After two ships sank in mid-December, the Kerch Strait is facing an oil spill.
Located between Russia and annexed Crimea, it is polluted by hydrocarbons released into the waters.
A heavy fuel oil whose nature poses specific problems and is very difficult to clean.
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An accident with serious consequences. The Kerch Strait, between Russia and the Ukrainian Crimean peninsula which it annexed in 2014, has been polluted since mid-December by the sinking of two Russian oil tankers during a storm. An oil spill continues to spread in the area and has become critical due in particular to the nature of the hydrocarbons released into the environment.
During an oil spill, oil behaves differently in the water depending on whether it is heavy or light: the pollution which has affected Russia and Crimea in the Black Sea since mid-December thus involves a type of fuel. “heavy fuel oil”which proves difficult to clean.
A type of fuel oil that does not float on the surface
The two tankers which sank contained 9,200 tonnes of fuel oil on board. According to the latest estimate by Russian authorities, at least a quarter (26%) of the cargo escaped at sea. “the first accident in the world involving heavy fuel oil of M100 quality”declared the Russian sea rescue service Morspasslouzhba. This type of fuel “does not float on the surface” et “there is no proven technology in the world to eliminate it in water”indicates the same source, “this is why the main method is collection on the coast.”
“Fuel oil is a trade name for a particular type of heavy fuel oil (Heavy fuel oil, HFO in English) produced in Russia and Kazakhstan”explained to AFP Rob James, senior vice-president Europe/Asia at Lamor, a company controlling pollution by hydrocarbons and chemicals. Heavy fuel oils are low-cost residual fuels from the distillation of crude oil in refineries, “usually used as fuel for large ships and industrial boilers”he specifies.
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There are two types of oil: heavy fuel oils first of all, with almost tarry consistencies, as well as so-called oils. “light”. These include diesel, gasoline or kerosene. The first, very polluting, are characterized by high viscosity and density. They can be as heavy or heavier than water, sink or be suspended, and persist longer in the aquatic environment. The latter, with low viscosity and density, degrade quickly.
Due to its characteristics, “heavy fuel oil (HFO) does not evaporate and dispersants have little effect on it.” It is described “as persistent, because climatic and biological processes that can naturally reduce the impact of a crude oil spill have little impact on heavy fuel oil”underlines Rob James. “Any heavy fuel oil generally presents more difficulty to clean up than a spill of crude oil or other refined petroleum products”he adds.
In such a case, cleaning requires “a mechanical or manual process that takes time and labor resources”like the sinking of the Erika in December 1999 in Brittany which released 20,000 tonnes of heavy fuel oil.
