earthquake-caused oil spill back in 1964). This hidden oil contained the same proportions of polycyclic aromatic hydrocarbons in it as the Exxon Valdez oil collected right at the initial time of the spill. "There was no question we were looking at Exxon Valdez oil," Short, who led the three surveys, told Livescience.
The lingering oil estimate for affected Alaskan beaches stood at 21,000 gallons (80,000 liters) in 2004. This Exxon Valdez oil is decreasing at a rate of 0 to 4 percent per year according to the Exxon Valdez Oil Spill Trustee Council (EVOSTC) – though the lower rate is much more likely – meaning it will take decades or even centuries for the oil to disappear entirely.
Though the lingering oil has broken down, in some locations it remains almost as toxic to the environment as the freshly spilled variety, according to EVOSTC's Web site. (EVOSTC oversees restoration use of civil money to clean up the Sound.)
And even though this leftover oil is "just a teeny fraction of what was originally spilled," Esler said, certain species can still be exposed to it.
Esler and his colleagues used a biomarker that indicates exposure to hydrocarbons (of which oil is one) to look at the potential exposure of harlequin ducks, a particularly vulnerable species, in the area affected by the spill. They found that these ducks were coming into contact with the spilled oil even 20 years after the incident.
The findings suggest that oil spills can have an impact on the environment for much longer than previously thought, even decades later.
In the case of the Gulf spill, the oil won't last as long if it stays in open ocean — there it will either evaporate or congeal into clumps and sink to the ocean floor, Esler explained. But if it reaches the coast, it could encounter the types of environments where it can stick around for a long time.
Given the number of places where oil spills have happened and oil has remained even after clean-up efforts, "it's not unreasonable" to think that oil could remain for some time if reaches the Gulf coast, Esler said in a telephone interview Thursday.
The situation at Prince William Sound isn't all bad though, as it seems some species are out of the woods in terms of exposure threats and "there are lots of hints that things are getting better," Esler said.
Additional reporting for this story was contributed by Denise Chow, Stuart Fox, Adam Hadhazy, Rachel Rettner, Karen Rowan and Andrea Thompson.