21. April 2022, updated 16. June 2022

Bilge Dumping: Probably the Worst, Widely Unknown Environmental Crime

Aerial view of a cargo ship
Source: Venti Views via Unsplash.

In this article, we want to address a fundamental problem of oil pollution in the oceans and yet many of you have probably not heard of it. We are talking about bilge dumping, the improper discharge of oil-contaminated bilge water that occurs during the normal operation of a ship. How can it be that such a severe problem of ocean pollution is hardly known? What can be done about it and who is already doing something to stop this? Let us give you an overview!

The Importance of the Issue

The problem of oil pollution is widely known, and no one doubts the worshipful consequences for the oceans. Very recently, at the beginning of the year, the images of the oil spill around the coast of Peru went around the world, where, according to the Peruvian Ministry of Environment, almost 2,000 m³ of oil spilled into the sea. While this figure is frightening and has caused much damage, the extent of bilge dumping is estimated by scientists from SkyTruth to be 200,000 m³ per year or possibly even more, in other words a hundred times the scale of the disaster in Peru!

One more comparison: we’re talking about an amount of oil deliberately spilled into the sea each year that is about five times the amount that spilled into the sea from the Exxon Valdez tanker in Alaska in 1989, the worst oil spill in history. At this point at the latest, it should be clear how big the problem of bilge dumping really is and that it is high time to develop an awareness of this issue and to stop it as soon as possible.

Clean up after Exxon Valdez oil spill catastrophe
Cleanup after the oil spill of Exxon Valdez in 1989. Source: U.S. COAST GUARD.

What Exactly Is Bilge Dumping?

Bilge dumping refers to the illegal discharge of oil-contaminated bilge water directly into the sea.

Every ship has a bilge, the lower inner part of a ship, in which dirty water collects. Among other contaminants, a lot of oil accumulates in this bilge water, which is emitted during normal ship operation, and which simply cannot be avoided. Just think of the huge propulsion engines and you can imagine what enormous quantities of oil are needed to keep them running. Larger ships are required to be equipped with oil-water separators, which separate the bilge water from the oil before it can be released into the sea. The separated oil residue is transferred to another tank, which is then properly pumped out at ports. Well, at least that is how it is regulated, because in practice the use of an oil-water separator is often simply bypassed, which significantly reduces the operational costs of the shipping company.

With the help of a portable pump, for example, the oil-contaminated bilge water can be pumped directly into the sea, and if this happens on the high seas, no one notices, right? Indeed, for a long time hardly anyone noticed, but modern technologies and courageous whistleblowers brought more and more to light what deliberate environmental damage is happening out there and this is exactly what we discuss in the following.

Growing Awareness

Although bilge dumping has been widespread practice for many decades, awareness of this type of oil pollution has only really grown in recent years. This is also reflected in the bibliographic analysis, in which we looked at the number of scientific publications over time that address bilge dumping. We used Google Scholar as database and performed a qualitative check of the results on their relevance. As you can see in the figure below, especially within the last five years, the number of publications on this topic have increased sharply.

Graph showing the total number of publications per year on bilge dumping from 1975 to 2021. Over the last five years the trend is sharply inceasing.
Total publications per year on bilge dumping from 1975 to 2021. © Maritime Affection.

The organization SkyTruth has certainly contributed to this increase in scientific interest, as it is one of the pioneers in the field of bilge dumping. SkyTruth uses satellite imagery and analyzes it using advanced techniques to document bilge dumping and is even able to identify suspicious vessels. For this purpose, SkyTruth has launched the project Cerulean, which makes it possible to analyze enormous amounts of data with the help of artificial intelligence and thus allows conclusions to be drawn about illegal oil dumping. For more information on this exciting project, watch this short video from SkyTruth:

Video by SkyTruth about project Cerulean.

Be sure to check out SkyTruth, the team is doing a fantastic job researching many environmental issues using satellite imagery and promoting global transparency through their philosophy that “seeing is believing”. In the picture below you can see for example a satellite image from SkyTruth, on which oil traces of a tanker can be seen, which were caused by bilge dumping. We agree with SkyTruth in their philosophy, if you can actually see the issue, it is easier to change it.

A satellite image from SkyTruth, on which oil traces of a tanker can be seen, which were caused by bilge dumping.
Satellite image of bilge dumping traces. Source: SkyTruth via Flickr.

Furthermore, the news channel DW recently published its own investigation on bilge dumping, in which they worked closely with SkyTruth. It is highly recommended to watch the video report on their channel DW Planet A, because there you will learn some more details about this topic:

Video by DW about bilge dumping.

Much of the information that helps to expose bilge dumping on the high seas is based on undercover footage and reports from courageous whistleblowers who are taking a stand against this illegal practice. Since there are unfortunately many ways to circumvent the legal requirements for oil disposal, we depend on these whistleblowers and should be profoundly grateful to them for their courage; after all, they take the risk of losing their jobs.

While public awareness of the problem of bilge dumping is growing slowly over time, in many countries the threat of punishment is still too lenient in relation to the enormous cost savings that can be realized through illegal disposal.

Help to Make a Difference!

We hope that with this article we have made you aware of an unfortunately still very unknown environmental problem and that you can now understand the serious dimensions of bilge dumping. Now it should be clear how urgent it is to stop this environmentally damaging activity and that what has been widespread practice for a long time now must finally come to an end.

The easiest and most powerful way to help is to raise transparency and awareness and thereby increase social pressure on shipowners, governments, and other involved stakeholders. That’s why we urge you to support great organizations like SkyTruth and share articles like ours to get a little closer to our common goal: improving the health of our marine environment.

If you have questions, ideas, criticisms, or anything else, feel free to write it in the comments, we’re looking forward to hearing from you!

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