Open-loop scrubbers are the biggest threat to the marine environment near ports, a study from Chalmers University of Technology in Sweden says, calling for stricter regulations on water discharge from scrubber systems.

The researchers looked at four different ports to figure out how much pollution was going into the marine environment around them. They found that water discharged from scrubbers was the source of more than 90% of the contaminants in the samples they tested.

“The results speak for themselves. Stricter regulation of discharge water from scrubbers is crucial to reduce the deterioration of the marine environment,” a researcher at the Department of Mechanics and Maritime Sciences at Chalmers Anna Lunde Hermansson said.

Scrubber usage has picked up significantly after the International Maritime Organisation (IMO) announced a global sulphur emissions cap of 0.5% from 2020. Thereby forcing ship owners to choose between costlier, low-sulphur-emitting marine fuels or opt for cheaper scrubber systems to meet the sulphur norms while still burning heavier fuel oils.

Open-loop scrubber systems capture sulphur dioxide pollutants from the engine’s exhaust and release them into the water body, which can lead to acidification of the water. That is not all, it also releases contaminants like heavy metals and toxic organic compounds, which can impact pristine sea areas, the Chalmers study found.

399 ships representing 13% of the global fleet had installed scrubbers as of last year, according to the global shipping association BIMCO. A study published by International Council on Clean Transportation (ICCT) in 2021 shows that around 10 gigatonnes of scrubber washwater is discharged into water bodies per year.

Over the years, opposition to open-loop scrubbers has also grown. According to scrubber maker LiqTech, at least 30 ports have imposed some kind of restriction on the discharge of scrubber water into the port area or the region’s territorial waters.
Source: Engine