Assessment of tannery solid waste management : a case of Sheba Leather Industry in Wukro (Ethiopia)

Abstract

This cooperation project was born with the motivation of helping and proposing solutions for a real environmental problem in a developing country that do not have easy access to facilities and services. The main objective of the project is based on analysing the solid wastes generated by a tannery named Sheba Leather Industry from Wukro, Ethiopia, in order to suggest appropriate solid waste management practices. The project studies the possibility of implementing the composting method as a solution to treat part of the waste. Ethiopia is well known for its largest livestock population. The production of leather from skins and hides is one of the leading industrial sectors in the country. The tanning industry is one of the most polluting industries generating large quantities of solid wastes and creating negative environmental impacts. Aiming to approach this problem, in this study, assessment on solid waste management practices and characterization of the solid wastes generated by Sheba Leather Industry were carried out so that suitable tannery solid waste management solutions could be proposed. The different operations performed during the leather manufacturing were examined and it was found that the company generates a total of 5,190 tonnes of solid waste every year. These wastes were physicochemically characterized. At that moment, the overall solid wastes generated are disposed to an open dumping area on the surrounding of the industry without receiving any previous treatment and, therefore, the surrounding area is being polluted. Consequently, it was suggested the possibility of composting the non-containing chrome wastes such as hair, fleshings and trimmings with other organic matter in order to obtain a soil fertilizer that could be used to improve the quality of the damaged soils. One sampling was conducted showing that the decomposition of the raw materials occurred conveniently. However, the hair waste showed difficulties to decompose, and the company carried out a second sampling excluding that waste. In order to perform this study, it was necessary to travel to Wukro, Ethiopia, and work on site. The research entailed 5,584.55 €. The possibility of composting with the sludge, a hazardous solid waste containing chrome from the wastewater treatment, has been also theoretically studied. It is feasible to use this technology in order to reduce significantly the volume of the waste and improve its quality before disposing it in a secure landfill. In addition, a composting plant capable of treating the free of chrome tannery wastes generated was designed and described. It occupies a total area of 2,500 m2 and includes a reception/mixing unit, a piles unit, a deposit for leachate collection, and a site office. The idea is based on a unique pile of great dimensions (90.21 m of length x 18 m of width x 3 m of height) that needs to be periodically turned and water. The dimensions were determined considering that the plant receives 72 tonnes of waste every three days. The composting plant will give work to three operators and the economic study has shown the necessity of a financial aid of 25,500 € every year to assure its continuity. This proposal has been considered as an environmental friendly solution to deal with part of the waste and obtain a benefit from it. Further research is recommended in order to propose more solutions and avoid the adverse consequences of disposing waste without treating it previously.