Process Simulation and Techno-Economic Analysis of <em>Wolffia</em>-Integrated Recirculating Aquaculture Systems for Nutrient Recovery and CO₂ Utilization

Recirculating aquaculture systems (RAS) enable efficient fish production but generate nutrient-rich effluents requiring sustainable management. Integrating aquatic biomass cultivation offers a circular approach for nutrient recovery, CO₂ utilization, and biomass production. This study presents a process simulation and techno-economic analysis (TEA) of a pilot-scale Wolffia globosa-RAS system in Thailand, comparing static and well-mixed suspended aeration cultivation. Within the same system boundary, the suspended configuration required only 5.90 m² for 28.00 m³, whereas static cultivation required 131 m² for 32.80 m³, corresponding to a 19-fold improvement in land-use efficiency (0.21 vs. 4.00 m² m⁻³). Higher annual biomass production was achieved in the suspended system (1056 kg dry weight (DW) yr⁻¹) compared with the static system (690 kg DW yr⁻¹), corresponding to CO₂ fixation of ~1.50 and ~0.98 t CO₂ yr⁻¹, respectively. The static system achieved higher nutrient removal efficiencies (97% N and ~100% P), while the suspended system showed lower removal (64% N and 65.3% P) but higher productivity. Economic analysis confirmed feasibility, with the suspended configuration showing superior performance, achieving higher return on investment (17.56% vs. 12.35%) and a shorter payback period (5.70 vs. 7.76 years). These results demonstrate the potential of RAS-Wolffia integration for sustainable aquaculture and resource recovery.