25 research outputs found

    Profitability of multi‐loop aquaponics: Year‐long production data, economic scenarios and a comprehensive model case

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    This case study examined the productivity and economic performance of a double recirculation aquaponic system in Germany with a total interior area of about 540 m2. Calculations were carried out as an ex post analysis based on one-year production data. The initial situation was not profitable; therefore, two scenarios were developed, which envisaged a significantly improved productivity of the fish as well as of the plant unit and a more than threefold enlargement of the greenhouse to make maximum use of the fish effluent. An ex ante analysis was performed and showed that the second scenario was profitable with a payback period of about 12 years. On the basis of this scenario, a simple but comprehensive model case with the complete set of economic key indicators showed that aquaponics is feasible if it exploits its potential, regardless of the high initial investment costs. The model case would cover an overall space of about 2,000 m2, which is suitable for professional aquaponics in urban and peri-urban areas with their limited space availability. Furthermore, multi-loop aquaponics with its inherent circles fits into the circular city concept and implements resource-efficient and sustainable food production into the urban fabric, which is important with increasing urbanization.Belmont Forum and the European Commission via CITYFOODINAPR

    Overcoming major bottlenecks in aquaponics - A practical approach

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    Aquaponik-Systeme stellen an sich einen sehr nachhaltigen, innovativen Ansatz fĂŒr die zukĂŒnftige Lebensmittelproduktion dar. Allerdings hat sich bis heute noch kein flĂ€chendeckender, ökonomischer Erfolg eingestellt und wesentliche systemische EngpĂ€sse wurden wissenschaftlich nicht untersucht. Daher waren die Hauptziele dieser Dissertation, (I) sichere Nitratkonzentrationen in geschlossenen Kreislaufanlagen (RAS) zu ermitteln, unter denen optimales Wachstum und Tierwohl produzierter Tilapien gewĂ€hrleistet ist, (II) die Evaluierung des besten Designkonzeptes fĂŒr die optimale, kombinierte Produktion von Fisch und Pflanzen und (III) die allgemeine Effizienz bei der Wiederverwertung des Abwassers und der NĂ€hrstoffe aus dem Schlamm der mechanischen Filtrationseinheiten in aquaponischen Systemen zu erhöhen. Das Wachstum und die Gesundheit von Niltilapien (Oreochromis niloticus) wird durch hohe Nitratkonzentrationen (> 500 mgL-1 NO3--N) negativ beeinflusst. Nitratkonzentrationen, die fĂŒr die Produktion von Pflanzen in aquaponischen Systemen (~ 200 mgL-1 NO3--N) optimal sind, haben keinen negativen Einfluss auf das Tierwohl. Entkoppelte Kreislaufsysteme sind bei einer professionellen aquaponischen Produktion von Fisch und Pflanzen zu bevorzugen. Bei der Produktion von Fisch ergab sich keinerlei Unterschied, jedoch wurde eine deutlich gesteigerte Tomatenproduktion von 36 % in entkoppelten Kreislaufsystemen erreicht. Die aerobe Mineralisation zeigte das beste RĂŒckgewinnungpotential von Phosphat und nur geringe Nitratverluste und kann in der Gesamtheit eine deutliche Effizienzsteigerung aquaponischer Systeme zur Folge haben. Die Ergebnisse dieser Dissertation zeigen die EngpĂ€sse in der Aquaponik klar auf und liefern gleichzeitig LösungsansĂ€tze, wie diese Hindernisse in Bezug auf das NĂ€hrstoff- und Ressourcenmanagement ĂŒberwunden werden können. Dadurch kann die Nachhaltigkeit dieser Anlagen gesteigert und die Wahrscheinlichkeit des wirtschaftlichen Erfolges erhöht werden.Aquaponics is the combination of fish production in aquaculture and hydroponic (soilless) production of crop plants. Despite of representing already a sustainable, innovative approach for future food production systems, aquaponics are still missing economic success and up to date major bottlenecks were not scientifically addressed. Therefore the main aims of this thesis were (I) to identify safe nitrate concentrations under which best growth and health status of tilapia can be guaranteed in aquaponics, (II) to evaluate the best design concept for an optimal combined production of fish and plants and (III) to increase the overall system efficiency by recycling waste water and nutrients deposited in the sludge of the mechanical filtration unit. The growth and health status of Nile tilapia (Oreochromis niloticus) is negatively affected by high nitrate concentrations (> 500 mgL-1 NO3--N) commonly reported for RAS. Nevertheless, optimal nitrate concentrations for plant production in aquaponic systems (~ 200 mgL-1 NO3--N) are not affecting fish welfare and allow for an efficient production of Nile tilapia. Decoupled aquaponics proved to be favorable for professional aquaponic production, whereas coupled systems were suboptimal for a combined production of fish and plants. There were no differences in fish production, whereas tomato production within the decoupled system was considerably increased by 36 %. Aerobic mineralization of phosphate revealed best phosphate recovery with only minor losses of nitrate. Recycling of water sludge mixture from clarifiers resulted in a substantial phosphor recovery, an increase in potassium and additional water savings. Conclusively, the results of this holistic thesis clearly revealed the bottlenecks in aquaponic technology and provided guidance in overcoming mayor obstacles in terms of optimized nutrient and resource management to increase the overall sustainability of these systems and improve production efficiency and profitability

    The effect of compulsory schooling on vaccination against COVID and Influenza

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    We study the effect of education on vaccination against COVID-19 and influenza in Germany and Europe. Our identification strategy makes use of changes in compulsory schooling laws and allows to estimate local average treatment effects for individuals between 59 and 91 years of age. We find no significant effect of an additional year of schooling on vaccination status in Germany. Pooling data from Europe, we conclude that schooling increases the likelihood to vaccinate against COVID by an economically negligible effect of one percentage point (zero for influenza). However, we find indications that additional schooling increases fear of side effects from COVID vaccination.Wir untersuchen die Auswirkungen von Bildung auf die Impfung gegen COVID und Influenza in Deutschland und Europa. Unsere Identifikationsstrategie nutzt Änderungen in Pflichtschulzeiten aus und ermöglicht die SchĂ€tzung lokaler Treatmenteffekte fĂŒr Personen im Alter zwischen 59 und 91 Jahren. Wir finden keinen signifikanten Effekt eines zusĂ€tzlichen Jahres an Schulbildung auf den Impfstatus in Deutschland. FĂŒr die europĂ€ischen Daten, kommen wird zu dem Schluss, dass die Schulbildung die Wahrscheinlichkeit erhöht, sich gegen COVID zu impfen, allerdings nur um einen vernachlĂ€ssigbaren Effekt von einem Prozentpunkt (Null fĂŒr Grippe). Wir finden jedoch Hinweise darauf, dass zusĂ€tzliche Schulbildung die Angst vor Nebenwirkungen der COVID-Impfung erhöht

    Decoupled systems on trial: Eliminating bottlenecks to improve aquaponic processes

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    In classical aquaponics (coupled aquaponic systems, 1-loop systems) the production of fish in recirculating aquaculture systems (RAS) and plants in hydroponics are combined in a single loop, entailing systemic compromises on the optimal production parameters (e.g. pH). Recently presented decoupled aquaponics (2-loop systems) have been awarded for eliminating major bottlenecks. In a pilot study, production in an innovative decoupled aquaponic system was compared with a coupled system and, as a control, a conventional RAS, assessing growth parameters of fish (FCR, SGR) and plants over an experimental period of 5 months. Soluble nutrients (NO3--N, NO2--N, NH4+-N, PO43-, K+, Ca2+, Mg2+, SO42-, Cl2- and Fe2+), elemental composition of plants, fish and sludge (N, P, K, Ca, Mg, Na, C), abiotic factors (temperature, pH, oxygen, and conductivity), fertilizer and water consumption were determined. Fruit yield was 36% higher in decoupled aquaponics and pH and fertilizer management was more effective, whereas fish production was comparable in both systems. The results of this pilot study clearly illustrate the main advantages of decoupled, two-loop aquaponics and demonstrate how bottlenecks commonly encountered in coupled aquaponics can be managed to promote application in aquaculture

    Chronic exposure to nitrate significantly reduces growth and affects the health status of juvenile Nile tilapia (Oreochromis niloticus L.) in recirculating aquaculture systems

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    Studies on chronic or acute toxicity of nitrogen species on fish in recirculating aquaculture systems (RAS) usually focused on adverse effects of total ammonia nitrogen (TAN: sum of NH3 + NH4+) and nitrite (urn:x-wiley:1355557X:media:are13174:are13174-math-0001), while underestimating the potential effects of high nitrate accumulation on growth and health status of fish. In our study, Nile tilapia (Oreochromis niloticus) were exposed to five different nitrate concentrations (0, 10, 100, 500 and 1000 mg L−1 urn:x-wiley:1355557X:media:are13174:are13174-math-0002‐N) over 30 days. Growth parameters (feed conversion ratio (FCR), specific growth rate (SGR), hepatosomatic index (HSI)), blood samples (concentrations of haemoglobin, methaemoglobin, plasma urn:x-wiley:1355557X:media:are13174:are13174-math-0003/urn:x-wiley:1355557X:media:are13174:are13174-math-0004) and the histology of the gills were studied to evaluate growth and health status of the fish. At the highest nitrate concentration, the fish showed significantly reduced growth and impaired health status (SGR, FCR, plasma urn:x-wiley:1355557X:media:are13174:are13174-math-0005/urn:x-wiley:1355557X:media:are13174:are13174-math-0006, haemoglobin and methaemoglobin concentration), demonstrating that too high nitrate concentrations can negatively influence tilapia production in RAS. Here, we recommend not exceeding concentrations of 500 mg L−1 urn:x-wiley:1355557X:media:are13174:are13174-math-0007‐N in juvenile tilapia culture to ensure an optimal health and growth status of the fish, as below that concentration no effects on the tilapia have been observed

    Estimated fate of nitrogen in RAS and potential nitrate supply to the crop plants (tomatoes) in aquaponics.

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    <p>Estimated fate of nitrogen in RAS and potential nitrate supply to the crop plants (tomatoes) in aquaponics.</p

    Potential of aquacultural sludge treatment for aquaponics: evaluation of nutrient mobilization under aerobic and anaerobic conditions

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    In recirculating aquaculture systems (RAS), mechanical removal of suspended solids by clarifiers or drum filters provides an organic mixture rich in nutrients. Still, in most traditional RAS, this sludge is discharged directly or following dewatering. Here, the potential recycling of nutrients from sludge is assessed, comparing aerobic and anaerobic mobilization of nutrients experimentally, ultimately aiming at an application in aquaponic systems. Nutrient mobilization processes were studied, monitoring soluble nutrients photometrically in the treatment tanks (NO3--N, NO2--N, total ammonia nitrogen, soluble reactive phosphorus [SRP], K+, Mg2+ and Fe2+), the nutrient composition of the sludge (total phosphorus, Fe, Mn, Al, S, Mg, Ca) by inductively coupled plasma optical emission spectrometry, as well as C:N ratio, total solids (TS) and total suspended solids (TSS). Aerobic treatment (aerated, AT) resulted in a 3.2-fold increase in mean (±SD) SRP from 9.4 (± 0.7) to 29.7 (± 2.1) mg l-1, most likely owing to a decrease in pH. In contrast, in the anaerobic treatment (unaerated, UT), SRP remained unchanged between 9.4 (± 0.7) and 9.3 (± 0.4) mg l-1. Both treatments resulted in increased K+ concentrations from 28.1 (± 1.5) to 36.8 (± 2.3) mg l-1 in AT and to 32.2 (± 2.3) mg l-1 in UT. AT revealed best mobilization of P and K+ without major losses of NO3--N. Thus, aerobic treatment of water-sludge mixture has a high potential for significant improvements of nutrient recycling in aquaponics

    Schematic illustration of classical (coupled) and decoupled aquaponics.

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    <p>(a): Classical aquaponic system consisting of a RAS (blue: rearing tanks, clarifier and biofilter) directly connected to the hydroponic unit (green: NFT-trays). Water is constantly circulated from RAS to hydroponic and back to RAS. (b): Decoupled aquaponic system consisting of a RAS connected to the hydroponic unit (with additional reservoir) via one-way-valve. Water is separately recirculated in each system and water is just supplied on-demand from RAS to the hydroponic unit, but not back.</p

    Rearing conditions (dissolved oxygen (O<sub>2</sub>), pH, temperature and conductivity) in the fish (RAS) and hydroponic (Hydro) units of a conventional aquaculture reference (A), a coupled (C) and a decoupled (D) aquaponic system, assessed over the experimental period of 154 days (07.04–07.09.2015).

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    <p>Rearing conditions (dissolved oxygen (O<sub>2</sub>), pH, temperature and conductivity) in the fish (RAS) and hydroponic (Hydro) units of a conventional aquaculture reference (A), a coupled (C) and a decoupled (D) aquaponic system, assessed over the experimental period of 154 days (07.04–07.09.2015).</p

    Plant growth (fresh weight of fruit, leave, root, stem), fertilizer supplementation and water consumption in the hydroponic unit of the coupled (Hydro C) and decoupled (Hydro D) aquaponic system after 30, 63, 94, 122 and 154 d.

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    <p>Water consumption is only indicated for Hydro D, since Hydro C is coupled to the RAS C and is only given for the entire system (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0183056#pone.0183056.t002" target="_blank">Table 2</a>). Roots and stems were only sampled at the end of the experiments and fresh weight therefore not determined (n.d.) earlier.</p
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