Keeping ships’ hulls free from just a thin layer of slime can reduce a ship’s GHG emissions by up to 25%, according to the preliminary findings of a new study, launched at COP 26.
Namely, IMO released the “Impact of Ships’ Biofouling on Greenhouse Gas Emissions” study, highlighting the importance of biofouling mitigation measures, as an essential component in the toolbox for GHG emissions reduction by the shipping industry.
To remind, biofouling, which is the build-up of microorganisms, plants, algae or small animals, is known to increase the roughness of the colonised surfaces. When those surfaces form the underwater parts of a ships’ hull, the increased roughness will increase a ship’s hydrodynamic drag. The immediate effect is a loss in ship speed at a constant power – or a power increase to maintain a constant speed.
As explained, both of these have negative economic and environmental impacts through increased fuel consumption and atmospheric emissions, including GHG.
The preliminary findings of the study revealed that a layer of slime as thin as 0.5 mm covering up to 50% of a hull surface can trigger an increase of GHG emissions in the range of 20 to 25%, depending on ship characteristics, speed and other prevailing conditions.
According to the study, more severe biofouling conditions can lead to higher emissions, showing the importance of good biofouling management. With a light layer of small calcareous growth (barnacles or tubeworms), an average length container ship can see an increase in GHG emissions of up to 55%, dependent on ship characteristics and speed.
Fortunately, there are a range of commercially available options today that can significantly reduce the impact of biofouling on shipping and thereby enhance the performance of ships. Those include using optimised biofouling control coatings, in-water cleaning technologies and ultrasonic systems, all of which can form part of a holistic hull management approach by the ship operator.
…IMO concluded.