Comparing emissions of polyaromatic hydrocarbons and metals from marine fuels and scrubbers

Abstract

• Presenting emission factors to the marine environment from the use of scrubbers. • Scrubber discharge water is enriched with metals and polyaromatic hydrocarbons (PAHs). • Heavy fuel oil combustion with scrubbers increase the relative environmental load. • Scrubbers introduce new contamination sources of chromium to the marine environment. In January 2020, new global regulations were implemented to limit the maximum sulphur content in marine fuels. As an alternative to switch to compliant fuels, the regulations allow for installations of exhaust gas cleaning systems, e.g. scrubbers, that enables a continued use of less expensive heavy fuel oils (HFOs). Characterization of scrubber discharge water shows that the acidified water also becomes enriched with contaminants, and large quantities of metals and polyaromatic hydrocarbons (PAHs) are thus being discharged directly to the marine environment. When emissions of contaminants to the atmosphere and the marine environment are evaluated simultaneously, the results show that HFO, with scrubbers installed, generates higher emission factors of both metals and PAHs compared to MGO. This highlights the importance of including both the marine and the atmospheric perspective when comparing environmental loads and impact of contaminants from shipping.