How do scrubbers affect pollution in the Baltic Sea?

Environmental protection efforts can sometimes be a double-edged weapon. Controversial International Maritime Organization (IMO) regulations were supposed to increase air cleanliness, but in the meantime they have intensified pollution of the Baltic and other seas around the world. Is there a way out of this stalemate? What is worth knowing about ship scrubbers and their impact on the environment?

Where did the scrubbers come from?

Recall that on January 1, 2020. The IMO introduced new regulations aimed at reducing the emission ballast of ships. Thus, new limits were set for the sulfur content of marine fuel – 0.10 percent in designated emission zones and 0.50 percent outside them. This is a fairly significant reduction from the previously prevailing limits of 3.5 percent.

The reduction of sulfur oxides emitted by ships was expected to fundamentally benefit the environment and people living near ports and coasts. And these are highly toxic compounds with negative effects on the human respiratory, cardiovascular and nervous systems. IMO experts have predicted a 77 percent reduction in sulfur oxide emissions from maritime transport, which is expected to reduce premature deaths by up to several hundred thousand.

How have shipowners dealt with the new regulations? Many of them, instead of switching to more expensive fuel with lower sulfur content, relied on so-called scrubbers, devices that spray the outlets of exhaust pipes with seawater to catch harmful sulfur oxides and prevent them from entering the atmosphere. Unfortunately, this has had a very negative impact on the state of the water in the Baltic Sea.

The problem of open-circuit scrubbers

Scrubbers, or scrubbers, come in two basic variants – closed circuit and open circuit. In the former, the seawater used for spraying is stored and transported to ports in special tanks. In the second, the sulfur slurry is released directly into the sea, saving space on board and reducing the weight of the ship. It is hardly surprising that many vessel owners choose open-circuit scrubbers for economic reasons. Also, their purchase price is lower.

Unfortunately, water from scrubbers contains not only sulfur compounds, but also heavy metals and polycyclic aromatic hydrocarbons (PAHs). These make their way into coastal waters, poisoning the marine environment. The extinction of copepods and the impaired growth of clams, algae and marine bacteria have already been found.

According to the results of a study by Swedish scientists published in the journal Nature in May, more than 10 billion^{cubic meters of} toxic water enters seas around the world every year due to scrubbers. According to modeled estimates, the damage associated with pollution of the Baltic Sea because of this has already amounted to $750 million. This figure is equivalent to the amount that society is willing to pay to avoid the degradation of marine ecosystems.

Demand for scrubbers is not decreasing

Despite these clearly adverse effects, the latest market research from August this year shows that scrubbers are still the preferred solution. Contrary to analysts’ predictions, who expected a one-time and extinct wave of interest in scrubbers shortly after the IMO 2020 regulations were introduced, shipowners are still investing in the controversial technology.

According to an analysis published by Lloyd’s List, one of the world ‘s leading shipping-related publications, the difference between the price of low-sulfur fuel and the cost of using conventional fuel while investing in a scrubber is so small that it still pays for investors to equip ships with scrubbers. To make matters worse, it is most financially advantageous to install scrubbers in newly built ships, and demand is particularly high in the tanker and bulk carrier segments.

Comparing data from January 2020, when the IMO regulations went into effect, with August 2024, there is a clear increase in the share of ships with scrubbers in the total number of vessels worldwide. As many as 71 percent of the tankers ordered this summer will be equipped with scrubbers.

Baltic pollution raises concerns

Scrubbers are a worsening environmental factor in the Baltic Sea, the world ‘s youngest, but also one of the most polluted. The almost completely closed, very shallow body of water is particularly vulnerable to toxic discharges. And there are quite a few sources of them, from agriculture in the Baltic countries to wrecks lying on the bottom from which fuel leaks.

During the 2024 HELCOM ministerial meeting in Riga, the results of the HOLAS 3 report were cited, confirming that there has been minimal or no improvement in the Baltic environment between 2016 and 2021. Danish Environment Minister Ida Hannibal was outspoken about the threat of scrubbers, pointing to the problem of toxic accumulation in fish and seafood.

Heavy metal pollution of the Baltic Sea is evidently increasing. In May this year. A report has been published on rising levels of thallium, which is highly toxic to humans. Cadmium, lead and mercury, considered harmful to all living organisms, are also regularly detected along the Polish coast. They are also present in randomly tested fish and marine sediments. In addition, significant amounts of chromium, copper, zinc and nickel flow into the sea via rivers.

Pollution of the Baltic Sea with polycyclic aromatic hydrocarbons and their metabolites is also a concern. In studies conducted between 2016 and 2021, exceedances of limits were recorded at 10 of 15 points in the open sea and 73 of 95 points along the coast. Most of these come from incomplete combustion of fossil fuels, so the very essence of scrubbers is a serious threat here. In humans, PAHs can cause respiratory, gastrointestinal and nephrological problems, as well as increase the risk of cancer.

Future of scrubbers in question

The negative consequences of IMO 2020 regulations are already obvious, so many countries are trying to take control of the scrubber problem on their own and protect their own coasts from toxic discharges. China and Singapore have already issued bans on open-circuit scrubbers in their territorial waters, and Germany has followed suit. Growing concerns about Baltic pollution and its effects have also prompted Sweden and Denmark to take the same steps. In both of these countries, from 2025, it will not be possible to discharge water from scrubbers within 22 kilometers of the coastline. It remains to be hoped that other countries, including Poland, will eventually follow suit.

IMO defends itself that scrubbers were never intended to be the ultimate solution to the problem of sulfur oxide emissions, and any innovation carries some risk. The fact remains, however, that there are more and more ships equipped with scrubbers, and the rules vary from country to country and even from individual ports, making it difficult for vessel owners to make investment decisions. According to the International Council on Clean Transportation (ICCT), it is local bans on port discharges that could be the right step to force change on the entire sector.