When a vessel approaches ten-years-old, or more, it is reaching an age where it could be too young to be scrapped while also posing a return-on-investment headache for owners looking to achieve emissions reductions through technological improvements.

More stringent global regulation could change the economics of emissions reduction technology, but the need for global regulation is seen as paramount by many in the industry.

The direction of travel appears to be clear, leaving a cohort of existing vessels – those around their mid-operational lifespan – caught in a kind of retrofit limbo often with insufficient payback time for high-cost retrofits, such as engine or fuel tank modifications.

Although some vessels have been successfully converted, such as Seaspan’s collaboration with Hapag-Lloyd to convert a 12-year-old vessel, the first of five, to methanol power.

“Seaspan has committed over US$230 million across 86 vessels, executing more than 550 efficiency and retrofit projects,” said the company.

Some cost-effective retrofits do present themselves, most obviously, rotor- and suction-sails, each expected to share the lifespan of the vessel, their OEMs highlight that the life of the sail, however, need not end when the vessel is scrapped, it can be refurbished and sold on.

In a recent case study for a membrane LNG carrier to be equipped with Oceanwings sails – a pioneering first-of-its kind installation with all the first-mover pitfalls that implies – the partners identified a timeline of 18 months for planning, a 12-week design period, and some 21 days for the installation.

In this case, Oceanwings sails were chosen because of their ability to turn to a neutral orientation parallel to the heading of the ship, presenting a small profile in the event of a headwind – a state which this particular vessel type appears to experience often.

“For an LNGC offloading in the Gulf of Mexico and serving either Europe or Japan, 70% of the time is spent with apparent wind angles lower than 45°,” an analysis of the trade found.

Hull modifications are more challenging as these efficiency additions are produced for a particular vessel in a particular trade, they are unlikely, to be transferable at the end of the ship’s operational life.

One hull modification that has shown promise through research conducted by MIT, entitled “Net Drag Reduction in High Block Coefficient Ships and Vehicles Using Vortex Generators” published in December 2025, is the vortex generator. The report illustrated how aft-hull vortex generators on high block coefficient ships like bulk carriers or tankers, could reduce fuel costs.

The test case was a 300m newcastlemax bulk carrier travelling at 14.5knots – cutting drag by around 7.5%. The economics appeared sound, as well, with a steelwork and retrofit cost of around US$140,000, and assumed annual fuel savings of US$750,000.

The vortex generators had a positive effect on propulsion efficiency, as the more closely adhering laminar flow across the keel helped to optimise inflow and drive more water through the blades… “mean[ing] a reduction in the magnitude of the unsteady loads on the propeller and the rudder,” and “impl[ying] less vibratory loads and stresses and potentially a reduction in cavitation and ventilation effects.”

Since this study’s publication fuel costs have reached significantly higher levels than at the time of publication, increasing potential cost savings.

Another efficiency gain presents itself through fitting a Propeller Boss Cap Fin (PBCF), which optimises the flow aft of the propeller, improving rudder responsiveness and preventing propeller hub vortex cavitation, a source of noise and inefficiency.

Recently, an EcoNavis PBCF was retrofitted to YC Fortitude, a 32,491dwt Panama-flagged bulk carrier constructed not 10, but 15 years ago. The installation followed a similar retrofit on even older SYFC Araya, a 31,807dwt Thai-flagged general cargo vessel built in 2010, which led to verified fuel savings of 2.5%.

It should be noted that some naval architects have challenged data on EcoNavis’ PCBF savings.

One said: “In practice [PCBF savings of 2.5%] are very difficult to demonstrate and the effectiveness of boss cap fins in general is quite controversial” – one shipowner presented data purporting to show a similar level of improvement at the RINA Ship Energy Efficiency conference but were challenged by another large shipowner from the audience.