A new study by the University of Southampton commissioned by the International Chamber of Shipping (ICS) assesses the interrelationship, and highlights the significant synergy, between measures aimed at enhancing ship energy efficiency and underwater radiated noise (URN) emissions.
Underwater radiated noise is the unintentional noise generated by vessels as they move through the water. Previous studies have found that URN generated by shipping can impede marine life, particularly marine mammals, both in the short- and long-term. In recognition of this issue, IMO issued guidelines in 2014 that have now been revised following MEPC 80 in July 2023.
The maritime industry is moving forward with reducing GHG emissions in order to meet net zero emissions by or around 2050. The new study reviews the IMO’s initiatives and strategies for decarbonising the shipping industry and identifies the measures and tools available that can contribute to expediting the transition. By adopting certain energy efficiency strategies that also reduce underwater radiated noise, shipowners and the environment can co-benefit.
ICS commissioned the comprehensive study to explore the synergies between energy efficiency measures and URN reduction. The report highlights the opportunity to reverse the upward trends in URN, simply by leveraging these synergies.
Chris Waddington, ICS Technical Director, said: “At ICS we welcome this report. It recognises that most energy efficiency measures will also reduce URN, and therefore presents a win-win situation for shipowners. For safe and cost-effective operation, it is important that shipowners retain discretion on the selection of measures. But for example, modest speed reduction, such as we have seen as a consequence of the EEXI regulation can improve both efficiency and reduce URN for vessels fitted with fixed pitch propellers. Similarly, both wind-assisted propulsion and air lubrication improve efficiency and can each provide around 10 dB URN reduction. Considering the aging fleet of vessels, the forthcoming, more stringent CII requirements, and the likely high cost of the alternative fuels, the study anticipates a growing trend of vessels implementing energy efficiency measures to align with the IMO’s revised GHG strategy targets. There is no one size fits all solution for the challenge we have ahead but we recognise that by improving energy efficiency, URN can also be reduced and our oceans can be healthier.”
University of Southampton Marine and Maritime Institute (SMMI) Maritime Fluid Dynamics Prof Stephen Turnock added: “The ICS commissioned report shows that shipping has an opportunity to embrace energy efficiency technologies that will both help ensure it meets its essential greenhouse gas emission reduction targets as well as reducing underwater radiated noise. Overall, the report should help in choices being made for future ship design and operation that reduce the overall environmental impact of shipping.”
ICS is actively encouraging industry adoption of the revised non-mandatory IMO guidelines on the reduction of URN. ICS is also in consultation with its member associations to ensure this new comprehensive study is shared and that the potential co-benefits are understood.
The full report: The impact of shipping’s energy efficiency measures on reduction of underwater radiated noise, and opportunities for co-benefit can be downloaded here.