Evaluating Kelp Feedstock for Alginate-Based Materials: Physicochemical Characterization of Sodium Alginate and Aquaculture Considerations

Cultivated kelps are a scalable marine feedstock for renewable polymers, but regional aquaculture supply chains lack engineering benchmarks for the alginate yield and quality. Here, we apply a lower-hazard citrate-based process to quantify bioplastics-relevant alginate metrics across cultivated northeast Pacific kelps from commercial farms in British Columbia (Canada) and Alaska (USA). Ten blade biomass samples spanning five species were screened. Two samples failed to undergo phase separation after extraction and centrifugation, indicating biomass-dependent extractability as a process risk. For the remaining eight feedstocks, yields ranged from 11.95 to 26.11% (dry weight). Weight-average molar mass (Mw) ranged from 36.6 to 623 kDa, with 7/8 samples exceeding 400 kDa. Uronic acid composition spanned M/G = 0.14–1.38, with variation in G/M block compositions (block fractions and block lengths) relevant to cross-linking. Multivariate analysis resolved dominant gradients linking the uronic acid composition and molar mass distributions. The studied kelps were evaluated in the context of known seasonal, tissue-specific, and environment-driven effects and climate-related stressors that can alter productivity. Collectively, these results provide a regional benchmark for lower hazard alginate production from cultivated kelps and an engineering screening framework to support consistent feedstock selection for scalable manufacturing of alginate-based films, coatings, and related bio-based materials.