A study conducted by UCL and UMAS has revealed that optimising port arrivals to account for congestion and waiting times could significantly reduce voyage emissions for various vessel types. The analysis, which examined ship movements between 2018 and 2022, found that the average potential emissions savings for voyages could be approximately 10% for container ships and dry bulkers, 16% for gas carriers and oil tankers, and nearly 25% for chemical tankers.
The study underscores that these ships spend between 4-6% of their operational time, roughly 15-22 days per year, waiting at anchor outside ports before being granted a berth. This waiting time represents substantial inefficiency and a missed opportunity to reduce greenhouse gas (GHG) emissions.
Dr Tristan Smith, Professor of Energy and Transport at the UCL Energy Institute, emphasised the urgency of addressing these inefficiencies. “The IMO set ambitious GHG reduction targets in 2023. Meeting those targets means unlocking all efficiency opportunities – including voyage optimisation and operations around ports. This will only happen if CII remains a holistic metric covering all emissions, and incentivising shipowners, charterers, and port stakeholders to break down long-running market barriers and failures.”
Over the period 2018-2022, chemical tankers, gas tankers, and bulk carriers experienced increasing waiting times at anchor before berthing, rising to 5.5-6% of time per annum by 2022. Waiting times for oil tankers and container ships remained relatively constant at around 4.5% and 5.5%, respectively. Some of this increase may be attributed to port congestion caused by the COVID-19 pandemic and the subsequent surge in maritime trade.
The study also found that smaller vessels generally experience longer waiting times, though this varies by vessel type. The authors’ previous report, Transition Trends, indicated that poor operational efficiency is one of the main reasons for increased emissions from 2018 to 2022.
Dr Haydn Francis, a consultant at UMAS, highlighted the broader implications of these findings. “Our analysis highlights that the no-value-add emissions associated with port waiting times are a current and growing issue across the shipping sector. This is just one piece of the broader operational inefficiency puzzle that can be targeted to generate the short-term emissions reductions that will need to be achieved before 2030. By targeting these idle periods, the IMO can help unlock significant emissions reductions while also driving broader improvements in voyage optimisation and overall operational efficiency.”
The waiting behaviour is rooted in common operational practices such as “first-come, first-served” scheduling and the “sail-fast-then-wait” approach. These issues are exacerbated by systemic problems like port congestion, inadequate data standardisation, inflexible charterparties between ship owners and charterers, and limited coordination among the many stakeholders involved in loading and unloading operations, including port authorities and cargo owners.
The study suggests that the carbon intensity regulations should encompass all aspects of the voyage, not just the ‘sea-going passage,’ as some have proposed. This holistic approach can incentivise stakeholders to collaborate and find solutions to reduce the GHG intensity of ships across the value chain rather than isolating parts where the shipowner or charterer has full control. Limiting the carbon intensity to only parts of the voyage would mean that well-known market barriers at the interface of ship-port operation would remain under-incentivised and continue to persist, making the 20%-30% absolute GHG reduction by 2030, relative to 2008, specified in IMO’s Revised Strategy more difficult to achieve.
The work also highlights the contribution of port congestion to system-wide inefficiencies. Port congestion has been identified by low-income member states as a disadvantage to their decarbonisation efforts. Although not explored in depth in this study, this suggests potential links between finding system efficiencies at the interface between ships and ports and enabling a just and equitable transition, which is a crucial feature of the design of mid-term measures.
As the shipping industry grapples with the challenges of decarbonisation, addressing port waiting times and operational inefficiencies will be critical in achieving the IMO’s ambitious GHG reduction targets.
