Scrubber savings reach 13 billion USD in the entire sector
NewsInstead of switching to low-sulfur fuel, it is more cost-effective to use regular fuel in combination with scrubbers.
Chalmers study exposes costly toll of scrubber discharge
Chalmers University study unveils €680 million toll of scrubber discharge on the Baltic Sea, calling for a ban on scrubber discharge in Sweden.
A new study from Chalmers University of Technology, Sweden, shows that discharge from scrubbers caused pollution corresponding to socio-economic costs of more than € 680 million between 2014 and 2022.
The calculations are based on models for willingness to pay to avoid marine environmental degradation, but according to the researchers, the estimates should be regarded as an underestimate. For example, direct costs associated with heavy fuel oil spills from ships using scrubbers are not included.
Scrubbers, also known as exhaust gas cleaning systems, are installed on vessels to reduce harmful emissions, particularly sulfur oxides (SOx), by removing pollutants from exhaust gases. The process typically involves washing the exhaust gases with water or other chemical solutions, thereby capturing sulfur and other pollutants before they are released into the atmosphere.
Scrubbers emerged as a prominent compliance solution for the 2020 sulfur cap regulation implemented by the International Maritime Organization (IMO). With the sulfur cap restricting the sulfur content in marine fuels to 0.50% mass/mass, scrubbers offered shipowners an alternative pathway to compliance while continuing to use high-sulfur fuel oil (HSFO), which is typically cheaper than low-sulfur alternatives.
Scrubbers come in three main types: open-loop, closed-loop, and hybrid systems. Open-loop scrubbers faced severe criticism because they utilize seawater directly in the scrubbing process, leading to the discharge of washwater containing pollutants back into the ocean.
Numerous studies argued that this discharge contributes to marine pollution, prompting calls for more sustainable compliance solutions such as alternative fuels. As a result, numerous port authorities, and even countries have banned the discharge of washwater in their territorial waters, Denmark being the most recent one to join the list.
The ban in Denmark will come into effect on July 1, 2025, for ships with scrubbers in open operation, and on July 1, 2029 for closed-loop scrubbers.
Germany, France, Portugal, Turkey and China, have also adopted national bans or restrictions.
In Sweden, there is currently no general ban, although some ports, such as the Port of Gothenburg, have banned the discharge of scrubber water in their area.
“We now hope that the issue will also be given priority in the Swedish Parliament. This is a low-hanging fruit where we can reduce our negative impact on the vital marine environment,” says Chalmers doctoral student Anna Lunde Hermansson, who is one of the authors of the new study, published in Nature Sustainability.
Chalmers’ researchers noted that the shipping companies’ investments in the much-discussed technology, have already been recouped for most of the ships.
According to the calculations, the total surplus by the end of 2022 for all of the 3,800 vessels that invested in scrubber technology was € 4.7 billion. The researchers also noted that more than 95% of the open-loop scrubber system are repaid within five years.
“From the industry’s point of view, it is often stressed that shipping companies have acted in good faith by investing in technology that would solve the problem of sulphur content in air emissions and that they should not be penalised. Our calculations show that most investments have already been recouped and that this is no longer a valid argument,” says Lunde Hermansson.
“This means that the industry is now making billions of euros by running its ships on cheap heavy fuel oil instead of cleaner fuel,” the study said. Despite criticism, scrubber-fitted vessels often earned premiums for their “environmental credentials”.
“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,” adds Lunde Hermansson.
The study has been prompted by the ongoing discussion on a potential ban of scrubber water discharge, which has been included in the agenda at multiple levels within the IMO and is also being discussed at EU level as well as on national levels such as the Swedish Parliament.
Anna Lunde Hermansson and Chalmers colleagues Erik Ytreberg and Ida-Maja Hassellöv have been researching the environmental impact of shipping for many years and are contributing with their expertise in both international and national contexts.
In 2023, the university said that water discharged from ships’ scrubbers, whose purpose is to clean their exhaust gases, accounted for more than 90% of the contaminants.
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