Turning waiting time into savings: Lessons from Cargill's port call optimisation pilot

Executive summary

Commercial ships spend between 4% and 6% of their operating year waiting outside ports. That idle time is one of the clearest inefficiencies in shipping, and port call optimisation is how to turn it into emissions savings. Instead of sailing fast only to then wait at anchor, port call optimisation allows a ship to arrive when its berth is ready. The voyage takes the same time, no extra vessels are needed, and less fuel is burned.

Port call optimisation is sometimes seen as niche, hard to apply outside a few special cases, or too insignificant to matter. Cargill Ocean Transportation (Cargill) set out to test its application in live commercial operations. Across three ports, three different mechanisms and 16 voyages, the results indicate that port call optimisation has the potential to deliver meaningful emissions savings across a range of operational and commercial settings, where there is waiting time to absorb.

At Santarém in Brazil, a bespoke virtual notice-of-readiness scheme set up internally by Cargill demonstrated potential savings of approximately 222 tonnes of CO₂ over ten voyages without disrupting the terminal schedule. At the Port of Newcastle in Australia, voyages through an established port-run arrival system reduced ballast-leg emissions by an estimated 6-11%. At CBH Group’s Albany terminal, the Blue Visby Solution saved close to 10% on a ship that was already sailing at very low speed, with the savings shared between the terminal and the operator.

The scale of emissions savings varies between situations, but the results show that port call optimisation can be applied through different mechanisms and commercial structures. The key is to identify where sufficient waiting time exists, understand how much the vessel can slow down, and select an approach suited to the port and its stakeholders. Well-designed pilots can help companies identify where port call optimisation can have the greatest impact and how to capture those savings in practice. Cargill’s work starts that process and gives others a practical route to follow.

What the pilot project shows:

Finding	What the pilot project showed	Applying this to other pilot projects
Port call optimisation works through many routes	A company-run scheme, a port-run system, and a third-party platform all demonstrated potential savings.	Whether the same company runs the terminal or calls at a port with its own arrival system, there is a model to start from.
Waiting time creates the opportunity	The most congested Newcastle voyages delivered the largest estimated savings, demonstrating that port call optimisation can turn otherwise unproductive waiting time into emissions reductions.	Focus on ports and trade lanes with significant waiting time, where the greatest opportunities are likely to exist.
Ship design and ultra-slow steaming capability need to catch up with operational ambitions	Greater flexibility in vessel speed can unlock further savings, particularly where ships can make use of ultra-slow steaming or favourable ocean currents.	Ultra-slow steaming readiness and ship design can unlock more fuel and emissions savings; select ships and voyages with real opportunity to slow down.
The right tools and planning help capture more savings	Weather routing, pre-pilot assessment, and good scheme design all aid emissions reductions.	Before starting a pilot, estimate the waiting time, voyage length, and ship speeds involved, agree on the baseline to measure savings against, and line up weather-routing support.
Barriers can be managed	Split incentives and contract clauses were each navigated in different ways.	Early shore-side engagement and contract mapping clear the path. Talk to the port or terminal early about what they gain (less congestion, safer anchorages, cleaner air, lower Scope 3 emissions) and check the charterparties and commodity contracts before the pilot project begins.

Speed reduction can help the shipping industry decarbonise now, without waiting for new technology and infrastructure, and port call optimisation can unlock its commercial benefits. If more companies run well-designed pilot projects across more ports, vessel types, and commercial structures, and share what they learn, the industry can move port call optimisation from promising theory to standard practice and capture its full potential.

Introduction

Slowing ships down is one of the immediate operational levers available to reduce shipping emissions. The challenge is to capture those savings without increasing the number of vessels required to move the same amount of cargo. Port call optimisation provides a way to do this: instead of wasting time and emissions at anchor, a vessel can arrive when its berth is available. As demonstrated in an earlier companion piece to this insight brief, the result is the same voyage duration, no additional vessels required, and lower fuel consumption.

The opportunity is significant. Commercial ships have been found to spend between 4% and 6% of their operating year waiting outside ports, equivalent to some 15 to 22 days of idle time. Alongside the fuel and emissions savings, reducing time at anchorage also cuts local air pollutants, underwater noise and hull fouling,¹ and strengthens the economics of the eventual switch to more expensive zero-emission fuels—because these fuels are expected to cost considerably more per tonne, every tonne of fuel a ship avoids burning reduces the size of the bill.

While previous studies, including the predecessor to this brief, have examined the potential of port call optimisation, real voyages are shaped by factors that generalised models cannot fully capture. For example:

• how slowly a particular ship can safely run, and the fuel efficiency of ultra-slow-steaming;

• non-avoidable idle time (e.g., time for pre-loading hold inspections);

• requirements set by the charterparty;²

• how the commodity contract defines readiness by the ship’s physical arrival;

• weather and current; and

• the willingness and ability of a terminal to change how it manages its queue.

Testing port call optimisation against these operational realities helps establish what can be delivered in practice, where the greatest opportunities lie, and what is needed to capture them. Cargill Ocean Transportation set out to test this in live commercial operations through a pilot project explored in this insight brief. The pilot had three key objectives:

1. Quantify real-world emissions savings potential

2. Identify practical and contractual barriers

3. Understand which conditions determine whether a given port, trade lane, or vessel offers a worthwhile opportunity.

Together, the pilot project and the supporting analysis that follows set out what port call optimisation can deliver in practice, what shaped the savings potential in each case, and what the maritime value chain needs to do differently to capture more of the opportunity.

Pilot project summary

As part of its pilot project, Cargill tested one new approach in a live setting and carried out two analysis exercises on existing port call optimisation schemes. A summary of the three studies is provided below. The following sections detail the relevant contexts, results, and lessons learned.

	Study 1	Study 2	Study 3
Location	Santarém, Brazil	Port of Newcastle, Australia	Albany, Australia
Number of voyages	10	5	1
Approach	Bespoke virtual notice of readiness	Port of Newcastle Vessel Arrival System	Blue Visby Solution
Deferral time	0-3 days (18.5 hours on average)	0-13 days	2 days
Estimated emissions savings (vs baseline)	Average of 22t CO₂ per voyage	Average of 51t CO₂ per voyage	33t CO₂

Study 1: Santarém, Brazil

The first study was held at Cargill’s grain export terminal in Santarém, Brazil, situated on the Amazon River. This terminal, which handles grain exports, was selected for the pilot project because it is Cargill-owned and operated, simplifying discussions among the various stakeholders.

After reviewing different options, a port call optimisation approach based around virtual notice of readiness (VNoR)³ was selected for this trial. An advantage of this approach was that it was relatively simple to set up and could be implemented with limited disruption and changes to existing processes and systems, with the required changes remaining within internal Cargill stakeholders.

To kick off the study, internal meetings were held between the terminal, disponent owner,⁴ charterer, and port agent to explain the concepts and identify risks and barriers. The group drafted and agreed on the VNoR rules with the goal of minimising disruption, maximising implementation simplicity, and allowing refinement of the methodology during follow-up trials.

Inbound ballasting⁵ ships’ estimated times of arrival (ETAs) were monitored against the terminal berthing schedule to identify suitable candidates for the trial, focusing on ships where the ETA would result in surplus waiting time prior to berthing. The selected ships were typically travelling from Europe or West Africa. These ships were then instructed to slow down to target a requested time of arrival (RTA) rather than the original estimated time.

Aligning the RTA with available berths allows a ship to spend negligible time idling at anchorage. However, in dry bulk trades (particularly grains), ships are typically required to undertake hold cleanliness inspections on arrival, before being cleared for loading. Therefore, the ship must arrive at the anchorage with sufficient time to conduct the inspections in advance of the required berthing time. Further, it is not uncommon for ships to fail hold inspection, in which case they need more time to undertake remedial cleaning and re-inspection and may no longer be ready to berth as per the planned schedule. To avoid an empty berth in this scenario, the terminal needs to be able to call up another ship as a substitute, which requires at least some vessel(s) at anchor.

Recognising this, Cargill’s approach for this pilot was to define a “functional queue” for the terminal; this being the minimum number of vessels at anchorage required to sufficiently mitigate the risk of having an empty berth at the terminal. The RTA for each ship was then determined by combining the ship’s planned berthing time with the functional queue.

A total of ten voyages were assessed over six months, including Kamsarmax, Supramax, and Handysize bulkers. The assessment compared the consumption and emissions of the VNoR voyage against the “business-as-usual” baseline of arriving at the original ETA. The assessments were undertaken by ZeroNorth, taking into account the weather and currents, and the specific ship characteristics (including speed-consumption curves⁶ and minimum continuous engine power⁷).

Results:

Under the business-as-usual scenario, the average ballast leg was 12 days (ranging from nine to 16 days, except for one voyage of five days), at an average speed of 12.8 knots (ranging from 11.7 to 13.7 knots).

With VNoR, arrival was deferred by an average of 18.5 hours, ranging from 0 to 74 hours. Notably, in every case, the deferral in arrival was limited by the minimum speed the ship could sail due to the minimum continuous main engine power, rather than by laycan⁸ or RTA. In no case did the ship’s delayed arrival disrupt the terminal’s plans/schedules.

The average speed with VNoR was reduced to 12.0 knots (ranging from 10.4 to 13.7 knots), for a 6% speed reduction. The 13.7 knots at the high end of the speed range were due to strong favourable currents that meant the ship was not able to sail slower.

Total emissions savings for the ten ballast voyages were estimated at 222t CO₂, or 3% of the total ballast-leg emissions. This includes the additional emissions whilst anchoring on arrival on the business-as-usual voyages. To put this into perspective, the estimated savings are equivalent to the emissions produced by an average car in the United Kingdom over approximately 12 years.⁹

Average emissions savings per voyage is equivalent to approximately 12 years of average UK car driving.

Lessons learned:

Even with ships already slow-steaming and optimised through ZeroNorth rather than sailing at charterparty speed(s), VNoR delivered an estimated 222t of CO₂ savings with no disruption to terminal operations. Because of this optimisation for the trial voyages, speeds were already quite slow, and in most cases close to the minimum slow-steaming speeds for each ship. To slow down further, the ships would be required to ultra-slow steam,¹⁰ which none were capable of doing and is not common practice for these types of bulkers.

In today’s dry bulk market, ultra slow steaming is uncommon (with the possible exception of the Capesize segment). Wider adoption would likely require contractual changes to cover technical applications such as additional spare parts, increased inspections and condition monitoring in many cases. Further analysis of the role of ultra-slow steaming can be found later in the report.

The pilot demonstrated an estimated 3% reduction in ballast-leg emissions despite the vessels already operating close to their practical slow-steaming limits. This is below the approximately 11% reduction suggested by the cubic speed-power relationship¹¹ for the same speed reduction, highlighting the importance of using vessel-specific operating characteristics when estimating the opportunity. The 3% figure should therefore be understood as a lower bound for VNoR rather than a ceiling, with greater savings potentially available on vessels with more ability to slow down, including those capable of ultra-slow steaming.

This aspect of the pilot highlighted the importance of considering existing speeds and the minimum continuous engine powers (and associated speeds) when predicting potential savings from slow steaming and/or port call optimisation. Without considering these parameters, the potential savings may be overestimated.

Study 2: Port of Newcastle

A second Cargill study took place at the Port of Newcastle in Australia. Unlike the Santarém pilot, which trialled a bespoke VNoR framework developed internally by Cargill, the Port of Newcastle had already been operating a mandatory arrival system based on the VNoR principle, titled the Vessel Arrival System, since 2010. This study, therefore, gathered data from ongoing participation in the existing scheme rather than building a new one.

Cargill monitored five voyages ballasting inbound to load at Newcastle, and assessed the emissions savings achieved by participating in the VNoR scheme. This was done by comparing two scenarios: one in which the voyage arrived at its Notified Arrival Time (NAT) assigned by the port seven days in advance to allocate queue priority, and another in which the deferred voyage arrived at the RTA. This methodology is consistent with that used for the Santarém pilot, and emissions savings were again calculated by ZeroNorth, taking into account weather, currents, and the specific ship characteristics.

One notable feature of the Port of Newcastle system is that ships cannot anchor for more than 48 hours before their RTA. Where the RTA would require a speed below the ship’s minimum continuous engine load, ships often drift on the prevailing southbound East Australian Current, which pushes them towards the port and allows for further emissions savings. For the pilot study voyages, Cargill utilised weather routing advice from ZeroNorth to determine where and when to position the ship to maximise the benefit of the currents whilst drifting.

Results:

• Voyage 1 (Panamax): Estimated 34t of fuel saved, accounting for a 107t reduction in CO₂ emissions (or 10% of ballast-leg emissions), supported by drifting on the favourable currents

• Voyage 2 (Kamsarmax): Estimated 31t of fuel saved (97t CO₂, 11% of ballast-leg emissions), again supported by drifting on the favourable currents

• Voyage 3 (Post Panamax): Estimated fuel savings of 17t (53t CO₂, 6% of ballast leg emissions), supported by drifting on favourable currents

• Voyages 4 & 5 (Kamsarmax and Post Panamax): The vessels had no additional waiting time to absorb and therefore no additional savings opportunity

Over the five voyages, the average estimated saving was 51t CO₂ per voyage; this is equivalent to the emissions produced by an average car in the United Kingdom over approximately 27 years.

Average emissions savings per voyage is equivalent to approximately 27 years of an average UK car driving.

CO₂ emission savings per voyage

Voyages 4 & 5: Berth available on arrival, so no opportunity to slow down and no savings. Percentages show savings as a share of ballast leg emissions.

Lessons learned:

An important thing to note with these observations is that the Port of Newcastle system was designed to reduce the number of ships at anchor, not specifically to reduce emissions or costs. The points below are therefore assessed from the perspective of a company considering adopting a similar approach at another port, with the explicit goal of reducing voyage emissions.

The Newcastle model’s clearest strength is its minimal disruption to existing commercial arrangements. No changes to charterparty terms are required, and implementation is straightforward for the ship operator. Because demurrage¹² continues to be paid as usual (i.e., as though the ship had arrived at its NAT), the shipper is no worse off, while the ship operator captures the bunker savings. Critically, there is no cost-sharing mechanism, so there is no need to calculate fuel savings against a hypothetical baseline, a step that adds complexity and scope for contention in other models. The model also allows for larger savings than schemes tied to contractual arrival windows. Because commercial protections are anchored to the NAT, a ship can slow down to the point that its physical arrival falls after the original laycan without further contractual changes, as seen in Voyage 1.

The favourable East Australian Current also contributed to the savings achieved at Newcastle. While not every port has comparable conditions, local currents and weather patterns can provide similar opportunities to reduce fuel consumption, which can be identified and incorporated through weather routing.

Replicating this model requires active involvement from the port or terminal rather than significant changes on the ship side. Setting up and running the scheme requires port-side effort, including tracking each inbound ship for seven or more days to determine its NAT. The port, terminal and cargo interests do not directly share in the resulting fuel savings or benefit from reduced demurrage, so a clear operational or environmental driver is important. The contractual picture may also need to be considered carefully, as the VNoR approach can conflict with standard commodity contracts in other locations, for example where contracts specifically refer to the physical arrival of the ship to tender a notice of readiness and would therefore need to be amended.

The system’s design also caps the achievable savings. Ships can only begin slowing down a maximum of seven days out (once the NAT is confirmed), limiting how much idle time can be converted into slower sailing, and operators are structurally incentivised not to slow down during the earlier, monitored part of the voyage, since doing so would worsen their NAT. In principle, this poses a risk that operators will game the system to secure an earlier NAT and negate the savings made later in the voyage, though no evidence of this was observed during the pilot.

Finally, weather-routing advice on where and when to drift to make the best use of the favourable currents proved important in increasing savings. Automatic Identification System records of other ships ballasting towards Newcastle over the same periods show that vessels are not always drifting in the optimal areas, suggesting that even within an established scheme, there is meaningful room to optimise further.

Study 3: CBH Albany

The third study took place at the port of Albany in Western Australia, at a grain terminal operated by CBH Group. CBH utilised the Blue Visby Solution,¹³ which it had already deployed across several of its Australian terminals. The pilot project tracked a single voyage of a Kamsarmax bulk carrier ballasting from Zhoushan, China, to Albany, Australia.

Note: The route shown is illustrative only and does not necessarily reflect the actual route taken by the vessel during the study.

Under the normal scenario, the ship was due to arrive earlier than required, and before the commencement of the laycan, and therefore had already been instructed by the vessel operator to sail at minimum speed, with a predicted average voyage speed of 8.6 knots, which is well within the slow steaming range.

Under the pilot, the RTA issued via the Blue Visby Solution was two days later than the business-as-usual ETA. As a result, the ship was requested to slow down even further, to an average speed of 7.4 knots.

Results:

The ship slowed down as requested, delaying the arrival by 2.06 days, arriving 1.73 days after the commencement of the laycan. According to the Blue Visby calculations, this resulted in savings of 10.73t of fuel (equivalent to approximately 33.4t CO₂), which accounted for 9.6% of the ballast voyage emissions for the period. Under the Blue Visby agreement, the bunker savings were shared between CBH and the vessel operator (Cargill), and the operator was also compensated for any demurrage impact of the delayed arrival, ensuring that both stakeholders benefited.

Average emissions savings per voyage is equivalent to approximately 18 years of an average UK car driving.

Lessons learned:

For the trial voyage, the solution reduced CO₂ emissions and yielded cost savings for both the shipper and the vessel operator. Despite the vessel already sailing at a very low speed of 8.6 knots because it was expected to arrive well ahead of the required arrival time, the Blue Visby Solution delivered a further 9.6% emissions reduction. This demonstrates the potential for even greater savings on voyages where the ship isn’t arriving so early.

Notably, this was the only vessel in the pilot study that could ultra-slow steam, providing a valuable opportunity to demonstrate that it is technically possible; and to gather useful real-world data on the consumption characteristics of the ship at very low speeds, which enabled further analysis of the savings achieved by ultra-slow steaming in general.

A key feature of CBH’s approach is that it can be implemented with minimal disruption to the terminal rules and queuing systems, thereby removing a key barrier to adoption. For the voyage conducted under this study, the RTA remained within the existing laycan period, minimising the terminal’s involvement whilst still incentivising savings from delayed arrival. However, in other cases where there is a benefit of further delaying the RTA until after the original cancellation date,¹⁴ this can also be accommodated via coordination with the terminal.

Analysis

Given the small sample of voyages in the pilot project, the findings of this brief provide specific insights that should be interpreted in the context of each voyage rather than generalised.

Opportunities for port call optimisation

The most encouraging finding from the pilot project is that the three studies all demonstrated measurable emissions savings despite using fundamentally different mechanisms for port call optimisation. Santarém trialled a bespoke VNoR framework designed and agreed internally; Newcastle relied on an established, mandatory port-run system; and Albany used the third-party Blue Visby Solution alongside its established laycan-based queuing system.

Importantly, the differences in the savings achieved, estimated from around 3% of ballast leg emissions at Santarém to 9.6% at Albany and up to 11% on voyages through the Port of Newcastle, should not be read as a ranking of the three mechanisms. The savings achieved reflect the circumstances of each pilot rather than merely the solution used: the higher Newcastle savings owe much to the favourable East Australian Current, which few other ports can offer, Santarém’s 3% saving was held down by the ships already being at their slow-steaming limit with no ultra-slow-steaming headroom, while the Albany figure rests on a single voyage and is illustrative rather than representative. Overall, the pilot project points to the flexibility in achieving port call optimisation, which is not tied to a single mechanism or commercial structure. Companies can adopt whichever model best fits their degree of control over the terminal (if any) and the stakeholders they can bring on board.

Pilot	PCO mechanism used	Voyages monitored
Santarém, Brazil (Cargill-owned terminal)	Bespoke VNoR framework, designed and agreed internally	10
Newcastle, Australia (Port of Newcastle)	Established, mandatory port-run system since 2010	5
Albany, Australia (CBH terminal)	Blue Visby Solution, third-party, ship-side, laycan-based queuing system	1

Average estimated savings achieved (% of ballast leg emissions across all voyages monitored)

A second consistent benefit is how little port call optimisation asks of the ship-side. Across all three models, the change required of the ship operator or disponent owner was negligible in practice (assuming the ships don’t ultra-slow steam). Because the resulting fuel savings accrue directly to the operator (and are shared with the charterer in the case of the Blue Visby Solution), the three pilot projects produced a rare alignment of commercial and environmental incentives on the ship-side. The same action that cuts emissions also cuts bunker costs, with little additional effort or contractual friction for the operator.

Cargill’s three-pronged pilot project also highlighted where the greatest opportunities lie. The biggest determinant of fuel, emissions, and cost savings potential is the amount of excess idle or waiting time available to absorb. This is most apparent in the Newcastle voyages, where, when a berth was available on arrival, there was no waiting time to absorb and therefore no additional savings opportunity, while the congested cases produced the most.

Most of the monitored voyages involved idle waiting time before a berth was available. Wherever ports are congested, the waiting time represents an untapped opportunity for emissions savings through port call optimisation. Therefore, the greatest potential lies at ports and along trade lanes with long waiting times, and identifying these high-idle-time situations is the most direct route to meaningful savings.

Local conditions can further amplify the opportunity. Newcastle demonstrated that favourable natural conditions—in this case, the East Australian Current—that allow ships to drift towards the port with engines stopped can materially increase savings. While this advantage will not exist everywhere, it highlights the value of identifying and prioritising locations where the geographical benefits can be compounded, particularly when paired with weather-routing support that can position vessels to exploit it.

Beyond the direct fuel and emissions savings demonstrated, the pilot project suggests port call optimisation acts as an enabler of other decarbonisation levers. As the ultra-slow steaming analysis below sets out, slowing down further only delivers a clear net benefit when the time saved is taken from idle waiting at anchor, rather than simply resulting in an earlier arrival followed by a longer wait. By fixing the berthing time, port call optimisation ensures that a slower voyage shortens the idle period. Without it, the gains from reducing speeds beyond conventional slow steaming are limited, and in addition, more ships are needed to deliver the same amount of transport work. Port call optimisation can therefore be understood not only as a standalone measure but as a catalyst for complementary efficiency gains.

Impact of ultra-slow steaming

The pilot project demonstrated that vessels’ ability to slow beyond typical slow-steaming speeds is an important factor in determining the emissions savings achievable through port call optimisation. To better understand the potential, an analysis was conducted to quantify the additional savings that could be achieved if vessels could operate at lower speeds, including through ultra-slow steaming.

Using real data from Kamsarmaxes that have performed ultra-slow steaming, Cargill calculated efficiency (tonnes of bunker consumed per nautical mile sailed) for speeds from 10-15% of the engine load up to 85%. The results for a modern Kamsarmax sailing in ballast, with a typical weather factor¹⁵ of 10%, are shown in the graph below. The results will vary with different weather and load conditions, and with different ship designs and types; the intention here is to compare relative trends rather than absolute savings.

The baseline (set at 0% on the vertical axis) represents the vessel operating at its maximum ballast speed. Values below 0% indicate an improvement in efficiency relative to this baseline by slowing down (i.e., less fuel burned per nautical mile).

The orange line shows the benefits of speed reduction without port call optimisation and assumes that if the ship slows down and arrives later, it will also berth later (i.e., no change in idle/waiting time). The blue line shows the port call optimisation case, where berthing time is unaffected by changes in voyage speed. Sailing at a slower speed reduces idle time and, in turn, reduces auxiliary consumption,¹⁶ therefore increasing the overall efficiency of the voyage. The green line indicates the savings predicted by the typical cubic speed-power relationship (in this case, the cubic speed-power rule of thumb is applied to the main engine consumption, and the auxiliary consumption per day is held constant).

The graphs confirm the steeper improvement in energy efficiency achieved by slow steaming, initially exceeding the cubic speed-power relationship. However, the curves confirm the pilot observations that the benefits beyond this point are reduced to levels well below those estimated by the cubic relationship. Further, port call optimisation increases the benefits of just (ultra)slow steaming alone, due to the additional reduction in idle consumption.

Several factors lead to these reduced savings at slower speeds on bulk carriers, including:

• Ultra-slow steaming typically requires an auxiliary genset (a diesel generator used to produce electricity for onboard equipment) to supply sufficient power to the auxiliary blowers, which provide additional air to the main engine at low engine loads. This increases auxiliary fuel consumption and reduces the efficiency gains of slowing down. However, this additional consumption could be significantly reduced where the ship is equipped with a suitably sized and specified shaft generator¹⁷ for ultra-slow steaming.

• At lower engine loads, reduced heat energy in the main engine’s exhaust gases can mean that the economiser, which recovers exhaust heat to produce steam, is unable to meet the ship’s steam demand. The auxiliary boiler, which produces steam by burning fuel, may therefore need to be used, further increasing fuel consumption.

• Base seagoing auxiliary consumption is generally constant on a tonnes-per-day basis (aside from the effects described above). As ship speed decreases, voyage duration increases, raising the total auxiliary consumption. Since the distance travelled is unchanged, this increases the consumption per nautical mile (nm).

• Operating at low engine loads for prolonged periods can cause deposits such as soot to build up on components such as economisers and turbochargers, which use exhaust-gas energy to supply compressed air to the engine. Engine makers, therefore, recommend periodically increasing engine load to remove these deposits. This variation in speed and engine load reduces the ship’s average fuel efficiency (increased tonnes/nm), effectively flattening the speed-consumption curve at lower speeds when measured on a ‘noon-noon’ basis.¹⁸

• The main engine efficiency is reduced at lower engine loads as the specific fuel consumption increases.

• The impact of adverse weather (measured in a percentage weather factor or percentage additional tonnes per nautical mile) is typically larger at lower speeds (i.e., as speed reduces, the fuel reduction in calm weather consumption is more pronounced than in weather-added consumption).

Therefore, the material efficiency gains from ultra-slow steaming are smaller than those estimated by a simple cubic speed-power rule of thumb and are not guaranteed. There are two key enablers to maximising these savings:

• Ship design: In the cases studied, the ultra-slow speeds are generally well below those for which the engine, hull, and propeller were designed. Therefore, optimising ship designs for these lower speeds and engine loads could enable better savings. As slow steaming becomes common practice, there are growing benefits and incentives to adopt it. However, competing requirements (such as minimum safe engine power requirements) must still be met.

• Port call optimisation: Without port call optimisation, the waiting time on arrival would increase, and the benefits limited. Port call optimisation is thus an enabler of increased benefits and emissions savings from speed reduction.

Shipowners may require specific charterparty clauses (such as the standard BIMCO slow/ultra-slow steaming clause) and/or additional spare parts before agreeing to ultra-slow steaming. Within the dry bulk sector, the practice of ultra-slow steaming is relatively uncommon on ships up to and including Kamsarmax/Panamax size.

What are the key barriers, and how are they addressed?

Aligning incentives between the ship and shore sides is the first challenge to address. Efforts to enable port call optimisation tend to fall on the port or terminal, while the bunker savings go to the ship operator. The Newcastle pilot illustrated this most clearly, with the port bearing the cost of running the scheme, including tracking each inbound ship for several days, but receiving no share of the savings it made possible. The pilot project shows there are ways to close this gap: CBH’s implementation of the Blue Visby Solution removed much of that effort and provided a mechanism to share savings between the ship and the implementer, thereby incentivising and compensating both sides. However, introducing such a mechanism introduces its own complexity, as any value-sharing arrangement requires an agreed counterfactual against which the savings are calculated, adding effort and scope for dispute, whereas models that let the operator keep the bunker savings avoid the need for a baseline altogether.

Given they are often the deciding factor, securing shore-side stakeholder buy-in early is the single most important step, and will be addressed further in the practical guidance that follows.

Navigating contractual requirements is the second challenge to overcome. Standard commodity contracts and charterparties were not written with port call optimisation in mind. For example, some contracts include specific requirements for the ship’s physical arrival, which would need to be amended for a virtual arrival¹⁹ approach to function as intended. Charterparties may also require a specific slow steaming clause before an owner will agree to slow down. The way to address this is to map the contractual landscape at the outset, identify any clauses that conflict with the intended port call optimisation mechanism, and put the necessary bespoke rules or supplementary agreements in place before the pilot begins. Limiting the scope of port call optimisation can also help avoid certain challenges: for example, assigning an RTA that falls after the laycan will typically have knock-on consequences (such as requiring modifications to terminal queuing procedures and/or changes to contractual clauses). However, by limiting the RTA to within the existing laycan, these problems can be avoided, albeit at the expense of reduced emissions-savings potential.

Making the most of ships’ ability to slow down is a third way to avoid implementation barriers. Vessels are already frequently slow-steaming, and ultra-slow steaming remains uncommon on bulkers, apart from Capesize vessels. Market conditions, including bunker prices, freight rates and vessel supply, may also influence decisions to slow down. This was the main factor shaping the savings achieved at Santarém. The pilot project also shows the upside when ships can slow further: at Newcastle, savings could have been increased with ultra-slow steaming, and at Albany, ultra-slow steaming is what made the pilot voyage’s savings possible. In the near term, the most effective approach for addressing this is to select ships and voyages for pilots with a genuine capacity to slow down. In the short to medium term, changes in operating practices can widen that headroom, and in the longer term, ship design can extend it further, as explored in the ultra-slow steaming analysis above.

Finally, capturing the full potential of port call optimisation requires planning for variability. The realised savings depend heavily on how much idle time is available to absorb, and are affected by weather, currents, and individual vessel characteristics, which is why they can differ from theoretical estimates. The mechanism design can also significantly impact potential savings; for example, in the Port of Newcastle system, ships are only required to slow within a fixed window before arrival, thereby capping the achievable savings. Operators could, in theory, be incentivised to sail faster earlier in the voyage before this window to secure a more favourable arrival time, though this has not been observed in practice.

All of these factors can be planned for. Before committing, companies can estimate savings potential by evaluating typical idle time, functional queue length, voyage duration, and the relevant ships’ ability to slow down. Weather-routing support can be used to further realise available savings, and scheme rules can be designed to limit any incentive to game the system. Assessing each case upfront will allow companies to realise the full potential of port call optimisation.

Practical learnings on running a pilot project

This section is aimed at those considering running their own pilot projects and draws out the practical lessons from Cargill’s experience that are most likely to determine whether a project gets off the ground and produces reliable findings.

Port call optimisation is not a one-size-fits-all solution; savings are context-dependent, and that is why well-designed pilot projects matter. The more pilot projects that are run across different ports, vessel types, and commercial structures, the clearer the picture of where the opportunity is largest and how best to capture it.

The following summarises key practical elements of running a pilot project and can serve as a basis for future pilots.

Identify the opportunity and the changes needed to capture it

Assessing the potential:

Before committing to a pilot project, it is worth estimating the potential savings to understand whether the opportunity justifies the effort. Key questions include:

• What are the typical idle times at the terminal, and what is the functional queue length?

• What is the realistic potential for ships to slow down, taking into consideration voyage length, typical speeds, and whether ultra-slow steaming is common among the relevant vessel types?

• What are the speed-consumption characteristics of the relevant ship types, and in particular, what are the auxiliary and boiler consumptions during slow steaming, ultra-slow steaming, and at anchor?

• Who will calculate the savings achieved during the trial? Do they sufficiently capture the characteristics of the trial ships (e.g., consumption characteristics at slow speed and minimum engine power)? What is the counterfactual baseline that will be used to measure savings against?

Assessing the change required:

It is also important to understand what changes will be required to achieve the estimated savings. Key questions to answer include:

• What queuing systems are currently in place?

• Who is responsible for managing the queuing system and implementing any changes to it?

• What stakeholders will be impacted by implementing port call optimisation?

• What solution strikes the best balance between cost and change, while also providing scalability?

There are several different solutions available, each with its own relative strengths and weaknesses. The best fit for a particular terminal will depend on several factors, such as the queuing system, typical inbound voyage leg lengths, and cargo type.

Engage shore-side stakeholders early

Stakeholder engagement is a critical factor in the success of a pilot and should be treated as a prerequisite, not an afterthought.
The terminal, port, shipper, charterer, and agent must all be on board for a pilot to work. In almost all cases, one or more shore-side stakeholders will need to make changes in their processes and/or systems to implement a solution. At Santarém, early consultation with each party was essential to understand the terminal’s operational realities and secure cooperation, made easier here because Cargill operates the terminal.

Understand the contractual landscape

Identify the contracts that could be impacted by port call optimisation. It is important to assess the flexibility to modify or supplement existing contracts, and to put any necessary agreements in place before the pilot begins. In the Cargill trial, bespoke VNoR rules were drafted ahead of execution to provide the required contractual framework. For early-stage trials, the scope of the solution can be limited to avoid contractual issues and reduce the effort required to set up the scheme. The scope can then be expanded in later phases of the trials.

Consider data sharing and systems

In the execution phase of Cargill’s pilot studies, no significant changes to data exchanged among the ship, disponent owner, terminal, and other stakeholders were required from the ship operator/owner; any changes were easily managed within the existing ship operational communication channels and personnel. Carefully consider what data is required to deliver the pilot and how this is delivered (for example, whether a service provider is required).

What does this mean for scaling operational efficiency?

Across three ports, three mechanisms and 16 voyages, the Cargill pilot confirmed the potential of port call optimisation to deliver emissions savings. What mattered most was not the sophistication of the scheme but how much excess waiting time existed for ships to absorb. Anyone approaching port call optimisation should assess their own case rather than aim for a specific emission reduction target.

Ships’ ability to reduce emissions by slowing down was a central constraint exposed by the pilot project. The commercial and operational machinery of port call optimisation can be made to work, but fuel and emissions savings are limited by the ship’s capabilities. This showed up in two ways. Firstly, most of the pilot ships could not ultra-slow steam, so they had little room to go slower than they already were. Secondly, where ships can ultra-slow steam, the savings show diminishing returns, with each further reduction in speed delivering smaller savings per nautical mile than the one before.

Port call optimisation and speed reduction are not two independent levers, but two parts of the same operational strategy. Slowing beyond conventional slow-steaming speeds delivers only limited incremental savings on its own, because auxiliary blowers, additional gensets, and boiler use progressively flatten the speed-consumption curve. Port call optimisation restores the value of going slower by ensuring the time saved comes out of idle waiting at anchor rather than simply producing an earlier arrival and a longer wait. Equally, port call optimisation can only exploit the slowdown headroom a ship possesses. Each depends on the other.

The consequence is that ship design and ultra-slow steaming capability need to catch up with operational ambitions. Today, ultra-slow steaming is uncommon in dry bulk. Widening the practice will require charterparty clauses that permit it, in addition to spare parts and technical readiness. However, without port call optimisation, there is limited incentive to do this, as the benefits are constrained by the reasons described above. In the longer term, ship designs should be optimised for the lower engine loads at which they will increasingly be asked to sail, thereby increasing the benefits of slow steaming and port call optimisation.

The largest opportunity for port call optimisation uptake today is in helping to solve an existing problem the port or terminal faces, such as congestion and safety concerns at anchorage, local air quality concerns, or reaching Scope 3 emissions targets. Where this is not the case, a benefit-sharing mechanism could serve as an incentive for the port or terminal to take action. However, this introduces the need for an agreed counterfactual, and per-voyage savings may be too small to compensate a terminal for the additional risk it assumes.

Cargill’s pilot incentivised port call optimisation uptake in three different ways: by starting where the terminal was under its own ownership and the incentive was internalised; by joining a pre-existing port-run scheme; and by adopting a shipper-led solution that asks nothing of the terminal. None of these is a general answer, but together they point to the same lesson: framing port call optimisation in terms that matter to the port or terminal, rather than to the shipowner, is likely the key to unlocking fuel and emissions savings.

None of this argues against acting now. The barriers identified here are real, but are practical rather than fundamental, and the pilots show a clear path for others to follow:

• Begin where control is greatest, and the incentives are aligned, as Cargill did at Santarém.

• Choose ports with genuine excess waiting time and ships with genuine room to slow down, because that combination determines the size of the prize.

• Map the contractual landscape before, not during, the pilot.

• Engage the shoreside early and on their own terms.

• Use weather-routing support to realise and quantify the available savings.

• Accept that a modest, well-measured result is more useful to the industry than a theoretical one.

The estimated savings from these pilots show that port call optimisation can deliver meaningful reductions in live commercial operations, and the pilots have mapped out what stands between the theoretical opportunity and its realisation. Port call optimisation is not a one-size-fits-all solution, but Cargill’s successful trials support the case for more pilots across more ports, vessel types, and commercial structures, and a willingness among shipowners, charterers, ports, terminals and other value chain actors to share what they learn. Speed reduction is one of the largest decarbonisation levers available to shipping this decade. Port call optimisation is what realises the commercial benefits of doing so.

Have you been involved in a pilot? Please get in touch

This brief draws on a narrow set of pilots, and closing the gap between opportunity and practice will take many more. If you’re running, planning, or considering an operational efficiency pilot, we’d welcome the chance to learn from it. Please reach out to ach@globalmaritimeforum.org.