Application of dispersants – is the cure worse than the ailment?
In case of an oil spill at sea, Equinor has to decide on the most effective response to minimise damage. The dominant strategy remains the removal and containment of spilled oil by mechanical technology. Such containment may be difficult in the Great Australian Bight, considering its rough waters. The other option that Equinor have outlined is the use of chemical dispersants.
Dispersants enhance the natural break-up of floating oil into small drops. In this way, coating of coastal areas and oiling of sea birds and mammals can be reduced. To the human eye, chemical dispersants make oil spills disappear.
However, the treatment could be worse than the ailment. Dispersants essentially break up the oil and reallocate it from the surface to the water column. The effect of an oil spill on surface dwelling marine organisms (e.g. birds and sea-lions) is reduced as a consequence. However, the increased concentration of oil in the water increases the toxic effects on organisms in the water column and on the bottom of the sea floor.
It is important to note that toxic effects caused to organisms in the water column and on the bottom of the sea floor, are likely to work their way back up to the surface dwelling organisms anyway. For example, a bird may no longer be at risk of being coated in oil; however, the fish it feeds on are dying off or contaminated with oil. Thus, that bird may die from starvation or due to the toxic effects of oil.
Additionally, usually less than 100% of the treated oil will disperse. This means that the effect from undispersed oil will still occur.
Understandably, there are conflicting views concerning the potential risks and benefits for human health and the environment generated by the use of dispersants during oil spills. Currently, there is not enough data to make an informed decision on the most environmentally friendly response. Importantly, each case varies so what worked in one scenario may not necessarily work in the Great Australian Bight.
What does appear to be clear is that even cleaning up oil spills has toxic effects. In the words of South Australian senator Tim Storer – the risks of drilling in the Bight simply don’t justify the rewards.