Potential assessment of typical pathways for low/zero-carbon marine fuels in China based on expert decision-making system

Alternative marine fuels, such as low/zero-carbon methanol and ammonia, are the predominant mid to long-term solutions for reducing greenhouse gas emissions in international shipping sector. However, the development potentials of low/zero-carbon marine fuels vary depending on different pathways. An expert decision-making system was established based on the Delphi, Analytic Hierarchy Process, and Fuzzy Cluster Analysis method. For 19 typical candidate pathways, seven evaluation factors including energy availability, economy, technological maturity, environmental performance, policies and regulations, safety, and future scalability were considered to evaluate the development potential of low/zero-carbon methanol and ammonia under different pathways, based on the expert decision-making system. Through conducting a weight survey with 18 industrial experts, the weights of seven evaluation factors were found to be 21.52%, 23.68%, 7.83%, 15.26%, 11.11%, 10.79%, and 9.81%, respectively; meanwhile, regarding the importance of technological maturity, safety, and future scalability, there is some controversy among experts. Methanol produced from municipal solid waste, methanol produced from CO₂ capture from fossil point sources and renewable electricity-based H₂, ammonia produced from renewable electricity-based N₂ and renewable electricity-based H₂, methanol produced from crop straws, methanol produced from fossil fuels combining with carbon capture and storage technology, methanol produced from coke oven gas, and methanol produced from CO₂ captured from fossil point sources and biomass point sources, are currently pathways with great development potential. The established expert decision-making system and evaluation results can provide valuable references for the development route selection, technology development and policy formulation of low/zero carbon alternative fuels in the shipping industry.