Seaweed is seen as one of the most promising aquaculture crops of the future, yielding products ranging from human food, animal feed, cosmetics, bioplastics and fuel. The cultivation of seaweed in increasingly busy coastal waters poses many challenges. In this project five applied research institutes, ECN, TNO, WUR-DLO, Marin and Deltares, worked closely together to assess a seaweed value chain, covering issues relating to engineering for offshore cultivation, growth of seaweed and carrying capacity of locations, extraction of carbohydrates and proteins as well as the economic costs and benefits of production. This required a multi-disciplinary approach to tackle various critical hurdles in developing an economically viable seaweed industry. The physical boundary conditions of selected North Sea locations (wave height and currents) were input for computational fluid dynamic calculations of the most appropriate seaweed support construction. Model outcomes were compared to physical tests on scale models carried out in a large wave tank. These results were used to assess the ability of cultivation infrastructure to withstand regularly occurring storm conditions at sea. This has indicated that further technical developments are required to cope with the dynamics and the expected current / wave loads at most offshore locations. In laboratory tests the growth rates of seaweed species, as function of water quality and other environmental parameters, were determined. These parameters were used to set up a numerical model to calculate potential yields of seaweed production at different locations in the North Sea. Furthermore the effects of different harvest frequency on the production of seaweed were assessed. Increasing harvest frequency appears to have little effect on yield, allowing cost reduction. However, we did find changes in the ratio of carbohydrates to proteins in sea lettuce, Ulva sp., in response to physical conditions in the cultivation set-up. This means that the ultimate product for which seaweed is cultivated can dictate design and positioning of installations. Pure mannitol, both a building block and a food ingredient, was successfully isolated from sugar Kelp (Saccharina latissima) along with alginic acid. In vitro research indicated that the remaining fraction is valuable as feed component for monogastric animals (e.g. pigs). The consortium, based on its know-how in food and feed, and chemical building blocks, selected species specific valorisation strategies for Ulva and Saccharina. These valorisation strategies integrated this know-how by encompassing all these applications in one cascading value chain. Finally we compared the total estimated costs for production of seaweed with the economic revenue of the seaweed products. As production costs are strongly scale dependent, we assessed the effects of a realistic level of up-scaling of production. Even in the up-scaled plant, the costs of production are still around six times higher than the benefits. This number suggests that developing a seaweed value chain is within reach. Investments in optimisation will improve yields of biomass and selective breeding will result in higher production of extracted substances. Also on the costs side, technological developments will lead to lower costs. Cost reductions in the biobased economy of a factor ten have been achieved with sustained research and long term funding thereof. Next to this we do realize that prices for protein are rising and that the prices for oil are very inpredictable. The outcome of this project warrants optimism about the future of seaweed. The Dutch maritime industry together with the Dutch agriculture sector can develop a large-scale economically viable seaweed cultivation sector. With this new form of aquaculture The Netherlands can contribute to important transitions towards sustainable energy, sustainable proteins and a bio-based society. Last but not least, this project has forged a solid base for productive and very enjoyable future cooperation.