By Eric Huang.    Photo：Kelly

In order to achieve the goal of energy saving and carbon reduction, the International Maritime Organization (IMO) took the lead in proposing the 2030/2050 emission reduction target in 2018 to reduce the carbon emissions of various types of ships.  At the meeting of the Marine Environment Protection Committee (MEPC75) in 2020 the IMO's short-term carbon reduction measures are passed and proposed the Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator CII. The proposition is a rating system for all cargo ships, ro-ro passenger ships and cruise ships over 5,000 gross tonnages, which will assess the carbon intensity of a ship's operations each calendar year from 2023. CII is likely to change the traditional division of responsibilities between shipowners and time charterers and may significantly change the way ships are operated.

Carbon intensity describes the link between greenhouse gas (GHG) emissions and the volume of goods transported within distance. To help reduce the carbon intensity of all ships by 40% by 2020 compared to 2008 levels, IMO now requires ships to calculate two ratings: the Energy Efficient Existing Vessel Index (EEXI) to determine their energy efficiency and annual operational carbon intensity Indicators (CII). The first annual report must be completed by 2023, with an initial rating given in 2024.

Many shipowners around the world are planning to use an old fashion way: slow down and keep trading their older, less fuel-efficient tonnage. Reducing a ship's rated sea speed by 10% can reduce fuel consumption by 25% because drag decreases exponentially as the ship slows down. However, new analysis by the Clarksons Green Transition team suggests that the potential for slowing down to improve carbon emissions may be overestimated, not working as well as expected especially under the real-world objective conditions. The analysis discusses the limitations of slow sailing as a general solution to ship emissions and explores other alternatives that may be needed.

Jon Leonhardsen, principal analyst at Clarksons, emphasized that traditional calculations based on textbook speed consumption curves may not accurately reflect the complexities of real-world sailing conditions. While slow sailing can save a lot of fuel at economical speeds, the benefits diminish when the ship is operating at lower speeds. This discrepancy suggests that the efficacy of slow sailing in lowering emissions ratings may be grossly overestimated. Clarksons has developed a modeling tool to help shipowners more accurately predict their Carbon Intensity Index (CII) compliance strategy. By taking into account the variability of real-world sailing conditions and the multitude of consumers on board, the tool can result in more realistic data when providing ship owners with an assessment of the emissions performance of their ships. This also enables them to make informed decisions about compliance measures and investments.

Furthermore, the impact of CII compliance extends beyond environmental concerns and extends to impacting shipowners' financial planning. According to VesselsValue, the CII rating has already had an impact on the value of second-hand vessels. The regulations classify ships into five classes - A, B, C, D and E - based on emissions performance, with lower rated ships facing challenges in the secondhand market. B- and C-class ships can be traded at healthy levels of 11-13% per year, but E-class ships are difficult to sell, with only 3% being traded in 2022. As the shipping industry places greater emphasis on ships with better emission classes, ships at lower class may experience reduced liquidity and lower profitability potential. The financial stakes are high and aggressive measures are required.

While slow sailing can offer some short-term benefits, it is clear that broader solutions are needed to address the complexities of reducing emissions in the shipping industry. Investments in innovative technologies such as alternative fuels, hybrid propulsion systems and advanced energy management systems can significantly improve emissions performance. In addition, optimizing operational efficiency through route planning, hull cleaning and propeller retrofits can also contribute to significant reductions in emissions.

Hence while slow sailing has long been hailed as a practical way to reduce fuel consumption and emissions, it's crucial to understand its limitations, especially in real-world conditions. The shipping industry must acknowledge the complexities and variables involved in achieving emissions reductions and explore multiple solutions. By investing in advanced shipbuilding mold and adopting innovative technologies, shipowners can develop more accurate compliance strategies while making a positive contribution to the continued development of the shipping industry.

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