Parameters for composting tannery hair waste

Abstract

Solid hair waste is generated by the leather industry as a by-product of the leather manufacturing process. Keratin, the main structural constituent of hair proteins, is highly resistant to degradation and their disposal is of environmental concern. The aim of this study was to develop conditions favorable for the degradation of bovine hair in a composting environment as an environmentally friendly option for the management of solid tannery hair waste. The thermophilic optimum temperature, 40 – 50C, moisture content 55%, pH 7.0 and a carbon to nitrogen ratio of 35:1 were found to be favorable to sustain metabolic functions of thermophilic microbial flora, responsible for degrading keratins. The biodegradation and structural transformation of the substrate was assessed using scanning electron microscopy. The results show that under these conditions the bovine hair lost most of its integral structural stability and that the cuticular components were more resistant to degradation. The compost stability as evaluated by monitoring the degree of humification and carbon to nitrogen ratio indicated that the final product achieved reasonable stability by attaining 73% degree of humification, 26% humification rate and carbon to nitrogen ratio of 29:1. Hence the composting technology used in this study has potential application in the leather industry for the production of an economically viable produc