Methanol as an alternative fuel for marine engines: A comprehensive review of current state, opportunities, and challenges

In response to the increasingly severe environmental issues and emission reduction policies, green and renewable energy are the primary choices for the shipping transportation industry. Methanol, especially green methanol, has gained significant attention due to its ability to reduce greenhouse gas emissions while remaining liquid at room temperature. However, using methanol impacts combustion processes, emission outputs, and the working environment of engine components. Therefore, it is imperative to provide a comprehensive review regarding the application of methanol within the maritime industry. Herein, the fundamental characteristics of methanol and its production were systematically reviewed, as well as its safety in transportation and storage. Additionally, it discusses the combustion and emissions characteristics of methanol in marine engines. Subsequently, the potential operational reliability issues of methanol marine engines were analyzed from the perspective of lubrication, corrosion, wear for possible failures. The review also highlights methanol applications in the ship transportation industry. Finally, it summarized the significant opportunities and challenges of methanol for marine engines, along with potential research trends and future development directions. This study aims to advance methanol's role in shipping and provide theoretical guidance for the reliability and maintenance of methanol-fueled marine engines.