Compost tea is widely recognized for its beneficial effects on crop growth and soil health. However, its efficacy varies depending on the composition of the feedstock and brewing conditions. This study investigates the chemical composition and agronomic impact of compost tea prepared from a commercial mixture of plant residues and animal manure. Standard chemical analyses, combined with solid-state 13C CPMAS NMR spectroscopy, were employed to characterize the organic chemistry of the feedstock. High-throughput sequencing of bacterial and eukaryotic rRNA gene markers was used to profile the microbiota. Compost tea was applied to three crops, Allium cepa, Beta vulgaris, and Lactuca sativa, grown in protected Mediterranean environments on volcanic soils. The 13C CPMAS NMR analysis revealed that the feedstock is predominantly composed of plant-derived tissues, including grass straw, nitrogen-fixing hay, and animal manure, with a significant presence of O-alkyl-C and di-O-alkyl-C regions typical of sugars and polysaccharides. Additionally, the chemical profile indicated the presence of an aliphatic fraction (alkyl-C), characteristic of lipids such as waxes and cutins. The compost tea microbiome was dominated by Pseudomonadota, with Pseudomonas, Massilia, and Sphingomonas being the most prevalent genera. Compost tea application resulted in significant yield increases, ranging from +21% for lettuce to +58% for onion and +110% for chard. Furthermore, compost tea application reduced slug damage and enhanced the shelf life of lettuce. These findings highlight the bio-stimulant potential of this standardized compost tea mixture across different vegetable crops.

Tea is one of the most widely consumed non-alcoholic drink in the world. Green tea, black tea, white tea, and oolong tea are derived from the Camellia sinensis plant, a shrub native to China and India. It contains unique antioxidants. The most potent antioxidants may help against free radicals that can fight against cancer, heart disease, and clogged arteries. The polyphenols present in the tea help the cells from damage and reduce the risk of chronic diseases. The health benefits of these compounds remarkably increase the demand for tea. Tea production is rising drastically; consequently, enormous amounts of tea waste are also generated. Improper disposal and dumping of this tea waste creates a serious problem due to the incineration and the emission of greenhouse gases. This issue can be overcome by adopting suitable technology. Effective microbial degradation and composting of tea waste will contribute to high crop production and plant disease control. The value added products from tea waste can be used in different fields. Planned tea waste valorization processes could generate more income and create rural livelihood opportunities. This review highlights the valorization processes and value-added products from tea waste. The application of value added products for energy generation, wastewater treatment, soil conditioners, adsorbents, biofertilizers, food additives, dietary supplements, animal feed bioactive chemicals, dye, colorant, phytochemicals, bioplastics, cutlery products, scope, and future directions in sustainable utilization has been reviewed. This review article will be beneficial to the researchers for acquiring an in-depth knowledge on the versatile applications of tea waste.