The Decarbonization Fairway

Decarbonization in shipping is currently evolving along two main paths.

The first is technological. New vessel designs, alternative fuels, improved propulsion systems and structural innovations. This path is strategically essential. However, it requires time, significant investment, and cannot materially change how the existing fleet operates in the near term.

The second path is operational. This is where the industry has made tangible progress in recent years. Tools operating at the level of voyage execution enable more precise control of speed, routing, and fuel consumption – and, as a result, reduce emissions within already selected voyages.

This layer should not be underestimated. On the contrary, it demonstrates how effective a system can be when the problem is clearly defined and the tools have reached sufficient maturity.

Yet as regulatory pressure increases, it becomes clear that this level alone is no longer enough.

The reason lies in the way decarbonization is structured.

Environmental performance in shipping is formalized through the CII (Carbon Intensity Indicator) rating, which is assigned to a vessel – annually and determines its position within the A-E scale.

At the same time, this rating is based on the vessel’s actual carbon intensity – AER – which is accumulated over time, voyage by voyage, through every commercial decision made during the year.

In other words:

the result is measured annually
but it is built through a sequence of local decisions

This is where the fundamental misalignment emerges.

The Horizon Gap

Voyage optimization operates on a short-term horizon. The result, however, is evaluated over a long-term one.

This means that even a perfectly executed voyage does not guarantee an optimal annual outcome.

A voyage that appears commercially and operationally efficient in isolation may reposition the vessel unfavorably, reduce future employment options, increase ballast exposure and ultimately deteriorate its annual environmental rating.

Conversely, a decision that appears less attractive in the short term may create a more stable trajectory across a sequence of voyages and improve the final result.

Decarbonization, therefore, extends beyond a single voyage. It becomes a problem of managing a trajectory – a voyage chain.

In practice, most emission reduction efforts today take place within already selected voyages.

The commercial decision – cargo, position, route – is made first. Only then does voyage optimization begin, including adjustments aimed at reducing CO₂ emissions.

This means that optimization operates within a predefined scenario.

That scenario effectively defines the decarbonization fairway – the space of permissible movement within which execution is optimized.

A fairway is not just a route. It is a viable trajectory within a constrained and complex Decision Space, where choosing the wrong path can matter more than how well it is executed.

If we look at the Decision Space as a whole, it becomes clear that such a fairway is not unique.

In reality, the Decision Space is a structured system of alternatives:

cargo combinations,
fleet positioning,
sequences of voyages,
market and regulatory constraints.

This is where the real decarbonization potential resides.

The fairway can – and should – be defined at the level of exploring this space, at the stage of commercial decision-making, before voyage execution begins.

This is where a natural link between commercial optimization and voyage optimization should emerge.

However, most existing voyage optimization tools are architecturally designed to operate within an already selected scenario and do not allow for exploration of alternative fairways.

Which leads to a critical question: not how well a vessel performs within a chosen path, but whether the right path was chosen in the first place.

The Limits of Optimization: When the Goal Is Not to Improve, but Not to Deteriorate

Voyage optimization is inherently constrained.

If a commercial decision places a vessel into an inefficient or overly narrow fairway, no amount of execution-level refinement can fully compensate for that initial choice.

In practice, the task often shifts. Not to improve performance, but simply to stay within acceptable limits.

This is directly linked to how commercial decisions are made today.

Voyage selection is typically based on fragmented calculations across multiple tools, each capturing only part of the problem and none providing a complete view of the Decision Space.

Environmental metrics – including CO₂-related indicators – are often evaluated post factum, once the route or cargo combination has already been chosen. And even then, they are frequently assessed at an aggregated level, without accounting for sequence effects.

Execution then unfolds in real-world conditions – with weather deviations, delays, speed variations – all of which tend to deteriorate initial estimates.

As a result, even a theoretically acceptable scenario can drift toward the boundary.

A voyage expected to result in a C rating, for example, leaves no realistic path to A, only a limited chance of B and a very real risk of slipping into D, depending on its structure.

This is why fairway selection must incorporate not only optimality, but robustness.

Environmental constraints cannot be applied post factum. They must be embedded into the decision itself – at the stage of trajectory formation.

And this requires tools capable of fully exploring the complexity of the Decision Space.

Two Layers of One System

At this point, a clear distinction between decision-making layers becomes essential.

If we continue the fairway metaphor, different tools operate at different levels.

The role of an Optimization Engine is to explore the Decision Space and define the fairway – the trajectory that makes both commercial and environmental objectives achievable over the relevant horizon.

This is the level of path selection.

Voyage Optimization operates differently. It does not define the fairway. It works within it.

Its role is execution – adjusting for real-world conditions and guiding the vessel along the selected trajectory as efficiently as possible.

The two are not in conflict. They are complementary. But they are not interchangeable.

Attempting to compensate for the absence of fairway selection through better execution inevitably reaches its limits.

If the path is wrong, no level of steering precision can correct it.

Decarbonization as Part of Commercial Logic

Decarbonization is not an external constraint opposing commercial logic. It is becoming part of it.

As regulatory pressure intensifies, environmental performance begins to directly affect economic outcomes.

The challenge is no longer choosing between profitability and sustainability. It is designing decisions where the two align. This is only possible through proper exploration of the Decision Space.

When this is achieved, it becomes possible to identify fairways that simultaneously:

meet commercial objectives,
maintain fleet positioning,
satisfy environmental requirements.

Environmental performance ceases to be a reporting metric. It becomes a planning parameter.

This introduces a new dimension – trade-offs.

In some cases, the commercially stronger option in the short term may lead to worse environmental performance over time. In others, a slightly less attractive decision may preserve the vessel’s rating and long-term viability.

A drop to D or E is not merely a compliance issue. It is a commercial risk.

The ability to anticipate this trade-off becomes a defining feature of decision quality.

Broken Loops

In practice, however, this transition is constrained by an internal structural divide.

In many organizations, commercial operations and decarbonization remain separate loops. On one side – short-term efficiency and market responsiveness. On the other – annual environmental performance control.

Formally, these objectives do not conflict. But in practice, they rely on different data, different models, and different time horizons.

As a result:

decisions are made within one logic,
and evaluated within another.

This divide is not a failure of competence. It is a consequence of process architecture.

However, as environmental metrics begin to influence commercial outcomes, this separation becomes unsustainable. An effective fairway cannot be defined if commercial planning and environmental management operate on fundamentally different representations of the problem.

Decarbonization is no longer an external control layer. It becomes a condition of decision quality.

Where No Fairway Exists

At the level of commercial planning, another limitation becomes visible.

There are combinations of vessel characteristics, regions, distances and cargo patterns where achieving a higher environmental rating is simply not possible.

Not due to poor decisions, but due to the physical characteristics of the vessel and the structure of the market. This creates a “geographical trap”.

A vessel may lose its annual rating not because of poor execution, but because it was placed in a segment where the required performance is unattainable.

Such situations cannot be identified at the level of a single voyage. They only become visible through analysis of the Decision Space.

Continuous Planning

Long-horizon planning in shipping is constrained by data availability.

At the same time, for industrial fleets operating with known cargo flows, this challenge is largely manageable: data availability allows for building multi-voyage sequences and managing performance at a system level.

The spot market is different. Full visibility of future cargoes is not available, making classical long-term planning difficult.

But this does not mean decisions must remain isolated.

Even under partial visibility, a different approach becomes possible:

evaluating not a single voyage, but a chain of available options,
defining an exit point,
and continuously recalculating as new information emerges.

This enables a form of continuous planning in a discrete structure, through a sequence of connected decisions. And this is what makes it possible to manage environmental performance on an annual horizon.

However, implementing this in practice requires tools capable of rapidly exploring the Decision Space and recalculating scenarios as inputs evolve.

Conclusion

The industry has reached a high level of sophistication in voyage execution. The next step lies above – at the level of decision formation. Decarbonization is not an external factor or an additional constraint. It is a new dimension of commercial decision quality.

It cannot be achieved through execution improvements alone. It requires the ability to:

select the right fairway within the Decision Space,
align decisions with the relevant time horizon,
and operate at the level of systems rather than individual voyages.

Without this level, decarbonization in its current form cannot be achieved.

This is where the boundary lies today – between local optimization and system-level control.

Deep dive into implementation tools:
See how trajectory fairways are handled by our algorithms in the Environmental Planning Parameter Insight or explore our foundational framework in Optimization as Control.