Challenges of Sustainable and Commercial Aquaponics

Simon Goddek‘s and Boris Delaide‘s publication in the peer review journal ‘Sustainability’ summarizes the challenges of “aquaponics”, that is combining fish production (aquaculture) and out-of-ground crop production (hydroponics), in particular nutrient recycling advantages and knowledge gaps concerning nutrient forms and flows. Hydroponic systems allow precision controlled dosage of both water and nutrients (macronutrients, in particular N, P and K, and micronutrients) to crops, as a function of their growth and needs. This is more difficult in aquaponics, where the nutrient supply is a function of the fish production. Nutrients and micro-nutrients therefore should be monitored and supplemented where necessary for plant needs.

In particular, the form of the nutrients in aquaponics is complex. Nitrogen and phosphorus, particularly, are present in a range of organic and inorganic forms, which may be more or less available for plants. The authors’ assessment of literature suggests that data on macro- and micro-nutrients in aquaponics is currently inadequate, and that aquaponics concentrations of nutrients are often below what is considered the optimal level in hydroponics. However, nutrient data from aquaponics and hydroponics are largely non-comparable, because nutrients are in different forms, again indicating that further investigation and data collection are needed.

 

One of the most striking findings of this study is the need of further research in the domain of decoupled aquaponic systems (DAPS) that allow enhanced nutrient levels for the hydroponic part in commercial aquaponics systems. This nutrient accumulation can be achieved by integrated remineralisation solutions. The importance of its need is underpinned by the Phosphorous (P) example. Phosphorus is identified as “deserving specific attention”; i.e. 30 – 65% of P in fish food is present in solid fish excreta, so not readily transferable to aquaponics crops, and soluble phosphorus in the system can further be lost by precipitation as calcium or other phosphates.

Aquaponics literature reports levels of 1-17 mgP-PO₄/l compared to aquaponics recommendations of 40 – 60 mgP-PO₄/l. Solutions to access and reuse the fish tank discharge phosphorus therefore need to be investigated, e.g. by digestion of filter sludge using P-solubilising microorganisms. This is especially important when it comes to the development of commercial aquaponics systems, as in commercial aquaponics the main profit is made with the crops. Filling the gap between optimal hydroponics and optimal commercial aquaponics nutrient solutions will most likely be the challenge of the next years of research.

The article on Challenges of Sustainable and Commercial Aquaponics is freely accessible and re-usable (Open Access) and can be accessed via the following link: http://www.mdpi.com/2071-1050/7/4/4199/htm