The conventional approach to building inland methanol bunkering networks has been to treat fuel supply as a fixed-node problem, a port either has a station or it does not. This new optimization framework, tested on a 15-port Yangtze River network, demonstrates that such thinking is unnecessarily expensive. By integrating mobile bunker barges that can conduct ship-to-ship refueling across ports, the model reduces total system cost by approximately 37.7% relative to traditional alongside bunkering. That is not a marginal efficiency gain; it is a structural shift in how we should phase green-fuel infrastructure. For operators and policymakers navigating the early-stage deployment of methanol-powered inland vessels, this study provides a calibrated, empirical method to avoid over-investing in fixed stations while vessels still have limited cruising range and demand remains spatially dispersed. The practical implication is clear: the most cost-effective path to scaling green methanol in inland shipping may not be more dockside pumps, but a coordinated mix of fixed hubs and mobile capacity.
This work arrives alongside real-world milestones in alternative fuel bunkering that underscore the urgency of network-level planning. The recent 5 000 metric tonnes of certified bioethanol fuel a Maersk vessel in Singapore and the first 1 000 Metric Tons of Green Ammonia Delivered in First Ship-to-Ship Bunkering show that the marine industry is moving beyond pilot projects into operational supply chains. Yet those achievements are point solutions, successful single transactions at major ports. The Yangtze River study addresses a different, harder problem: how to build a viable network when demand is thin and spread across many smaller ports. It suggests that mobile bunkering can substitute for part of fixed infrastructure deployment by extending the service coverage of regional methanol hubs, effectively turning a single large investment into a distributed, flexible system.
What matters most for decision-makers are the sensitivity findings. Bunkering-barge service radius and vessel methanol tank capacity are the dominant cost drivers, producing system cost variations of approximately 37.9% and 32.8%, respectively. This means that engineering choices, how far a barge can travel and how much fuel a vessel can carry, matter more than methanol price fluctuations, which had only a limited effect within the tested range. The implication is that infrastructure planners should prioritize investments that extend barge range and vessel tank capacity before negotiating fuel contracts. Additionally, higher fixed-station construction costs strengthen the relative advantage of cross-port bunkering, while rising barge sailing costs weaken but do not eliminate it. The takeaway is direct: as long as inland ports face dispersed demand and high construction costs, mobile bunkering is not a niche supplement but a core strategy.
A specific consequence worth watching is how this framework handles the transition from pilot to scale. The model jointly optimizes fixed-station siting, freight assignment, bunkering-port selection, and mobile service allocation. That level of integration is rare in practice, where infrastructure and operations are often planned by separate entities. The open question is whether port authorities, fuel suppliers, and vessel operators can coordinate on a single optimization horizon, or whether the real-world fragmentation of inland shipping will erode the theoretical 37.7% savings. The answer will determine whether the Yangtze River case becomes a template for other inland waterways, or a cautionary tale about the gap between integrated models and fragmented markets.