Radar satellite image showing a 92 mile long bilge-dump slick identified by Skytruth,. Image taken on April 6, 2012. Envisat ASAR image courtesy European Space Agency.

Illegal Bilge Dumping at Sea Remains All Too Common in Shipping, Investigation Reveals

Mike Schuler
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April 22, 2022

The illegal dumping of oily wastewater into the ocean from ships is likely much more widespread than previously known and largely goes unpunished, according to an investigation from German media company DW.

Despite oily waste dumping being prohibited globally under the International Convention for the Prevention of Pollution from Ships (MARPOL), it continues to be shockingly common as vessels continue to pollute the world’s ocean with oil wastewater.

The DW conducted its investigation illegal oily wastewater dumping working in collaboration with the European nonprofit newsroom Lighthouse Reports and other European media outlets.

Satellite imagery and data provided by the environmental monitoring group SkyTruth helped identify hundreds of potential bilge dumps across the globe in 2021 alone, but the number of spills is likely to be much higher considering satellites used by SkyTruth only cover a portion of the world’s oceans.

According to the group’s estimate, the amount of oily water dumped into the oceans from ships could exceed 200,000 cubic meters (52.8 million gallons) annually, or roughly five times the equivalent of the 1989 Exxon Valdez spill in Alaska.

During the months-long investigation, DW and its partners spoke to experts and multiple whistleblowers who say they have witnessed illegal dumping but did not want to reveal their identities over a fear of retaliation. They all described using a small, portable pump to bypass their vessel’s oily water separator, a pollution prevention control device that separates water from oil and other wastes in oily bilge water. Only after passing through an Oily Water Separator may oily bilge water legally be discharged overboard.

Because much of the dumping happens at sea, it can be difficult (but not impossible) for authorities and researchers to track and prosecute offenses. Most violations stem from whistleblowers alerting the authorities, but advances in publicly available satellite imagery have led to new methods for finding illegal dumping at sea and identifying perpetrators.

From July 2020 through December 2021, SkyTruth, DW and its partners were able to identify more than 1,500 potential illegal dumps globally. For about 180 them, it was possible to identify the vessel based on tracking data.

More from the DW’s investigation can be found in the video below or read more in their exclusive article: Cargo ships dumping oil into the sea go unpunished.

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