Oil Spill Dispersant Article
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CONTENTS PREFACE ................................................................................................................................................................................... 3 INTRODUCTION ...................................................................................................................................................... 4 EFFECTS OF OIL SPILLS ............................................................................................................................ 4 OIL SPILL RESPONSE ....................................................................................................................................... 5 PRINCIPLE OF USING DISPERSANTS ............................................................................. 6 HOW DISPERSANT WORK .................................................................................................................... 7 WHAT DISPERSANT DO AND CANNOT DO ..................................................... 8 Spilled oil properties................................................................................................................................................ 9 Oil weathering .............................................................................................................................................................. 9 Dispersant type, application method and treatment rate ............................................... 10 THE ‘PROS’ AND ‘CONS’ OF DISPERSANT USE ........................................... 11 THE DISPERSANT DEBATE .................................................................................................................. 13 Case study 1 The Torrey Canyon oil spill fi rst use of detergents on a massive scale .......................................................................... 13 After the Torrey Canyon .................................................................................................................................... 13 Oil spills in the 1970s, 80s and 90s ......................................................................................................... 15 The ecological effects of spilled oil ......................................................................................................... 15 The “fi sh versus birds” debate ..................................................................................................................... 18 Case study 2 The Braer oil spill - an example of natural dispersion of oil............................. 20 Exposure and toxicity ........................................................................................................................................... 19 Biodegradation of dispersed oil .................................................................................................................. 23 PLANNED USE OF DISPERSANTS ........................................................................................... 24 Quantifying the risk of using dispersants ......................................................................................... 24 NEBA (Net Environmental Benefi t Analysis) ............................................................................... 24 Comparing the outcomes of different response methods ............................................ 24 Case study 3 The Sea Empress oil spill - the use of oil spill dispersants ................................ 25 CONCLUSIONS ............................................................................................................................................................ 26 Putting dispersant use in the context of other options..................................................... 26 Concerns over dispersed oil........................................................................................................................... 26 Identifying the real unknowns and the real potential risks............................................. 26 Reassuring people that possible concerns have already been considered..... 27 SUGGESTIONS FOR FURTHER READING ............................................................... 27 2 PREFACE This document has been produced as an up-to-date guide on oil spill dispersants and is intended for a non-specialist reader with a particular interest on oil spill response. More scientifi c information, together with supporting references, is given in a recent literature review on the same subject (Lewis, 2001). Oil spills can cause a lot of distress to affected communities. It is important that oil spill response actions are explained to everyone involved, including those likely to be worst affected by the oil spill. The use of oil spill dispersants can sometimes be controversial because of misunderstandings about the principle of dispersing oil and the lack of knowledge of the limitations of alternative response techniques. This document aims to inform and educate the general reader about dispersants. SFT has recently prepared new regulations for the use of dispersants. These regulations require that oil spill response is carried out within the “Principles of Internal Control” - meaning that the companies that have operational control of the response also have the responsibility to provide adequate documentation. This document elucidate the documentation needed for use of dispersants in general, but with the focus on spill response in coastal water and sensitive areas. Trondheim, August 2001 Alun Lewis Per Daling Oil Spill Consultant Senior Scientist 3 INTRODUCTION Dispersing spilled oil into the sea by the use A great deal of research work has been car- of oil spill dispersants can be an environmen- ried out on dispersants over the last 30 years. tally acceptable method of oil spill response. A Topics that have been studied include: “net environmental benefi t” will be achieved if the damage that might be caused to marine • The development of more effective disper- life by dispersed oil is less than the damage sants. that would have been caused if the oil had come ashore or drifted near to particularly • The capabilities of dispersants as a function oil-sensitive resources. of spilled oil properties and weathering time at sea. This justifi cation for dispersant use cannot, however, be imported into every oil spill sce- • The ecological effects caused by dispersants nario. Dispersing spilled oil in some circum- and dispersed oil. stances might have the potential to damage marine life that exists in the close vicinity of Any potential use of oil spill dispersants a dispersing oil slick. Dispersed oil droplets should be justifi ed by a rigorous scientifi c and the chemical components in oil that are examination of the relevant facts. The con- transferred into the sea have the potential cerns and fears of those people not normally to exert toxic effects, but only if the oil is concerned with oil spill matters need to be present at high enough concentration for pro- addressed because the sea and the coastline longed periods. This will only occur if there is are a common heritage of everybody, not not suffi cient dilution of the dispersed oil and solely those involved in the oil production or oil components into the sea. shipping industries. EFFECTS OF OIL SPILLS When an oil spill has occurred, some sections of the general public and some environmental pressure groups might say that the only acceptable oil spill response strategy is the total removal of the oil and complete res- toration of the environment to the pre-spill condition. Since this can never be achieved, these expectations can never be met and some people always consider that any oil spill response is only a partial success. Dead seabird covered in sticky oil from the “John R - Spilled oil has the potential to cause ecological incident”, Norway, 2001, effects, yet crude oil has been seeping into the sea for thousands of years at some locations tively localised area. This can cause temporary around the world. These natural oil seeps have ecological damage, although natural recovery not caused major damage and the ecology will eventually occur. The physical effects of of these areas has adapted to persistent and the spilled oil, plus the less visible effects chronic oil pollution. Accidental spills of oil caused high concentrations of toxic compo- can deposit very large volumes into the sea nents released from the oil, will affect the over a short period of time and in a compara- some marine resources in a localised area. 4 The dead and dying seabirds covered in thick, sticky oil have become the ‘icon’ of oil pollu- tion in the last decades. Shorelines affected by oil spills go through a predictable sequence of affects; dead and dying crabs, lobsters and shellfi sh will be washed ashore if crude oil or diesel fuel is spilled. On rocky shores, many limpets will become detached from the rocks and gulls will feast on them. The rocks will then start to be cov- ered in fi lamentous green algae. Dead and dying clams and shellfi sh washed on-shore due to toxic effect of light fuel oil freom the North Nature will recover after even the worst oil Cape spill, RI, USA, 1996. No visual oil on-shore. spills; it may take up to 20 or 30 years or longer in particularly sensitive areas, but even- and dead and dying creatures is a distressing tually almost all of the affected habitats will be sight. It can take some time and a lot of as biodiverse and as productive as they were effort to clean it up. The perception is that before the oil spill. In most cases it can