Vol. 7, Issue 11, Part A (2025)

The shift towards a bio-based economy requires the search for sustainable and renewable feedstocks alternative to the finite fossil resources. Seaweeds or marine macroalgae have become an attractive 3rd generation biomass. Unlike other food crops, seaweeds can grow on arable lands that are marginal for the production of food and use brackish/saltwater as a media and thus grown without competition to agriculture practices. Seaweed are endowed with higher productivity compared to terrestrial plants including carbon sequestration. This paper presents an in-depth overview of the current status of seaweed biorefineries featuring possible pathways focusing on various fractions, used for several different end-uses such as biofuels, biochemicals and biomaterials. The paper reviews the state-of-art of seaweed growth, composition and principal transformation pathways (biochemical- -anaerobic digestion, fermentation-, and thermochemical- -pyrolysis, hydrothermal liquefaction-) in a combined approach. It evaluates each pathway with respect to both the opportunities and challenges which it may pose - ranging from feedstock availability/variability, processing intensity and economics to scalability. Additionally, this review emphasizes the significance of integrated, multi-product biorefining approaches for optimal biomass valorization and improved sustainability in the context of a seaweed-based bioeconomy. Research gaps and future perspectives needed to overcome the existing barriers and enable seaweeds to be a cornerstone of our sustainable industrial future are also discussed in this article.