Discharges from ships equipped with so-called scrubbers are causing significant damage to the Baltic Sea, according to a new study from Chalmers University of Technology in Sweden.
The study reveals that these emissions have resulted in socio-economic costs exceeding EUR 680 million between 2014 and 2022. Despite this, the study notes that most shipping companies have already recouped their investments in this controversial technology, which “washes” exhaust gases and discharges them into the sea. This has allowed the industry to profit billions of euros by using cheap heavy fuel oil instead of cleaner alternatives.
“We see a clear conflict of interest, where private economic interests come at the expense of the marine environment in one of the world’s most sensitive seas,” says Anna Lunde Hermansson, a doctoral student at Chalmers and co-author of the study published in Nature Sustainability.
The study is timely, as the potential ban on scrubber water discharge—where large volumes of polluted water are produced and released from ships’ exhaust gas cleaning systems—is currently under discussion at various levels within the International Maritime Organisation (IMO), the EU, and national bodies such as the Swedish Parliament, which has yet to make a decision.
Researchers Anna Lunde Hermansson, Erik Ytreberg, and Ida-Maja Hassellöv from Chalmers have long studied the environmental impact of shipping. In a previous study, they reported that over 200 million cubic meters of environmentally hazardous scrubber water are discharged into the Baltic Sea annually, accounting for up to 9% of the total emissions of certain carcinogenic polycyclic aromatic hydrocarbons (PAHs).
In their latest study, the researchers calculated the external costs of scrubber water discharge and analyzed the financial records of over 3,800 vessels that adopted scrubber technology. They found that between 2014 and 2022, the pollution caused by scrubber water discharges in the Baltic Sea resulted in costs exceeding EUR 680 million. These figures are based on models estimating the public’s willingness to pay to prevent marine environmental degradation and are likely underestimated as they do not include direct costs from heavy fuel oil spills.
“If scrubbers didn’t exist, ships wo“If the scrubbers had not existed, no ships today would have been allowed to run on this dirty residual fuel. That is why the scrubber issue is highly relevant to push the shipping industry towards less negative environmental impact,” said Lunde Hermansson.
The researchers also evaluated the shipowners’ perspective, examining the costs of installing and maintaining scrubber systems versus the financial benefits of using cheaper, dirtier heavy fuel oil. They found that most shipping companies have already broken even on their scrubber investments, with a total surplus of EUR 4.7 billion by the end of 2022. Furthermore, over 95% of the most common scrubber systems (open-loop) repay their costs within five years.
Several countries, including Denmark, Germany, France, Portugal, Turkey, and China, have already implemented bans or restrictions on scrubber water discharge. In Sweden, there is no general ban yet, although specific ports like the Port of Gothenburg have prohibited scrubber water discharges within their areas.
