Hides come to the tanner as a by-product of the meat industry. The tanning process, in turn, generates much greater quantities of by-products and wastes than leather. One ton of wet salted hides yields only 200 kg of leather but over 600 kg of solid waste, or byproduct if a market can be found. In the United States, nearly 60,000 metric tons of chromium-containing solid waste, i.e. chrome shavings, are generated by the leather industry each year, and approximately ten times this amount is generated worldwide. Land application for the disposal of chromium-containing tannery and other leather wastes has been widely practiced during most of the twentieth century, but fewer landfill sites can be found every day and the cost of transportation and disposal increases. Historically, these materials were used in the production of fertilizer or composite boards, but while once the company producing and marketing fertilizer or boards would pay for the waste and its transportation, nowadays, the tanner has to pay for such things. Over several years, we have demonstrated that it is possible to isolate protein products (gelatin and collagen hydrolysate) from chrome shavings by using an alkaline protease under mild conditions. The objective of the present work was to perform pilot plant trials to isolate protein products from chrome shavings, treat and purify the remaining chrome cake and tan hides with the recovered chromium. Because of the high nitrogen content, the isolated collagen hydrolysate has potential use as a fertilizer and in animal feed additives. The gelatin has potential use in cosmetics, adhesives, printing, photography, microencapsulation, films or even as an additive in finishing products for the leather industry. Published by Elsevier Science Ltd.
