Sustainability assessment of methanol steam reforming reactors for shipboard coupling with PEM fuel cells

Onboard methanol steam reforming (MSR) coupled with proton exchange membrane fuel cells (PEMFCs) is investigated as a pathway for maritime decarbonization. Joule heating, flue-gas heating, and condensing-steam heating of multitubular fixed-bed MSR reactors are compared using steady-state one-dimensional models and technological, economic, environmental, and safety indicators. Selected configurations achieved weighted- average methanol conversions higher than 99%. Joule heating produced inlet cold spots of 442-445 K, whereas condensing steam maintained nearly uniform temperatures of 477-478 K. Within the investigated candidate set, normalized aggregated sustainability indicators ranged from 0.64 to 0.88 for Joule heating, 0.87-0.96 for flue-gas heating, and 0.997-0.999 for condensing steam. Condensing-steam heating attained the highest aggregate ranking across the examined decision-making perspectives and aggregation procedures. These relative indicators are not absolute sustainability levels, and the ranking remains conditional on the investigated steady-state design space, system boundaries, model assumptions, and economic and emission factors.