A new study by London’s UCL Energy Institute and shipping decarbonisation consultancy UMAS, which analysed ship movements between 2018-2022, found that optimising port arrivals to take into account port congestion or waiting times could reduce voyage emissions by up to 25% for some vessel types.
The average potential emissions saving for the voyages is approximately 10% for containerships and dry bulkers, 16% for gas carriers and oil tankers, and almost 25% for chemical tankers. The study finds that these ships spend between 4-6% of their operational time, around 15-22 days per year, waiting at anchor outside ports before being given a berth.
The study also found that smaller vessels generally experience longer waiting times, though this varies by vessel type.
The waiting behaviour stems from the common operational practices such as first-come, first-served scheduling and the sail-fast-then-wait approach—and is exacerbated by systemic issues such as port congestion, inadequate data standardisation, inflexible charter parties, and limited coordination between the many wider stakeholders involved in a loading/unloading operation.
Dr Tristan Smith, professor of energy and transport at the UCL Energy Institute, said: “The International Maritime Organization set ambitious greenhouse has reduction targets in 2023. Meeting those targets means unlocking all efficiency opportunities – including voyage optimisation and operations around ports. This will only happen if the Carbon Intensity Indicator remains a holistic metric covering all emissions, and incentivising shipowners, charterers and port stakeholders to break down long-running market barriers and failures.”
