Toward a greener maritime industry: A review on current onboard waste management strategies, challenges, and future...

As a foundation for global trade, the maritime industry continues to expand, contributing to rising emissions and maritime pollution. Each year, various types of waste are generated onboard, including food waste, engine oil residues, sewage, and plastics. The International Maritime Organization regulations have shaped waste management practices onboard, yet most strategies still rely on treatment and overboard discharge rather than recovering value. This review critically examines these conventional methods while uniquely focusing on waste valorization as a pathway toward decarbonization and circular economy integration onboard ships. Anaerobic digestion and pyrolysis are both tempting techniques that could be installed onboard, generating biogas and biooil. A key contribution of this work is the systematic assessment of the upgrading pathways required to bring these products to marine fuel standards, including pressure swing adsorption and water scrubbing for biogas, and chemical, physical, or biological refining for biooil. Beyond fuel generation, integrating a valorization unit onboard reduces dependency on multiple dedicated waste management machines, such as shredders and sewage treatment systems. Nevertheless, initial investment costs and space limitations remain the primary barriers to implementation. This review guides and informs research initiatives focused on the onboard valorization of ship-generated waste.