Sustainable aquaculture production systems through nutrient recycling from fish farming effluents using duckweed

Shortage of water, food and mineral resources, along with the increase in waste generation, are among the main challenges that humanity will face in the coming years. Changes in consumption habits induced by the continuous increase of global population and raise of household income are creating pressures on water security and food supply systems, particularly regarding the production and supply of animal protein. As a result, the entire aquaculture sector has become a focus of attention as it provides healthier options to meat products at affordable prices. However, its higher-than-average growth in the past decades is creating negative impacts to aquatic ecosystems – i.e., untreated effluents from fish farming containing large loads of nutrients can cause eutrophication and hypoxia in receiving water bodies. Sustainable solutions like the use of aquatic plants (e.g., duckweed) for nutrient control and recovery from fish farm effluents have been studied over years, but the mechanisms governing nutrient uptake and accumulation are still unknown.
Preliminary work conducted by the BioResource Systems Research Group at Leeds on the use of duckweed for phosphorus control from wastewater effluents, has demonstrated the possibility to uncouple biomass growth from luxury phosphorus uptake even under winter conditions in the UK, with the potential to meet stringent discharge consents (< 1 mg P L-1). This outcome, however, has not been tested under tropical climate conditions, nor integrated to current aquaculture systems. This work presents the opportunities and hurdles to fully develop sustainable aquaculture production systems through nutrient control using duckweed ponds and recycling by the valorisation of enriched harvested duckweed biomass. Moreover, it highlights current research gaps to efficiently control nitrogen and phosphorus discharges from fish farms effluents. At the end, the proposed research seeks to apply lab-based outcomes on nutrient recovery by duckweed to the design of plant-based ponds for the treatment of aquaculture effluents in Indonesia.