Approved design for the world’s first methane oxidation catalyst system; Promote the development of technology to reduce methane leakage on LNG fueled vessels to further reduce environmental impact

Hitachi Zosen Company, Mitsui OSK Lines, Ltd. (MOL), and Yanmar Power Technologies Co. (YPT), have received approval in principle for the methane oxidation catalyst system (Note 1) from Nippon Kaiji Kyokai (NK-class).

The system reduces methane slip by placing a methane oxidation catalyst in an LNG fuel engine and oxidizing the methane. This is the first time in the world that a catalytic methane oxidation system has received approval in principle (Note 2).

This project was adopted by the Organization for the development of new energies and industrial technologies (NEDO) as “Development of Methane Slip Reduction Technology from LNG-Fueled Vessels by Improving Catalysts and Engines” (Note 3) under the New Generation Vessel Development Project of the Green Innovation Fund (Note 4). Hitachi Zosen and YPT created the system design with MOL and Namura Shipbuilding Co., Ltd. together to build the actual demonstration vessel and design the system installation. The companies work closely together to carry out risk assessments and implement other measures. This time it was confirmed that the proposed system meets the requirements of the International Safety Code for ships using gas or Other low flash point fuels (IGF Code) (Note 5) and other regulations.

The project aims to further reduce the environmental impact of the LNG fuel engine by achieving a methane slip reduction rate of more than 70% over a six-year period from FY 2021 to FY 2026 by combining a methane oxidation catalyst and engine improvements and by verifying the design concept in actual vessels. The approval is an important first step towards establishing the technology for this system.

Artist’s impression of a coal transporter planned for on-board demonstration.

Approval in principle from ClassNK.

Note 1: Methane Oxidation Catalyst System

This system is placed in the exhaust pipes of LNG fueled engines and generators that contain unburned methane, and the methane is oxidized on the catalysts to reduce methane slip.

Note 2: Approval in principle

An AiP is issued to equipment and systems that are unprecedented or have very little precedent where the Classification society confirmed that the set-up and security of equipment and systems meet applicable rules and guidelines.

Note 3: Methane slip

In gas engines, part of the methane in the LNG fuel is emitted into the atmosphere as unburned methane, via the exhaust gases. Methane has a greater greenhouse effect than CO2, and reducing methane releases is necessary to achieve greenhouse gas reductions.

Note 4: Please refer to the following press releases dated October 27, 2021 regarding this project.

Hitachi Zosen



Note 5: IGF code

International Safety Code for Ships Using Gases or Other low flash point fuels published in 2017 to specify safety requirements for ships using gaseous fuels and low flash point fuels.

Hitachi Zosen

Hitachi Zosen has been providing NOx removal catalysts and NOx removal systems to domestic and overseas applications for over 50 years. Moreover, since 2015, Hitachi Zosen has installed them in marine diesel engines to provide the solutions needed to prevent air pollution.

Utilizing technology grown as the only manufacturer of “catalysts” and “marine diesel engines” in Japan, Hitachi Zosen will develop catalysts that oxidize the methane slipped into this project. Hitachi Zosen contribute to the prosperous future of land and people.


MOL develops various social infrastructure activities such as maritime activities and wind energy activities, focusing on maritime transport activities such as dedicated vessels that transport various raw materials and fuels, tankers and ships transportation of products such as automobiles. With the largest fleet in the world, experience and technology cultivated over 130 years of history, and a spirit of challenge aimed at creating new value, we contribute to the development of the world economy and the preservation of ‘environment. In this project, we aim to further reduce the environmental burden of LNG-powered ships by establishing how methane reduction technology works on real ships. We will contribute to the reduction of greenhouse gas emissions from our ships, the low carbonization of the supply chains of customers such as shippers and the low carbonization of society as a whole.


With beginnings in Osaka, Japanin 1912, Yanmar was the first to successfully manufacture a practical-sized compact diesel engine in 1933. A pioneer in diesel engine technology, Yanmar is a global innovator in a wide range of industrial equipment, small and large engines, agricultural machinery and plants, construction equipment, energy systems, marine, machine tools and components – Yanmar’s global business operations cover seven areas. On land, at sea and in the city, Yanmar provides advanced solutions to the challenges customers face, towards realizing a sustainable future.

For more details, visit the official website of Yanmar Holdings Co., Ltd.