Tannery Solid Waste Research Articles

Acid hydrolysis of untanned proteinous wastes from tannery industry in Bangladesh

Leather tanning industry, considered one of the polluting industries, poses various environmental threats to its every sphere. It produces various types of solid wastes as well as liquid wastes. Among the solid wastes, untanned raw trimmings contribute for about 5-7% of the total quantity of raw materials processed. If suitably utilized, these by-products of tanning industry could be a useful resource for various applications. This research work deals with utilization of raw trimmings of tannery solid waste to protein hydrolysate by acetic acid with varying acid concentration, acid solution, temperature and time. The maximum about 76% protein hydrolysate was obtained at 1.5M acid concentration and 80ºC.

Conversion of tannery solid waste to an adsorbent for high-efficiency dye removal from tannery wastewater: A road to circular utilization

The high value-added use of tannery solid waste and elimination of tannery liquid waste in the leather-making industry have attracted widespread attention. In this study, a MgO-doped biochar (MgO/BC) adsorbent was successfully prepared by utilizing tannery solid waste (i.e., non-tanned hide wastes) as the biomass material for dye removal from tannery wastewater. Characterization results indicated that MgO was uniformly embedded into the porous BC structure. The adsorption capacity of acid orange II by MgO/BC reached up to 448.4 mg g−1, which drastically exceeded the pure BC and other reported adsorbents. The adsorption behavior of acid orange II by MgO/BC matched nicely with Langmuir isotherm and pseudo-second-order kinetic model. This satisfactory adsorption capacity of MgO/BC for acid orange II was mainly due to the large specific surface area and the enhanced electrostatic interaction. According to the BET, zeta potential and XPS analysis, the possible mechanism towards acid orange II removal was attributed to the pore filling, surface complexation, electrostatic attraction and π-π interaction. In addition, MgO/BC showed the efficient removal towards anionic dyes from actual tannery wastewater. This work could provide guidance for the value-added utilization of tannery solid waste and a practical way to remove dyes from tannery wastewater.

Management of Tannery Solid Waste (TSW) through Pyrolysis and Characteristics of Its Derived Biochar

Management of Tannery Solid Waste (TSW) through Pyrolysis and Characteristics of Its Derived Biochar

Nano fibrous carbon produced from chromium bearing tannery solid waste as the bitumen modifier

Bitumen binders play a major role in reducing the aging and oxidation property of bitumen. Carbon nanomaterials act as an effective bitumen modifier due to its stiffness and strength. Thus, nano fibrous carbon (NFC) was prepared from Chrome Tanned Buffing Dust (a solidwaste generated from leather industries) with proper care of avoiding oxidation of Cr(III) to Cr(VI) through pulse pyrolysis system. Morphology analysis using TEM confirmed the nano fibrous structure of NFC. XRD pattern of NFC depicts the graphitic phases of carbon along with the Cr2O3. Prepared NFC has been used as bitumen modifier and the blending of NFC with bitumen were done using both conventional and microwave heating methods to study the proper blending methods to enhance the bitumen properties. Thermogram of the modified bitumen showed that the decomposition temperature increases by increasing the percentage of NFC (5–25%) in both the heating methods, but comparatively the thermal stability is more in microwave mixing than in conventional mixing. The morphology analysis of the modified bitumen showed that non-uniform blending in conventional type of heating and homogeneously blended mixture in microwave type of heating. The penetration value and ductility decreases while softening point and kinematic viscosity increases by increasing the quantity of NFC from 5 to 25% in modified bitumen. Microwave heat mixing method yielded better modified bitumen with NFC than conventional heating method in terms of stability, uniform blending and physical properties. The non-leachability of the Cr(III) in the NFC modified bitumen was confirmed through total chromium analysis in the leachate. But, chromium analysis in leachate of NFC immersed in acetate buffer for one month showed leaching of Cr(III) 5.5 μg/L in the 25% NFC modified bitumen block mixed using conventional heating method.

Biogas from Tannery Solid Waste Anaerobic Digestion Is Driven by the Association of the Bacterial Order Bacteroidales and Archaeal Family Methanosaetaceae.

The search for renewable energies has been one of the biggest challenges of the last decades. Sludge and solid wastes of many sources have been used to produce biogas of high calorific value. Thus, this work aimed to evaluate the biogas production of solid waste originating from a tannery that uses chromium salts as a tanning agent and to characterize the physicochemical parameters and microbial composition of the biogas-producing biomass. Wastes were collected and the parameters were evaluated at the initial and final time points of the anaerobic incubation process. At the end of 150days, there was a production of 26.1mLg-1 VSS of biogas with 52% of methane. The highest amount of biomethane observed was related to the archaeal family Methanosaetaceae and bacterial order Bacteroidales. Knowledge about changes in the microbial composition can provide tools for manipulation, isolation, and inoculation of the microorganisms inside the bioreactors to maximize methane production.

NGS-based characterization of microbial diversity and functional profiling of solid tannery waste metagenomes

Tanneries pose a serious threat to the environment by generating large amount of solid tannery waste (STW). Two metagenomes representing tannery waste dumpsites Jajmau (JJK) and Unnao (UNK) were sequenced using Illumina HiSeq platform. Microbial diversity analysis revealed domination of Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Planctomycetes in both metagenomes. Presence of pollutant degrading microbes such as Bacillus, Clostridium, Halanaerobium and Pseudomonas strongly indicated their bioremediation ability. KEGG and SEED annotated main functional categories included carbohydrate metabolism, amino acids metabolism, and protein metabolism. KEGG displayed 5848 and 9633 proteases encoding ORFs compared to 5159 and 8044 ORFs displayed by SEED classification in JJK and UNK metagenomes, respectively. Abundantly present serine- and metallo-proteases belonging to Bacillaceae, Clostridiaceae, Xanthomonadaceae, Flavobacteriaceae and Chitinophagaceae families exhibited proteinaceous waste degrading ability of these metagenomes. Further structural and functional analysis of metagenome encoded enzymes may facilitate the discovery of novel proteases useful in bioremediation of STW.

Chromium Concentrate Recovery From Solid Tannery Waste in a Thermal Process.

Leather processing requires substantial inputs of energy, water and chemicals. Additionally, it generates significant amounts of liquid and solid waste, severely impacting the environment. Processing 1 Mg of raw hides yields up to 600–700 kg of waste, considerable amounts of which are solid tannery waste. Such waste contains chromium (Cr) compounds, which are commonly used as tanning agents. This paper reviews solid tannery waste treatment technologies, with emphasis on waste incineration in a specially designed experimental tunnel incinerator. Three different types of tannery waste were subjected to tests: trimmings, shavings and buffing dust. As the research revealed, the process can be applied to all types of solid tannery waste. Moreover, it enables the reuse of the heat of the process and results in a Cr concentrate in the process residues. The conducted analyses (carbon, hydrogen and nitrogen elemental analysis; inductively coupled plasma optical emission spectroscopy; powder X-ray diffraction) proved that there is no or little organic content in the obtained residual ash, which contains up to 53.1%(w/w) Cr in the form of Cr (III) oxide. Such material may be used as a Cr ore substitute in the chemical or metallurgical industries.

Dissolution of collagen fibers from tannery solid wastes in salt aqueous solutions: Hofmeister series evaluation

AbstractBACKGROUNDCollagen fibers from tannery solid wastes were treated with aqueous solutions of inorganic salts. The effect of the inorganic salts on the dissolution of collagen fibers and degradation of collagen were investigated. Tests of reduced viscosity and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS‐PAGE) were applied to evaluate the degree of degradation during the dissolution process. The specific ionic effects of the Hofmeister series on the dissolution of collagen fibers in salt aqueous solutions were demonstrated.RESULTSAccording to all the results, the dissolution abilities of inorganic salts were in the order of Br− > Cl− > SCN− > CH3COO− > H2PO4− > CO32− as well as Na+ > Mg2+ > Ca2+ > NH4+ > K+ > Li+. The results indicated that NaBr aqueous solution could have potential ability as a solvent to dissolve collagen fibers without excessive degradation of collagen.CONCLUSIONSNaBr aqueous solution could have potential ability as a solvent to dissolve collagen fibers without excessive degradation of collagen. By analyzing the results of the reduced viscosity tests, SDS‐PAGE and amino analysis, proper dissolution conditions were evaluated with the conditions of NaBr aqueous solution concentration of 1 mol L−1, contacting time of 4 h and temperature of 60 °C. From amino analysis and in situ optical microscopy observation, a possible process of collagen fiber dissolution in NaBr solution was demonstrated. This work provides a method for treating and recycling tannery solid wastes with some information for the investigation of collagen‐based materials. © 2019 Society of Chemical Industry

Anaerobic co-digestion of tannery solid waste: optimum leather fleshings waste loading

In this study, loading of optimum leather fleshings was investigated with four identical batch reactors with different fleshings and treatment sludge ratios (0:1, 0.25:1, 0.35:1, 0.50:1) to contribute to the state of art of the biogas production from tannery solid wastes. Results showed that lipids-containing leather fleshings boosted the methane production potential. However, H2S inhibition and volatile fatty acids accumulation were the main concern in the anaerobic digestion of these wastes. The modified Gompertz model was applied to the batch tests data to determine the kinetic constants of anaerobic digestion of tannery solid wastes. It was calculated with the model outputs that the ultimate methane production potential and maximum methane production rate in reactors having mixing ratio of 0.35:1 and 0.5:1 (dry basis) were highly similar. 0.35 was found to be an optimum leather fleshing and treatment sludge ratio with a 54% more methane production potential than that of control reactor in this study.

Tannery wastewater as nutrient supply in production of biogas from solid tannery wastes mixed through anaerobic co-digestion

The possibility of using tannery raw wastewater as substitute for the nutrient supply in the anaerobic co-digestion of two tannery solid waste was investigated with regard to energy efficiency, waste treatment efficiency and economic efficiency. The results showed that the use of tannery wastewater as a source of nutrients for the AD of solid tannery waste proved to be adequate from the point of view that the three residues are being treated simultaneously. There was a biogas production of only 1.9±0.3mL/VSS. However, the percentage of methane in the biogas reached 33 % at the beginning of the process, proving that there was methanogenic activity and that AD established. The cost analysis showed that there is a great reduction in the cost of wastewater treatment and solid waste disposal of 23 % and 18 %, respectively, in terms of electricity consumption and 11 % and 8 % respectively in terms of thermal consumption.

Anaerobic Co-digestion of Tannery Solid Wastes: A Comparison of Single and Two-Phase Anaerobic Digestion

Performances of single and two-phase mesophilic anaerobic co-digestion of the leather fleshings and the leather industry’s wastewater treatment sludge were compared for the first time in this study. With a methane yield of 0.46 m3/kg volatile solid, the single-phase digestion system produced 15% more methane gas than that of the two-phase digestion system. However, H2S concentrations, which are over 1% in biogas, was the major problem causing inhibition in the biogas production for the single-phase digestion system. Sulfides, which entered to the reactor with the leather fleshings and caused H2S inhibition, were able to be eliminated easily by rinsing the leather fleshings before being fed to the digester. Although the no H2S inhibition was observed in the two-phase system, the hydrolysis reactor and thus subsequently the methane reactor suffered from serious operational problems causing process failure in the biogas production performance. Regarding methane production performance and simplicity in its operation, the single-phase digestion system is considered to be more convenient for the anaerobic co-digestion of leather fleshings and treatment sludge.

Tannery Solid Waste into Wealth by Non-Edible Gelatin Production from Raw Trimmings

During the conversion of raw hides or skins into leather involves generation of enormous amount of solid waste which has been major concern for environment and cause detrimental effect on it. In leather industry solid wastes can be generated almost from all operations including pre-tanning, tanning, and even post tanning operation. Solid wastes are mainly raw trimmings, fleshing, chrome shaving, buffing dust, keratin, finished scraps etc. The economic development of a country depends on the utilization of indigenous raw materials and their by-products. This paper focuses on utilization of raw trimmings into useful product like non edible gelatin those demand is going up day by day due to its versatile application in various fields. Raw trimmings are mainly originated during sorting of leather before actual tanning process happens and best for non- edible gelatin production as it does not contain any harmful chemicals. This study will also describe the chemical properties of gelatin, gelatin manufacturing process, manufacturing parameters from the leather wastes like raw trimmings. Optimum extraction of non-edible gelatin from raw trimmings found at 75-85?C for 12 hours in slightly basic condition. This study found that huge amount of raw trimmings which generally thrown directly to environment can serve as potential raw materials for the manufacture of non-edible as well as edible gelatin.

Tannery Solid Waste into Wealth by Non-Edible Gelatin Production from Raw Trimmings

During the conversion of raw hides or skins into leather involves generation of enormous amount of solid waste which has been major concern for environment and cause detrimental effect on it. In leather industry solid wastes can be generated almost from all operations including pre-tanning, tanning, and even post tanning operation. Solid wastes are mainly raw trimmings, fleshing, chrome shaving, buffing dust, keratin, finished scraps etc. The economic development of a country depends on the utilization of indigenous raw materials and their by-products. This paper focuses on utilization of raw trimmings into useful product like non edible gelatin those demand is going up day by day due to its versatile application in various fields. Raw trimmings are mainly originated during sorting of leather before actual tanning process happens and best for non- edible gelatin production as it does not contain any harmful chemicals. This study will also describe the chemical properties of gelatin, gelatin manufacturing process, manufacturing parameters from the leather wastes like raw trimmings. Optimum extraction of non-edible gelatin from raw trimmings found at 75-85ₒC for 12 hours in slightly basic condition. This study found that huge amount of raw trimmings which generally thrown directly to environment can serve as potential raw materials for the manufacture of non-edible as well as edible gelatin.

Isolation and Characterization of Bacterium isolated from Bantala Tannery Solid Wastes

Leather industries that uses the conventional chrome tanning process are subjected to high risk of contamination due to the emission of toxic Cr(VI) that poses a serious threat to the environment and human’s wellbeing. The present study were made to isolate and characterize chromium tolerant bacteria in the samples collected from four different plots of Bantala Tannery, Kolkata, West Bengal, India. Pure chromium tolerant bacterial strains were isolated from the tannery sludge samples and their relative MIC (Minimum Inhibitory Concentration) were recorded at different concentrations of Cr (VI) salts to select the highest chromium tolerant bacterium. The selected bacterium was further taken for their growth studies followed by different cultural, morphological and molecular analysis (16S rDNA). The bacterial strain was further studied through SEM (Scanning Electron microscopy) and EDX (Energy Dispersive X-ray) spectroscopy which revealed that TW4 was a gram positive, rod shaped, endospore forming, pleomorphic bacterium with phylogenetic similarities with Isoptericola sp. and genebank accession number SUB1732465 TW4 KX640927.

Leather solid waste: An eco-benign raw material for leather chemical preparation – A circular economy example

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 re-tanning 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.

Anaerobic co-digestion of tannery wastes using two stage anaerobic sequencing batch reactor: focus on process performance of hydrolytic–acidogenic step

This study was carried out to optimize the working conditions hydrolytic–acidogenic step of the two stage anaerobic sequencing batch reactor (ASBR) system during anaerobic co-digestion of tannery wastewater (TWW) and tannery solid waste (TSW) under mesophilic temperature (38 ± 2 °C) for enhanced acidification products. For this purposes four laboratory scale digesters with 0.4 L working volume performed in semi-continuous mode operation were used. Four mixing ratios of substrate (100:0, 75:25, 50:50, 25:75) at hydraulic retention time (HRT) of 5, 3 and 1 days and equivalent organic loading rate (OLR) were examined to assess the effect of each operating parameter on process performance of hydrolytic–acidogenic step in the two stage ASBR. The optimized operating conditions obtained in this study for enhanced performance of hydrolytic–acidogenic step were substrate mixing ratio of 50:50, HRT of 5 days, OLR of 1.20 gCOD/L/day and pH of 6.2. The degree of acidification and hydrolysis (%) achieved in the reactor operated at those optimized parameters were 36.55% and 54.8%, respectively. In general anaerobic co-digestion of TWW with TSW is more important than using TWW alone for enhanced acidification products. This is because of the positive synergistic effects of the TSW in terms of well-balanced nutrients and an appropriate C:N ratio.

Preparation and characterization of activated carbon produced from tannery solid waste applied for tannery wastewater treatment.

The removal of toxic compounds (azo dyes) from dyeing wastewater was investigated by an environmentally friendly activated carbon produced from solid waste generated in the tannery process, the cattle hair (CHW), activated with H3PO4 (AC-CHW), suggesting a life cycle extension for this material from leather processing. Preliminary tests with aqueous solutions containing Acid Brown 414 (AB-414) and Acid Orange 142 (AO-142) removed 71.06% and 73.05%, respectively. The activated carbon was characterized by zeta potential (ZP), functional groups (FTIR), elemental composition, sorbent specific surface area, and pore size distribution (BET/BJH). The specific surface area showed low values when compared to commercial activated carbon, but average pore diameter was higher, which facilitates the adsorption of larger and complex molecules, such as those present in real wastewaters. Through SEM and FTIR, the presence of the toxic compounds studied in the AC-CHW after sorption process was observed, where the results indicated that the functional groups of -CH=CH- participated in the removal process for these compounds. The removal efficiency obtained with AC-CHW was 51.94% and 49.73% for the dyeing wastewater containing AB-414 and AO-142, respectively. The obtained results open a promising via to use AC-CHW as efficient eco-friendly sorbent for the treatment of leather wastewater.

Dissolution of Collagen Fibers from Tannery Solid Wastes in 1-Allyl-3-methylimidazolium Chloride and Modulation of Regenerative Morphology

Collagen fibers from leather-making solid wastes were successfully dissolved in 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). Polarized optical microscopy, temperature-dependent Fourier-transformed infrared spectroscopy (FTIR), and dynamic light scattering were applied to characterize the structural changes of collagen fibers during the dissolution process. The results demonstrated that a single collagen fiber could be totally dissolved in 40 min, at a maximum of 100 °C. During the dissolution process, the average molecular weight of the collagen chains decreased, suggesting that the structure of collagen was destroyed to some degree. Collagen was regenerated from the solution by treatment with alcohol reagents. The regenerated collagen had the characteristic structure of the initial collagen in FTIR spectra. The morphologies of regenerated collagen included nanospheres aggregation, nanosphere dispersion, and networking, which could be adjusted by changing the alcohol type, alcohol temperature, and col...

Conversion of tannery solid waste to sound absorbing nanofibrous materials: A road to sustainability

Leather making process necessitates the effective utilization of potential waste from the meat industry through tanning. This results in the generation of solid wastes leading to serious environmental concerns. Fleshing waste is considered to be one of the major solid wastes, which contains proteins and fat. The current disposal methods of fleshing wastes have various challenges and limitations. In order to overcome these drawbacks/limitations, we propose a novel approach for converting fleshing waste into a value-added material for acoustics application. Herein, protein hydrolysate was prepared from the fleshing waste through acid hydrolysis and was blended with polyvinyl (alcohol) (PVA) to produce nanofibers through the electrospinning process by optimizing the electrospinning parameters. Acid hydrolysis was done at varying conditions and its effect on the properties of the nanofibers was studied. Nanofibers were characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and x-ray diffraction (XRD) studies. The experimental observations indicated that the nanofibers produced with fleshing hydrolysate- PVA showed enhanced thermal stability than neat PVA nanofibers. The prepared nanofibrous membrane was placed on the natural sound absorbing material coir and the sound absorbing potential of this bilayer material was characterized. The sound absorption studies revealed that the bilayer material, which consisted of fleshing hydrolysate- PVA nanofibers with coir disc has better sound absorbing potential in the lower frequencies when compared to pure coir and PVA nanofibers with coir material. This gives new insights into the potential use of fleshing waste derived nanofibers as sound absorbing layer in acoustic applications.

Evaluating co‐substrates to supplement biogas production from tannery solid waste treatment – cattle hair, microalgae biomass, and silicone

AbstractThe sustainability of bioenergy production depends largely on the biomass resource and technology used. Several types of organic wastes can be converted into biogas via anaerobic digestion. The purpose of this research was to evaluate the influence of the addition of cattle hair waste, microalgae biomass, or commercial silicone as a third co‐substrate in the co‐digestion of the two solid wastes of major concern to the leather industry: leather shavings and sludge from tannery wastewater treatment plants. The addition of cattle hair did not influence the total cumulative biogas production of 19.4 mL g−1 of volatile suspended solid added, adsorbed practically all the chromium present, and increased by 16% the organic load of the medium, due to the hydrolysis of the hair damaging the treatment of the residues. The addition of microalgae doubled the cumulative biogas production, tripled the maximum daily biogas production, and adsorbed three times more chromium, showing its beneficial effect on the treatment of tannery solid waste for biogas production. The addition of commercial silicone did not influence the total cumulative biogas production but led to a high adsorption capacity for both chromium and organic matter. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd