open-loop scrubbers

Open-loop scrubbers safe for marine environment, ecotoxicity study finds

A recent independent ecotoxicity study undertaken in accordance with the IMO GESAMP guidelines has given open-loop scrubbers the all-clear, the Exhaust Gas Cleaning Systems Association (EGCSA) said.


The study, entitled “Ecotoxicity testing and risk assessment of wash water from open loop scrubbers”, indicated that both in a standard OECD port and in a highly trafficked seaway the operation of open-loop scrubbers did not create an unwarranted risk.

“The fact is that the forecast for scrubber uptake in IMO’s 2016 Fuel Availability Study by CE Delft Consortium ensured that administrations agreed to introduce the global sulphur cap in 2020. Without scrubbers, the world would be facing another 3.5 years of high sulphur emissions,” Don Gregory, Director of the EGCSA, commented.

Specifically, the ecotoxicity study addresses the concerns that the discharge water from scrubbers, whilst infinitely low in concentrations of substances that might be considered hazardous, “might” produce an unexpected toxic cocktail.

EGCSA appointed research group DHI to undertake the ecotoxicity assessment in accordance with GESAMP guidelines. To date, DHI has dealt with over 50% of the USCG requirements for ballast water management systems approvals. Ecotoxicity is a GESAMP requirement for assessing the risk arising from toxic substance preparations in BWMS and also in anti-fouling systems.

Discharge water was taken from four ships operating in northern Europe with open-loop scrubbers. The samples were homogenised and presented to different levels of marine organisms including algae & crustaceans in a step-wise process, culminating in testing the toxicity with fish. The steps towards assessing the possible toxicity to fish were possible because at no stage were the measured assessment parameters exceeded.

The final step in the risk assessment is the translation of the data to the real-life situations of several scrubbers discharging into a port or into a busy sea lane. In all cases, the risk of ecotoxicity was well below the unacceptable level, according to EGCSA.

Gregory commented that the study gives certainty to ports, harbours and other authorities about the acceptability of operating open loop scrubbers in their jurisdictions.

Nevertheless, the association said it will be seeking partnerships with ports to undertake more studies to provide ongoing assurance that ecotoxicity of the open-loop scrubber wash water remains at a safe level to discharge into the marine environment.