Trial Achieves 98% Methane‑Slip Reduction Using Catalyst System

A multi‑year Japanese research programme has reported a major breakthrough in cutting unburnt methane emissions, commonly called methane slip, during sea trials aboard Mitsui O.S.K. Lines’ (MOL) bulker Reimei. 

The project, funded under the New Energy and Industrial Technology Development Organisation (NEDO) Green Innovation Fund, combines a methane oxidation catalyst with exhaust gas recirculation (EGR) to oxidise slip at the funnel and reduce overall engine emissions.

The initiative, launched in 2021, set an objective of achieving at least a 70% reduction in methane slip. Land‑based tests conducted in December 2023 recorded a 93.8% reduction at full engine load. 

After adapting the land test equipment for onboard installation, the project partners, Kanadevia Corporation, Yanmar Power Technology, and MOL, began full‑scale sea trials in May 2025 on the 95,792 dwt Panamax bulker Reimei, operating on commercial routes that include Japan–Australia.

During the demonstration, the onboard catalyst system delivered a methane‑slip reduction rate of 98% in practical operating conditions around 75% engine load, substantially outperforming the project’s original target. 

The trials ran amid normal voyage variables, including weather‑driven fluctuations in load, and the results were independently verified by ClassNK and reviewed by NEDO.

The technology works by mounting a methane oxidation catalyst on the vessel’s exhaust, where residual methane is chemically converted to carbon dioxide, thereby cutting the stronger short‑term greenhouse effect of methane. 

The system is paired with EGR to reduce unburnt methane formation at source and to provide simultaneous NOx control, creating a combined emissions‑reduction package suited to LNG‑fueled engines.

Methane has a substantially higher near‑term global‑warming potential than CO2, so curbing methane slip is essential for genuinely lowering lifecycle greenhouse‑gas emissions from LNG propulsion. 

The developers say the onboard demonstration is the first of its kind at this scale for maritime applications and is an important step toward commercialisation.

Onboard trials will continue through 2026 to evaluate catalyst durability, operational integration and lifetime performance before planned social implementation and commercial availability from 2027. 

If sustained results are confirmed, the system could be retrofitted to existing LNG‑fuelled ships and installed on newbuilds, offering shipowners a practical route to cut methane emissions while maintaining operational schedules.

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