Biofloc technology is a sustainable aquaculture practice that enables efficient nutrient recycling. By minimizing nutrient losses, biofloc systems offer a promising solution to environmental concerns associated with traditional aquaculture.
To better understand the intricate nutrient cycling dynamics within biofloc systems, a study published in Biosystems Engineering by researchers from Wageningen University and Research and IPB University employed a semi-physical modeling approach. This model focused on three key nutrients: carbon (C), nitrogen (N), and phosphorus (P). By analyzing the interactions among these nutrients and various system components—such as feed, fish, biofloc, and periphyton—the researchers gained valuable insights into system efficiency and nutrient retention potential.
Biofloc Technology
For optimizing biofloc technology (BFT) systems, it’s essential to have an in-depth understanding of nutrient dynamics. Researchers have developed mathematical models to simulate and predict nutrient behavior within these systems. By analyzing the flow of carbon, nitrogen, and phosphorus throughout the system, scientists can identify strategies to improve nutrient use efficiency and reduce environmental impact.
The Role of Diet in Biofloc Systems
The type of diet provided to the farmed organisms can significantly influence nutrient dynamics in BFT systems. Diets rich in non-starch polysaccharides (NSP), which are high in fiber, can stimulate the growth of biofloc microorganisms, leading to better nutrient utilization and waste reduction. By carefully selecting the appropriate diet, it is possible to enhance the sustainability of aquaculture practices.
Model Validation and Scenario Analysis
The model was rigorously validated by scientists using experimental data obtained from two dietary treatments: a control diet and a high-NSP diet. The high-NSP diet, rich in non-starch polysaccharides, was designed to promote the growth of beneficial bacteria and algae within the biofloc. The model accurately predicted the behavior of most system variables, with the exception of biofloc biomass.
Scenario Analysis: Maximizing Sustainability
To explore the potential of biofloc systems, the researchers conducted scenario analyses using the validated model. A key finding was that doubling the stocking density in biofloc systems can lead to increased fish production while reducing nutrient losses. This suggests that biofloc technology can contribute to more sustainable and intensive aquaculture practices.
The study also compared the impact of different diets on nutrient dynamics. While the high-NSP diet generated more organic waste, the biofloc and periphyton in the system were able to effectively assimilate this additional waste, particularly carbon. This highlights the importance of dietary factors in influencing nutrient cycling and waste management in biofloc systems.
Implications for Sustainable Aquaculture
This study provides valuable insights into the complex nutrient dynamics of biofloc-based aquaculture systems. By optimizing factors such as diet composition and stocking density, it is possible to further enhance the environmental sustainability of this promising technology. As the aquaculture industry continues to grow, a better understanding of nutrient flows is essential to minimize negative impacts on aquatic ecosystems.
Conclusion
Advancing our understanding of nutrient flows in biofloc systems, this study offers valuable information to optimize system design and management. The developed model can be a powerful tool to predict system behavior and identify strategies to minimize nutrient losses and maximize resource utilization.
The study’s key conclusions can be summarized as follows:
Model Accuracy and Predictive Power:
- The semi-physical model effectively captures the dynamics of carbon (C), nitrogen (N), and phosphorus (P) in the fish-biofloc system.
- Model accuracy, measured by RMSE/μ, is satisfactory for most simulated outcomes, indicating its reliability in predicting system behavior.
Impact of Management Strategies:
- Stocking Density: Doubling the stocking density can lead to increased fish production without significantly increasing nutrient losses. However, careful management is required to maintain water quality and prevent oxygen depletion.
- Feeding Rates: Adjusting feeding rates can influence nutrient loads and system performance.
- Diet Composition: While the high-NSP diet produces more organic waste, it can be effectively managed by biofloc and periphyton communities. This suggests that dietary manipulation can be a tool to optimize nutrient utilization and minimize environmental impact.
Nutrient Dynamics and Flow:
- Sankey diagrams provide a visual representation of nutrient flows within the system.
- The high-NSP diet results in higher production of particulate organic carbon (POC) and particulate organic phosphorus (POP), as expected.
- However, POC loss is similar between the two diets, indicating that biofloc and periphyton communities can handle higher organic loads.
- Nitrogen flows were relatively similar between the two diets, suggesting that dietary changes may have a more significant impact on carbon and phosphorus dynamics.
The study was funded by Smart Indonesian Agriculture (Smart-In-Ag project) through the Interdisciplinary Research and Education Fund (INREF) of Wageningen University & Research, the Netherlands.
Contact
Nurhayati Br Tarigan
Aquaculture and Fisheries, Animal Sciences Group, Wageningen University and Research.
P.O. Box 338, 6700 AH Wageningen, the Netherlands.
Email: nurhayati.brtarigan@wur.nl
Reference (open access)
Tarigan, N. B., Verdegem, M., Ekasari, J., & Keesman, K. J. (2024). Nutrient flows in biofloc-Nile tilapia culture: A semi-physical modelling approach. Biosystems Engineering, 248, 108-129. https://doi.org/10.1016/j.biosystemseng.2024.09.021
