What is Aquaponics?

Aquaponics is an integrated multi-trophic system comprising elements of recirculating aquaculture (RAS) and hydroponics, wherein the water from the fish tanks that is enriched in nutrients is used for plant growth (Fig.1). The appeal in this approach lies in the fact that it is possible to grow both aquatic animals and plants in an environmentally-friendly way in one system. Irrespective of varying water quality requirements in both components (i.e. RAS and hydroponics), the traditional aquaponics practice has been based on finding a balance between the needs of plants and fish within a single water process loop. Consequently the efficiency of one-loop aquaponic systems is being reduced  compared to the sum of single crop and fish production.

Fig. 1 – Illustration of the basic aquaponics principle in one-loop systems.

The reason why aquaponics could be a game changer in the is due to the fact that we are faced with growing food insecurity across the world, since the world population is growing. This brings inevitably challenges for both nutrition and environment. More and more space is needed to feed the population, while soil fertility, phosphate deposits, and oil sources are declining. Besides population growth-inhibiting policies, the development of sustainable production systems is necessary and unavoidable to avoid a global disaster. This applies in particular to the urban tissue. Urbanization especially occurred due to advanced technology and power availability. Whereas a farmer in the 19th century was only able to feed 1.5 people, nowadays several hundred of people can be fed by the same manpower resource. This, however, is clearly at the expense of fossil fuels, over-fertilization and irrigation, and soil depleting monoculture farming approaches. A change of current practice is required to challenge this problem.

One-Loop vs. Multi-Loop Aquaponics

Recently, there have been plenty of discussions, about multi-loop systems (aka decoupled aquaponics). If we now compare one-loop aquaponic systems (Fig.2) with multi-loop aquaponics (Fig.3), we can clearly see that the conditions in multi-loop systems are better for all components and thus lead to higher growth efficiencies. Also the remineralized sludge (i.e. concentrated liquid fertilizer) is only led to HP, where it is needed. Unnecessary dilution is thus avoided. However, sizing the system is a bit more complex, as water flow from RAS to HP is only evapotranspiration dependent. The global radiation plays thus an important factor. Summa summarum, one-loop systems are very much suited for personal usage. Commercial systems should rather look into decoupled systems as higher growth performances can be expected.

Fig. 2 – The one-loop aquaponic system is the traditional aquaponics approach. Instead of supplementing the hydroponics part with fertilizer both components are exposed to quite similar conditions

Fig. 3 – Contrary to a one-loop aquaponic system, a multi-loop aquaponic system aims at providing optimal conditions for both fish and plants. In this case, RAS-derived fish sludge is being remineralized and supplemented to the hydroponics.

Impact of Aquaponic Systems

We are asked a lot what the impacts of (decoupled) aquaponic systems are compared to other agricultural practices. It has to be stressed out, that aquaponics alone does not solve global nutrition problems we are currently challenging. Instead, it can contribute to more efficient, more decentralized, and environmentally friendlier food production. The social, environmental, and economic impacts are as followed:

Social impacts:

• Local aquaponics production systems puts emphasis on the consciousness on food
• Ensuring future food security especially in urban regions, where people do not own enough land to grow food themselves and thus are dependent on sufficient food supply
• Increase the quality of offered food. High quality food instead of pesticide contaminated vegetables and fish grown in water that contains hormones and antibiotics.

Environmental impacts:

• Maintaining water and soil quality of conventional production systems by avoiding the use of pesticides, nutrients and pollutants, as well as and cross-contamination
• Aquaponics does not lead to eutrophication (as long as one does not discharge water unnecessary). Natural habitats can be conserved, and/or recover from the disastrous consequences of industrial farming.
• Three-loop systems are close to “zero discharge” system. However, zero discharge as such is utopian and cannot be achieved (e.g. even when using a digester, some parts of the sludge are not totally degradable. Even putting the demineralized sludge somewhere on the fields means that there is some kind of discharge irrespective of the avoided adverse impact on the environment). Plants in greenhouses serve as a CO2 sink, and aquacultural sludge will be recycled to the highest degree possible. The demineralized waste sludge can easily be distributed on agricultural land without causing any environmental problems.
• Contrary to intensive agriculture, no fossil fuels are required to run the big machines that are necessary for pest control and harvest.

Economic impacts:

• Increasing diverse and local food production and securing socio-economic dynamism and jobs (i.e. technology requires skilled personnel)
• Reducing the need of long distance food transport and thus the dependency upon oil.
• Local food production is crisis resilient.
• Aquaponics as a water-efficient production system makes it possible to grow food in the most arid areas of the world. Even in desert areas with sufficient sunshine (i.e. high solar power potential) water that leaves the system via the food products could be compensated with water extracted from the air (humidity).
• Aquaponics does not require fertile soil for both plant and fish production and thus can also be applied in urban areas. However, the economic feasibility of roof-farms still needs to be clarified, due to high construction costs, and relatively low surface areas per system.
• Possible enhanced growth rates of decoupled aquaponic systems compared to conventional hydroponic installations.