A new study by UMAS and the UCL Energy Institute has found that optimising port arrivals to account for port congestion and waiting times could reduce voyage emissions by up to 25% for some vessel types.
The “Port congestion, Waiting Times and Operational Efficiency” study investigated the total magnitude of potential GHG reduction that this waiting time represents, identifying it as a large and critical opportunity. On average, these ships spend between 4–6% of their operational time per year (15–22 days in total) waiting at anchor outside ports before being given a berth.
The GHG emission saving is estimated from the reduced voyage speeds that could be employed if ships sailed to arrive just as the berth became available.
Key findings from this investigation include
- Waiting time at anchor before a berth totals an average of 4–6% of total time per year. Container ships and bulk carriers generally have lower pre-berth waiting times than tankers (oil, chemical, and gas).
- In addition to this waiting time, there is a further ~20% of waiting time (e.g., time spent at a speed less than 3 knots). This can include canal queuing and time waiting for a new charter, depending on physical and market factors. Though not included in emissions savings estimates, this suggests further potential for cost and productivity improvements.
- Trends from 2018–2022 show that waiting time has generally increased, varying by ship type.
- Pre-berth waiting times outside a port indicate that ships could have traveled more slowly, reducing GHG emissions without affecting the total time or vessel utilization. These emissions include PM, NOx, and SOx, which may impact local populations near anchorage zones.
- Chemical tankers experience the greatest waiting times, likely due to the complexity of their operations, including tank cleaning between loading and unloading.
- Smaller ships generally have longer pre-berth waiting times, representing significant opportunities for speed reductions.
- GHG emissions can be reduced by converting waiting times into longer voyage durations at lower speeds. Due to the non-linear relationship between ship speed and fuel consumption, a 4–6% waiting time translates to significantly higher emission reductions (~10–25%).
- Waiting times and GHG emission reductions have a “long tail,” with a small subset of voyages contributing a large proportion of the total emissions reduction potential. Analyzing these cases could help target strategies to reduce waiting times.
- Total emissions reduction potential varies by ship type. For example, container shipping, despite lower waiting times, offers the highest absolute reduction potential due to its high total emissions—exceeding 5 million tonnes during 2018–2022.
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 optimization and overall operational efficiency.
… said UMAS’ consultant, Dr Haydn Francis.
To remind, the Untapped Potential of Just-In-Time Port Arrivals white paper by PortXchange found that JIT Port Arrivals could reduce global container shipping emissions by at least 5%, translating to approximately 17 million tonnes of CO2 emissions annually.
