Valorization of tea waste: Composition, extraction technologies, and sustainable applications across agriculture, industry, and biotechnology

Amid growing global interest in sustainable resource management, tea ( Camellia sinensis ), the second most consumed beverage after water, generates substantial biomass waste throughout cultivation, processing, distribution, and consumption. A significant portion of this waste is still managed through conventional practices such as composting, incineration, or landfilling, which limits its potential value recovery and may increase operational and environmental burdens across the supply chain. However, tea waste contains a wide range of valuable bioactive and structural compounds, including polyphenols (e.g., catechins and flavonoids), caffeine, proteins, polysaccharides, cellulose, hemicellulose, lipids, and essential micronutrients. This systematic review examines the physicochemical characteristics of tea waste and evaluates its potential for valorization in multiple sectors. Reported applications include its use as organic fertilizers and soil amendments in agriculture; biosorbents and activated carbons for environmental remediation; functional ingredients and natural additives in the food industry; bioactive compounds for pharmaceutical and cosmetic formulations; eco-dyes in textiles; raw materials in papermaking; and feedstock for bioenergy production, such as biogas, bioethanol, and biodiesel. Recent advances in extraction technologies, including ultrasound-assisted, enzyme-assisted, and supercritical fluid methods, have improved the recovery efficiency of high-value compounds and support the development of integrated biorefinery approaches. Despite promising laboratory-scale results, several challenges remain for large-scale implementation, including variability in raw material composition, techno-economic limitations, and supply chain optimization requirements. By identifying current research gaps and discussing opportunities for industrial integration, this review underscores the role of tea waste valorization in reducing environmental impacts, lowering operational inefficiencies, and supporting circular bioeconomy strategies.