Abstract
There is growing global demand for seaweed as a sustainable alternative source of food, feed, bio-materials, chemicals, and energy. Unlike terrestrial crops, it does not require freshwater or nutrient inputs and can be cultivated globally. Its capacity for carbon sequestration positions it for climate mitigation and as a replacement for petrochemical-based materials. However, few proponents of seaweed as a climate change solution apply Life Cycle Assessment (LCA), despite its criticality for scientifically validating sustainability claims of emerging industries.
This systematic literature review identified context-specific environmental hotspots of diverse seaweed-based supply chains. Thematic analysis of 75 journal articles revealed a significant discrepancy between regions of production and those studied. Asia produces over 90% of global seaweed, yet ~70% of LCAs focus on European supply chains. Upstream production of farm infrastructure, was identified as a major contributor to climate impacts (20-70%). Emissions from boat fuel during farm operations also showed significant contribution to climate impacts (5-40%). Processing impacts were mainly driven by energy-intensive machinery and chemical inputs, while plastic waste recovery added to impacts through high energy demand. Despite these emissions, accounting for carbon fixation and co-products revealed significant emission offsets and net-negative impacts across multiple categories.
This suggests that, tropical, low-input farms using simple grow-out methods may deliver greater carbon benefits than intensive offshore temperate systems. However, the percentage contributions of materials, and energy use to climate impacts vary widely across studies. This highlights the limitations of transferring LCA findings between contexts and the need for a nuanced, supply chain specific understanding of environmental hotspots. These findings are discussed within a comprehensive LCA framework for Pacific Island seaweed supply chains, following ISO 14040/14044 guidelines, to identify hotspots and their drivers, guide policy, propose resource-efficient and circular farming designs and communicate the seaweed industry’s potential as a nature-based climate solution.