Dr. Ralitsa Mihaylova presented at the Technical Conference: Managing CII and Associated Challenges 2025 organised by RINA at IMO HQ

Dr. Mihaylova presented on effective biofouling management strategies – including hull coating specification, selection and potential in-water cleaning regimes. Although these activities can be effective energy efficiency levers that require relatively low initial investment, their effectiveness hinges on appropriate planning. Best practice requires a ship-specific approach to biofouling management, however, the number of commercially available hull coatings and emerging in-water cleaning equipment as well as the lack of data on the in-service performance of these systems and their ’compatibility’ hinder informed decision-making. This talk aims to highlight some of the challenges with hull coating specification & selection with the help of case studies and to suggest practical solutions for avoiding common pitfalls based on experience from 700+ technical coating specification reviews and hull coating performance data from 900+ dry dock projects.

The role of hull coatings

Hull coatings are usually claimed to offer between 1% to 10% GHG mitigation potential depending on type and operational assumptions ^[1]. Although the energy saving potential of a hull coating system and the effect on GHG emissions may be difficult to measure, poor in-service coating performance or the ability of the coating to control biofouling over time, can result in increased biofouling accumulation rates, which will have a direct impact on operational efficiency. Biofouling is the collective term used for the accumulation of aquatic organisms on surfaces and structures that are immersed in, or exposed to, the aquatic environment.  The attachment of such organisms on ships’ hulls translates into additional fuel costs and subsequently to increased emissions.  A recent study commissioned by the GEF-UNDP-IMO (Global Environment Facility, United Nations Development Programme, and International Maritime Organization) GloFouling Partnerships Project collated findings on the impact of biofouling on GHG.  According to the preliminary findings, a thin layer of slime (0.5mm) covering up to 50% of the surface can amount to 20% to 25% increase in GHG emissions, whereas a light layer of small calcareous growth could lead up to a 55% increase ^[2].

Biofouling has also been identified as a significant vector for the translocation of non-indigenous marine aquatic species, which could potentially become invasive.

Optimal performance in terms of biofouling control is associated with increased predictability / reduced risk of abnormal biofouling accumulation given specific conditions. A robust biofouling control strategy, ideally capable of coping with additional levels of uncertainty, should result in ensuring that suitable systems are selected and that they can perform as intended.

What is Carbon Intensity Indicator (CII)

International shipping faces several challenges related to environmental performance, with the reduction of greenhouse gas emissions (GHG) being high on the international sustainability agenda.

In June 2021, the International Maritime Organization (IMO) adopted short-term measures to reduce GHG emissions as amendments to the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI.  The measures require ships to calculate the Energy Efficiency Existing Ship Index (EEXI) and to determine their annual operational carbon intensity indicator (CII). The CII rating scheme addresses operational performance by measuring how efficiently ships transport goods or passengers in terms of grams of carbon dioxide (CO₂) emitted against cargo carrying capacity and distance in nautical miles.