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The utilization of natural fibers obtained from leather industrial wastes contributes to a circular economy and aids to the reduction in the usually high loadings of mineral flame-retardant additives employed to impart the flame retardancy in polymer systems. The present work investigates the relationship between viscoelastic properties and flame retardancy of thermoplastic starch multicomponent systems loaded with leather waste, aluminum trihydroxide used as flame-retardant additive, and bentonite clay. Different blending temperatures and rotational speeds during extrusion process are tested for the multicomponent systems. Rheological, morphological, flammability, thermal analysis, and tensile mechanical test are also used to characterize the obtained multicomponent systems. A detailed investigation of the viscoelastic properties through Han, Cole–Cole, and van Gurp–Palmen diagrams indicated that the fibers have to be well dispersed in the polymer matrix forming a network structure and that the material has to exhibit viscoelasticity to a moderate level, i.e., not too viscous and not too elastic as observed in the VGP diagram in order to impart the flame retardancy effect in the multicomponent system. These multicomponent systems with enhanced properties are a promising and sustainable alternative to traditional high-loaded flame-retardant systems taking advantage of the landfill disposal in local areas where leather wastes are a problem the great attention contributing to a circular economy. [ABSTRACT FROM AUTHOR]

The global leather industry generates large quantities of tannery waste. These leather wastes have a high fat content, which could be used for valuable products. This study focuses on the conversion of such fats into a biocrude to be distilled into a bio‐based hydrocarbon fuel blendstock. A biorefining technology defined as 'gas‐phase catalytic cracking' (GCC) over activated carbons, also referred to as 'greasoline', was used for conversion, and GC–MS/FID and simulated distillation for product characterization. The experiments were performed at ambient pressure and 450 °C reaction temperature, with 40 g h−1 of fat being processed over 55 g of steam‐activated carbon under a nitrogen atmosphere for a duration of 4 h. Fleshing oil obtained from the pre‐fleshing of double‐face lambskins by extraction with supercritical CO2 yielded almost the same mass fraction of organic liquid product (OLP) (59 wt%) as palm oil used as a reference (62 wt%). In both OLPs, n‐alkanes from heptane to heptadecane predominate, with a clear predominance of n‐pentadecane and n‐heptadecane and no unsaturated molecules among the major components. For both oils, about 85 wt% of the OLP is in the boiling range of diesel fuel, and about another 12 wt% is in the gasoline boiling range. The results show that mixtures of fatty acids extracted from leather tanning wastes can be used for value‐added products – in particular for the production of bio‐based hydrocarbon fuel blendstock. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing interest in improving energy efficiency and thermal comfort in low-income housing, especially in regions prone to extreme climatic conditions. Conventional construction materials such as bricks and concrete exhibit shortcomings in energy efficiency, resulting in high indoor temperatures. This scenario not only impacts residents' well-being but also increases energy consumption, especially for air conditioning systems, potentially straining the electrical infrastructure in hot climate areas, leading to power outages and adverse consequences for the community and local industry. This study proposes an innovative and sustainable solution: the use of expanded styrene-butadiene rubber (SBR) with micronized leather shavings, possessing thermal insulation properties. The thermal insulation capacity of the composites was evaluated using heat flow methods, hot/cold plate heat flow analysis, and impedance tube acoustic method. The SBR/Leather waste composite at 20 phr emerges as a viable, promising, and sustainable alternative, exhibiting significant thermal insulation capacity with a thermal conductivity of 0.073 Wm-1.K−1 and temperature attenuation close to 15 °C, potentially enhancing comfort and quality of life in urban areas. The thermal insulation results of the other composites also surpassed traditional construction materials such as building boards, plywood, fiberglass, asphalt roofing, and cement tiles. The study demonstrates the feasibility of reusing leather as a reinforcing filler in rubber-based foams to produce thermal insulation materials, offering a sustainable solution to mitigate urban heating and improve quality of life in cities.

The design of a single-sided cutting tool and a novel method of dimensional vibration dispersion of waste generated from collagen-containing materials are developed. Computer modeling of complex spatial vibration movements of the cutting part of the tool is used to construct hodographs and cross-section views. Options for controlling of the dimensions of generated chips are determined. Expressions for calculating the cutting force during chip separation and the dependence of the cutting force on angular velocities of complex movements of the tool are derived. [ABSTRACT FROM AUTHOR]

Abstract Footwear industries generate leather waste during the operation. Some of these wastes contain chromium, which may bring environmental concerns. This study aimed to reuse finished leather waste, the major part of these hazardous wastes, via producing a composite with thermoplastic polyurethane (TPU) for shoe soles. Finished leather waste containing black dyes and pigments was used to color the TPU. The finished leather waste was fragmented, milled, micronized and blended with TPU in a ratio of 10%, 15%, and 20% w/w to produce composite materials. The composite materials were evaluated by morphological and thermal characterizations, physical–mechanical analysis, and environmental tests (leaching and solubilization), which presented that the physical–mechanical and thermal properties were within the standard of shoe soles, and the composites can be classified as non-hazardous. The composites enabled a new way of coloring polymeric matrices and reusing leather waste. Graphical abstract

Micronutrients such as Zn, Cu, Fe, and Mn are required metals for plant crops to increase their yield and quality. Metals are included in numerous biochemical reactions as enzymes, co-enzymes, and co-factors. Copper, zinc, and manganese are essential for the development and growth of animal as pigs and broiler chicks. Amino acids are of significant importance and are used in many applications, fields, and industries such as food, animal feed, supplement, pharmaceutical production, and as biofertilizers. Fertilizers of inorganic mineral structure are hardly diffused from the leaf surface into the plant, while chelated minerals with amino acids provide a great advantage in increasing the absorption efficiency and translocation of minerals within the plant. Also, it was known that derivatives of free or chelated amino acids have marked antioxidant activity and are able to inhibit the development of tumor tissues and leading to increase immune protective abilities of the organisms. Nanotechnology increased the application efficiency of metal-amino acid complexes. Using nano fertilizers to plants is one of critical importance due to their unique properties in size and increased surface areas. It released the nutrients on demand and regulates plant growth (such as wheat, rice, barley, and rapeseed plants). Metal chelating complexes have found extensive applications in various fields of human interest. Chelators are used in medical applications; water softeners are included as ingredients in many commercial products such as shampoos and food preservatives and control heavy metal pollution in aquacultures. Amino acids may be used separately in chelation process as free amino acids or can be separated from plant or animal wastes. It can be separated by hydrolysis of plant or agricultural crop wastes as thrones of tomato and sugar beet plants. Also, it can be separated from animal origin as leather wastes and chicken feather waste or from whey of cow milk after mozzarella cheese formation. So, amino acid production from wastes decreases the cost of metal-chelated complex formation. [ABSTRACT FROM AUTHOR]

The article considers aspects of leather waste processing aimed at using dispersed waste for creating composite materials of various purposes. It is shown that a reduction in the relaxation and creep of the material is achieved by increasing the cutting speed. The proposed method of dimensional dispersion uses a claw-shaped impact cutting tool, the complex movement of which is powered by a high-frequency vibration motor. A model of the process of leather waste dispersion is developed in the LSTC LS-Dyna software for continuum mechanics modeling. [ABSTRACT FROM AUTHOR]

In this research, a new eco-friendly collagen polypeptide-based foaming agent (CPFC) was prepared via a hydrophobic grafting modification of the collagen polypeptide (CP) from oily acrylic resin, in which the CP was extracted from leather wastes. The molecular structure of CPFC was characterized by FTIR, TGA, XRD, and laser particle size tests. The results showed that the oily acrylic acid molecular chain segments effectively copolymerized with CP, improving the hydrophilic and lipophilic balance of CP molecules. Given the increase of acrylic resin content in CPFC, the surface tension of CPFC at the critical micelle concentration gradually decreased and tended toward the critical value (30 mN/m). The foamability and foaming multiple of 9-CPFC and 7-CPFC reached 535 mL and 31.89 times, respectively. Next, we prepared a CPFC-based foam concrete with a dry density of 500 Kg/m3 via compounding a mechanical CPFC foaming agent with concrete. The resulting CPFC-based foam concrete was then characterized using a universal testing machine, thermal conductivity meter, ultra-depth 3d microscope, and other analysis techniques. The results indicated that the 5-CPFC foam concrete possessed good foam stability and compatibility. Moreover, the pore size distribution of the foam concrete was uniform, showing a less stringy pore structure, and the water absorption rate and thermal conductivity levels were 27.8 % and 0.61 W/m·K, respectively. The compressive strength of cement was approximately 1.37 MPa, which exceeds the national standard. Moreover, it was found that the CPFC possessed certain retarding properties that were similar to cement, suggesting that it is a highly suitable additive for foam concrete.

The leather sector is currently under heavy threat to reduce environmental pollution problems associated with the generation of leather waste, especially in terms of public acceptance issues related to environmental welfare requirements. Leather waste must be disposed of in landfills, which has a significant environmental impact. The development of natural polymer/paper mill sludge-based leather replacements for the production of leather goods and footwear products is an alternative solution supported by the recycled leather industry. In this work, a study is carried out to prepare natural polymer leather sheet (NPLS) from leather waste (chrome shavings and buffing dust), paper mill sludge, and natural polymer [natural rubber latex (NRL)] by vacuum-pressure method, for their potential application in leather products industries. The NPLS was characterized by its physicochemical and mechanical properties. Various types of NPLS were produced by comprising different ratios of the NRL. Results portrayed that 300 mL w/v NRL significantly improved the physicochemical and mechanical properties of NPLS. Hence, the research has revealed a revolutionary idea of NPLS developed which is cost-effective, eco-friendly, and energy efficient. [ABSTRACT FROM AUTHOR]

This review delves into the processing of tannery solid waste, emphasizing fleshings and chromium-tanned leather waste. This paper centers on fat recovery, chromium elimination, and protein preservation, aiming to make them apt for animal consumption. This paper also assesses the potential of introducing such recycled products to the global market. Drawing on the literature from the past two decades, sourced comprehensively from Scopus and Web of Science, 36 articles were selected because of their significant contributions from leather production powerhouses such as India and Brazil. Fleshings have shown immense potential as animal feed, and the extraction of tallow and collagen from rawhide trimmings yields up to 98% and 93%, respectively. Fermented tannery fleshings, notably with Enterococcus faecium HAB01, also demonstrate strong antioxidant capabilities. The overarching consensus emphasizes the need for rigorous purification when dealing with chromium-containing wastes, addressing concerns tied to Cr (III) and Cr (VI). Furthermore, raw tannery fleshings stand out as a sustainable, cost-effective, and globally marketable solution for animal feed production. [ABSTRACT FROM AUTHOR]

Technology has progressed a lot in the last 20 years, today it is possible to obtain new polymer composites that show performance properties. The ever-increasing demand for new high-performance materials has determined the appearance of new polymer structures based on elastomers and various wastes (protein, cellulosic, elastomeric, etc.) from various fields (shoes, leather goods, etc.). This paper describes the obtaining and characterization of polymer composites based on NBR rubber (butadiene-co-acrylonitrile) and protein waste from the footwear and leather goods industry, cryogenically ground to micrometric dimensions and modified with PDMS (polydimethyl siloxane). PDMS has the role of a plasticizer, but at the same time it improves the dispersion of protein waste mixed in the polymer matrix. The polymer composites were obtained by the mixing technique and tested from a physical-mechanical point of view according to the standards in force. The characterization in normal condition and accelerated aging at 70°C for 168 h (it was carried out hot, using the hot air circulation oven method) was carried out after the samples were subjected to conditioning for 24 h at ambient temperature. Also, the polymer composite samples were subjected for 365 days to atmospheric conditions (sun, rain, wind, hail, light, etc.) to see their influence on the properties of the obtained polymer composites. [ABSTRACT FROM AUTHOR]

Chrome containing leather waste (CCLW) produces lots of air and soil pollution. CCLW is produced from leather industries. CCLW is very harmful to the human health after rotting. However, by using this waste at right time and right place, the pollution generated by them can be prevented. Though various attempts have been made to utilise CCLW in various applications, some attempts were also observed in the development of bio-composite material. But, still no researchers used CCLW in the development of aluminium-based composite material as reinforcement by FSP technique. This study attempts to use CCLW as reinforcement after the extraction of Cr in the form of collagen powder. Ball-milling of collagen powder and alumina has been carried out for 100 h. Mixture of ball-milled reinforcement particles were used to develop aluminium-based composite material. FSP technique was used to develop surface composite. FSP process parameters were first optimised using Box-Behnken Design. Optimum PSP parameters were found to be the number of tool pass of 1, tool rotational speed of 943.12 RPM and transverse speed of 23.56 mm/min. Tensile strength and hardness of composite developed at optimum FSP parameters improved by about 17.95% and 32.44%, respectively, with respect to the base material. [ABSTRACT FROM AUTHOR]

The carbonization of collagen-based leather waste to nitrogen-containing carbon is reviewed with respect to the preparation, characterization of carbonized products, and applications proposed in the literature. The resulting nitrogen-containing carbons with fibrous morphology have been used as adsorbents in water pollution treatment, in electrocatalysis, and especially in electrodes of energy-storage devices, such as supercapacitors and batteries. Although electrical conductivity has been implicitly exploited in many cases, the quantitative determination of this parameter has been addressed in the literature only marginally. In this report, attention has been newly paid to the determination of conductivity and its dependence on carbonization temperature. The resulting powders cannot be compressed into pellets for routine conductivity determination. A new method has been used to follow the resistivity of powders as a function of pressure up to 10 MPa. The conductivity at this pressure increased from 9.4 × 10−8 S cm−1 for carbonization at 500 °C to 5.3 S cm−1 at 1000 °C. The conductivity of the last sample was comparable with conducting polymers such as polypyrrole. The carbonized leather thus has the potential to be used in applications requiring electrical conduction. [ABSTRACT FROM AUTHOR]

Tannery waste–based gelatin composite film reinforced with cellulose II nanocrystal (CNC II) extracted from wet wipes using three different hydrolysis techniques is explored for its functional properties and possible utilization as a biodegradable packaging material. CNC II isolated using hydrogen peroxide (PCNC), citric acid (CCNC), and hydrochloric acid (HCNC) differed in morphological and crystalline character as investigated using DLS, FE-SEM, FTIR, and XRD analysis. The crystallinity of PCNC, CCNC, and HCNC was found to be 81.1%, 75.4%, and 86.1%, respectively. The highly crystalline CNC II (PCNC) incorporation improved mechanical stiffness of rawhide trimming waste–based gelatin films by 50% compared to control gelatin film. Maximum thermal decomposition with Tmax of 329 °C was obtained for gelatin films with PCNC nano-reinforcement. Films with CNC II were structurally stable and sufficiently antibacterial against Gram-positive S. aureus microbial strain. Strong interfacial non-covalent and hydrogen bonding interactions between gelatin and cellulose II nanocrystal have likely enhanced the properties of the composite films. Incorporation of CNC II reduced the surface wettability of the films and nanocomposites absorbed UV radiation as evidenced by transmittance value T280 of 0.19%. Nanocomposite films degraded up to 79.9% of initial mass within 7 days of soil burial. Furthermore, based on the optimized system, single-use packaging application of eggplant seeds has been demonstrated. [ABSTRACT FROM AUTHOR]

Leather and wool waste represent a high concern due to the low level of valorization and circular economy demands for upcycling of biomass resources. Both biomasses can be easily processed as protein hydrolysates and used as functional additives due to the amphiphilic and tunable properties of collagen and keratin proteins. The chemical, physical, and structural investigations of collagen and keratin hydrolysate properties showed that the chelating abilities due to carboxylic groups can be exploited for gypsum retardant additives. The molecular weights and amino acid compositions of three different hydrolysates showed only slight influences on the setting time of gypsum; all three proteins delayed the setting time of gypsum between 60 and 120 min, as compared to the commercial plaster with a 30 min setting time. Higher molecular weight and more carboxylic active groups showed slight improvements in the setting time of mortars. The improved properties of keratin hydrolysate as compared to low molecular collagen hydrolysate were attributed to foaming and conductive properties. The mechanism of mortar setting delaying through calcium ions complexation by protein hydrolysates was shown by electric conductivity evolution of plasters with and without protein additives over time, supported by foaming properties, amino acid, and functional groups' composition. Lower bending strength values for the higher concentration of proteins do not reduce the potential to use the protein hydrolysates as retardant additives in mortar fabrication. [ABSTRACT FROM AUTHOR]

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 extractable chromium content (Cr2O3) in the dried leather waste samples was found to be 3.67%. The new method was found to be relatively more efficient, environmentally sound and less cumbersome than all the other methods investigated in this work. At P-Value of < 0.05, concentrations of chromium extracted and %TKN in residual collagen hydrolysate reached up to 99.89% and 52.89%, respectively. The levels of total ash and total organic carbon were also relatively high in the resultant collagen hydrolysate (i.e. 12.42% and 23.27%, respectively). The t distribution test on the results of the various dechroming methods confirmed that there was a significant difference at 95% confidence interval, since t (calculated) was greater than t (tabulated). It was concluded that nearly all the chromium in chrome-tanned leather wastes can be removed with a simple technology, which is sustainable and environmentally sound.

In this study, a blend of graphene oxide (GO), leather waste (leather sludge(LS)/leather fleshings (LF)), nanocellulose (nano-C) (biopolymer), and glycerol (Gly) homogeneously in alkaline aqueous solution is used to produce biopolymer blended solution (BBS), by chemical polymerization, for use in bioenergy. The efficient and eco-friendly BBS was characterized by its physicochemical and electrical conductivity properties. The BBS achieved the highest current density energy value (0. 53 mA cm-2) at 1. 2 V. The results of the research show the significance of evaluating bioenergy technological environmental performance from comparable perspectives to examine and identify environmental exchange from existing bioenergy developments.

Enzymes are the substances that speeds up a chemical reaction suitable for green chemistry and can be used to achieve ecological industrial processing in order to reduce the effects of industrial pollution. Microbiological degradation of pelt waste is amongst the permanent concerns of tanners. Several enzymes have been used in the leather industry to substitute the conventional process, mainly proteases. The objectives of this study were to isolate and identify bacteria which produced protease enzyme from tannery solid waste. The selected bacterial strains showed increased protease biosynthesis capacity, which had a significant hydrolytic action on pelt waste. The results obtained in this study demonstrated the ability of strains belonging to the Bacillus genus to synthesize increased amounts of proteolytic enzymes and to degrade pelt waste, as well as the possibility of using these microorganisms as a source of protease in various biotechnological processes. [ABSTRACT FROM AUTHOR]

In this work, we report preparation of bio-derived hybrid composite films from the protein extracted from raw trimmings emulsified with lipid obtained from tannery fleshing. Effect of varying concentrations of lipid at 10%, 20% and 40% v/w, homogenization rate and plasticization effect of lipid without glycerol were studied on the films' functionality. Chemical composition of the developed films was determined using ATR-FTIR. The influence of emulsification conditions on the surface topography was studied by scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). FTIR and microscopic evaluation indicated the heterogeneity of the films, which is caused due to phase separation. Mechanical, spectral and thermal studies revealed that the lipid addition without glycerol had an anti-plasticization effect caused by the irregularly dispersed solid lipid phase. Films prepared with 40% v/w lipid at 8000 rpm homogenization speed (TF40-8K) showed reduced water vapor permeability of 1.33 × 10-8 g/m.s.Pa and increased water contact angle of 82.2º as compared to control films. Transparency, color and optical characteristics indicated that the films became less transparent with increasing lipid concentrations. Valorization of different biomolecules from industrial wastes for preparation of eco-friendly plastics will be environmentally sustainable with application potential in agricultural mulching, packaging and bioelectronics. [Display omitted] • Tannery wastes – fleshings and trimmings – valorized for making eco-friendly biocomposites. • Fleshing lipid impacted mechanical and barrier properties of films. • Homogenization variation induced phase separation creating hydrophobicity. • Glycerol-free lipid emulsion films exhibited anti-plasticization effect. [ABSTRACT FROM AUTHOR]

Production of low-cost blended bricks from various solid leather wastes for use in the construction industry is effective waste management and an important approach to prevent pollution. Using leather sludges as a raw material in building materials have the potential to reduce environmental pollution. In this study, various solid leather industrial wastes were used, such as chrome shavings powder (CSP), buffing dust powder (BDP), and finished leather powder (FLP), respectively, and Clay: CSP, Clay: BDP, and Clay: FLP bricks were prepared by mixing clay. The physicochemical and mechanical properties of the bricks were investigated. The structure and compactness of the bricks were revealed by scanning electron microscopy (SEM). The blended bricks have unique mechanical characteristics and are promising models for new construction applications. Compared to clay, an improvement was observed in the mechanical properties with an increase in the ratio of leather waste (50%) in the sample composition. The blended bricks are environmentally safe and cost effective for the novel brick manufacturing approaches. [ABSTRACT FROM AUTHOR]

Chromium tanned leather wastes (CTLW) and vegetable tanned leather wastes (VTLW) were used as adsorbent materials to remove the Biebrich scarlet dye (BS), as an anionic dye from wastewater, using an adsorption method. The effects of various factors, such as weight of leather waste, time of shaking, and the starting concentration of Biebrich scarlet dye, temperature and pH were studied. It described the adsorption process using Langmuir and Freundlich isotherm models. The obtained results agreed well with the Langmuir model, and the maximum adsorption capacities of CTLW and VTLW were 73.5294 and 78.1250 mg.g-1, respectively, suggesting a monolayer adsorption process. The adsorption kinetic was found to follow a pseudo-second-order kinetic model with correlation coefficients R² > 0.9982 and 0.9900 for CTLW and VTLW, respectively. The results predicted that chromium leather wastes were more suitable adsorbents for the removal of BS dye from wastewater than vegetable tanned leather wastes, and the adsorption process is endothermic, according to the study of the effect of temperature. [ABSTRACT FROM AUTHOR]

• Activated carbon from leather waste was prepared and used as a catalyst carrier for toluene removal. • The interaction between Ce and Co leads to an increase in the lattice oxygen content and oxygen mobility. • Ce 3.5 Co 3.5 AC catalyst has the optimal catalytic activity and excellent water resistance. • The reaction mechanism and pathways are investigated by in situ DRIFT. A series of CeCoO x /AC catalysts using leather waste based activated carbon as the carrier were prepared by a modified impregnation method, and the catalytic performance of toluene oxidation was investigated. Among them, Ce 3.5 Co 3.5 AC catalyst with Ce and Co loading being both 3.5 wt% exhibited the optimal catalytic activity (T 90 = 246 ℃). SEM (Scanning Electron Microscope), Raman, XRD (X-ray Diffraction), H 2 -TPR (Hydrogen Temperature Programmed Reduction), O 2 -TPD (Oxygen Temperature Programmed Desorption) and XPS (X-ray Photoelectron Spectroscopy) characterization results revealed that there is interaction between Ce and Co, leading to improved redox ability and oxygen mobility, more oxygen vacancies and lattice oxygen, higher Ce3+/Ce4+ and Co3+/Co2+ ratio, multi-factorial synergies which are positively responsible for its superior catalytic activity. Additionally, the in situ DRIFTS results on Ce 3.5 Co 3.5 AC catalyst verified that benzyl alcohol, benzoate are the main intermediates. Meanwhile, Ce 3.5 Co 3.5 AC catalyst has good resistance ability to water (10 Vol%) and catalytic stability, which has the potential to be applied in practice. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper reviews the advantages and disadvantages of the use of fertilizers obtained from leather waste, to ameliorate the agricultural soil quality. The use of leather waste (hides and skins) as raw materials to obtain biopolymer-based fertilizers is an excellent example of a circular economy. This allows the recovery of a large quantity of the tanning agent in the case of tanned wastes, as well as the valorization of significant quantities of waste that would be otherwise disposed of by landfilling. The composition of organic biopolymers obtained from leather waste is a rich source of macronutrients (nitrogen, calcium, magnesium, sodium, potassium), and micronutrients (boron, chloride, copper, iron, manganese, molybdenum, nickel and zinc), necessary to improve the composition of agricultural soils, and to remediate the degraded soils. This enhances plant growth ensuring better crops. The nutrient release tests have demonstrated that, by using the biofertilizers with collagen or with collagen cross-linked with synthetic polymers, the nutrient release can be controlled and slowed. In this case, the loss of nutrients by leaching into the inferior layers of the soil and ground water is minimized, avoiding groundwater contamination, especially with nitrate. [ABSTRACT FROM AUTHOR]

Currently, environment-friendly high water-absorbing, water-retention, water-resistant, and water erosion resistance materials are the research hotspot in agricultural film. In this research, a new type of leather waste-based liquid film mulching (WG) was prepared by waterborne polyurethane (WPU) grafted with gelatin(G) extracted from leather waste. The interacting behavior of the prepared WG with soil particles was characterized including soil particles morphological changes, water-retention, water-resistant, water erosion resistance, and farming experiments. The SEM revealed that the WG could form a "coating layer" on the soil surface. The coating layer could improve the water-retention and water resistance of the soil. Meanwhile, the farming applications found that the soil sprayed WG could form a certain closed space which played a role in water-resistant, water erosion resistance, heat preservation, and moisture retention for maize. Especially, the water-absorbing, water retention, and thermal-retention efficiency reached 80.5%, 20.2%, and 23.1 °C, respectively when the WG content was 50 g/m² in the soil experimental sample. Moreover, after the WG was sprayed evenly on farmland, the germination period of the maize seeds was significantly shortened, the germination rate reached 92%, which was far higher than that of the bare soil. As an environment-friendly leather waste-based liquid film mulching, the WG could not only meet the growth of maize, increase yield, but also provide new ideas for the recycling of leather waste. [ABSTRACT FROM AUTHOR]

The combination of carbon and nitrogen-rich co-substrates results in a better balance and increases the stability of the anaerobic co-digestion (AcoD) process. In this work, the AcoD process of waste from the leather industry (shavings and sludge) with waste from agriculture (oat straw) was assessed with regard to the energy (biogas production) and waste treatment efficiency (reduction of organic matter). The results indicate that the addition of untreated oat straw improved the AcoD process, increasing biogas production (25.44 mL of cumulative biogas/g of VSS added) by almost 60% when compared to the AcoD of only leather waste (16.17 mL/gVSS). Also, the effect of acid, alkaline, thermal, and the combination of these pretreatment techniques was evaluated on the lignocellulosic composition of oat straw and on methane yields. Pretreatments improved the characteristics and bioavailability of oat straw, particularly in methodologies that use alkali, with a significant increase in cellulose content accompanied by a decrease in hemicellulose and lignin content. However, the possible formation of secondary products or sterilization of important microorganisms did not reflect in a greater production of biogas: 21.06 mL/gVSS for oat straw pretreated only with HCl and 21.91 mL/gVSS for oat straw pretreated with HCl in autoclave; 5.20 mL/gVSS for oat straw pretreated with NaOH; and 3.43 mL/gVSS for oat straw pretreated with NaOH in autoclave; thermal pretreatment probably has generated toxic compounds from hemicellulose and cellulose degradation, which inhibited the AcoD process and, as consequence, virtually no biogas was produced. [ABSTRACT FROM AUTHOR]

Currently, environment-friendly high water-absorbing, water-retention, water-resistant, and water erosion resistance materials are the research hotspot in agricultural film. In this research, a new type of leather waste-based liquid film mulching (WG) was prepared by waterborne polyurethane (WPU) grafted with gelatin(G) extracted from leather waste. The interacting behavior of the prepared WG with soil particles was characterized including soil particles morphological changes, water-retention, water-resistant, water erosion resistance, and farming experiments. The SEM revealed that the WG could form a "coating layer" on the soil surface. The coating layer could improve the water-retention and water resistance of the soil. Meanwhile, the farming applications found that the soil sprayed WG could form a certain closed space which played a role in water-resistant, water erosion resistance, heat preservation, and moisture retention for maize. Especially, the water-absorbing, water-retention, and thermal-retention efficiency reached 80.5%, 20.2%, and 23.1 °C, respectively when the WG content was 50 g/m2 in the soil experimental sample. Moreover, after the WG was sprayed evenly on farmland, the germination period of the maize seeds was significantly shortened, the germination rate reached 92%, which was far higher than that of the bare soil. As an environment-friendly leather waste-based liquid film mulching, the WG could not only meet the growth of maize, increase yield, but also provide new ideas for the recycling of leather waste. [Display omitted] [ABSTRACT FROM AUTHOR]

Hair waste from unhairing of bovine hide has high protein content and is also a current issue in tanneries as it causes high organic load to the wastewater. Given that, this study aims to recover keratin from bovine hair by investigating its hydrolysis from remaining solid hair from leather processing and unprocessed hair. For the keratin hydrolysis, 2-mercaptoethanol, Na2S, H2O2, NaOCl, NaOH, C2H4O2S, and HCOOH were tested. SDS-PAGE and the yield analysis of the extracted solution indicated that it was possible to recover proteins with molecular weights around 20 kDa, reusing this hair waste. In an oxidizing pathway (H2O2), 75% of the protein was extracted from the recovered hair powder, and a yield of up to 40% was achieved with Na2S in a reductive pathway. Overall, the results demonstrated good recovery of keratin from bovine hair, turning what was previously considered waste into an interesting source of this protein. [ABSTRACT FROM AUTHOR]

The leather industry is known as one of the potentially hazardous and polluted sectors due to the large consumption of water and chemical materials. There are many companies with a high level of environmental protection systems in the leather industry, with Zero Hazardous Substances Certificate and using chemical materials with exhaustion yield. There is also a great effort to replace and reduce potentially hazardous materials, petroleum origin materials, and solid waste generated by hide processing. It is not only about discharging chemicals to the environment but also about releasing valuable biomass sources (collagen, keratin, etc.). Bovine hair is one of the low biodegradable wastes during bovine leather processing. In this study, bovine hair was converted to keratin hydrolysate (KH) by an alkaline process. KH was selected to enhance the biocompatibility of the hydrogel and grafted with acrylic acid (AA) and acrylamide (AAm) monomers to obtain superabsorbent hydrogels. Polymerization was conducted in the presence of N, N'-methylene bisacrylamide (NMBA) which was used as a cross-linking agent, and ammonium persulfate (APS) as an initiator. Different keratin/monomer ratios, cross-linking agents, and initiator amounts were kept as variables to aim for the highest swelling capacity. Synthesized hydrogels were chemically, morphologically, and thermally characterized via Fourier Transform Infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and thermal gravimetric analyzer (TGA). FTIR, DSC, and TGA results confirmed the grafted structure. The maximum swelling ratio was recorded at pH 9, at the end of 48 h as 1791%. Sponge-like hydrogels were successfully synthesized, and waste keratin was successfully valorized through hydrogels which can be used in high-value-added areas such as health, agriculture, hygienic products. [ABSTRACT FROM AUTHOR]

Summary: The following paper presents in detail the results of two separate test runs of the leather waste gasification process. The first one was conducted in a laboratory and the second in an industrial installation with 2.5 MW of thermal power. The aforementioned gasification plant transforms 1000 kg/h of various leather waste with ER = 0.38‐0.4 producing hot producer gas with a calorific value of 4.1‐6.5 MJ/m3 used for steam production. This local energy center uses waste from a leather processing factory to secure the energy needs of the host plant and produces ashes with up to 55% of Cr2O3 suitable for Cr recovery and reuse in the tanning process. The gasification of refuse‐derived fuel derived from the used leather goods illustrating the effectiveness of separate collection and thermal transformation of Cr containing waste was tested as a path to closing the chrome economy cycle in the leather industry. Moreover, the effectiveness of Ca(OH)2 for the purification of flue gas resulting from syngas burning and removal of SO2 and HCl was taken into account. Ashes analysis from gasification and flue gas cleaning showed very low Cr(VI) content. The study, according to the laboratory and industrial‐scale tests, proves that gasification leads to effective energy conversion of leather waste and can be advantageous in comparison to incineration, mainly due to producing safer ashes that are easier for handling and processing, with the simultaneous production of valuable syngas. [ABSTRACT FROM AUTHOR]

Leather is among the most ancient, widely used materials worldwide. Industrial-scale leather production produces large quantities of organic waste attained during shaving and buffing steps during processing. In this study, leather wastes (LW) are used as fillers in flame retarded polymer composites. LW is investigated as a multifunctional bio-filler that enhances the fire performance of flame retarded poly(ethylene–vinyl acetate) (EVA) containing phosphorus flame retardants (P-FRs) ammonium polyphosphate (APP) or a melamine-encapsulated APP (eAPP). Using LW from tanneries as adjuvants to enhance P-FRs in EVA reduces industrial wastes that otherwise require costly waste management solutions. Materials are characterized multi-methodically via mechanical tests, electron microscopy, rheology, thermogravimetric analysis, evolved gas analysis, and condensed phase FTIR, also reaction-to-small-flames and cone calorimeter tests. EVA containing 10 wt-% LW and 20 wt-% P-FRs achieve 20% reductions in fire loads versus EVA, and up to 10% reduction in effective heats of combustion versus EVA with equal (30 wt-%) P-FR loadings. Enhanced char stabilization of EVA composites with LW and P-FRs lowered peaks of heat release rates up to 53% compared to EVA, and up to 40% compared to equal P-FRs loadings. Synergisms between LW and P-FRs in EVA are quantified. A chemical decomposition mechanism is proposed.

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Abstract Pressure sensor can be applied in a wide range of fields, such as voice recognition, human motions detection and artificial electronic skin, the sensing of which is greatly influenced by the flexibility and stretchability of substrate materials. Here, based on the piezoresistive effect, new kinds of flexible pressure sensors have been realized from a pair of flexible and biocompatible collagen films: one is coated by silver nanowires (Ag NWs) and the other by interdigital electrode, respectively. The collagen films are regenerated from leather waste and could bring economic benefits to society. The prepared pressure sensors are applied for voice recognition and human motion detection. Graphical abstract A flexible pressure sensor based on two layers of regenerated collagen films coated silver nanowires (Ag NWs) and interdigital electrodes respectively are obtained. The flexible collagen films are prepared by dissolving leather waste into ionic liquid, [BMIM]Cl. The fabricated pressure sensor displays potential applications in voice recognition and human physical motion detection, such as finger and wrist bending-releasing, which are expected to access the training data of athletes, monitor some physical activities of patients synchronously and act as a voice recognition device.

The processing of leather into leather is one of the oldest known manufacturing practices. The subsequent refinement of this technique over recent centuries has led to an increase in production, which in turn has led to an increase in waste production. Today, many of the by-products and waste streams from the leather industry have applications in industries such as petfood and in the production of collagen and derivatives, while others, such as waste from trimming and scraping the material, are disposed of in landfills, causing a detrimental environmental impact. For this reason, new alternatives for the treatment of these wastes, such as pyrolysis, are being investigated. The aim of this work is to assess the feasibility of recovering non-recyclable waste from the leather industry by pyrolysis. Waste from the tanning of cowhides with vegetable tannins and tanning with chrome salts, without pre-treatment, were used as raw materials. The operating conditions of the microwave-assisted pyrolysis were analysed by varying the time (15–30 min), the power (600–1000 W) and the dopant (carbon from the pyrolysis itself) in a batch reactor that allows to treat about 30 g of a sample. Three fractions (liquid, solid and gaseous) were obtained from the waste treatment, and the liquid and gaseous fractions were characterised using different analytical techniques. The solid fraction can be used as fuel due to its high calorific value of more than 20 MJ/kg and its low ash content, with the residue containing vegetable tannins giving the best results with a calorific value of up to 28 MJ kg−1. In addition, the solid fraction can be used as activated carbon after activation treatment, which allows for a more technical use, e.g., in the chemical industry. The liquid fraction contains significant amounts of phenolic groups, such as pyrrole and phenol, as well as other derivatives. Pyridine, aniline, cresol and succinimide, among others, were also found. This makes it a valid source of chemical compounds of high added value in the chemical industry. In addition, the heavy liquid fraction has a good heat capacity of more than 21 MJ/kg, which makes it suitable for use as a fuel. The microwave-assisted pyrolysis process results in the possibility of obtaining products from waste that would otherwise be destined for landfill, thereby obtaining a large number of products and bioproducts with the ability to be reintroduced into the value chain quickly and easily.

Zero-waste is an ambitious goal to encourage sustainable production, consumption optimum recycling and resource recovery. The recycling and resource recovery of chrome-tanned leather waste is a difficult proposition because of the three-dimensional chemical network of collagen, which renders leather waste incompatible to polymer matrices. Many attempts have been undertaken to reuse leather waste, most of them require technological processes and challenging chemical pretreatments, which make the reuse an economically disadvantageous industrial operation. The paper aims to show how a very fine separation of leather solid waste leads to raw materials suitable for mixtures with natural rubber, without any chemical pretreatment. In other words, the paper intends to be a stimulus to manage leather solid waste carefully to start a cleaner and more profitable production. In particular, various industrial compounds containing different concentrations of post-tanning dyeing, or chrome shaving or oil-tanning and natural rubber were vulcanized through a standard preparation. Some compounds were also reinforced with carbon black and the vulcanization kinetics were monitored through rheometer. Experimental results indicate that there exists an optimal concentration of waste such that post-tanning dyeing post-tanning and chrome shaving are suitable for manufacture floor mats, soles and heels while oil-tanning waste can be used for making hose or conveyor belts. The mechanical performances of the articles prepared by direct mixing with leather waste are the same as those of commercially distributed rubber products. [ABSTRACT FROM AUTHOR]

Gelatin extracted from chromium-tanned leather wastes (CTLW) has a lower molar mass because of the more aggressive extraction process needed to disrupt chromium-collagen bonds when compared to gelatin extracted from the bones, skin, and connective tissues of animals. As a consequence, CTLW gelatin is more hydrophilic, thus it is harder to apply in the production of polymers. To overcome this issue, in this study, films produced with starch, CTLW gelatin, commercial gelatin (as a comparative), and their blends were cross-linked with glutaraldehyde. The cross-linking reduced the crystallinity of the films, impairing the reorganization of gelatin chains into a triple helix structure, which balanced the effect of the higher molecular chain, while not altering the films' tensile strength. It increased the elongation at break and reduced the solubility and the swelling degree by up to 53% and 69%, respectively. These results stand as a great advance for the practical use of starch-CTLW gelatin films. [ABSTRACT FROM AUTHOR]

Alkaline hydrolysis of chromium-tanned leather wastes (CTLW) is a well-known process that allows the extraction of its most valuable portion: the protein. However, alkaline hydrolysis is time-consuming. It usually takes from 2 to 10 h to be completed. In this work, alkaline hydrolysis was performed in a steam explosion reactor, using CaO as the alkalinizing agent and aiming at a short-time process. Three different temperatures and residence times were tested: 130, 140, and 150°C; 5, 10, and 15 min. When performed at 140°C for 10 min, the steam explosion in alkaline medium resulted in the optimum combination of protein extraction yield (30%) and gelatine quality (viscosity of 2.4 cP at 25°C in a 24.6 g/L protein solution – 39 kDa of molecular mass M ¯ w). Not only a high extraction yield was achieved, but when compared to traditional methods, steam explosion in alkaline medium reduced the process time by a factor that varied from 12 to 36 times. It also reduced chromium content in the gelatine by a factor that varied from 16 to 96 times. Finally, to produce a high quality product, the ash content of the gelatine was reduced from 11.8% (dry basis) to 1.2% (dry basis) through diafiltration. This purification allows the application of the gelatine, for example, in the production of polymeric films. [ABSTRACT FROM AUTHOR]

The current tendency of road builders and managers is to make asphalt mixtures with improved performance in terms of aging and fatigue resistance, better traffic behavior both in summer and in winter, as well as increased values for dynamic properties: elasticity, tracking, etc. In this sense, there is a permanent concern to find new materials and technologies for the preparation and implementation of asphalt mixtures that convey the desired properties to the layers. In this sense, the addition of microfibres and fibres, with dimensions ranging from 0.01-10 mm when preparing asphalt mixtures, transforms the bituminous binder used into a “composite material”, in which the matrix is the bitumen, and fibres are the dispersed phase, leading to the stabilization of the bitumen inside the mix, as well as to the reinforcement of the asphalt mixtures, giving them special properties. The paper presents laboratory experiments for obtaining smart biocomposites (leather fibres-asphalt mixtures) with applications in the field of road infrastructure. The resulting biocomposites were characterized by chemical, physical-mechanical and structural analyses. [ABSTRACT FROM AUTHOR]

• Substitution-based method for Cr leaching from CTLW was proposed. • Leaching process without destroying the collagen matrix. • Thermodynamic and kinetic parameters were obtained in this study. • The substitution-based Cr leaching mechanism was proposed. A substitution-based method for chromium (III) leaching from chromium-tanned leather waste (CTLW) without destroying the collagen matrix was proposed. The leaching efficiency of Cr (III) from CTLW using different organic salts was investigated and sodium oxalate (OA-2Na) was considered to be the best Cr leaching agent. The effects of leaching time, temperature, pH, concentration, shaking speed and leather thickness on Cr leaching rate were investigated and a Cr leaching rate of 98% was obtained. Thermodynamic parameters (Δ G0 < 0, Δ H0 > 0 and Δ S0 > 0) were obtained in this study. The kinetic data fitted well with the first-order kinetic equation. The apparent activation energy (Ea = 82.9563 kJ/mol) and the frequency factor (A = 2.96 × 1011) were obtained. The collagen matrix remained intact after Cr leaching by the characterization of SEM and FTIR. A substitution mechanism was proposed that Cr (III) in CTLW was complexed with oxalate and dissociated from the collagen matrix. [ABSTRACT FROM AUTHOR]