Optimisation of green investment under shipping alliance and hub-and-spoke collusion

As global climate change and environmental pollution issues intensify, ports and the shipping industry are accelerating their transition towards green and low-carbon practices. Consequently, this paper contends that ports and shipping firms will undertake green investments, defined as activities promoting environmental sustainability and mitigating pollution and carbon emissions. Specifically, shipping firms will adopt clean energy, while ports will establish shore power infrastructure to aid in emission reductions within the industry. This paper constructs a game theory model involving a port and two shipping companies to optimise the green investment under shipping alliance and hub-and-spoke collusion, and their impact on profits. The study analyses the strategic equilibrium in the context of green investment. The findings indicate that green investment can effectively enhance the profits of shipping companies across different cooperative models, but excessive investment may lead to increased costs, which in turn affects the final profit. Additionally, this paper identifies two critical regions, 'hub-and-spoke dominance zone' and 'shipping alliance dominance zone', and highlights that the relative advantages of hub-and-spoke collusion versus shipping alliances vary under specific green investment coefficients and the degree of substitutability between shipping companies. [Submitted: 10 September 2024; Accepted: 24 March 2025]