Clarksons warns against misunderstandings of CII speed

Marine consultancy Clarksons has developed a velocity-based Carbon Intensity Indicator (CII) modeling tool that it says is more accurate for assessing a ship’s environmental efficiency than traditional methods. The operational measure came into force earlier this year and means a large part of the world’s fleet could be obliged to reduce their sailing speeds. CII measures CO2 emissions per unit of cargo moved, with a lower rating indicating better efficiency. Cutting sailing speeds was expected to reduce fuel consumption, but Clarksons’ Green Transition team found that CII improvement through velocity reduction can be wildly overestimated.

When standard speed-consumption curves are factored into calculations, the marginal fuel savings decrease with distance travelled, flattening the curve at lower speeds, said Jon Leonhardsen, Clarksons Green Transition team’s lead analyst. Kenneth Tveter, the team’s leader, said this understanding can give a misleading impression of a ship’s CII efficiency, with other costly measures and improvements needing to be implemented instead of slowing down. Tveter said Clarksons’ CII evaluation modeling tool was up to 30% more accurate than traditional methods in predicting fuel economy and CII, particularly at lower speeds.

Tags: cii,clarksons,decarbonization,slow steaming


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