Will IBC 2021 Persistent Floater rule avoid contaminated beaches?

With the new IBC 2021, a new rule was set up to prevent so-called persistent floaters from causing pollution on the beaches of the North and Baltic Seas.

Such substances have a melting point above 0° C, are also quite viscous, insoluble in water, and float on the surface. This leads to clingage on the walls of the cargo tanks after unloading, which are not very easy to remove.

The rule before January 1, 2021 only required discharging above a certain temperature, which should ensure that this buildup does not occur. If this temperature cannot be reached, an additional prewash should be carried out. Sounds pretty logical and effective. However, frozen cargo remains were still found on many European beaches. People were unhappy about this, to say the least.

From January 1, 2021, the above-mentioned additional rule was introduced, which states that these substances, the so-called persistent floaters, always require a prewash. Surprinsingly this rule applies only in European waters.

Prewash in this context means: If possible, heat the tank, then wash it with hot seawater (> 60 ° C) using the built-in tank washing machine. The amount of water is prescribed according to a specific algorithm that should ensure that the buildup is removed. These new prewash rules apply to about 45 substances identified as persistent floaters by their physical properties.

Nothing can go wrong now, right?

We consider this to be a step in the right direction, but by no means sufficient, as not all of the clingage of the identified persistent floaters can be reliably removed with this procedure. To illustrate this, we would like to look at the characteristics of a cargo transported quite frequently, namely WAX. The IBC Name is Paraffin wax, highly refined. It is probably known to most people as candle wax.

Many of you have probably tried to remove old candle wax from a candle holder at some point. Then you already know that it only works if you run very hot water over it for a while. With only warm water and only a few seconds, on the other hand, it does not work. Now imagine a cargo tank with wax residue stuck to its large surface after the cargo has been discharged, and think about your experience with the candle wax.

Effective removal of the wax would require very hot water and a lot of time to treat the entire surface of the tank. The IBC prewash method just described is therefore not suitable in some cases. For this reason, we would now like to present a method that can reliably remove such clingage with little effort. In doing so, we use the property of the persistent floater to float on the surface.

Our recommendation:

Fill enough water into a relatively small service tank so that the fill level is sufficient to enable a separation of water and non-water-soluble substances.

Create a closed circuit by pumping hot water from the bottom of the service tank (settling tank) over the butterworth heater into the tank cleaning system and wash the tank to be cleaned sufficiently long with hot water via the fixed tank cleaning machines.

Pump the wastewater generated in the tank continuously back into the service tank (settling tank).

The heat and the long and repeated mechanical impact of the hot water will melt the wax, detach it from the tank wall, and flush it out of the tank. When entering the settling tank, the wax floats to the surface (persistent floater).

Recirculation by a service tank
Of course, there should be no ballast water adjacent to the tank to be cleaned. When everything has been washed out of the first cargo tank, you can even use the cleaning water in the service tank to clean all other cargo tanks loaded with the same product. After all tanks have been cleaned, all that remains is to dispose of the residues floating on top of the settling tank.

To minimize the slop quantity to be disposed of, you could carefully pump a large part of the water from the service tank back into an already cleaned tank. This water can be discharged during the subsequent wash to the required commercial standard.

Finally, the slop is pumped ashore from the service tank, and the tank is washed with hot water, which is directly pumped to shore as well.


  • Tanks are free of cargo residues and only need to be cleaned to the required standard.
  • The environment is protected. Cargo residues no longer end up in the sea.
  • The ship’s command has a clear conscience (no pollution risk) since the proposed procedure leads to the desired success, and no cargo residues arise during subsequent cleaning at sea and have to be pumped into the sea.
  • The disposal company gets more cargo residues, i.e., the slop has a higher value (recycling).
  • Considerable energy savings and CO2 emission reduction because the recirculation only requires the water to be warmed up once plus some compensation of energy losses of the system.
  • This concept works with noxious liquids (Annex II cargoes) and many oil cargoes (Annex I products) because many heavy oils are also non-water-soluble, lighter than water, and have a relatively high melting point.
  • Amazingly, this rule would also reduce pollution from cargo residues worldwide, and not just on European coasts.


  • Longer lay times of the ship after unloading in port.

In the future, however, one could clarify with MARPOL whether this cleaning can also be carried out at sea and whether the slop can be disposed of in the nearest port.


This described solution is easy to implement and incredibly effective. The physical properties of these products, initially considered a disadvantage become a great advantage when using our solution.

If you would like to learn more about this topic, we recommend that you attend one of our webinars where you will not only learn from our expert Sascha, but you can also ask him your burning questions directly.

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