ICES Viewpoint background document: Impact from exhaust gas cleaning systems (scrubbers) on the marine environment (Ad hoc).
Report, 2020

Shipping is a diverse industry that connects the world. The distribution and intensity of commercial shipping is increasing and there is a growing need to assess and mitigate the impacts of vessel activities on the marine environment. New global standards on sulphur content in marine fuels have led to an increasing number of ships installing exhaust gas cleaning systems (EGCS), also known as scrubbers, to reduce their emissions of sulphur oxides to the atmosphere. Ships equipped with a scrubber can continue to use heavy fuel oil, and the process results in discharges of large volumes of acidified water that contain a mix of contaminants, such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), oil residues, and nitrates. For the most common type of scrubber, open loop, this polluted water is directly discharged back to the sea, trading reductions in air pollution for increased water pollution. The scrubber discharge mixture has demonstrated toxic effects in laboratory studies, causing immediate mortality in plankton and exhibiting negative synergistic effects. The substances found in scrubber discharge water are likely to have further impacts in the marine environment through bioaccumulation, acidification and eutrophication. The impacts of scrubber discharge water can be completely avoided through the use of alternative fuels, such as distilled low sulphur fuels. Distilled fuels have the added benefit that they remove the threat of heavy fuel oil spills from shipping activities. If the use of alternative fuels is not adopted, and scrubbers continue to be considered an equivalent method to meet the sulphur emissions limits, then there is urgent need for:
1) significant investment in technological advances and port reception facilities to allow zero discharge closed loop scrubber systems;
2) improved protocols and standards for measuring, monitoring and reporting on scrubber discharge water acidity and pollutants;
3) evidence-based regulations on scrubber water discharge limits that consider the full suite of contaminants.



sulphur regulation


exhaust gas cleaning system



Ida-Maja Hassellöv

Chalmers, Mechanics and Maritime Sciences (M2), Maritime Studies

Marja Koski

Technical University of Denmark (DTU)

Katja Broeg

Federal Maritime and Hydrographic Agency (BSH)

Octavio Marin-Enriquez

Federal Maritime and Hydrographic Agency (BSH)

Jacek Tronczyński

Institut Francais De Recherche Pour L'exploitation De La Mer

Valérie Dulière

Royal Belgian Institute of Natural Sciences

Cathryn Murray

Fisheries and Oceans Canada

Sarah Bailey

Fisheries and Oceans Canada

Jessica Redfern

Anderson Cabot Center for Ocean Life at the New England Aquarium

Karen de Jong

Norwegian Institute of Marine Research

Emmanuel Ponzevera

Institut Francais De Recherche Pour L'exploitation De La Mer

Maria Jesus Belzunce-Segarra


Claire Mason

Centre for the Environment Fisheries and Aquaculture Science

Josephine C. Iacarella

Fisheries and Oceans Canada

Brett Lyons

Centre for the Environment Fisheries and Aquaculture Science

Josean A. Fernandes


Koen Parmentier

Royal Belgian Institute of Natural Sciences

Sustainable shipping

The Swedish Agency for Marine and Water Management, 2020-04-01 -- 2020-12-31.

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