Tea byproducts biorefinery for bioenergy recovery and value-added products development: A step towards environmental sustainability

•Biofuel synthesis from spent tea waste can be a sustainable waste management option.•Biochar, activated carbon, and nanoparticles synthesis from tea wastes are highlighted.•Utilization of tea waste as adsorbent for pollutants abatement is discussed.•Hierarchical porous supercapacitor development from tea waste is summarized.•Development of carbon dots from tea waste for environmental application is promising.