A novel tool for cost and emission reduction related to ship underwater hull maintenance

Preprint, 2022

International shipping plays a vital role in the world’s transport system and economy. However, shipping faces challenges in terms of reducing its environmental and health impact, namely emission of greenhouse gases, air pollutants, and chemical substances to the marine environment. In particular, the roughness condition of underwater surfaces of a ship hull affects the ship’s energy efficiency, with marine growth (biofouling) and mechanical roughness leading to propulsion powering penalties. Measures to control biofouling, using antifouling coatings and in-water hull cleaning, may also be associated with significant impacts to the marine environment. In the current study, a new tool is presented, HullMASTER (Hull MAintenance STrategies for Emission Reduction), which aims at enabling the shipping industry and authorities in the Baltic Sea region to make evidence-based decisions on hull maintenance strategies. HullMASTER simulates emissions to air and water, to calculate the differences in economic cost for operators, as well as health- and environmental damage costs between different hull maintenance scenarios. Validation of HullMASTER predictions against 40 vessel-years of in-service performance data on propulsive performance, with operations in the Baltic Sea region, shows good agreement, averaging within 5 percentage-point difference in propulsion penalty. Further, a scenario-based demonstration of HullMASTER on a general cargo vessel shows that, in the comparison between a silicone foul-release coating and business-as-usual scenario of a biocidal coating, retrofitting the coating to a foul-release coating can result in significant savings for society, i.e., along with marginal savings in cost for ship operators. Results for such comparisons and analysis will however be dependent on specific vessel cases and operational profiles, thence the value of an interactive tool such as HullMASTER.