Abstract

In the United States, over 60 000 metric tons of chromium containing solid waste is generated by the leather industry each year, and approximately ten times this amount is generated world-wide. Environ mental concerns and escalating landfill costs are becoming increasingly serious problems to the leather industry and alternative disposal methods are needed. We have developed two processes in which this waste is treated with alkali and enzymes to extract hydrolyzed and gelable protein products and a recyclable chromium cake. We have demonstrated that these processes are repeatable with respect to their chemical and physical properties and that good and repeatable material balances are obtained. The isolated chromium can be chemically treated and recycled into the tanning process. The recovered protein fractions, practically devoid of chromium, could be used in a wide range of products, including adhesives, cosmetics, films, animal feed and fertilizer.