Brown algae, particularly L. hyperborea, represent a largely untapped renewable resource in Europe, present in huge volumes along the coastlines of Norway (approximately 60% of global biomass), Sweden, Denmark, Ireland, Iceland, and France. L. hyperborea contains alginate, cellulose, functional polysaccharides like fucoidan and laminarin, phlorotannin’s (polyphenols), as well as protein, vitamins, and minerals, all ingredients in demand in Europe’s biobased value chains. However, current harvesting techniques, particularly widespread use of formaldehyde, is limiting the huge valorisation potential of this promising renewable feedstock. Once brown kelp is exposed to air, chemical and enzymatic reactions quickly begin to rot the harvest. Currently, harvesters mitigate this by treating brown kelp with formaldehyde during and after harvesting. However, formaldehyde causes undesirable browning of some compounds and is toxic, so must be removed through expensive, energy and water intensive washing prior to further processing. This makes valorisation of all but the most valuable alginate fraction (~15% of L. hyperborea biomass) uneconomic; consequently, about 85% of the residual brown kelp biomass is flushed back into the sea unused. PROTEUS addresses the challenge of maximising valorisation of Europe’s L. hyperborea biomass through the optimisation of ALGINOR’s (coordinator) and HYPOMAR’s formaldehyde-free harvesting and extraction technologies and approaches. This will enable large-scale valorisation of Europe’s considerable L. hyperborea resource and conversion of 100% of the biomass into ingredients that will be tested in validated for use by ESSITY (personal-care), OLMIX (feed), VAESS (food), and BORREGAARD (industrial applications) as drop-in replacements for synthetic materials in sustainable biobased product lines.