Sustainable Valorization of Grape Pomace Digestate as Fertilizer: Effects on the Agronomic and Biochemical Performance of Calendula officinalis L. under Variable Irrigation Regimes

), supporting their potential in functional foods, nutraceuticals, and natural colorants. Seasonal variation influenced metabolic responses, with summer enhancing sugar and carotenoid synthesis and winter favoring pigment stability. The digestate was free from toxic elements and improved substrate fertility, confirming its agronomic safety and efficiency. A sustainability evaluation yielded an EcoScale score of 89.8, substantially higher than values reported in comparable literature, underscoring the high environmental performance and process greenness of this approach. Overall, this work presents a scalable, eco-efficient strategy to convert winery residues into high-value floral biomass, advancing circular bioeconomy principles and sustainable agricultural practices.