The very first living organism to be patented was, in fact, a bacterium engineered in the '70s to degrade components of crude oil. Others have been developed since. So can we just pour these specially engineered microbes onto the spilled oil en masse and wait for them to consume it?
According to Ronald Atlas of the University of Louisville, who has been studying oil-spill bioremediation—a process in which oil-eating microbes are used to degrade leaked crude—since 1968, it's unfortunately not that simple. Bioremediation has been used successfully to mitigate many previous oil spills, including the Exxon Valdez (to date the largest spill in U.S. history). But success is defined differently than one might think in these cases. Bioremediation can eliminate only a portion of the compounds present in oil, and the process can take years. "It's not a panacea. This is not like a physical cleanup where I pick it up and it's gone—this takes some time," Atlas says.
So what does the process involve? Believe it or not, naturally occurring bacteria that can degrade oil are already present in marine environments, so adding specially engineered oil-eating bacteria isn't even required. What is needed is fertilizer, since the limited availability of nutrients like nitrogen and phosphorus prevent these microscopic oil eaters from growing (and eating oil) to their full potential. Oil-degrading microbes start colonizing oil as soon as it is released, so adding fertilizer to crude that has washed up onshore can help the oil-degrading bugs propagate more quickly and ultimately eat more oil.
Atlas says it's a common misconception that adding specially engineered oil-degrading microbes is helpful, though field studies actually show that adding new microbes is no more valuable than providing nutrients to the ones that are already there. There's no major environmental drawback to increased populations of oil-degrading bacteria, although applying too much fertilizer can trigger a damaging eutrophication event in which algal blooms (thanks to the greater availability of nitrogen) use up oxygen in the water and cause die-offs of other marine species. During the Exxon Valdez cleanup, Atlas said that application of fertilizer sped up the rate of microbial oil degradation by three- to fivefold—a significant improvement, although the process is still slow.
There's not much value in fertilizing oil-degrading bacteria while the current oil slick is still offshore, since the oil is generally spread thin enough that nutrients are not as limiting, but the technique will be useful as the oil begins piling into the shoreline. Once the physical means of cleaning up oil from the shore, like vacuuming or scraping it up, have been exhausted, then bioremediation will likely be harnessed as a secondary approach to help clean what can't be gotten by physical means. "It's one of the tools in your toolbox, but it's not the only one, and it's not necessarily the penultimate," Atlas says.