A recent study related to aquaponics has shown that hydroponic lettuce grown in aquaculturederived supplemented water grew significantly better than lettuce grown in a conventional hydroponic system. The principal objective of this study was to verify this finding in a larger setup. Even though the aquaculture water that was added to the aquaculture-based hydroponic system contained relatively high amounts of sodium, we were still able to observe an enhanced growth performance of the lettuce in that system compared to the lettuce grown in the conventional hydroponic nutrient solution. The lettuce final fresh weight was 7.9%, and its final dry weight even 33.2% higher than the one of the hydroponic control.
Aquaponics -the co-production of fish and plant products -is gaining interest both by entrepreneurs and researchers. This article evaluates both the technical setup as well as the economic potential of aquaponic systems and is aimed at identifying relevant knowledge questions for further improvements. Using system requirements for hydroponic systems and aquaculture, the aquaponic system was compared to a typical Dutch rockwool system. Aquaponics was found to be an improvement on current practices when using Deep Flow Technique (cultivation in a flowing thick water layer), resulting in better nutrient availability for the plants and re-use of nitrate. However, the technical challenges of the direct linkage between the two production systems in terms of needed technology and disease management was found to make the total system suboptimal when compared to conventional practices. The technological advantages of efficiency in use of land and energy and re-use of nutrients were found to be a marginal cost reduction of 1.2%. The article concludes that the added value of aquaponics can be found in the total business concept of producing in an urban environment with direct relationship with consumers. Further improvement of aquaponics can be found in improved disease management of the system -through management or improved design.
INTRODUCTIONUrban farming creates value through the production of small scale, sustainable and local produce, often in direct interaction with the consumer. Sustainability is achieved through the re-use of waste streams of water, nutrients and energy by combining different (agricultural) activities. A sustainable, applicable and small scale system for such re-use is the combination of fish production in Recirculating Aquaculture Systems (RAS) and horticulture -so called Aquaponics. For professional aquaponics to take off in Europe the production systems need to have added value, be robust and easy to use. Research has focused on plant aspects (nutrients and quality; Pantanella et al., 2012) and fish production (densities, diseases) and technology. But less on the business rationale and design structure. However, designing for such complex systems requires a systematic approach, where an analysis of functions and quantified requirements is used to select and improve on the technical lay-out. Functions and requirements are based on insights and needs from both researchers and experts as well as users and stakeholders -in the case of urban farming city planners and the general public. However, such analysis has only recently been developed for both hydroponic systems and aquaculture, but not for the combination of the two nor the application in an urban setting. This paper describes the system requirements for both aquaculture as well as horticulture that would apply for aquaponics in an urban environment.
Soilless cultivation suggests a closed system of water flows, of which (drip) irrigation, evaporation andin more high-tech systemscondensation water are the main flows. However, in practice growers discharge water during the process of filter cleaning and actively discharge water due to high levels of sodium or contamination with chemical or biological components. On average in the Dutch greenhouse situation 2-5% of the annual irrigated water is discharged, spread over the year. These discharges lead to pollution of surface water with nutrients as well as (residues of) plant protection products (PPPs). This awareness led in 2008 to the start of a working group that aimed to develop an risk evaluation tool for pesticide authorisation in Europe. The evaluation tool consists of a modelled approach for determining expected concentrations in surface water based on a reference scenario per crop i.e. a description of an actual situation including the technical layout of the glasshouse, the climatological year and the receiving ditch.
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