According to a new study from Chalmers University of Technology in Sweden, the combined emissions of metals and other environmentally toxic compounds from ships endangers the marine environment.
When the researchers calculated the contaminant load from these emissions into the marine environment in four ports, it was found that water discharged from ships’ scrubbers, whose purpose is to clean their exhaust gases, accounts for more than 90% of the contaminants.
The results speak for themselves. Stricter regulation of discharge water from scrubbers is crucial to reduce the deterioration of the marine environment
… said Anna Lunde Hermansson, a doctoral student at the Department of Mechanics and Maritime Sciences at Chalmers.
Traditionally, environmental risk assessments (ERA) of emissions from shipping are based on one source at a time. For example, the ERA might look at the risk from copper in antifouling paints. But as with all industries, shipping is an activity where there are multiple sources of emissions.
A single ship is responsible for many different types of emissions. These include greywater and blackwater, meaning discharges from showers, toilets and drains, antifouling paint, and scrubber discharge water. That is why it’s important to look at the cumulative environmental risk in ports
… added Anna Lunde Hermansson who, with colleagues Ida-Maja Hassellöv and Erik Ytreberg, is behind the new study that looked at emissions from shipping from a cumulative perspective.
Scrubbers mean that ships can comply with the requirements introduced by the International Maritime Organization (IMO) in 2020. The research finds that the only problem is that the water not only takes up the sulphur from the exhaust gases, leading to acidification of the scrubber water, but also other contaminants such as heavy metals and toxic organic compounds. The contaminated scrubber water is then often pumped directly into the sea.
Although new guidelines for ERAs of scrubber discharges are in progress, the ERAs still only assess one source of emissions at a time, which means that the overall assessment of the environmental risk is inadequate
… commented Lunde Hermansson, Senior Researcher, Maritime Studies, Mechanics and Maritime Sciences
The researchers found that three out of the four port environments were prone to unacceptable risks according to the assessment model used. They also saw that it was emissions from antifouling paint and scrubber discharge water that accounted for the highest levels of hazardous substances in the marine environment and had the highest contribution to the risk.
More than 90% of the environmentally hazardous metals and PAHs (polycyclic aromatic hydrocarbons) came from scrubber discharge water, while antifouling paints accounted for the biggest load of copper and zinc, according to the research.
But it’s the large ships with high fuel consumption that install scrubbers, because it is more economical for them to do so. So we anticipate that they would account for somewhere around 30 per cent of total fuel consumption in shipping
… said Lunde Hermansson
The Swedish Agency for Marine and Water Management and the Swedish Transport Agency have submitted a proposal to the Swedish Government to prohibit the discharge of scrubber water into internal waters, that is, waters that lie within the Swedish archipelago.
It’s a step in the right direction, but we would have liked to see a stronger ban that extends across larger marine areas, while we also understand the challenge for individual countries to regulate international shipping
… commented Erik Ytreberg, an associate professor at the Department of Mechanics and Maritime Sciences at Chalmers.
