Recovery and utilization of proteinous wastes of leather making: a review

Abstract

Hides and skins, by-product of the meat industry is converted into a value added product namely leather by the tanners. Tanning essentially is the process of converting raw hides and skins into imputrescible substance. The tanning process has number of steps and generates significant quantities of by products and wastes. These solid and liquid wastes pose major environmental problem if not managed effectively. Large-scale production systems are adopted for leather processing in clusters and therefore, the industry receives focus of environmentalists and society. Consequently tremendous pressure is exerted by various pollution regulatory bodies. The hides and skins, after trimming, removal of flesh and fat, are treated with chemicals, which cross-link the collagen fibers to form a stable, durable material. The chemicals used may be derived from traditional vegetable products, or inorganic metal salts. During leather processing number of size reduction, leveling and purification operations are carried out which results in generation of untanned and tanned proteinous waste materials. In this paper, various recovery processes and utilization methodologies of proteinous solid wastes, emanating from leather processing operations prior to tanning is reviewed.

Removal of chromium from tanning wastewater and its reuse

“…Processing of one metric ton of rawhide results in 200 kg of tanned leather, 190-350 kg of non-tanned waste, 200-250 kg of tanned leather waste, and 50,000 kg of wastewater (Sundar et al, 2011). The tanning process in Brazil and worldwide is of great economic importance.…”

Optimization of inoculum to substrate ratio for bio-energy generation in co-digestion of tannery solid wastes

“…In the processing raw hides and skins into finished leather, around 500-600 kgs of process solid waste will be generated per tonne. In the waste so generated, 70-230 kgs will be fleshings (Sundar et al 2010). These fleshings were used in industries for glue production until recently but today they are not being used since other types of glues are available.…”

Experiments to obtain new bioproducts based on protein extracts from wet-white leather waste intended for the total or partial replacement of phenol formaldehyde resins in wet finishing of leather

“…The use of protein materials (collagen) to obtain new auxiliaries for leather processing is an important component of research in the field [3][4][5][6][7][8][9][10][11][12][13]. Figure 1 schematically shows the experimental model for obtaining collagen hydrolysates from chrome-free tanned (wetwhite) leather waste.…”