Direct emissions monitoring is not just essential for operational optimisation—it also plays a key role in making better commercial decisions. If emissions data is inaccurate or unverifiable, disputes can arise between shipowners, charterers, and cargo owners, particularly regarding compliance with charter party terms.
For example, if a vessel has burned more fuel than expected, precise data can reveal whether this was due to:
- A longer route taken to avoid bad weather
- A machinery failure that could have been prevented with better maintenance
Accurate emissions data provides clear, data-backed explanations, reducing conflicts and ensuring fair cost distribution.
CII And Data Accuracy Challenges
The CII scheme has exposed challenges in emissions data accuracy and analysis. Analysts at Clarksons found that the impact of speed reductions on CII is often overestimated due to reliance on textbook speed-consumption curves. These models assume an exponential relationship between speed and fuel consumption, but real-world conditions flatten the curve at lower speeds.
According to Kenneth Tveter, Head of Green Transition at Clarksons, some vessels need significant speed reductions to comply, while others find speed reduction unviable. In such cases, more costly efficiency measures or vessel improvements must be implemented.
During a DNV panel discussion, Jørgen Thuesen, Vice President of Technical at Hafnia, stressed that waiting a year to verify emissions is not an option, especially in spot markets where voyages are short-term, and costs must be passed on immediately to customers. Real-time emissions tracking is critical for accurate contractual settlements between shipowners and charterers, particularly when factoring in EU ETS costs.
Optimising Port Visits
Precise emissions data can help shipowners and operators optimise port visits and berth locations. Some ports offer reduced fees or incentives for low-emission vessels. For example:
- Under the Green Award scheme, the Port of Rotterdam offers up to 70% discounts on port dues for ships with a Green Award Certificate.
- The Ports of Los Angeles & Long Beach provide 25% discounts on port fees for vessels participating in the Vessel Speed Reduction Programme to cut emissions.
By knowing and reporting exact emissions, ship operators can plan routes to maximise port incentives, significantly reducing voyage costs.
Equipment Maintenance
Ships have multiple engines and equipment operating under varying conditions. Direct emissions monitoring helps track fuel combustion efficiency, providing insights into emissions and enabling real-time comparisons.
If one engine emits significantly more CO₂ or methane than others using the same fuel input, it may signal the need for maintenance intervention.
According to Pat Gerrity, Principal at Pat Gerrity Maritime Advisors, LLC, this data-driven approach enables ship operators to:
- Identify underperforming engines
- Schedule maintenance based on actual performance data, rather than fixed intervals
Detecting Hull Fouling
Direct emissions monitoring can also detect excess hull fouling, which increases water resistance and forces the engine to consume more fuel to maintain speed.
For instance, if CO₂ per nautical mile and fuel use increase without changes in speed, load, or weather, this could indicate an increased drag due to a fouled hull or higher engine power demand, leading to excess fuel consumption. Using fuel flow meters and engine performance sensors, direct emissions monitoring can help pinpoint when the hull needs cleaning and will allow a comparison between emissions and fuel consumption under similar conditions over time
36 Riviera (Oct, 2023) Clarksons: slow-steaming benefit for CII ‘grossly overestimated’
37 DNV (Apr, 2023) Webinar: DNV’s Emissions Connect – Advance from raw data to sustainable operations
38 Port of Rotterdam (accessed Jan, 2025) Green award discount
39 EPA (Jan, 2025) Marine vessel speed reduction reduces air emissions and fuel usage
For a more detailed understanding and exploration of the topics covered in this article, refer to our report, Transforming Maritime Operations: Unlocking Accurate Data for Sustainability and Compliance, commissioned by SailPlan.
