Denmark tightens environmental rules

The Danish government has announced a regulation that will ban the discharge of ship wastewater from open exhaust gas cleaning systems (scrubbers) into Danish territorial waters from 1 July 2025.

Scrubbers are used to comply with the limit value for the sulphur content of exhaust gases set by the International Maritime Organisation (IMO) in 2020. Such exhaust gas cleaning systems use a chemical solution (seawater and caustic soda) to "wash" sulphur out of the flue gases.

The wash water then contains heavy metals (mercury, lead, arsenic, etc.), nitrates, polycyclic aromatic hydrocarbons (PAHs) and sulphur: a toxic mixture that changes the pH value and makes the water acidic! As there is no further purification step in open systems, this wash water is pumped directly into the sea. A single ship is therefore responsible for several hundred cubic metres of heavily contaminated water per hour. The problem is therefore simply shifted from the air to the water.

Marineforum reported on the study situation and how scrubbers work on 11 July 2023 - "Scrubbers are not environmental angels".

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The Danish Ministry of the Environment expects that by banning the discharge of scrubber water into the marine environment, toxins can be significantly reduced and their uptake into the ocean's food chain reduced. Nevertheless, scrubbers remain an IMO-approved alternative and allow shipowners to continue using heavy fuel oil instead of investing in higher-quality, low-sulphur fuels or environmentally friendly propulsion technologies.

Scrubber - open system. Graphic: VDM Metals

As part of this new agreement, ships with open scrubber systems must switch to low-sulphur fuel or closed scrubbers with zero emissions by 2025, and those with closed scrubber systems by 2029. The residual product from these zero-emission scrubbers must then be disposed of in port.

Scrubber - closed system. Graphic: VDM Metals

Under the Convention on the Law of the Sea, a nation can impose requirements for the sea area up to 12 nautical miles from the coast. Areas beyond this are regulated by the IMO. Denmark is pushing for further, similar restrictions by the International Maritime Organisation in order to achieve binding regulation by the United Nations for the entire North Sea and Baltic Sea.

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Source: gCaptain