Product environmental footprint assessment of cultivated sugar kelp: A step toward Product Environmental Footprint category rules for cultivated seaweed

Harmonised environmental assessment is essential for integrating algae and seaweed products into EU sustainability policies, including the Green Deal and the forthcoming Green Claims framework. Yet, no Product Environmental Footprint Category Rules (PEFCR) currently exist for cultivated macroalgae, creating a major methodological gap for a fast-growing biomass sector. This study applies a PEF aligned life cycle assessment framework to cultivated sugar kelp ( Saccharina latissima ) produced in Denmark, using the EF 3.1 impact assessment method, and identifies methodological focus points for future seaweed PEFCR development. The cradle-to-gate system covered hatchery operations, deployment, cultivation, maintenance, and harvesting, ending with 1 kg fresh harvested sugar kelp delivered to the shoreline landing point. Primary inventory data were obtained from DanskTANG and complemented with literature and Environmental Footprint background datasets. Biogenic carbon uptake and nitrogen and phosphorus uptake were reported as additional environmental information, but no credits were assigned in the core PEF results. Contribution analysis identified hatchery electricity, polymer based cultivation materials, and marine fuel use as the main environmental hotspots. Yield variability strongly influenced impacts per kilogram fresh biomass, highlighting the need for transparent yield documentation and sensitivity testing. The results show that a PEF-aligned assessment can be implemented for cultivated sugar kelp and provides candidate rule relevant elements for future PEFCR development, including a fresh biomass reference flow, dry matter and composition reporting, biomass loss accounting, hotspot based primary data requirements, conservative carbon and nutrient reporting, and separate modelling of product specific downstream processing.