Introduction

Bioremediation offers an environmentally appropriate and cost-effective response to marine oil spills that reach shore and is deservedly part of the "tool kit" available to spill responders (29, 114). Huge amounts of oil are produced at sea, and even larger volumes are shipped; unfortunately, there are daily small spills and occasional major ones that require remediation. Given the staggering scale of daily oil usage, which is estimated at close to 3.5 billion gallons (1.2 X 1010 liters) per day (2), even the spillage of a tiny fraction (estimated at <0.0035% in 1997 [46]) means that more than 150 million liters is spilled into the world's oceans each year. Fortunately, despite the increasing volume of transported oil, the amount spilled from catastrophic spills has been generally decreasing (46). Even in the early 1980s, the amount of oil spilled from shipwrecks and oil platform blowouts was a little less than the amount that entered the sea from natural seeps (104), and recent estimates suggest that spills

Roger Prince, ExxonMobil Research and Engineering Co., 1545 Route 22 East, Annandale, NJ 08801. Ronald M. Atlas, Graduate School, University of Louisville, Louisville, KY 40292.

have declined to only some 10% of the natural input (106). The only exception to the general decline of the last few decades was the appalling environmental crime in the Arabian Gulf, where some have estimated that Iraqi forces deliberately released more than 450 million gallons (1.6 X 109 liters) of oil into the sea near Kuwait in 1991. An additional 350 million gallons (1.2 X 109 liters) was deposited in the Gulf as fallout from the smoke plumes of the >700 oil well fires in the Kuwait oil fields (1), making this by far the largest release of oil into the marine environment to date.

Even with continuing success in improving ship safety and operational practices to prevent environmental releases, there remains a continuing need for environmentally appropriate and cost-effective tools for dealing with oil spills, both catastrophic and deliberate, when such spills inevitably occur. Bioremediation offers one approach that works with natural processes to minimize the environmental impacts of oil spills, and it has already been used with notable success in Alaska following the spill from the Exxon Valiez (22, 126). Bioremediation relies on oil being consumed by numerous microbial species that over the millennia have evolved to exploit it. Safe stimulation of this biodégradation is the heart of bioremediation. In this chapter, we will give a brief overview of the

Bioremediation: Applied Microbial Solutions for Real-World Em'ironmental Cleanup Edited by Ronald M. Atlas and Jim C. Philp © 2005 ASM Press, Washington, D.C.

composition of crude oil and the refined fractions that may be spilled at sea, discuss the diversity of organisms able to degrade oil components, and then describe strategies for encouraging the growth of such organisms. We will describe how bioremediation can be integrated with physical techniques to deliver an optimal cleanup and also discuss the environmental harm that might be done if bioremediation were applied carelessly and how this potential can be minimized.

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