A Critical Review of Macroalgae Exploitation Pathways Implemented under the Scope of Life Cycle Assessment

Under the umbrella of Blue Economy, research interest is focused on harnessing the potential of macroalgae biomass, known as third-generation feedstock, from which multiple products can be extracted. As many of these exploitation pathways are not yet feasible for large-scale implementation, a significant number of publications adopt LCA as a tool to assess the sustainability of the proposed value chains. However, the complexity of such systems and the broad spectrum of alternative routes render a vague perspective on the sustainability of such applications. This study provides a critical review of previous research employing LCA to evaluate different pathways of macroalgae utilization. Ethanol, energy (biogas), and nutrition products were found to be among the most studied outputs in the past ten years from an LCA perspective. Different pathways leading to these products were mapped and analyzed, documenting their critical points and proposing measures to mitigate their environmental impact. A thorough SWOT analysis compiles for the first time the scattered information available in the literature, giving insights into the current state of macroalgae use and motives for further research. Insufficient or outdated inventory data for LCA, coupled with technical and technological struggles, were found to be the main barriers to large-scale applications.