Is Non-Thermal Plasma Treatment of Commodity Lettuce Seeds Worth It? Economic Impacts and Yield of Lettuce in Indoor Vertical Farming Testing Dry Air, Wet Air, N₂ and O₂ Plasmas

Agricultural seeds are sold as commodities yet seed quality can be non-uniform. Despite extensive literature plasma treatments of seeds providing advantages for many crops, lettuce studies are limited. This study provides a systematic investigation of the impacts of non-thermal plasma treatments with various feed gases (N₂, O₂, dry air, and wet air) on the germination and growth characteristics of four lettuce cultivars (Red Oakleaf, Black Simpson, Valley Heart Romaine, and Paris Romaine) under controlled cultivation conditions in an agrivoltaic agrotunnel. Results show a complex interaction between germination time, rate and yield across the different cultivars and plasma treatments. The energy consumption of plasma treatments was negligible for all treatments, while labor costs for small-batches of seeds accounted for the largest share of secondary operating costs. Despite additional expenses, including labor, O&M, and degradation costs, the reduced seed requirements from higher germination rates and higher yield increase net profit by 12.0% compared to non-treated cultivation in the most impacted (Valley Heart Romaine) lettuce. There is an opportunity for further cost optimization of the non-thermal plasma treatment for each type of lettuce seed, The results also indicate a need for a more granular view of lettuce seed commodity pricing.