Valorization of Unconventional Hair Waste: Unlocking Opportunities in Materials and Chemical Engineering

The waste generated from barber shops, households, hospitals and clinics has significant potential as valuable raw materials across various sectors, including chemical, materials, medical, and engineering. Despite typically being discarded, human hair (HH) contains essential proteins like keratins and Keratins Associated Proteins (KAPs) within its fibers, crucial for hair structure. Regrettably, much of this human hair waste is either incinerated or sent to landfills, with only a minimal fraction being recycled for purposes such as fertilizer or biodegradable surfactants. Minimizing the wastage of this material entails tackling existing usage challenges while simultaneously establishing utilization systems in locations where they are currently lacking. The unique characteristics of human hair, including its distinct chemical composition, slow degradation, remarkable tensile strength, thermal insulating properties, elasticity, textured surface, and specific interactions with water and oils, as well as its social and cultural significance, have resulted in a wide range of applications. These applications are further influenced by the diversity in hair types, characterized by five key parameters: length, color, texture, degree of damage, and presence of contaminants. This review aimed to consolidate various studies that utilize human hair for diverse applications within the realms of chemical and materials science by developing a systematic approach.