The city of Marseille has decided to tackle a “blind spot in the fight against maritime pollution”: “scrubbers”, these filters placed in the chimneys of ships to “wash” the fumes resulting from the combustion of fuel at seawater. And thus reduce, as the regulations impose by 2025 in the Mediterranean, the atmospheric emissions of sulfur oxides.
Except that to listen to scientists and associations, these so-called open-loop scrubbers, since they discharge washing water into the sea, only move air pollution towards marine pollution. “Currently, scrubbers are the new vector of pollution at sea, believes Jacek Tronczynski, Ifremer researcher in Nantes, who co-wrote a report on the subject. Discharges at sea are rich in heavy metals and chemical contaminants, which enter the food web. »
“The idea is to raise awareness among all the mayors of the Mediterranean on this issue of open circuit scrubbers, so that the international maritime organization bans them as soon as possible, there is an emergency”, launched Tuesday Sébastien Barles, deputy to the mayor of Marseille to the ecological transition, who supports the initiative launched by the associations Zéro Fossile Toulon and Cap au Nord to warn of the dangers of the device and demand its outright ban. “In 2025, the SECA zone will be created, limiting sulfur emissions to 0.1% in the Mediterranean Sea at the chimney outlet”, recalls Guillaume Picard, from the Zéro Fossile Toulon collective: “But instead of using a fuel at 0 .1% sulphur, two to three times more expensive than heavy fuel oil, shipowners are bending the rule and equipping ships with scrubbers to dump everything into the sea.”
“We are in the nails”
According to him, a polluting heavy fuel oil costs 400 euros per tonne, when diesel of better quality and in compliance with the regulations is around 1,000 euros. The calculation would thus be quickly done, on the back of biodiversity and the environment: “Discharges at sea instantly kill phytoplankton and acidify the oceans and seas which contribute to regulating global warming”, denounces Hervé Menchon, deputy mayor of Marseille in charge of marine biodiversity. For his part, Guillaume Picard reports the results of a scientific study which followed eleven ships in the Mediterranean equipped with scrubbers: “They pollute as much as what the Rhône river rejects in one year. Per ship, 2,000 to 3,000 tonnes per hour of polluted seas are discharged. »
President of the Maritime and River Union of Marseille-Fos, Alain Mistre refutes favoring an economic argument by using a cheaper and filtered fuel. “Equipping a ship that makes the connection with Corsica with a scrubber costs nearly 10 million euros,” he argues. According to him, the “scrubbers” respond above all to “an objective of reducing air pollution by sulfur oxide”. “We are in the nails”, he adds, specifying “that we must allow time for ships to equip themselves with closed loops”, in other words a system for recovering washing water.
Since the beginning of January, the State has prohibited the washing of smoke by seawater less than 3,000 meters from the coast and in the port area, a derogation existing however until 2025 for regular connections, such as Corsica Linea with Corsica. “The 3,000 meters, that’s 10 to 15 minutes of navigation”, procrastinates Guillaume Picard, noting the difficulty of controlling the quantity and content of discharges at sea, like degassing. Jacek Tronczynski, for his part, conjures up this image: “A ship is a factory that functions and moves at sea”. “There are alternatives to washing fumes at sea,” he adds. These are closed-loop scrubbers, which store washing residues on board instead of discharging them directly into the sea. This has an economic cost. We need recovery devices in the ports and a processing chain for this waste. In short, a whole logistics to be put in place.