INTEGRATING BIO-CO2 WITH RENEWABLE HYDROGEN FOR THE SYNTHESIS OF MARITIME METHANOL

Recognizing the growing emissions from the maritime sector and recent EU regulatory developments, this study explores the utilization of bio-CO2 with renewable hydrogen to produce e-MeOH as a renewable maritime fuel. Process models are developed in Aspen Plus™, including a conventional single-reactor setup and a novel four-reactor configuration with intermediate cooling and separation. First, the performance of the conventional, once-through process is assessed through a sensitivity analysis, which demonstrates that maximum reactant conversion remains below 40% under typical operating conditions. Recycling improves conversion but causes inert buildup, leading to higher compression needs, larger equipment and slower response. The four-reactor system, by contrast, achieves higher conversion without recycling, reducing feedstock demand by 65% under once-through conditions. Finally, to assess the industrial relevance of the proposed technologies, three methanol production scales (150–600 tpd) are evaluated. Depending on those three production scales, 0.1-0.4 Mtpa of bio-CO2 are required, indicating that only large bio-CO2 emitters can meet this demand directly whereas smaller facilities would need to aggregate CO2 at regional hubs. Green hydrogen requirements range from 13–150 ktpa (0.1–1.2 GW), indicating an additional limiting factor based on current EU capacities. However, future expansion of electrolyser technologies, CO2 capture processes and planned EU initiatives could support e-MeOH adoption in the maritime sector.