The Marine Environment & Engine System Department of the National Maritime Research Institute (NMRI) was awarded the Marine Engineering of the Year 2022 by the Japan Institute of Marine Engineering. It received the award at the joint ceremony with the Japan Society of Naval Architects and Ocean Engineers and the Japan Institute of Navigation on July 14, 2023. The department, which is in charge of research and development of marine engine systems and environmental conservation research at NMRI, has been granted numerous paper awards in recognition of outstanding research results in the field of marine engineering over many years. In addition, the Department developed advanced technologies in FY2022 for the practical application of new fuels that contribute to the decarbonization of marine transport. This paper will introduce the Department's research projects initiated by its four groups.

  Measures to address environmental issues, such as global warming and SOx and NOx emissions, are increasingly gaining importance. With regard to global warming, IMO has set high goals for reduction of greenhouse gases. Biofuels are expected to play an important role in achieving this goal, and in addition to liquid biofuels, the use of gaseous biofuels, such as biomethane made from biogas or wood gas, will also become more crucial in the future. Moreover, active research related to methanation, a method to produce methane by synthesizing CO₂ and H₂, is being carried out. However, the use of gaseous fuels can lead to a problem in gas engines - methane slip. To address this issue, the authors proposed a system that makes it possible to mix gas fuel (such as CH₄) with liquid fuel (such as heavy fuel oil and biofuel) in one cylinder of the engine and introduce exhaust gas out of the cylinder into all other cylinders as EGR (exhaust gas recirculation) gas. When different fuels are used at the same time in the engine, they are usually mixed at first and then carried into all of the cylinders. In contrast, we conducted an experiment using the proposed system by adopting different fuel compositions to each cylinder to take advantage of various combustion characteristics and connecting them with EGR. In this way, we have achieved NOx and methane slip reduction.