Opportunities and Challenges of Multi-Loop Aquaponic Systems

Abstract

v Preface Which of us is not familiar with this situation during the student time: on a Wednesday night, one wants to go out to grab a beer ("just one Duveltje") with friends. Until the end of the night (and several beers later) one was trapped in several discussions about religion, politics, and one's field of study. I have to admit, that I have been involved in plenty of such discussions, which also stems from the fact that I am a very discussion-friendly and curious person. However, I caught myself often saying the same sentence "well, the idea is great, but it actually does not really work as it should" with respect to two topics: Aquaponics and Communism. This might appear to be a somewhat far-fetched statement, however, for those who have neither read Marx nor followed the development of aquaponics the last 30 years: in a nutshell it can be stated that both of these ideas follow bottom-up (i.e. local and circular) approaches (i.e. for small farmers and individuals).Additionally to the above, I honestly believe that in times of the financial crisis -in which multinational corporations such as [think of big corporations that produce GMO seeds that are immune to their pesticides] increase their quasi-monopoly positions on the global food market -a paradigm shift back to human-centred and sustainable agricultural development is required to ensure both (1) healthy (i.e. pesticide free) diets and (2) food independence. In contrast, organic, fair trade, and GMO-free food have recently gained rapidly increasing popularity. Consumers want transparent and extensive information about the origin and manufacture of the foodstuffs they buy. The development of agriculture and how to use (finite) resources efficiently will be crucial with respect to the global development and the future of the earth in general. Right now, we are at a crossroads in our history that will determine whether either the people or the corporations will be empowered. I intended to provocatively illustrate this new class conflict on the book cover with the objective to polarize and thus energize the readers themselves to make thoughts and reflections.So far, I have dedicated over 4 years of my life to study and improve aquaponic systems in the hope that one day their production efficiency will be able to compete with state-of-theart hydroponic food production systems, while improving circularity. In this thesis, I will try to demonstrate why aquaponics does not face the same pitfalls as communism, while sharing the empowering people-minded and bottom-up qualities that are required in the 21st century.

A Comparison of Plant Growth Rates between an NFT Hydroponic System and an NFT Aquaponic System

“…The studies of Delaide et al [13] and Goddek and Vermuelen [26] were, at least in part, predicated on the fundamental notion that hydroponic standards of nutrient strength and mixture represent the "ideal" situation for water-based, terrestrial plant culture, and that, therefore, these hydroponic standards must be adhered to for ultimate aquaponic method optimisation for maximising plant growth and production. However, the nutrient strengths and mixture standards (often represented by conductivity as a measure) applied by the standard hydroponic industry were developed in a different context than aquaponics; most notably, hydroponics is a sterile (and indeed actively sterilized) aquatic environment [14,30], whereas aquaponics mostly utilises, and depends on, an aquatically unsterile environment with an associated dense and diverse microbiological community present [30,33]. Microbial assistance to nutrient uptake by terrestrial plants is a well-known assistive pathway that improves the overall plant growth rates in soil environments.…”

“…Because hydroponic systems are sterile, they often require relatively high nutrient concentrations in order to achieve advanced growth rates [14]. Aquaponic systems contain a diverse and dense community of microbial flora [33], often with similarities to those found in soil-based systems [30]. If it is accepted that this microbial community assists plant nutrient access and uptake in aquaponic systems [33], and it is noted that aquaponic systems contain lower percentages of ionized or "charged" nutrients (the only nutrients that will register using conductivity as a measure) [30], then it would be reasonable to surmise that aquaponic systems may be able to operate at lower nutrient concentrations (measured as conductivity) than standard hydroponic systems, and be able to achieve similar plant growth rates.…”

“…Aquaponic systems contain a diverse and dense community of microbial flora [33], often with similarities to those found in soil-based systems [30]. If it is accepted that this microbial community assists plant nutrient access and uptake in aquaponic systems [33], and it is noted that aquaponic systems contain lower percentages of ionized or "charged" nutrients (the only nutrients that will register using conductivity as a measure) [30], then it would be reasonable to surmise that aquaponic systems may be able to operate at lower nutrient concentrations (measured as conductivity) than standard hydroponic systems, and be able to achieve similar plant growth rates. The current study supports this hypothesis, because the aquaponic system operated at conductivity levels well below those of the hydroponic system (Figure 4), yet the aquaponic system consistently produced plant growth rates equal to, and often better than, the hydroponic system to which it was directly compared.…”

Comparisons between Aquaponic and Conventional Hydroponic Crop Yields: A Meta-Analysis

“…More studies that compare AP and cHP crop yields using decoupled systems would allow for a comprehensive conclusion on decoupled versus recirculating systems. However, although the type of coupling is important for adjustment of growth conditions [54,55], coupling type alone cannot lead to improved crop yields if the same growth conditions are achieved for both system types. That is, in a decoupled system, if growth conditions, such as pH and plant nutrients, are not adjusted, crop yield cannot be improved.…”

Economically viable aquaponics? Identifying the gap between potential and current uncertainties

“…) and designing multiloop systems that involve separating hydroponic units from the recirculating aquaculture system unit (Kloas et al . ; Goddek ). However, the recent rise in the number of publications on aquaponics has not contributed equally to the different aspects so urgently required by policy makers to support the aquaponic industry, as described in the following section.…”