A groundbreaking study conducted by Chalmers University of Technology in Sweden has shed light on a critical issue affecting the marine environment – ship emissions. The research reveals that the combined emissions of metals and other hazardous substances from ships pose a significant threat to the delicate balance of oceans.
With water discharged from ships' scrubbers accounting for more than 90% of contaminants, the study emphasizes the need for stricter regulations to curb the deterioration of the marine environment.
Typically, environmental risk assessments (ERA) for shipping emissions have focused on analyzing individual sources, such as copper in antifouling paints. However, shipping activities involve multiple emissions sources, making a cumulative perspective crucial. Anna Lunde Hermansson, a doctoral student at Chalmers, highlighted the importance of assessing the cumulative environmental risk in ports, by considering emissions from various sources like greywater, blackwater, antifouling paint, and scrubber discharge water.
Scrubbers are exhaust gas cleaning systems used by ships to comply with regulations introduced by the International Maritime Organization (IMO) in 2020. These systems enable ships to use heavy fuel oil, the predominant fuel in the shipping industry while reducing airborne sulfur emissions.
However, scrubber systems introduce a new concern. While they effectively remove sulfur, they transfer contaminants like heavy metals and toxic organic compounds into the scrubber water. Unfortunately, this contaminated water is often discharged directly into the sea without any treatment.
The study conducted by Chalmers University focused on four different port environments and assessed contaminant concentrations from various sources. The results revealed that three out of the four ports were at risk due to unacceptable levels of contaminants. Both scrubber discharge water and antifouling paints were found to be significant contributors to the risk. Surprisingly, more than 90% of environmentally hazardous metals and polycyclic aromatic hydrocarbons originated from scrubber discharge water, while antifouling paints contributed substantial amounts of copper and zinc.
Assessing the cumulative impact of multiple emissions sources is vital since the marine organisms affected by contaminants do not distinguish their origins. Lunde Hermansson said that a total load of contaminants is what causes the damage to marine ecosystems. Looking at individual emissions sources may underestimate the risk level, making a comprehensive assessment necessary to protect the marine environment effectively.
The researchers' ERA indicated that only the port environment with high water exchange per tidal period demonstrated an acceptable risk level. However, it is essential to recognize that contaminated water does not disappear; it gets transported elsewhere. Discharged scrubber water, when washed out to sea, can reach pristine areas, exacerbating the environmental consequences. While the research primarily focused on ports, the wider implications call for stronger regulations across larger marine areas.
Installing scrubbers is an economic choice made by larger ships with high fuel consumption. By continuing to use heavy fuel oil, these ships can avoid switching to cleaner yet more expensive fuels. However, this practice contradicts the IMO's commitment to reducing greenhouse gas emissions from shipping by 50% by 2050.
As a step toward addressing this issue, the Swedish Agency for Marine and Water Management and the Swedish Transport Agency has proposed a ban on discharging scrubber water into internal waters.
The study from Chalmers University brings attention to the critical threat posed by ship emissions to the marine environment. By adopting a cumulative perspective and considering the total load of contaminants, we can gain a more accurate understanding of the risks involved. Stricter regulations on scrubber discharge water and a wider ban on scrubber water discharge are necessary to safeguard oceans and preserve their delicate ecosystems.
