Processing of leather waste: pilot scale studies on chrome shavings. Isolation of potentially valuable protein products and chromium

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 wast es 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 t he United States, nearly 60,000 metric tons of chromium-containing solid wa ste, i.e. chrome shavings, are generated by the leather industry each year, and approximately ten times this amount is generated worldwide. Land appli cation for the disposal of chromium-containing tannery and other leather wa stes has been widely practiced during most of the twentieth century, but fe wer landfill sites can be found every day and the cost of transportation an d disposal increases. Historically, these materials were used in the produc tion of fertilizer or composite boards, but while once the company producin g and marketing fertilizer or boards would pay for the waste and its transp ortation, nowadays, the tanner has to pay for such things. Over several yea rs, we have demonstrated that it is possible to isolate protein products (g elatin and collagen hydrolysate) from chrome shavings by using an alkaline protease under mild conditions. The objective of the present work was to pe rform 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 hydr olysate 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.