Advanced and clean technologies for chromium tanned leather waste recycling and green energy production

Abstract

Chromium tanned leather wastes are difficult to valorise by chemical and biological processes dueto the strong bonds established between collagen and chromium. Thus a one-step fast clean pressureassisted alkaline hydrolysis method has been studied to disrupt recalcitrant bonds. The effects of calciumoxide, temperature, time, liquid to solid ratio and leather scrap size on organic matrix destruction, chromiumdissolution and anaerobic biodegradability of hydrolyzates obtained were evaluated. The results show thatpressure-assisted hydrolysis with CaO may be a good alternative to reduce leather waste volume, obtainbiodegradable solutions with low Cr concentration and final residues usable as a chromium bearingresource. In the optimised conditions, about 50% to 55% of the leather is dissolved. The slurries obtainedcontain above 90% of the chromium. The hydrolyzates show good anaerobic biodegradability mostly in therange of 50% to 70 %, indicating them as a source of biogas.