Plasma nitrogen fixation system with dual-loop enhancement for improved energy efficiency and its efficacy for lettuce cultivation

Plasma nitrogen fixation (PNF) has been emerging as a promising technology for greenhouse gas-free and renewable energy-based agriculture. Yet, most PNF studies seldom address practical application-specific issues. In this work, we present the development of a compact and automatic PNF system for on-site agricultural applications. The system utilized a gliding-arc discharge as the plasma source and employed a dual-loop design to generate \mathrmNO_x^- from air and water under atmospheric conditions. Experimental results showed that the system with a dual-loop design performs well in terms of energy costs and production rates. Optimal operational parameters for the system were determined through experimentation, resulting in an energy cost of 13.9 MJ mol⁻¹ and an energy efficiency of 16 g kWh⁻¹ for \mathrmNO_3^- production, respectively. Moreover, the concentration of exhausted NO_x was below the emission standards. Soilless lettuce cultivation experiments demonstrated that \mathrmNO_x^- produced by the PNF system could serve as liquid nitrate nitrogen fertilizer. Overall, our work demonstrates the potential of the developed PNF system for on-site application in the production of green-leaf vegetables.