Modeling innovative aquaponics farming in Kenya

Designing an aquaponic system is based on guidelines found in literature. However, it is uncertain whether these guidelines are optimal in the case of a multi-loop decoupled aquaponic system (DAPS) with an anaerobic digester. The objective of this study was to build and analyze a model of a multi-loop DAPS with digester, and use it to review system performance in terms of sustainability criteria. In particular, the computer-aided case study of a multi-loop DAPS in Nairobi (Kenya) was performed to evaluate the design, in terms of water and nutrient use efficiencies and energy consumption. Furthermore, the model was used to perform a sensitivity analysis, and to perform further optimization of the design. The findings of a model-based design clearly indicate that aquaponic system design guidelines, as found in literature, do not necessarily lead to an optimal system design of a multi-loop DAPS with digester. The main reason for this deviation is the presence of a digester in the multi-loop DAPS. Moreover, the results showed that nutrient concentration ranges have a large impact on the performance of any aquaponic system, in terms of sustainability, since these ranges determine when dilution or supplementing of the nutrient solution is needed. Optimization of the system design resulted in a nutrient use efficiency (NUE) of nitrogen of 77.74%, a NUE of phosphorus of 95.09%, a water use efficiency of 99.74%, and a feeding rate ratio of 5.19 g m⁻² day⁻¹.