Scrubber Technology: Bad News for the Marine Environment

Abstract

From January 2020, stricter global regulations apply regarding maximum allowed sulphur content in marine fuels. To comply with the new limit of maximum 0.5% sulphur content, ships can instead of using the intended cleaner fuel, continue to use residual fuels and install an Exhaust Gas Cleaning System, also known as scrubbers. The scrubber removes sulphur oxides from the exhausts to a level corresponding to combustion of low sulphur fuel. The simplest and most common scrubber is the open-loop type, where the exhausts are washed in a fine spray of seawater. The acidifying sulphur oxides are readily dissolved in the seawater and large volumes of heavily acidified wash water is then discharged back to the sea. Further, other pollutants such as polycyclic aromatic hydrocarbons (PAH) and heavy metals are also washed out from the exhausts. From a marine environmental perspective, the use of scrubbers implies an increased load of pollutants on an already stressed marine environment. Considering UNCLOS Article 195 on the duty not to transfer damage or hazards or transform one type of pollution into another, it is questionable whether scrubbers can be considered as an adequate alternative to the use of distilled low sulphur fuel oils. Assessment of the environmental impact of large-scale use of scrubbers is not trivial. The discharge of scrubber water implies a complex mixture of different contaminants, eutrophying and acidifying substances reaching the marine environment. As for all assessments of mixture toxicity, this is truly challenging. Yet, both PAH and heavy metals are well known for their toxic properties in the marine environment. Eutrophication is a problem in many coastal and estuarine areas as well as semi enclosed basins such as the Baltic Sea. To conclude, wide-scale use of scrubbers includes all elements to qualify for inclusion in the next update of ‘Late lessons from early warnings’; well-known environmental impact of the different components, high probability of synergetic effects, and a sudden shift to wide-scale use result in an imminent risk that the pressure of shipping on the marine environment is exacerbated.