“We must remember the premise of using chemical oil dispersants: Diluting the oil from a surface slick into the water column at sea to reduce its concentration to below toxic levels, enhance its degradation rate, and reduce its probability of reaching shore.” – Kenneth Lee
Kenneth Lee has a Doctor of Philosophy (Ph.D.) in microbiology and limnology – the study of inland waters – and is a prominent expert in the field of oil spill response technologies, both in Canada and internationally. Over the past 35 years, Dr. Lee has focused his research on oil spill clean-up, including the use of chemical dispersants to counter the environmental impact of oil spills.
Dr. Lee is currently the National Senior Science Advisor for Oil Spill Research, Preparedness, and Response for Fisheries and Oceans Canada. Since 2016, he’s been leading the Multi-Partner Research Initiative (MPRI) for oil spill response under Canada’s Oceans Protection Plan. MPRI has the mandate to promote collaborative research between government, academia and industry at the national and international levels and aims to provide expert advice on best practices to respond to oil spills in Canadian waters.
What are chemical oil dispersants and how do they work?
Spill Treating Agents (STAs) such as oil dispersants change the behavior of oil to aid clean-up and remediation strategies. To put it in simple terms, oil dispersants act like dishwashing soap that transfer the oil and grease off your pots and pans into the dishwater of your sink. Dispersants transfer the oil from surface slicks into the water column by breaking it down in small droplets. There’s a common misconception that this process merely moves the oil from one part of the environment into another and that the dispersant formulations are highly toxic as chemically dispersed oil is more toxic than the oil itself. However, when dispersants are used properly, oil droplets are diluted rapidly by natural processes, such as ocean currents, to concentrations below that which causes toxic effects. Another important consideration is the presence of natural bacteria in the water that are known to break down oil naturally over time. The formation of small oil droplets by the addition of dispersants increases the surface area of oil available to microbial attack and thus the rate of its removal from the ocean.
What drew you to chemical oil dispersants as a field of research?
Part of my Ph.D. was working on trace metals and contaminants that spilled into lakes and streams. I wanted to broaden my understanding of chemistry and undertook a post-doctoral fellowship in chemical oceanography at the Institute of Ocean Sciences on Canada’s West Coast. That’s when I started working on chemical oil dispersants, looking at their effectiveness and potential effects on the environment.
Is the use of chemical oil dispersants a recent development in oil spill response?
No. Chemical dispersants have been used for decades. They were first used on an operational scale in 1967, following a spill from the supertanker Torrey Canyon off the English coastline. While the dispersants were successful at their task of reducing the amount of oil arriving ashore and subsequently expediting onshore cleanup operations, the excessive and indiscriminate use of these early dispersants and solvent-based cleaning agents were also found to cause considerable environmental damage. Since then, much research has been conducted on the application of dispersants and their potential environmental effects. Today, only low-toxicity formulations of dispersants are approved for use by regulatory agents on the basis of their effectiveness, toxicity and environmental persistence.
How do chemical oil dispersants compare to other response measures?
We must keep in mind that no single oil spill response measure – clean-up technique – is 100% effective. The key to successful oil spill response is to pick the right tool or tools for use at the right time, and there are a number of options available.
One of them is mechanical recovery, which consists of using booms to contain the oil and skimmers to collect it. Unfortunately, under high wave or strong tidal conditions, booms have difficulty containing the oil. Moreover, mechanical recovery can be cost and labour-intensive; response teams must transport the oil and water collected along with it back to shore for waste treatment and disposal.
Another option is removing the oil by burning it at sea – a technique called in-situ burning. However, oil on the ocean can only be burnt if it is thick enough. After a spill, the water cools and spreads the oil making it difficult to ignite. The use of fire-resistant booms and new technologies such as chemical herders – similar to oil dispersants to enhance oil thickness for its ignition – are currently being studied. Environmental concerns over in-situ burning include effects on air – emissions – and water – burn-residues – quality. Still, in-situ burning can be very effective in removing high quantities of oil in a short time. For example, some days during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, response teams burned as much oil as was spilled.
Chemical oil dispersion or natural dispersion – which essentially consists of letting nature take care of the spill – are other measures that can be considered to respond to a spill. As noted, over the long term much of the oil spilled at sea is naturally degraded by bacteria which consume it as a carbon source. Personally, I consider natural dispersion an operational oil spill response technique. You aren’t walking away from the spill; you are monitoring it and making sure it is resolving. Otherwise, you treat it.
In sum, due to a number of logistical and environmental challenges, there is a limited amount of oil that can be removed through mechanical recovery or burning in the open sea. In fact, according to the National Oceanic and Atmospheric Administration (NOAA), during the Deepwater Horizon oil spill, about 2% to 4% of the oil was skimmed using mechanical recovery while about 5% was burned, under quasi-ideal conditions. NOAA also estimated that chemical oil dispersants accounted for 10% to 29% of the clean-up during the incident. Chemical oil dispersants can be applied from aircraft to address a large oil slick very quickly under a much wider range of environmental and sea-state conditions than other response strategies such as booming and skimming.
When can’t chemical oil dispersants be used?
Only certain types of oils can be treated with dispersants. When an oil spill occurs, some components start evaporating and the remaining oil becomes thicker. As the oil becomes more viscous, chemical dispersants are less effective. Therefore, when using oil dispersants, they must be deployed as quickly as possible, before the spilled oil becomes too viscous. The window of opportunity for the effective use of chemical oil dispersants to respond to a spill can be quite limited. Chemical oil dispersants would typically not be applied in shallow coastal waters where oil dilution could be hampered by water depth or in known ecologically sensitive areas, for example fish spawning grounds.
What type of oils would chemical oil dispersants be most effective treating?
Light and medium viscosity oils are treated most effectively with dispersants, but the technology is improving. For example, current formulations have now been found to be effective on waxy crude oils such as those recovered off the coast of Newfoundland.
What are the environmental effects of chemical oil dispersants?
Keep in mind that the premise of using chemical oil dispersants is to dilute the oil to reduce its concentration below toxicity threshold limits and to enhance its degradation rate by natural bacteria.
There can be toxic effects from the use of dispersants; however, we have to remember that chemical oil dispersants, when used, are not applied to a pristine environment. The spilled oil has more toxicity in the marine environment than the dispersants added to that environment at a very low concentration to facilitate a rapid dilution of the residual oil.
Chemical dispersion is primarily an offshore spill response technology to keep the oil slick from coming to shore and near-shore waters, where biodiversity is higher and where environmental impacts from oil may be much greater. Oil spill response is about making the best decisions to reduce the overall environmental and socio-economic impacts of a spill by determining whether there is a net environmental benefit of adding chemical dispersants to the marine environment.
How do we determine if oil dispersants should be used?
When responding to an oil spill, it’s important to identify and make a decision on the right technology or the right combination of response measures to contain and reduce the spill. That combination of tools changes over time after the spill occurs because the chemistry of the oil is changing and external factors like weather can change too. Response teams have to pick the best set of tools under the given circumstances.
Could fertilizers provide an alternative to chemical oil dispersants?
In the ocean, there are huge amounts of oil released from the sea floor in a process called natural seepage and bacteria have adapted to degrade or consume this oil. I’ve spent my whole career as a microbiologist trying to understand how bacteria degrade oil in the environment, and what can be done to speed this process up. One of the things research looks at is the use of fertilizers to speed up the production of bacteria to fight oil spills. Fertilizers were used effectively following the Exxon Valdez oil spill in Alaska in 1989 to clean up the beaches. However, the application of fertilizers is not an effective technique when dealing with spills of oil in the open ocean due to their rapid dilution.
In terms of an alternative to chemical oil dispersants for use at sea, under the Multi-Partner Research Initiative, we are studying the potential use of “bio-surfactants” produced by natural bacteria found in the ocean that may be more effective and environmentally acceptable.
What are the rules in Canada around the use of chemical oil dispersants?
Any chemical dispersants that are going to be used in any country almost invariably have to be approved for use. When an oil spill occurs, the response teams can’t just take any product off the shelf; they have to use an approved product. Products are tested by government agencies such as Environment and Climate Change Canada to prove two things. One is to see if they actually work and, if they do work, what are the biological or other effects of their use.
Under a number of federal acts and regulations, including the Fisheries Act, deleterious substances can’t be introduced to the marine environment. Therefore, chemical oil dispersants are not approved for general use at this time. In Canada, only two products – one oil dispersant and one shoreline treating agent – are approved and their use is to be assessed on a case-by-case basis.
What is the future of chemical oil dispersants in Canada?
At Fisheries and Oceans Canada, where I lead the Multi-Partner Research Initiative program, together with other federal science-based agencies – Environment and Climate Change Canada, Transport Canada and Natural Resources Canada – we are exploring alternative response measures. These are technologies that we would like to use in the future to complement the mechanical clean-up of oil spills. We are looking at research on chemical oil dispersants, in-situ burning, oil translocation (processes controlling the mobilization and removal of stranded oil within shoreline environments), decanting (the separation of oil from water collected by skimmers), and waste management. The idea is to develop the science to generate best practices and support policies and regulations in the field of oil spill response as well as the use of alternative response measures in the future.
More about Dr. Kenneth Lee
Dr. Lee was the founding Director of Fisheries and Oceans Canada’s Centre for Offshore Oil, Gas and Energy Research (COOGER). He has also served as the Director of Oceans and Atmosphere, Commonwealth Scientific and Industrial Research Organization of Australia’s national science agency. He was appointed Chair of the Royal Society of Canada’s Expert Panel on the Behaviour and Environmental Impacts of Crude Oil Released into Aqueous Environments. He had three appointments on the US National Academies of Sciences, Engineering, and Medicine Committees on the effects of the Deepwater Horizon oil spill on ecosystem services; Arctic oil spill response; and the use of chemical oil dispersants. Dr. Lee has published over 450 academic and technical publications and is a two-time recipient of Fisheries and Oceans Canada’s “Prix d’Excellence” and the Government of Canada’s “Federal Partners in Technology Transfer – Leadership Award” for oil spill countermeasures.
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Published July 14, 2020