Navigating towards environmental impact assessment of shipping

Licentiate thesis, 2022

The shipping sector exert multiple pressures on the environment, affecting climate change, human health and the marine environment. From a policy perspective, shipping is usually assessed based on the emissions to air (e.g. carbon dioxide (CO2), sulphur and nitrogen oxides (SOX and NOX) and particles) with the focus on limiting impact on climate and human health. Shipping is generally not considered as a main contributor of other hazardous substances to the marine environment. At the same time, none of the Baltic Sea basins has achieved Good Environmental Status in accordance with the Marine Strategy Framework Directive goals. Therefore, this thesis aims to lay the foundations to enable environmental impact assessment of the shipping sector, following the DAPSIR approach. DAPSIR connects society, environment and policy within a structured framework where for example; Driver can be human needs, Activity is the shipping sector, Pressures are contaminants that enter the environment which may change the environmental State that result in Impact on both the environment (e.g. biodiversity loss) and human welfare. Finally, Responses represent the actions needed to reduce adverse effects.

One objective within this work is to quantify the contaminant loads of metals and polycyclic aromatic hydrocarbons (PAHs), from different ship-activities with a focus on scrubbers. A scrubber is installed on ships as an abatement technique to meet the requirements stated in the new regulations of sulphur content in marine fuels. In a scrubber, the ship exhausts are led through a spray of water and SOX is easily dissolved and particles are scavenged. The scrubber system can be open (where seawater is pumped through the system continuously), closed (where water is recirculated with a small bleed-off) or hybrid (where the mode of operation can be shifted between open and closed). The scrubber technique has moved the emissions from air to water with unknown impacts.

Emission factors of metals and PAHs from usage of marine gas oils (MGOs) and heavy fuel oils (HFOs), with and without the use of scrubbers, where derived from an extensive literature review. The results show that HFO combustion with a scrubber result in much higher emission factors of metals and PAHs as compared to the use of MGO. These emission factors were then used to determine the relative load contribution from scrubbers compared to other ship-activities, coastal industries, atmospheric deposition and riverine input to the Baltic Sea. The comparison revealed that open loop scrubber discharge and release of biocides from antifouling paints are the two largest anthropogenic sources of several metals and PAHs, e.g. copper, vanadium and anthracene, to the Baltic Sea. In addition, the cumulative environmental risk assessment of 9 metals and 16 PAHs from near-ship atmospheric deposition, antifouling paint, bilge water discharge, closed and open loop scrubber water discharge) show unacceptable risk in three out of four ports.

The total contaminant load from shipping and subsequent risks of adverse effects on the marine environment can be assessed with existing tools. The use of HFO and scrubbers result in high emissions, in absolute and relative terms, of metals and PAHs to both air and water. The result suggests that the use of scrubbers cannot offer a sustainable solution and the discharge of scrubber water should be prohibited to increase the probability of achieving Good Environmental Status in the Baltic Sea.