Exploring multi-use platforms: A literature review of marine, multifunctional, modular, and mobile applications (M4s)

Multi-purpose offshore infrastructure, integrated with various user functions within the same space, is increasingly hailed as a way to address issues arising from multiple demands placed on coasts and seas. In this paper, we review how recent literature addresses the conditions enabling marine-multifunctional-modular-mobile (M4) solutions' contribution to a sustainable transition in the provision of critical services on islands and along coastlines. We are particularly interested in understanding the synergies and the most common themes surrounding their deployment as analyzed in previous research. We find that mobility and modularity have been less researched compared to multifunctionality of marine applications, despite the benefits these could have in decreasing operation costs and improving resiliency in coastal environments. With multifunctionality, wave-wind is the most common combination of services, followed by wind-aquaculture and wave-aquaculture. However, so far, the literature has mostly focused on European marine applications of this kind, so there need to be explorations of other methodologies that capture other regions, as well as explorations of nonscientific literature. We recommend more detailed evaluations of impacts, benefits, drawbacks, and institutional frameworks needed for realizing mobile and modular multifunctional applications in marine environments.