Duckweed-based systems in the water-energy-food nexus: controlled environment agriculture (CEA) for industrial water reuse and nutrient recovery

Duckweed ( Lemnaceae ) is gaining increasing attention as a multifunctional bioresource for wastewater treatment, nutrient recovery, food, feed, and bioenergy production, as well as for closed-loop life support systems. Its rapid growth, high nutrient uptake capacity, and aquatic growth habit make it particularly suitable for integration into controlled environment agriculture (CEA) systems within the water-energy-food nexus. This review synthesizes recent advances in indoor duckweed cultivation, focusing on laboratory- and pilot-scale systems with working volumes exceeding 1 L. The aim is to identify key biological and engineering factors governing system performance and to assess the feasibility of scaling duckweed-based CEA for industrial and municipal water reuse applications. Comparative analysis of reported studies shows that short-term laboratory experiments frequently overestimate long-term productivity, with relative growth rates declining as cultivation duration and system complexity increase. System performance is strongly influenced by hydraulic design, culture depth, mat density, harvesting strategy, nutrient dosing, microbiological control, and energy input, particularly for lighting and climate regulation. Pilot-scale studies demonstrate that stable operation and realistic productivity require integrated management of biological processes and engineering subsystems rather than optimization of single parameters. Major knowledge gaps remain in long-term nutrient management, microbial stability, standardized performance metrics, and techno-economic assessment. Overall, duckweed-based CEA represents a promising but still emerging technology for sustainable water reuse and biomass valorization. Progress toward practical deployment will depend on pilot-scale validation, improved process integration, and robust evaluation of economic and safety constraints, with additional insights emerging from space life-support research. • CEA enables duckweed cultivation for wastewater treatment and biomass recovery • Short-term laboratory growth rates overestimate long-term pilot-scale performance • System performance depends on integrated biological and engineering design • Duckweed-based CEA supports water-energy-food nexus and space life support concepts