A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1992

Leather shavings generated, when the thiclrn ess of the pre tanned hides and sl<ins is corrected either manually with a double handled lrnife or by machines in the chrome-tanned leather processing, are toxic wastes, high in chromium content (about 3%). Generation of solid wastes in the tanning industry is estimated to be 1 million tons per year throughout the world. The bigger pieces of trimmings are utilized for the production of artificial l eather. However, most of them are just disposed of in environmentally unsound manner in spite of the growing environmental awareness. Chromium can be extracted from the leather shavings and recycl ed in the tanning process, leaving two kinds of byproducts; protein and protein residue. The former can be used as industrial glue or animal feed, while the latter can be utilized as organic fertilizer for non-edible crops. The experiments utilizing calcium oxide as the all<ali and the leather shavings from the Kwang Hah Lee Tannery was carried out in order to demonstrate the viability of recovery of chromium and protein from leather shavings in small scale tanneries. For this purpose, pilot-scale digeste r was designed based on the bench scale experimental data, and fabricated in the workshop of the AIT Physical Plant. From four pilot-scale experimental runs of which two were made in AIT and the rest performed in the tannery, it was verified that prolonged digestion does not increase the concentration of protein obtained while enhancing the concentration of chromium in t he protein recovered. Further these revealed that the particle size of l eather shavings has a profound effect on digestion of leather shavings. Results of the pilot-scale experiments indicate that the recovery of chromium and protein from leather shavings is technically feasible and viable on small scale applications provided the separation of chromium from protein is controlled carefully.