Thousands of cargo ships pollute the oceans with oily wastewater. An investigation shows how they deliberately circumvent environmental laws. The damage caused by these illegal oil spills is devastating.
Nothing he had learned at his naval college had prepared the young marine engineer for what he encountered at sea. The engineer said at first he was worried, sad even, as he witnessed how oily wastewater was routinely illegally dumped into the ocean from the giant tanker he worked on. But, as the pollution continued, he soon grew numb to it.
Dumping oily wastewater into the ocean has been outlawed globally for decades, but a months-long investigation by DW, in collaboration with the European non-profit newsroom Lighthouse Reports and eight other European press outlets, has found that the practice is still common, with potentially devastating effects for the environment.
Satellite imagery and data provided by the environmental group SkyTruth helped identify hundreds of potential dumps across the globe in 2021 alone. But the number of spills is most likely significantly higher because the satellites used by SkyTruth cover less than one-fifth of the world’s oceans. According to the group’s estimate, the amount of oily water dumped this way could be more than 2,00,000 cubic metres annually, or roughly five times the equivalent of the 1989 Exxon Valdez spill in Alaska — one of the worst maritime environmental disasters.
Global trade is fuelled by tens of thousands of merchant ships that are at sea every day. As the ships make their journeys, liquids from the engine room, oil, detergents, water and other substances collect in the bottom of the vessel. This noxious mixture, called “bilgewater,” is then stored in tanks. In a day, a single merchant ship can produce several tonnes of it.
International regulations require that large vessels treat the bilgewater with an “oily water separator” before it is discharged into the ocean. Each litre of bilgewater pumped into the sea after treatment is permitted a maximum residual-oil proportion of 15 parts per million, or 15 milligrams of oil per litre of water, according to a limit set by the International Maritime Organisation (IMO) in 1973. The remaining toxic mixture is stored in tanks onboard and later discharged at harbour in port reception facilities.
DW and its partners spoke to five whistle-blowers with years of experience working on container and chemical cargo vessels who say they have witnessed illegal bilge dumps. Whistle-blowers are often the only source of information for what happens when a ship is on the water. Though DW was not able to fully verify their accounts, the sources independently corroborated each other in key aspects and provided footage of the incidents they witnessed, as well as other documentation.
Almost all of them detailed a similar method for bypassing the oily water separator: a small, portable pump. “It’s very easy,” one of them told DW. “You can assemble this portable pump in five minutes and then detach (in) five minutes and hide (it) if someone is coming.”
The pump is used to transfer the oily water into a different tank — in most cases, the sewage tank. On the high seas, ships are allowed to dump their sewage untreated. Then, the toxic mix is released into the ocean, often under the cover of night or during inclement weather. At night it is harder for authorities to verify the crime, and bad weather can prevent the deployment of surveillance ships and planes.
“If you were to do this in the English Channel in broad daylight in perfect weather, for example, you’d immediately have the water police on your tail,” said Christian Bussau, a marine biologist with Greenpeace, who has been working on oil pollution in the North and Baltic Seas for over 25 years.
Maritime transport has more than quadrupled since the IMO arrived at its standard of 15 parts per million for oily-water discharges. Even bilgewater that has been treated to adhere to this legal limit has been found to be toxic to marine organisms, according to research published in 2021 by the Swedish Environmental Research Institute and co-authored by the ecotoxicologist Kerstin Magnusson. She said the current regulation should be reassessed.
Oil pollution is a more acute problem than micro-plastics because it has immediate and direct toxic effects, Magnusson said. The impact of small oil discharges on marine life remains under-investigated, she added, but academic research suggests that even small oil spills can have lasting harmful effects on marine life when they happen frequently. And repeated spills create a form of chronic pollution that can have severe effects on the environment.
Bilgewater can also contain a variety of hazardous substances, including various chemicals, detergents, inorganic salts, and metals such as arsenic, lead and mercury. They can damage the micro-organisms on which larger animals feed, and enter the human food chain via shellfish and fish.
Because the illegal dumps happen at sea, it is difficult for authorities and researchers to track them. That is why satellite imagery is used to monitor the seas for pollution. When a vessel discharges oily wastewater illegally, it usually creates a spill kilometres long and with a very distinct shape.
A system set up in 2007 by the European Maritime Safety Agency (EMSA) uses radar satellites to “see” through cloud cover and at night. It alerts the member states when a spill is found. By cross-referencing the location of the spills with ship-location data, EMSA can sometimes identify the possible polluter immediately.
Since its inception, the mechanism, called CleanSeaNet, has detected tens of thousands of possible oil slicks, and statistics show a reduction of illegal dumps in EU waters.
But illegal dumps “still regularly occur in European waters,” according to EMSA, and the number of spills detected and prosecuted remains low. Individual member states do not always follow up on the alerts, and, when they do, it is often not quickly enough to verify spills before they dissipate. In 2019, only 1.5% of spills were verified within a critical three-hour time frame. Polluters are only caught in a fraction of cases.
