Our modern “traditional” agricultural system is not sustainable. This system is highly dependent on limited resources such as land, oil and water. It also has numerous negative impacts, including the depletion of resources leading to higher prices, pollutions leading to health risks, global warming, deforestation and biodiversity loss. These dependencies and consequences are combined with a growing and ever more affluent global population which requires greater amount of resources to support its growth and which increases the negative impacts on the environment. All indicates that our system is reaching its limits and that there is a need for new solutions. This research introduces the general context (problem and existing research) and explores an alternative, namely: Intensive Vertical Urban Agriculture (I.V.U.A.). This method seems to offer two particularly interesting promises beneficial for Sustainable Urban Development: the reduction of transportation, and the integration of food production in the urban nutrient and energy cycles. However, to achieve these potential benefits the technology (in a broad sense) has to meet several challenges and there is a need for further experimentation. This study explores challenges of I.V.U.A. and key factors enabling or hindering experimentation in this field. This investigation identified key barriers to further development of I.V.U.A. through the use of a case study. The Plantagon International ABis a unique project which will be built in 2013, in Linkoping, Sweden. It will be the first vertical greenhouse of a considerable scale in the world with a research and commercial aim. Barriers to I.V.U.A. were identified as: - Lack of awareness about the problems with our modern food supply, and hence missed opportunities for S.U.D. - Attitudes that are working against I.V.U.A. and competition for recognition with other forms of agriculture as alternative to the problem of food production - Lack of technical abilities, knowledge and skills in I.V.U.A. - Funding/supporting infrastructures (physical or informational) - Blockages that are the result of administrations and policies which are largely based around “traditional” agriculture. Finally, a set of recommendations was drawn from the interviews of the case study and the literature review, to help planners and decision-makers lift these barriers and enable experimenting. These four implications to consider and explore are: - Gaining understanding of the complexity of S.U.D.problems and the need for a wide range of solutions which include I.V.U.A.; - Including a greater amount of stakeholders, and considering contexts - Improving access to land but also to resources and infrastructures - Building support to enable I.V.U.A. to thrive on its own

Durch die Nutzung des fischfutterbedingten Nährstoffeintrags für die kombinierte Produktion von Fischen und Pflanzen können Aquaponiksysteme eine nachhaltige Erweiterung von Kreislaufanlagen der Aquakultur (RAS) darstellen. Herkömmliche Aquakulturfutter zielen jedoch auf Fischproduktion mit geringer Umweltbelastung ab und sind somit nicht für die Aquaponik optimiert. Daher weist RAS-Wasser häufig Mängel im Profil gelöster anorganischer Pflanzennährstoffe auf. So war es Ziel dieser Arbeit, die Auswirkungen unterschiedlicher Proteinquellen auf die Nährstoffdynamik in RAS durch Fütterungsversuche mit Afrikanischem Raubwels und Nil-Tilapia zu untersuchen, bei denen Wachstum, gelöste anorganische Nährstoffkonzentrationen im RAS-Wasser und die Ausscheidung von Nährstoffen über den Kot verfolgt wurden. Der Fokus lag auf nachhaltigen alternativen Proteinquellen zu marinem Fischmehl und terrestrischen Pflanzenproteinen: Larvenmehl der Schwarzen Soldatenfliege (BSFM), Welsschlachtabfallmehl (CM), Geflügelschlachtabfallmehl (PM) und Geflügelblutmehl (PBM). Experimentalfutter, die phosphorreiches PM und CM enthielten, förderten erhöhte Ausscheidung von löslichem reaktivem Phosphor, erzeugten die besten gelösten N:P-Verhältnisse im RAS-Wasser verglichen mit einer Hydroponik-Nährlösung und ermöglichten in Kombination mit PBM besseres Wachstum beim Wels als ein vergleichbares kommerzielles Futter. In Futtern basierend auf einer einzigen Proteinquelle führte PM bei Wels und insbesondere bei Tilapia zu ähnlichem Wachstum verglichen mit marinem Fischmehl, wohingegen BSFM und PBM bei beiden Arten Wachstumsleistung beeinträchtigte. Meta-Analysen aller Versuche legen nahe, dass höherer Phosphor-, Kalium- und Magnesiumgehalt im Futter erhöhte Ausscheidung dieser Elemente in gelöster Form bedingt, was sie zu Zielnährstoffen in Aquaponikfuttern macht, während die Optimierung des Protein zu Energie-Verhältnisses im Futter die gelösten N:P- und N:K-Verhältnisse im RAS-Wasser verbessern kann. / By using the nutrient input from fish feeds for the combined production of fish and plants, aquaponic systems can be a sustainable extension of recirculating aquaculture systems (RAS). However, conventional aquaculture feeds are optimized for fish production and reduced environmental impact rather than aquaponics. Hence, RAS water is often characterized by deficiencies regarding its dissolved inorganic plant nutrient profile. Therefore, this thesis aimed to explore the effect of purposeful dietary protein choice on nutrient dynamics in RAS through four systematic feeding trials involving African catfish and Nile tilapia in which growth performance, dissolved inorganic nutrient concentrations in RAS water and solid fecal nutrient excretion were tracked. Focus was on sustainable alternative protein sources to marine fish meal and terrestrial plant proteins: black soldier fly larvae meal (BSFM), catfish by-product meal (CM), poultry by-product meal (PM) and poultry blood meal (PBM). Experimental diets including phosphorus-rich PM and CM supported increased excretion of soluble reactive phosphorus, produced the most favorable dissolved N:P ratios in RAS water when compared to a renowned hydroponic nutrient solution, and, combined with PBM, enabled better growth performance in African catfish than a comparable commercial diet. In single protein source diets, PM produced similar growth performance in African catfish and particularly Nile tilapia versus marine fish meal, whereas BSFM and PBM impaired growth performance in both species. Meta-analyses covering all trials suggest that higher dietary phosphorus, potassium and magnesium content leads to their increased excretion in dissolved form, making them target nutrients for aquaponic feed formulation, while the optimization of the dietary protein to energy ratio can further improve dissolved N:P and N:K ratios in RAS water.