Aquaponics is the aquatic integration of an aquaculture component (e.g. usually a RAS-based fish culturing component) and a plant culturing component (e.g. usually a form of hydroponic plant culturing component) to share waste nutrients from the animal(s) cultured in the aquaculture component with the plant culturing component in a way that assists plant growth. A key argument of aquaponics is that the nutrient wastes generated by the aquaculture component are essentially provided “free of cost” to the plant culture component, because the fish (or other aquatic animal) are being cultured and sold and their associated nutrient wastes would normally be disposed of in an aquaculture-only context. However, this “free of cost” argument only exists when the animal being cultured is sold and thus, animal sales cover the costs of fish feed and any other consumables or costs of production required to operate the system. Essentially, when fish are sold from the RAS component, those sales cover the costs of the fish feed and therefore, nutrient provision to the plants in an aquaponic context are considered “free of cost”.
A healthy proportion of aquaponic systems operated in a commercial context currently do not actually sell the animals cultured (e.g. the fish) and argue that the animal present is simply a “nutrient production device” for the culture of the plants, which account for the sales income from the enterprise. In this “no animal sales” aquaponic context therefore, profit generation solely sits with the sales of the plant products grown or produced. Therefore, the aquaculture component, with no animal sales present, substantially contributes to the cost of production associated with the saleable product of the aquaponic culturing system (i.e. the plants). If the vast majority of the nutrients required for plant growth and production are being generated by aquatic animal wastes (e.g. fish), and the fish are not being sold, this means the cost of nutrient provision for the plants is directly associated with the cost of the fish feed fed to the aquaponic system.
A desktop study was performed to determine the cost of supplying the nutrients required for plant growth in an aquaponic context via fish-generated wastes of the metabolism of fish feed versus the cost of direct nutrient provision to the plants via standard hydroponic nutrient solution salts. Nitrogen was selected as the representative nutrient in the study as it is the majority waste ion produced by the animal (fish) in the aquaculture component and is an essential nutrient required in plant growth that is generated and represented almost solely by fish wastes in an aquaponic context.
The study calculated the relative price of the Nitrogen produced in fish waste for a representative Tilapia spp fish being fed a 36% protein content fish feed commercially available on the USA market. It then calculated the relative price of the Nitrogen available in a representative, commercially available, standard hydroponic nutrient salt (Calcium Nitrate – Ca(NO3)2 ) commercially available on the USA market and compared the two relative prices for the Nitrogen mass required to culture a known number of standard hydroponic variety lettuce plants (based on standard plant Nitrogen uptake rates in an aquatic culture environment).
Results indicated that the Nitrogen required to culture the plants cost at least five (5) times more when supplied via a fish waste resource.
The study indicates that, if aquaponics is to be chosen as a commercial plant culturing technology, without any fish sales contributing to offsetting the costs of production, aquaponic farmers who do not sell fish are paying over five times as much for the nutrients required to culture the plants they sell than if they chose a standard hydroponic plant culturing approach. If fish sales were adopted, the potential exists for these fish sales to offset the costs of the nutrients required for plant culture and this would therefore, assist farmers to achieve nutrient costs that equal, or even better, those associated with standard hydroponic production technologies.