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Solid waste from all walks have registered their environmental impact by breathing out large amount of greenhouse gases. In this work, not only a waste to wealth strategy for effective utilization of trimmings (Solid waste) from tanning industry to recover gelatin is depicted, but also to use the extracted bio-polymer to develop a product alternative to non-biodegradable plastics. Ability of gelatin to form films is capitalized in the preparation of a composite film system comprising equal percentage ratios of gelatin (Gel) and poly vinyl alcohol (PVA) through solvent casting method. This Gel/PVA composite film is envisaged for producing sustainable packaging film materials. As the existing packaging film materials sourced from petroleum based products cause degradation and disposal concerns, the proposed value addition on the gelatin extracted from waste can be a greener alternative. Through progressive optimizations Gel/PVA film system was incorporated with percentages of glycerol (Gly) and glutaraldehyde (GA) to have performance similar to the low density polyethylene (LDPE) film taken as control. Mechanical, analytical, thermal sealability and printability tests on the developed composite film Gel/PVA/Gly/GA gave optimum results for packaging applications.

Raw hides and skins are preserved before processing them into leather, to protect the skin protein from microbial attack. The salting method of preservation using about 50% w/w common salt is the most popularly practiced preservation method worldwide. This conventional system results in high saline wastewater leading to a huge amount of pollution load in terms of total dissolved solids and chlorides which is discharged into the effluent during the soaking process in leather manufacture. In order to overcome these wastes problem at their source, researchers have been involved in search of alternative preservation methods using salt-less or less-salt options. In the present study, the herbal Rumex abyssinicus (mekmeko) roots, which were shade dried at room temperature and powdered was investigated for its effectiveness in the preservation of goat skins. The efficacy of this new preservation method was assessed at different curing period for a month. In the assessment, the following parameters viz., moisture content, extractable nitrogen content, soluble hydroxyproline, hydrothermal stability, bacterial count, and visual evaluation of skins (hair slip and putrefaction odor) were assessed. The mekmeko preservation experiments were compared with parameters obtained using the conventional curing method. After 30 days of preservation, the experimental and control skins were processed into upper leather and their quality was evaluated by analyzing the physical characteristics, organoleptic properties and fiber structure using scanning electron microscope. The results showed that the curing system using 10% mekmeko powder with 15% common salt is efficient in preserving the raw goat skins. The quality of the experimental crust leathers produced from the optimized preservation system is comparable with the control leathers. The generation of the pollution load during leather processing was determined by analyzing biochemical oxygen demand, chemical oxygen demand, total dissolved solids, and chlorides from soaking liquor. Most importantly, 55% total dissolved solids and 70% chloride reduction in the soaking liquor was achieved by using the plant-based method of preservation. The less-salt preservation system based on mekmeko is a cleaner alternative for the conventional salt-based preservation method.

Discharge of huge quantities of raw skin/hide trimming wastes by leather industries has raised serious concerns on account of their environmental impacts. It is imperative to develop a simple method for the utilization of this waste to provide a practically feasible and economically viable solution. The trimmings contain high amount of fibrous protein, which are actually a valuable bioresource. The study presents the extraction of collagen, a product of high value, from raw trimmings. Experiments were carried out using propionic acid and acetic acid for the solubilisation of collagen from skin matrix. Of these acid extraction methods, propionic acid method showed higher yield of collagen (∼93%) compared to the acetic acid extraction (∼85%). The extracted collagen was further characterised by physicochemical techniques such as SDS-PAGE, circular dichroism and infrared spectroscopy. It was concluded that the collagen extracted from trimming waste using both acids were of type I and also found to have similar physicochemical properties. Therefore, the raw skin/hides trimming waste can be a cheap source of collagen, which has many high end applications like tissue engineering, biomaterials, cosmetics and pharmaceutical industry.

Leather is extensively used in the production of various lifestyle accessories such as shoes, bags, garments, upholstery, and various other products. The leather waste generated from the manufacturing units of leather and after the intended usage of the leather products leads to the accumulation of solid leather wastes. The studies on making the leather amenable for easy disposal is a priority research. A unique process prepared for the development of the tanning system and leather, which would be manageable for easy disposal (degradation under certain environmental conditions) after the intended usage of the product is an important need. In this present work, Gramineae Saccharum officinarum L. (Sugarcane Bagasse), a byproduct of the sugarcane industry is used as a tanning agent after converting the cellulose and hemicellulose content into dialdehyde polysaccharides from hydrolyzed bagasse (DAPB) by oxidation process. Leather from goatskins after conventional pre-tanning process (Soaking to Deliming), tanned by developed dialdehyde polysaccharides. The developed leather provided resistance to collagenase degradation, which reflects the tanning efficiency of dialdehyde polysaccharides. Additionally, tanned leather also provided reasonable mechanical strength. The leathers made from dialdehyde polysaccharides were observed to have properties comparable to conventional chrome tanned leathers. From hydrolyzed bagasse solution fungal strains are isolated and tested for the degradation of the crust dialdehyde polysaccharides tanned leather, where delimed pelt (untanned), chrome tanned, and vegetable tanned crust leathers were set as control. In comparison to delimed (untanned) pelt, the newly developed tanning system showed significant resistance to degradation. However, compared to chrome and vegetable tanned leathers, the dialdehyde polysaccharides tanned leather showed better biodegradation. The developed bagasse tanning system paves the way for a cradle to cradle approach in creating a circular economy and sustainable development in leather manufacture.

Leather industry is forced to adopt green manufacturing options due to consumer awareness and statutory environmental stipulation norms. Conventional leather manufacture involves various physico-chemical treatment processes, leading to the generation of wastewater with high pollution load. Several alternative leather chemicals and in-process control measures have been developed to overcome the environmental issues. Till date, no such significant measures have been found out. Sustainable leather manufacture necessitates complete redefinition of the conventional leather making processes. Replacement of water with alternative sustainable carrier medium could be one of the possible redefined approaches. In this perspective, an attempt has been made to summarize the current status of different alternative carrier medium and its pros and cons with respect to leather manufacture. Solvent selection tool, usage of supercritical fluid and switchable solvents in different unit processes of leather manufacture are the green chemistry approaches to be employed in order to overcome the drawbacks associated with alternative carrier medium based leather manufacture. This review focuses on such possible green chemistry approaches, challenges and critical factors for usage of alternate sustainable carrier medium in leather industry.

Leather processing involves various unit processes in which deliming is an essential unit process carried out conventionally using ammonium salts. This results in the generation of a huge amount of ammoniacal nitrogen and a considerable amount of total dissolved solids in tannery wastewater. In the current work, an effort has been made to design a deliming process using dry ice (solid carbon dioxide). It was observed that 2% (w/w) dry ice is adequate for the complete deliming of limed pelts of goat skins in 45 min; whereas the conventional process using 2% ammonium chloride requires 60 min. Morphological analysis using scanning electron microscopy shows no surface deposition or grain damage on delimed pelts processed using dry ice. Experimental leathers exhibit organoleptic and mechanical strength properties comparable to that of control leathers. The alternative method developed using dry ice reduces the generation of ammoniacal nitrogen, total dissolved solids, total Kjeldahl nitrogen and chloride from the deliming process by 98, 88, 95 and 94% respectively compared to the control process. This method also helps in reduction of chemical oxygen demand and biochemical oxygen demand in wastewater. Moreover, the methodology of using dry ice for deliming is very simple for practical applications. The option of using dry ice for deliming would be effective for cleaner leather manufacture.

Concern about pollution related problems in the global scenario are persuading all the processing industries to adopt cleaner manufacturing practices. Thus, the leather industry is also under pressure to look for effective alternative tanning materials for chromium. Natural products like vegetable tannins are regaining importance. However, there are limitations in the use of vegetable tanning materials because of its high organic load in the effluent, which are difficult to degrade leading to high chemical oxygen demand (COD). Moreover, conventional vegetable tanning process requires partial pickling that involves the use of sodium chloride, to suppress osmotic swelling. This results in very high amount of total dissolved solid (TDS) content in wastewaters. In this investigation, an attempt has been made to design an eco-friendly vegetable tanning process combining pickle-free tanning and application of proteolytic enzymes to improve the exhaustion of vegetable tannins. Such an approach has resulted in more than 95% tannin exhaustion in the case of the experimental process, an increase of 10% compared with the conventional vegetable tanning process. The tanned leathers showed slight improvement in hydrothermal stability. Physical and tactile evaluation of experimental leathers has been better than conventionally tanned leathers. Surface colour values illustrated negligible variation in colour and shade between control and experimental leathers. The resultant leather showed opened up, split compact fibre structure that has been well coated, indicating that the enzyme assisted tanning process did not bring about any major change or destruction on the fibre structure of the leathers. The optimized system has been field tested in a commercial tannery. The results showed that the enzyme assisted tanning process is efficient in terms of improved quality of leather and also led to reduction in total solids (TS), chlorides and COD loads. The enzyme assisted tanning system presented appears to be a viable option for combating pollution arising from the conventional vegetable tanning system.