pressrelease | 2019-07-01

Study shows the environmental effects of scrubbing systems

Next year, new legislation will compel international shipping to reduce sulphur dioxide emissions to air. But instead of using expensive low-sulphur fuels, the global shipping fleet is expected to install so-called scrubbers to wash exhaust emissions with seawater that is then pumped back into the sea. New research from IVL Swedish Environmental Research Institute indicates that this scrub water will have a negative effect on zooplankton.

In an EU-funded study researcher at IVL have analysed the environmental effects of both open and closed scrubbing systems. The open-loop scrubber system uses large amounts of seawater to scrub exhaust gases, water that is then pumped back into the sea. The closed system recirculates the scrubbing water and discharges a lesser volume after treatment.

Individual ship passages do not impact the marine environment to any great extent, researchers point out, but in heavily trafficked waterways as well as in ports and estuaries environmental risks increase exponentially.

– Several of these pollutants break down relatively quickly but are at the same time acutely toxic. When the marine environment is continuously exposed to scrubbing water from new mercantile vessels, this acute toxicity becomes permanent. In my opinion scrubbing is a real threat to biodiversity, says Kerstin Magnusson, IVL marine ecotoxicologist and one of the authors behind the report.

– If we permit the discharge of scrubbed exhaust gases into the sea, we expose marine ecosystems to yet another source of pollution, in addition to all those they are already subject to. That conflicts with the UN global environmental goals, which require us to prevent or at least significantly reduce all kinds of pollution in the sea by 2025, says Kerstin Magnusson.

The price difference between bunker oil and low sulphur fuel is currently around $300 per tonne. Scrubber systems normally pay for themselves within a single year.

– Creating new environmental problems in this way, by giving a green light to scrubbing technology is wrong from a sustainability perspective. No comprehensive environmental studies were carried out prior to introducing the legislation. All we do when we fit exhaust gas systems, especially open-loop scrubbers, is move pollutants somewhere else, says Hulda Winnes.

Read the reports:
Environmental analysis of marine exhaust gas scrubbers on two Stena  Pdf, 806 kB.Line ships Pdf, 806 kB.

Air emission measurements Pdf, 7.9 MB.

Risk Assessment of marine exhaust gas scrubber water Pdf, 1.6 MB.

Cost benefit analysis Pdf, 1.6 MB.


For more information, please contact:

Kerstin Magnusson, kerstin.magnusson@ivl.se, +46 (0)10-788 69 07  

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Last updated: 2021-05-17

IVL Swedish Environmental Research Institute

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