MacroAlgaeBiorefinery (MAB3) may functions as production platform and raw material supplier for future sustainable production chains of biofuels and high value chemicals. Biofuels are interesting energy source but challenges in terms of the composition of the biomass and resulting energy efficiencies has to be compensated for to make the biofuel prices competitive in replacing fossil fuel. Since it is difficult to increase the yield of the single biorefinery, the overall system productivity can be improved integrating different sub-systems. In this study, macroalgae cultivation in Denmark is integrated with a biogas biorefinery, a bioethanol biorefinery and a fish feed industry. The modeled system is able to adapt itself to different amount and quality of feedstock and to maximize valuable outputs (e.g. bio-fuels and chemical). Macroalgae are harvested and utilized as feedstock in bioethanol biorefinery or biogas biorefinery. If the residues from bioethanol biorefinery are suitable they can be utilized as feedstock in the biogas biorefinery. Also biogas residues from can be utilized as source for protein extraction to produce fish feed. Not only products but also services are provided: macroalgae growth in open seas absorbs considerable amount of nitrogen, phosphorus (limiting water eutrophication) and heavy metals. The modeled system aims to valorize all the biomass components produced in the biorefinery processes and internalize all positive and negative impacts of the services provided. Different aspects of sustainability are discussed from a foreground and background point of view. This study is a part of a four year research project called “MacroAlgaeBiorefinery – sustainable production of 3G bioenergy carriers and high value aquatic fish feed from macroalgae” financed by the Danish Strategical Research Council.