Τεχνo-οικονομική αξιολόγηση χρήσης νεροφακής προς αντικατάσταση του βιοφίλτρου και παραγωγή φυτικής πρωτεΐνης σε κλειστό σύστημα υδατοκαλλιεργειών
Techno-economical assessment of using duckweed to replace biofilter and producing plant-based protein in recirculating aquaculture system

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Keywords
Υδατοδεξαμενή ; Απόνερα υδατοκαλλιεργειών ; Φυτοεξυγίανση ; Παραγωγή πρωτεΐνης ; Κλειστό σύστημα υδατοκαλλιεργειών (RAS) ; Επίπεδο συγκομιδής υδραυλικός χρόνος παραμονής (HRT) ; Συσσώρευση ; Βιοφίλτρο ; Απομάκρυνση αμμωνίας ; Καθαρή ταμειακή ροή ; Καθαρή παρούσα αξία ; Συντελεστής απόδοσης ; Ανάλυση ευαισθησίαςAbstract
Duckweed(Lemna minor) can help reduce the cost of fish feed and waste in a recirculating Aquaculture System . In this study, we developped duckweed cultivation in twelve ponds, with variation at the harvest level and the HRT (Hydraulic Retention Time). During cultivation, we added nutrient solution to ponds, as a replacement of the water derived from a recirculating aquacultutre system of tilapia (Oreochromis sp.). Based on measurements, the final biomass production was smaller than that of bibliographical resources. However, the protein content was significantly greater comparing to other plants rich in proteins. Additionally, we carried out a technoeconomical survey, aiming to compare, finacially and technically, a RAS (Recirculating Aquaculture System) that uses a biofilter (BFR) and a RAS (DWD), which, instead of biofilter, applies a duckweed culture, and the latter is utilized to cover the protein needs of fish.
Finally, the high protein content of the duckweed, the greater NPV (Net Present Value) and the IRR (Internal Rate of Return) of the initial RAS (BFR), showed up the financial sustainability of this technology. Nevertheless, the high nutrient accumulation that took place in the water, and the implied inefficiency of bioremediation, requires further experimentation, in oder to define the most suitable development conditions, e.g temperature, the selection of the best HRT, the choice of the appropriate daily harvest percentage etc.