Full-Scale Cocomposting of Hair Wastes from the Leather Manufacturing Industry and Sewage Sludge

Abstract

A full-scale cocomposting experiment using hair wastes from the leather manufacturing industry and sewage sludge as cosubstrates was carried out with the aim of producing compost that may be used as an organic amendment in agriculture. A 1:1 weight ratio of hair wastes and sewage sludge was used based on experiments at smaller-scale. The resulting mixture was then amended with pruning wastes acting as bulking agent in a 1:1 volumetric ratio (mixture:pruning wastes). The experiment was carried out using the windrow composting technology with a weekly turning frequency. Thermophilic range of temperature was quickly achieved and maintained for more than 8 weeks. This fact ensured the sanitation of the compost according to international requirements. Additionally, the quality of the product obtained expressed in stability terms was very high (Self-heating test grade: V; respiration index: 0.83 mg O2 per gram of organic matter per hour). The nitrogen content in the final product was also high (5.6%, dry basis). In conclusion, the recycling of hair wastes produced in the leather manufacturing industry using the composting technology is feasible and a valuable organic fertilizer may be obtained.