Technological Development of Aquaponic Systems to Improve the Circular Bioeconomy in Urban Agriculture: A Perspective

Aquaponic systems synergistically combine the processes for the breeding of aquatic fauna with the cultivation of plants in the absence of soil, i.e. aquaculture and hydroponics. Although aquaculture and hydroponics separately are well-known worldwide and consolidated systems, there is still limited diffusion of the technology that involves their advanced combination as hybrid technology. Their combination offers several positive impacts on the circular bioeconomy. The exploitation of fish by-products as a source of nutrients for plants can contribute to the reduction of the use of anthropic fertilizers. On the other hand, the aquaponic approach can contribute to the reduction of the overall amount of water necessary for both aquaculture and hydroponics. This article reports an overview of hydroponics, aquaculture and an aquaponic system and the several challenges that are still open in the development of these systems. Further research is necessary for the development of strategies effective to increase the degree of recycling of the water, for the control of the odours and the emissions of CO2, as well as for the control of the growth of undesired algae. In addition, the combination of aquaponic systems with techniques of purification and disinfection of the water, such as membrane filtration and the treatment with ozone and/or UV radiation, will improve the quantity of the nutrients conveyed to the plants and will reduce the presence of possible pathogens and other contaminants.