Marine biomass for a circular blue-green bioeconomy?: A life cycle perspective on closing nitrogen and phosphorus land-marine loops

A blue-green bioeconomy revolution is underway in Europe, with particular attention being paid to the development of new or underutilized marine biomass resources. The wild harvest and mariculture of low-trophic non-fed species of marine biomass may be contributing to circular economies, the mitigation of environmental problems such as eutrophication and climate change through the uptake of nutrients and carbon, while also recovering finite phosphorus from marine coastal environments, thus contributing to food security. The present study provides a cradle-to-gate life cycle perspective on seven established or innovative/emerging marine biomass utilization cases in Sweden: mariculture of sugar kelp, blue mussels, and ascidians and the harvest of invasive Pacific oysters along the Skagerrak coast, the mariculture of blue mussels in the Baltic sea, the harvest of common reed in the Stockholm archipelago, and the harvest of beach-cast seaweed in Gotland. Results showed that the mariculture cases were found to contribute to eutrophication and climate impact mitigation (at gate). All cases were found to contribute to closing the loop on phosphorus by enabling recovery from marine or coastal environments, bridging marine-land flows, all while performing well from an environmental perspective with a relatively low cumulative energy demand and low carbon and nutrient footprints. This highlights the potential of low-trophic biomass to contribute to phosphorus security in the future, and demonstrates the value of industrial ecology tools such as LCA in support of this imminent Decade of Ocean Science for Sustainable Development.