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.