Ready-to-eat products in vertical farming: advancing the research on improved lighting solutions and evaluation of sustainability for optimal baby-leaf kale production.

Vertical farming (VF) represents a promising urban agriculture solution, enabling efficient food production in controlled environments, using multi-layer shelves, artificial lighting, and soilless techniques with closed-loop irrigation. Despite its benefits in surface and water use efficiency, VF spreading is limited by high energy consumption due to lighting and climate control. This PhD project aimed to explore the VF sector focusing on baby-leaf kale, which represents a popular ready- to-eat product. The agronomic research carried out within AlmaVFarm facility explored the impact on baby-leaf kale growth and resource use efficiency (RUE) of light quality, through increasing Red and Blue ratios with and without a White light background in the ebb-and-flow system, and the effect of different combinations of photoperiod and photosynthetic photon flux density (PPFD) while maintaining a constant daily light integral in the aeroponics. Accordingly, the spectral composition with increased red component (RB3 and W-RB3) significantly improved fresh yield, dry biomass and RUE compared to RB=1. Following this result, testing increasing RB ratio up to 9, RB5 ratio provided the best balance of growth, yield, and RUE, highlighting its effectiveness for kale cultivation. Furthermore, continuous photoperiod (24 hours) matched with lower PPFD in the aeroponics resulted in the highest biomass, leaf area, and light use efficiency, but also in the highest RUE, indicating that longer light exposure at lower intensity promoted growth. Additionally, from the LCA environmental analysis of a Swedish commercial VF producing baby-leaf, preliminary results provided encouraging figures, especially when considering the potential of VF and possible further strategies. These insights suggest that managing light features can significantly enhance the productivity and RUE of VF systems for improved kale baby-leaf. Additionally, the implementation of strategies such as symbiotic relationship with the buildings, renewable energy or different waste handling may further optimize VF diffusion and efficiency.