Advancing a sustainable maritime future: Integrating energy efficiency and underwater radiated noise reduction strategies in commercial shipping

Underwater Radiated Noise (URN) from ships has an environmental impact which needs addressing to ensure shipping becomes more sustainable. This paper explores the nexus between energy efficiency (EE) measures and URN mitigation, aligning with the International Maritime Organization's (IMO's) greenhouse gas (GHG) reduction strategy. Investigating the synergy the study addresses the complexities of decarbonizing the maritime sector within a landscape of diverse energy efficiency technologies. Various EE measures, such as speed reduction, wind-assisted propulsion systems, energy saving devices, and air lubrication systems, show promise in achieving GHG emissions reductions. Reductions of 6 dB in URN can be achieved by a 20 % vessel speed reduction, while wind-assisted propulsion and air lubrication systems show even greater efficacy, surpassing 10 dB in URN reduction. Considering the aging vessel fleet and upcoming Carbon Intensity Indicator requirements, the adoption of EE measures is expected to grow, leading to individual vessel URN reduction. Despite a worstcase scenario in seaborne trade growth projecting a 2.38 dB increases in ambient noise levels by 2050, EE measures are anticipated to counteract this impact. Aligning with the Okeanos target of a 3 dB reduction per decade, these measures could effectively mitigate ambient noise. The effectiveness of GHG emission regulations in reducing URN from commercial vessels greatly depends on the approach taken to achieve zero-emission shipping by 2050. While carbon-neutral fuels may not significantly impact URN reduction, the greater role of EE measures in the industry's decarbonization efforts increases the likelihood of reducing URN from commercial vessels.