Retrofit of box ship’s large-bore, two-stroke to burn methanol shows promising decarbonisation path

Over the last few years, shipowners have been investing in dual-fuel newbuilds at a robust pace to support the uptake of low- and zero-carbon fuels. According to Clarksons’ World Fleet Monitor, 47% of the gross tonnage ordered as of Q3 this year is set to be alternative fuel capable. Deliveries of alternative fuel-capable vessels to the global fleet are also increasing. 317 alternative-fuel ships of 24.3M gross tonnes (gt) were delivered in January to September – 43% of deliveries. This is a higher percentage than 2024, when 35% of deliveries, a record 24.7M gt of alternative-fuel ships, were delivered.

But a major hurdle for shipping is how to reduce CO2 emissions and greenhouse gas from the existing global fleet. A recent retrofit on COSCO Shipping Lines’ container ship’s large-bore, two-stroke engine to allow it to burn methanol could well point the way.

This was the first conversion of an Everllence B&W S90 two-stroke engine to dual-fuel methanol running, according to the engine designer Everllence, formerly known as MAN Energy Solutions. Everllence said the 20,000+ TEU container vessel, COSCO Shipping Libra’s 11S90ME-C engine was retrofitted to an 11S90ME-LGIM (liquid gas injection methanol) unit.

The project involved a partnership between Everllence PrimeServ, the company’s after-sales division and COSCO Shipping Heavy Industry. The parties collaborated on developing the project from concept to execution in delivering the world’s first S90 methanol engine retrofit, a full-scope project covering engineering, project management, installation, commissioning and sea trials.

As part of the process, Everllence invested in a dedicated 4S90 testbed engine in Japan that was commissioned in early 2025. The testbed validated the S90 engine’s methanol performance under real operating conditions, accelerating its readiness for this ‘first-ever’ large-bore milestone.

Everllence senior vice president and head of Everllence PrimeServ, Denmark, Michael Petersen said the project highlights COSCO Shipping Lines as “a first mover and presents a practical path for reducing emissions from Everllence S90 engine vessels.” Mr Petersen noted the company has completed 26 dual-fuel conversions and has “an even larger pipeline across various alternative fuels."