Effects of physicochemically hydrolyzed human hairs on the soil microbial community and growth of the hot pepper plant

Acoustic and hydrodynamic cavitation assisted hydrolysis and valorisation of waste human hair for the enrichment of amino acids

Hair waste in large amount is produced in India from temples and saloons, India alone exported approximately 1 million kg of hair in 2010. Incineration and degradation of waste human hair leads to environmental concerns. The hydrothermal process is a conventional method for the production of hair hydrolysate. The hydrothermal process is carried out at a very high temperature and pressure, which causes the degradation of heat-sensitive essential amino acids, thereby depleting the nutritional value. This work deals with alkaline hydrolysis of human hair using acoustic and hydrodynamic cavitation, and comparison with the conventional method. The optimal operating conditions for highest efficiency was observed, for the hydrolysis of 1 g of sample hairs in 100 mL of solution, at 4:1 (KOH: hair) ratio, soaking time of 24 h, the ultrasonic power density of 600 W dm^-3 (20 KHz frequency and input power 200 W) or hydrodynamic cavitation inlet pressure of 4 or 7 bars. Cavitation results in rupture of disulfide linkages in proteins and mechanical effects lead to cleavage of several hydrogen bonds breaking the keratin sheet structure in hair. Breakdown of bonds leads to a decrease in viscosity of the solution. 10% and 6% reduction in viscosity is obtained at optimal conditions for ultrasonic and hydrodynamic cavitation treatment, respectively. FTIR analysis of produced hair hydrolysate confirmed that the disulfide bonds in hair proteins are broken down during cavitation. The amino acid of hair hydrolysate, prepared using cavitation, has a relatively higher digestibility and nutritional value due to the enhancement of amino-acid content, confirmed using amino acid analysis. Cavitation assisted hair hydrolysate has a potential application in agricultural engineering as a fertilizer for improvement of the quality of the soil and land. Cavitation based hair hydrolysate can also be used as an environmentally friendly and economical source of essential amino acids and digestibles for animal or poultry feed.

Human Hair “Waste” and Its Utilization: Gaps and Possibilities

Human hair is considered a waste material in most parts of the world and its accumulation in waste streams causes many environmental problems; however, it has many known uses. Preventing waste of such a material requires both addressing the problems in the current usage and developing its utilization systems at locations where they are missing. With focus on developing systematic utilization of human hair waste, this paper first reviews the possible uses of human hair gathered from large scale trades, local/traditional knowledge, upcoming innovations, and scientific research; along with the socioeconomic systems that have evolved around the known uses. Concerns and gaps in these systems are identified and possible directions to address these gaps are discussed. For expanding hair utilization to new contexts, important considerations such as knowledge, skill, and technology requirements and potential markets are discussed. Finally, a policy framework for socially and environmentally healthy utilization of human hair is outlined. This study shows that human hair is a highly versatile material with significant potential in several critical areas such as agriculture, medical applications, construction materials, and pollution control. Moreover, these uses are diverse enough for entrepreneurs ranging from unskilled to highly technical individuals and for the wide variety of human hair waste available in different locations.