ICAMS 2014 – 5 th International Conference on Advanced Materials and Systems EVALUATION OF LEATHER BIODEGRADABILITY RODICA ROXANA CONSTANTINESCU, VIORICA DESELNICU, MARIAN CRUDU, GABRIELA MACOVESCU INCDTP – Division Leather and Footwear Research Institute, 93, Ion Minulescu st., Bucharest, Romania, email: rodica.roxana@yahoo.com This paper presents a study regarding the biodegradability of tree types of finished leathers tanned with different tanning agents: based on Chromium (III), based on Ti-Al, based on Ti-Zr. For assessment of leather biodegradation, EN ISO 20200:2005 was used as method. Physical-chemical analyses were performed on leathers at initial state, after 90, 120 and 220 days of composting. The conclusion of the study is that all types of tanned leather studied undergo the biodegradation process but at different rates. A hierarchy was established for leathers taken in this study, as follows: leather tanned with Ti-Al, leather tanned with Ti-Zr, leather tanned with chromium, where chromium (III) tanned leather has the lowest rate of biodegradability. Keywords: leather tanned with inorganic salts, composting, biodegradation. INTRODUCTION Sustainable disposal of chromium tanned leather wastes is essential under current legislation and thus an appreciation of the extent of leather decomposition is essential. The microbial decomposition of tanned leathers is poorly understood with relatively few reported studies existing. Leather, containing high levels of nitrogen (ca. 16%) is generally considered a high quality resource capable of degrading readily. However, the tanning process, whereby tanning agents are incorporated into the collagen matrix, results in the reduction of substrate quality and reduced microbial decomposition. Relatively little is known about the toxicity of Cr(III) towards microorganisms. Generally, heavy metal toxicity affects bacterial growth, morphology, and biochemistry (Aftab, 2006; Bhat et al., 1998; Pillai and Archana, 2012) and is usually via one of three mechanisms: (1) blocking of essential functional groups, (2) displacement of essential ions, (3) modification of active conformation of biological molecules. In the past years, few determinations of leather biodegradability have been made using compost similar to the one used for plastics and which accelerate the natural degradation process (Thanikaivelan et al., 2004; Pantazi et al., 2014) or under natural conditions (Bacardit et al., 2011; Chirila et al., 2014). In this study, investigations into the microbial decomposition of leather, under a variety of simulated environmental conditions, were performed in accordance with standard EN ISO 20200:2005 - Plastics - Determination of the degree of disintegration of plastic materials under simulated composting conditions in a laboratory-scale test. The method determines the degree of leather disintegration at laboratory scale under conditions simulating an intensive aerobic composting process. The paper presents a comparative study regarding biodegradation in composting environment of various leathers, such as chrome, Ti-Al and Ti-Zr tanned leathers. Modification of some leather characteristics was monitored for 220 days and differences are discussed.