As the world steps up efforts to reduce greenhouse gas emissions and curb industrial pollution, the global shipping industry is under increasing pressure to clean up its act. One of the most controversial tools in this transition has been the marine exhaust gas cleaning system, more commonly known as the scrubber. Initially introduced to comply with new international limits on sulfur emissions, scrubbers allow ships to continue burning high-sulfur heavy fuel oil (HFO)—a cheap but dirty fuel—by cleaning exhaust gases before they are released into the atmosphere.
At first glance, scrubbers may seem like a win-win: they reduce air pollution while saving shipowners money on fuel costs. However, the environmental cost of this technology is becoming impossible to ignore. This in-depth report explores the darker side of scrubbers, particularly open-loop systems, which discharge the resulting polluted washwater directly into the ocean. These waste streams are laced with toxic chemicals including heavy metals, polycyclic aromatic hydrocarbons (PAHs), nitrates, nitrites, and sulphates, many of which persist in marine ecosystems and accumulate in the food web.
Marine chemists and environmental researchers now warn that the harm caused by scrubber wastewater is not just a theoretical concern—it is scientifically documented and potentially severe. Even in minuscule concentrations, the toxic compounds in scrubber effluent can impair the health of marine organisms, damage reproductive systems in marine mammals, and accumulate in coastal sediments. Critics argue that rather than solving the pollution problem, scrubbers simply shift it from air to water—a “solution” that may ultimately prove more damaging.
While closed-loop and hybrid scrubber systems were introduced as greener alternatives, they too come with drawbacks. Closed-loop systems collect the toxic sludge for later disposal on land, but appropriate treatment facilities are limited, expensive, and often inaccessible. Hybrid systems, meanwhile, allow operators to switch between modes—creating opportunities for abuse, such as dumping concentrated sludge outside of controlled zones.
Despite the scientific consensus around the ecological risks, global regulations remain inconsistent and fragmented. The International Maritime Organization (IMO) has yet to impose a blanket ban on scrubber discharge, though discussions are ongoing. In the meantime, individual countries and regions are taking matters into their own hands. China, for example, banned open-loop discharges in key coastal areas as early as 2019. Europe is moving toward harmonized regional bans through bodies like OSPAR and HELCOM. Still, many of the world’s most fragile marine environments, including the Arctic, remain at risk.
This article from Dialogue Earth lays out the case against scrubbers with clarity and urgency. Drawing on expert testimony, current research, and policy trends, it paints a picture of a maritime industry at a crossroads. The question is no longer whether scrubbers cause harm, but how much longer governments, regulators, and industry leaders can justify their continued use. As one campaigner puts it: “We know enough to understand how bad it is. We must continue to push for a change.”
Source: Dialogue Earth
Website: How ‘scrubbers’ became a huge ocean problem | Dialogue Earth
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