1a. Objectives (from AD-416):
1. Develop commercially viable hide preparation and leather processing methods that are environmentally friendly while maintaining and improving the quality and/or value of hide products. 1A: Develop computational and laboratory models for predicting the effectiveness of new chrome-free tanning agents. 1B: Develop improved environmentally friendly processes for hide preparation. 2. Create commercially viable hide-quality sensing technologies that are more rapid, accurate, precise, nondestructive, and cost-effective than current systems. 3. Develop technologies that enable new products from hides such as green composites (reinforced with hide fibers), nonwoven fabric filters, and new fillers and coatings for leather. 3A: Develop green composites and fibrous materials from hides. 3B: Develop new applications for tanning waste.
1b. Approach (from AD-416):
To develop a basis for designing or selecting effective chrome-free tanning agents, the results of studies of the interactions between collagen and current or proposed tanning processes will be integrated to give the best overall evaluation. The ERRC computational molecular model of collagen will be used to predict how the secondary or tertiary structure of collagen might be affected by a proposed modification. The model can predict if the modifier will fit into the structure, and how likely is the modifier to attach to telopeptide residues or form bonds with sidechains in the end-to-end gap between triple helices. Bench scale experimental model systems using collagen at different stages of molecular complexity (soluble collagen, milled collagen or powdered hide) will be used to evaluate by physical, chemical and biochemical methods the effect of these modifications on collagen. The development of effective and eco-friendly methods for removal of manure and other organic contaminants from animal hides will build on the incorporation of glycerol or biosurfactants or combination of both. Methods to enhance hide preservation using less salt or salt-free alternatives will also be developed. Environmental and economic concerns in terms of obtaining better quality hides and higher returns are the major criteria for developing and accepting new and alternative cleansing and preserving techniques. The goal is to not completely remove all of the manure prior to processing but to achieve a state where the manure/hair adhesion can be broken by a mechanical removal process without removing the hair at the root or tearing the grain. The advanced evaluation technology for the detection of hide defects and the evaluation of hide quality will be developed by incorporating airborne ultrasonic (AU) technology. Green composites will be designed and prepared with gelatin as the matrix reinforced with collagen fiber networks. Both components will be derived from hides. In addition, new fibrous products such as filters having a nonwoven fibrous structure will be prepared from fine diameter collagen fibers (fibrils). Collagen fiber networks will be obtained from split hides that have been processed to remove the noncollagenous materials. The use of chemical and biochemical techniques for enhancing the properties of tanning byproducts will proceed concurrently with the work on tanning. To demonstrate a potential role for protein recovered from leather waste, used alone or in conjunction with other renewable agricultural resources, model systems will be developed, in which these renewable resources will be treated with known chemoenzymatic crosslinking agents to determine functional properties. Effects then will be made to establish if these products would be appropriate to be used in leather processing, for example as potential fillers, coatings and encapsulating agents. Aqueous gelatin will also be combined with fibrous protein waste products, such as chrome shavings, buffing dust, feathers, and meat & bone meal, and then the mixture will be modified with enzyme to prepare products, such as films, with unique functional properties.
3. Progress Report:
For the development of models to predict the effectiveness of chrome-free tannages (Objective 1a), powdered hide was prepared at each step of the pretanning and tanning process from hides that had been dehaired by traditional and more eco-friendly methods. The effectiveness of typical tannages on hides dehaired by different methods were evaluated to assist the tanner in modifying later stage processes. Computational methods were used in the development of a fundamental understanding of tanning mechanisms. The collagen microfibril model was updated to incorporate newly published data on collagen structure. Methods were developed for the inclusion of water, an essential component of leather, and for the evaluation of tanning agent effectiveness. In the development of environmentally friendly processes for hide preparation (Objective 1b), a new soaking formulation, which incorporated crude glycerol and sodium carbonate, and reduced biocide and surfactant content by 75% compared to formulations currently in use, was developed and evaluated. The new formulation had significantly improved efficiency for removal of hardened manure from the hide. Because the new formulation was 30% less efficient as a microbial growth inhibitor, several eco-friendly additives such as enzymes that can attack the manure components and enhance microbial growth inhibition are being evaluated. For the creation of commercially viable hide-quality sensing technologies (Objective 2), project scientists applied airborne ultrasonic methods to characterize the defects in hides. Test parameters were fine tuned to optimize the detected images for leather and hide defects. Better detection of defects was achieved by increasing the ultrasonic wave frequency to above 200 MHz. Furthermore, by using statistical data/cluster analysis software recently purchased, project scientists are now able to numerically present the images on leather and hide defect detection. In the development of technologies for new products (Objective 3a), the fibrous networks were cross-linked with glutaraldehyde and transglutaminase to stabilize the network structure, thereby preventing significant shrinkage of fibrous networks after drying. Project scientists also developed the methods for construction of green composites, which consisted of 5-15% collagen fibers and 85-95% gelatin. In the development of new applications for tanning waste (Objective 3b), studies were continued on the use of polyphenols with gelatin in preparation of fillers to enhance the properties of wet blue and wet white leather. In a cooperative research for oxidative dehairing of cattle hides, ARS scientists worked with the cooperator to optimize parameters for the development of a reproducible dehairing process. The cooperator, based on ARS scientists’ suggestions, installed the appropriate equipment and made adjustments that resulted in successful removal of the hair. During discussions with the cooperator, several additional concerns with respect to the final product were identified. These have been addressed, and the next phase is full industrial scale trials, which are in the planning stage.
1. Environmental-friendly dehairing formula. ARS researchers at Wyndmoor, Pennsylvania have developed an oxidative formula which readily removes hair from cattle hides leaving them clean and ready for a typical tanning process, and eliminates the use of sulfide in the tannery and from the waste stream. The formula that was developed can be adjusted for the type of hide to be processed (summer hides which have short hair and winter hides in which hair is much longer). The waste stream from this process, free of sulfide, can be mixed with an acidic waste. One major tannery, driven by pending environmental restrictions with respect to sulfide odor and the desire to reduce waste stream treatment and water consumption in their tannery operation, has entered into a Cooperative Research and Development Agreement (CRADA). The results of this research should demonstrate a benign dehairing alternative for the American tanning industry.
2. The collagen microfibril model, a tool for biomaterials scientists. Animal hides, a major byproduct of the meat industry, are a rich source of collagen, a fibrous, triple helical protein that self-associates in a staggered array with gap and overlap regions, to form a matrix of fibrils, fibers and fiber bundles, is uniquely suitable as a scaffold for biomaterial engineering. A major challenge for biomaterials is the stabilization of the collagen structure by means that are acceptable for the proposed end use. The bovine type I collagen microfibril model developed over several years by ARS researchers at Wyndmoor, Pennsylvania and recently updated, represents a slice through a five helix super coil containing gap and overlap regions as well as nonhelical telopeptides. This model can serve as a tool for predicting or visualizing the results of reactions intended to stabilize the matrix, insert an active agent, or otherwise modify collagen. It is expected to assist biomaterial engineers in designing new collagen based products.
3. An economical, eco-friendly and effective process to remove the adobe type bovine manure from hides. Successfully developed soaking formulations urgently needed to effectively clean raw hides for their storage, proper preservation and shipment abroad where they are processed to leather. ARS researchers at Wyndmoor, Pennsylvania stablished a MTA (Material Transfer Agreement) with an international company that supplied the enzymes that can attack the different components of adobe type manure, thus softening and removing it from the hide. When eco-friendly cleansing agents were added, including the enzymes, lowering the concentration of the major ingredients in manure removal formulation was made possible. In addition to avoidance of unwanted holes, the cheaper and more eco-friendly formulations did not adversely affect the leather products. In fact, the overall quality was improved, compared to the control leather that was treated traditionally. Because of food safety applications, the meat packing industry and stakeholders have expressed a desire to collaborate in terms of applications of the newly developed formulations on live cows or stunned animals immediately before its slaughter.
4. High performance leather fillers derived from gelatin recovered from tannery waste and modified with vegetable tannin. The production of leather from cattle hides generates significant amounts of inedible gelatin, and currently produced chrome-free leathers have less desirable subjective properties than chrome tanned leathers. ARS researchers at Wyndmoor, Pennsylvania modified gelatin with the vegetable tannin, tara, a gallotannin, extracted from the pods of the small tara tree (caesalpinia spinosa) to produce a product that could be used effectively as a filler in leather processing. Tara modified gelatin is almost colorless, an advantage in production of light colored leather; it also imparts light-fastness to leather. Conditions (pH, time, temperature and concentration) for modification of gelatin by tara were optimized to give products with unique physicochemical properties. Conditions (pH, time, temperature and concentration) for modification of the protein were studied and characterized; products with unique physicochemical properties resulted. Thus a byproduct (gelatin) from leather-making process, modified with a common polyphenolic tanning agent (tara), can be employed to make finishing products for the leather-making process.
5. Superior fibrous structure developed for constructing novel products from hides. Hides are the most valuable byproduct of the meat packing industry. The US is the world’s 3rd largest hide producing country and currently produces approximately 35 million cattle hides annually. Due to fierce competition in global markets, the American leather and hides industries’ survival will depend on implementing new technology for producing novel products with superior quality. ARS researchers at Wyndmoor, Pennsylvania have addressed these challenges by developing high performance products such as green composites and high efficiency air filters from hides, which are more profitable than traditional leather products. The technology has been developed to produce fibrous materials having superior mechanical properties and high degree of fiber separation between fine collagen fibers. The results of this research will lead to the production of high quality fibrous products such as high efficiency air filters and fiber reinforced green composites. Several domestic tanneries have shown their strong interest in this new technology.Taylor, M.M., Lee, J., Bumanlag, L.P., Brown, E.M., Hernandez Balada, E. 2011. Use of high molecular weight biopolymers to improve the properties of chrome-free leather. Journal of American Leather Chemists Association. 106(12):353-359.