A potential new commercial method for processing leather to reduce environmental impact (original) (raw)
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Trends and advancements in sustainable leather processing: Future directions and challenges—A review
Journal of Environmental Chemical Engineering, 2020
In spite of sustained efforts by researchers, the gap between desired objectives with respect to sustainable leather technologies and achieved levels is still at large. At this juncture, this review presents an array of sustainable greener options addressing all major unit operations of leather making. As an alternative to traditional preservation, phyto-based preservation options for raw skins & hides reducing total dissolved solids and chlorides around 70 % are discussed. Oxidative unhairing reducing biochemical oxygen demand & chemical oxygen demand around 40 % is detailed as an alternate to traditional unhairing that is both harmful and polluting in nature. High-exhaust tanning technologies based on co-polymers increasing uptake to 95 % level are presented. The case of metal-free, organic only glyoxal/ wattle-tanned leathers with enhanced organoleptic properties is discussed. A starch-grafted collagen hydrolysate co-polymer exhausting dye up to 96 % is presented as high-exhaust dyeing system in this paper. Also, laccase-enzyme-based bio-degrading system for recalcitrant post-tanning effluent is furnished. A new method for extracting cellulose derivative from downstream wastes of sugar sector to be used in leather finishing is deliberated. A novel bio-filter based odour abatement system capturing noxious gaseous emissions from tannery environment is showcased as well. In all, this review reflects on the recent sustainable leather technologies that have potential for commercial exploitation in the near future.
Study and Practice on Alternative Eco-Friendly Processes for Leather Manufacture
2010
The inclusion of environmental issues in the definition and implementation of other policies is essential for achieving the objective of sustainable development. Leather industry, which has a considerable pollutant impact, must find efficient technological and economical solutions for this problem. Efficient raw material and energy usage, optimum process chemical utilisation, recovering and recycling of waste and substitution of harmful substances are important principles of the IPPC Directive. For tanneries the focal points are water consumption, efficient use and substitution of potentially harmful process agents and waste reduction within the process in conjunction with the recycling and re-use options. Chromium (III) salts are extensively used in the tanning process; about 90% of the leather manufactured worldwide is tanned using chromium (III). It has been used in the leather industry for almost 150 years, because it remains the most efficient and versatile tanning agent availa...
Waste Management, 2019
One of the long lasting problems associated with leather industry is to meet environmental standards for both liquid and solid wastes. Statistics show that one tonne of wet-salted hides/skins yields around 650 kg of solid waste. Among various wastes generated, trimmings for the most part have been underutilized. Collagen presents in trimmings waste are effectively used but hair goes unutilized or at the most as feed for boilers during gelatin manufacturing. Hence, newer technology is needed for complete and effective utilization of raw trimmings. In leather manufacture, formaldehyde condensates polymers are used as re-tanning agent to enhance the compaction of leather. However, these products are hard for biodegradation and also cause the release of free formaldehyde in leather, which is a known carcinogen. Here, there is a need for development of formaldehyde free re-tanning agent for eco-benign leather processing. In this work an attempt had been made to develop formaldehyde free biodegradable eco-benign retanning agent from raw trimming of tannery solid waste as a circular economy model. Alkaline (7.5% w/w NaOH)-hydrogen peroxide (10%w/w) pre-treatment followed by thermal hydrolysis at 100°C for 5 h was an optimized method for effective hydrolysis of trimmings and the process of preparation of product results in the holistic utilization of raw trimmings. The developed product was characterized using Dynamic light scattering and FTIR techniques. The product prepared was further used in leather manufacture as a re-tanning agent and was found to impart multifunctional properties to leathers such as fullness, grain tightness and shade of dye brilliance. Product improves the mechanical strength characteristics of leather and also the exhaustion of post-tanning chemicals. SEM analysis shows that the experimental leather is more compact and flat than control. This novel strategy had not only solved the issue of solid waste but also resulted in a greener leather auxiliary leading to greener environment.
The leather industry deals with proteinous skin material for the conversion of leather and this generates huge amount of solid and liquid wastes giving rise to pollution that needs to be overcome by introducing sustainable cleaner technologies. This review describes various eco-friendly challenges and major achievements for abatement of pollution in leather processing. Different cleaner technological methods in preservation of raw hides/skins, unhairing, tanning and dyeing operations are discussed here. Cleanerpreservation techniques by using chemicals and biological agents have been developed to reduce pollution problems of salt up to a great extent in leather processing operations. Process intensified operations have helped to achieve better uptake and to manage pollution load. Enzymatic dehairing are implemented to reduce Bio-chemical-Oxygen-Demand (BOD) at the level of 40%, Chemical-Oxygen-Demand (COD) up to 50%. Improved biological methods for bio-degradation of dyes, azo-dyes and their mixtures and to reuse the liquors in the process to reduce the dye pollution load in the effluent streams are reviewed. Nano-Particle polymers and improved retanning materials have been synthesized for high exhaustion of dyeing and retanning properties. Mathematical models predicting kinetics and growth for the above processes are also reviewed. It could be concluded by utilization of these technologies, a possible reduction in pollution loads such as BOD & COD, upto levels of 50% & 40%, could be achieved in leather processing.
2016
In today's move to "sustainable production" the leather industry, as well as many other industries is recognized as a polluting one. Traditional chemical operations are polluting because of the levels of inorganic chemical waste. Process chemicals which are not consumed within the reactions necessary to convert collagen to leather are currently discharged to waste. These are usually applied during bulk production, such as inorganic agents from beam house and tanning processes, e.g. lime, sulphide, ammonium salts, sulphuric acid and sodium chloride, mineral tanning agents – mainly Cr(III) and the less common Al(III), Zr(III), Ti(III), Fe(III) salts -, whereas depending on the tanning process and the leather article produced organic chemical waste discharged comprises aldehydic and polyphenolic tanning products, bating enzymes, organic carboxylic acids and excess electrolyte stable synthetic fat liquors. It is rare for chemicals and water to be recovered for re-use from ...
Solid wastes generation in the leather industry and its utilization for cleaner environmentA review
Leather industry, one of the polluting industries because of generation of huge amount of liquid and solid wastes, also emits obnoxious smell because of degradation of proteinous material of skin and generation of gases such as NH 3 , H 2 S and CO 2. Solid wastes are raw trimmings, fleshings, chrome shavings, buffing dusts and keratin wastes. Accumulation of these wastes lead to sludge problem and choking of treatment pipes and finally results in reduction in efficiency of treatment plant. Treatment of solid wastes also is not cost effective, posing economic burden to the tanners. Leather industry in the developing countries is facing lot of solid wastes problem and many tanneries closed for not meeting biochemical oxygen (BOD) demand and total dissolved solids (TDS) norms. The objective of this paper is to review the kinds of solid wastes generated in leather industry and the useful technologies developed to overcome the solid wastes problem.
Hydrolysis of used leather and application of hydrolysates
Proceedings of the Estonian Academy of Sciences, 2024
The leather industry generates a significant amount of various wastes, and their utilisation is a serious task for researchers. Ways to reuse or decontaminate such waste are being developed intensively. Unfortunately, the reuse of finished leather, which eventually becomes waste, is almost unexplored. The present research is designed to evaluate the potential of finished leather hydrolysis to obtain protein hydrolysates suitable for reuse in leather processing and to establish factors that influence leather quality during such an application. Enzyme preparation Vilzim PRO Conc was characterised as a potential agent for such hydrolysis. The addition of 3-4% Vilzim PRO Conc is appropriate for the enzymatic stage of the hydrolysis process. It was established that after alkalineenzymatic hydrolysis of used leather powder the obtained hydrolysates are complicated systems containing proteins, chromium compounds, dyes, fatliquoring materials, etc. Hydrolysates could be used for the dyeing of chromed leather. The method of preparation for dyeing and dyeing of wetblue leather with the use of hydrolysate influences the depth of dye penetration and the quality of finished leather. It was established that the neutralisation process is not necessary before such dyeing. Also, an increased amount of formic acid is necessary to improve the bonding of fatliquors with dermal tissue after treatment with hydrolysate.
Recovery and utilization of proteinous wastes of leather making: a review
Reviews in Environmental Science and Bio/technology, 2011
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.
Studies on biodegradation of tanned leather
Scientific Bulletin. Series F. Biotechnologies, 2012
Wastes from the leather industry as well as insoluble and hard-to-degrade animal proteins are currently eliminated by incineration, method with high ecological disadvantages. In order to avoid these inconvenients, microbiological and/or enzymatic methods are examined. Leather degradation was performed in two trials: one enzymatic-assisted and the other microbial-assisted. Enzymatic hydrolysis of collagen, the representative protein of leather, was performed with collagenase type IA, with six enzyme concentrations, for up to 10 days. The hydrolysis yield was evaluated by free amino acids determination. Microbial hydrolysis involved 35 bacterial strains belonging to various genera (Streptomyces, Bacillus, Pseudomonas, Serratia etc), screened for their ability of growth in minimal medium containing bovine leather, ovine leather or wool as unique carbon or nitrogen sources. Three of these strains: Bacillus licheniformis ATCC 14580, Pseudomonas fluorescens ATCC 13525 and a new bacterial ...
Development of an Eco-friendly and Sustainable Method of Dechroming Leather Wastes
Textile & Leather Review, 2021
Huge quantities of chromium-containing leather solid wastes are generated during the production of chrome-tanned leather worldwide. Disposal of these huge quantities of leather solid wastes is a major challenge due to the presence of chromium, which is highly toxic (mainly in its hexavalent form) and detrimental to the environment. Sustainable and environmentally friendly methods of their disposal and treatment options for removing chromium are required so that the dechromed waste can be utilized to make useful products, such as fertilizer for soil conditioning, to improve agriculture, or other applications. In this study, therefore, a new method of dechroming leather solid wastes was designed, whose procedure and results were compared with three other commonly used methods. The focus of the various dechroming methods was on the evaluation of the degree of chromium extraction from chrome-tanned leather wastes without destroying the collagen tissues. The average total amount of extra...