Sustainable recycling of café waste as natural bio resource and its value adding applications in green and effective dyeing/bio finishing of textile

Abstract

Cafe waste, such as spent coffee grounds and tea leaves, possesses abundant natural colorants and bio active chemicals, which can be extracted using simple and eco-friendly process. This work investigated cafe waste recycling process by optimizing natural colorant extracting condition, and then applied the extracted natural bio dye to textile dyeing and functional finishing. A simple and green process is carefully designed in an attempt to reduce cost and hazards to the environment, and a comparison is made between the two agriculture/food wastes. Results showed that 50% ethanol + sodium bicarbonate solvent system with a weak alkaline condition of pH 8, can be an effective solvent for extracting natural colorants and bio active chemicals from both spent coffee grounds and tea leaves. Silk and wool fabrics dyed with the extracts exhibited natural brownish color with satisfactory color fastness, owing to effective adsorption of natural dye onto the fibers through strong chemical interactions between protein polypeptide chains and dye molecules. In addition to the natural color, antioxidant and antibacterial properties are that textile can achieve from cafe waste through dyeing. It is seen in this work an extraordinary high level (>90%) of antibacterial activities (against E.coli, S.aureus and C. albicans) achieved by dyed fabrics in all cases. The recycling loop can be closed by processing leftovers directly and safely go back to nature as mulch or mixed with soil as fertilizer, free from prior composting.