关键词: 港口联盟, 碳交易市场, 双层规划模型, MPEC, EPEC

Abstract: Ports, as critical hubs in global trade, are significant sources of greenhouse gas emissions in the shipping industry. The carbon trading market, as a key economic tool for emission reduction strategies, not only provides long-term stability but also imposes additional operational and cost pressures on ports. A port alliance, which fosters port integration and promotes sustainable development through inter-port cooperation, facilitates resource sharing and cross-port investment, thereby alleviating operational and cost pressures. With the strengthening of government controls on carbon emissions and the growing prevalence of port alliances, the decision-making environment for ports has become increasingly complex.
Ports can optimize their facilities through rational investment in development to enhance their handling capacity. However, cargo handling operations increase, so do carbon emissions. To meet government emission requirements, ports need to participate in the carbon trading market by purchasing carbon allowances, which incurs costs. Ports must make rational investment decisions to maximize revenue from both cargo handling and carbon trading activities.
Port investment decisions also affect the transportation strategies of shipping companies. After ports make investment decisions, the capacity of nodes in the transportation network changes, creating a new network. Shipping companies react to this new network by adjusting their container transport and transshipment plans to minimize costs. These shipping strategies, in turn, impact port revenue and carbon emissions, which subsequently influence decisions in the carbon trading market and affect carbon trading prices.
To respond to changes in port demand and reduce emission pressures, this paper considers the carbon trading mechanism for ports and the cooperative strategies within port alliances, establishing a bi-level programming model. In this model, the upper level focuses on optimizing port investment strategies to improve the demand satisfaction capacity of both ports and the shipping system, while reducing the carbon emission intensity of ports. Shipping companies, as one of the entities at the lower level, optimize their transport strategies to minimize shipping costs, while the carbon trading market, as another lower-level entity, sets carbon trading prices based on port carbon emission demand. The alliance cooperation strategy forms a multi-leader and dual-follower game among the parties. To achieve equilibrium in this game, we employ KKT conditions and a diagonalization algorithm to solve an Equilibrium Problem with Equilibrium Constraints(EPEC), which includes multiple single-leader and dual-follower problems. Each problem is formulated as a Mathematical Program with Equilibrium Constraints (MPEC). This ensures that each port makes optimal decisions based on the decision sets of other ports, with no single port able to unilaterally increase its revenue by changing its investment decisions.
Through five years of simulation experiments, it is found that ports with higher cargo handling volumes are more willing to invest in reducing their carbon emission intensity. Regarding trends in carbon trading prices, both a reduction in carbon allowance supply and a decrease in carbon emission intensity lead to higher carbon trading prices. Concerning the effectiveness of port alliances, the presence of a port alliance within a shipping network increases the demand satisfaction rate. The larger the alliance, the higher the demand satisfaction rate. However, when growth is too rapid or emission reduction targets are too ambitious, port alliances may struggle to ensure continued growth in demand satisfaction rates.

Key words: port alliance, carbon trading market, bi-level planning model, MPEC, EPEC