Eggshell waste as catalyst: A review

3D Printed Eggshell Microparticle-Laden Thermoplastic Scaffolds for Bone Tissue Engineering

Three-dimensional (3D) printing, an additive manufacturing technique, is increasingly used in the field of tissue engineering. The ability to create complex structures with high precision makes the 3D printing of this material a preferred method for constructing personalized and functional materials. However, the challenge lies in developing affordable and accessible materials with the desired physiochemical and biological properties. In this study, we used eggshell microparticles (ESPs), an example of bioceramic and unconventional biomaterials, to reinforce thermoplastic poly(ε-caprolactone) (PCL) scaffolds via extrusion-based 3D printing. The goal was to conceive a sustainable, affordable, and unique personalized medicine approach. The scaffolds were fabricated with varying concentrations of eggshells, ranging from 0 to 50% (w/w) in the PCL scaffolds. To assess the physicochemical properties, we employed scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction analysis. Mechanical properties were evaluated through compression testing, and degradation kinetics were studied through accelerated degradation with the remaining mass ranging between 89.4 and 28.3%. In vitro, we evaluated the characteristics of the scaffolds using the MC3T3-E1 preosteoblasts over a 14 day period. In vitro characterization involved the use of the Alamar blue assay, confocal imaging, and real-time quantitative polymerase chain reaction. The results of this study demonstrate the potential of 3D printed biocomposite scaffolds, consisting of thermoplastic PCL reinforced with ESPs, as a promising alternative for bone-graft applications.

Eggshells & Eggshell Membranes- A Sustainable Resource for energy storage and energy conversion applications: A critical review

As the world strives to achieve a sustainable future, the exploration of alternative and renewable raw materials for energy storage and energy conversion has gained significant attention. A growing trend on "Waste to Energy" approach has attained prominence. Accordingly, chicken eggshells, a residual from poultry industry, have emerged as a promising candidate due to their abundant availability, low cost, and unique physical and chemical properties. This review article presents an overview of recent advancements in utilizing eggshell waste for energy storage and energy conversion applications. It discusses the transformation of eggshells usage into functional materials, along with their performance in various energy-related applications. The potential of eggshell-based materials in improving energy efficiency and reducing environmental impact is highlighted, providing insights into the future prospects of this sustainable resource.

Utilization of Waste Eggshell Powder as an Excipient for Vitamin D3 Tablet Preparation

Keeping in mind the health scenario in Kingdom of Saudi Arabia with respect to vitamin D3 (VD3) deficiency and its significant role in calcium homeostasis and human metabolism, this research is exploring the combination of eggshell (as a source of calcium) and VD3 as a very economical solution for this problem. Eggshells from local restaurant were collected, washed, ground, sieved, and characterized by Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) techniques. The results of FTIR, SEM, DSC, XRD, and BET indicate that eggshell powder (ESP) was properly processed. Directly compressed tablets containing 2.5 mg of VD3 (equivalent to 50,000 IU), that are based on the use of ESP as tablet filler, were manufactured based on mixing Avicel PH 101 with ESP in different ratios (9:1, 1:1, and 1:9) in addition to the use of both Avicel PH 101 and ESP alone as tablet filler. Tablets properties were evaluated according to USP30-NF25 pharmacopoeia tests in terms of weight variation test, drug content uniformity, tablet hardness, tablet friability, tablet disintegration, and in vitro dissolution profile. The VD3 contents were found to be 98.77-102.35% in all formulations. After 90 min of study, all formulations showed in vitro drug release content in the range of 99.29-101.05%. All of the tested parameters of ESP tablets were similar to those of commercial Avicel PH 101. All of the tested properties of tablets with ESP as a filler were found to be within the acceptable limits of the pharmacopeia recommendations. Therefore, ESP could be exploited for its use as a filler in direct compression tablets.

Sustainable Sources of Raw Materials for Additive Manufacturing of Bone-Substituting Biomaterials

The need for sustainable development has never been more urgent, as the world continues to struggle with environmental challenges, such as climate change, pollution, and dwindling natural resources. The use of renewable and recycled waste materials as a source of raw materials for biomaterials and tissue engineering is a promising avenue for sustainable development. Although tissue engineering has rapidly developed, the challenges associated with fulfilling the increasing demand for bone substitutes and implants remain unresolved, particularly as the global population ages. This review provides an overview of waste materials, such as eggshells, seashells, fish residues, and agricultural biomass, that can be transformed into biomaterials for bone tissue engineering. While the development of recycled metals is in its early stages, the use of probiotics and renewable polymers to improve the biofunctionalities of bone implants is highlighted. Despite the advances of additive manufacturing (AM), studies on AM waste-derived bone-substitutes are limited. It is foreseeable that AM technologies can provide a more sustainable alternative to manufacturing biomaterials and implants. The preliminary results of eggshell and seashell-derived calcium phosphate and rice husk ash-derived silica can likely pave the way for more advanced applications of AM waste-derived biomaterials for sustainably addressing several unmet clinical applications.

Recent advances and progress in biotemplate catalysts for electrochemical energy storage and conversion

Complex structures and morphologies in nature endow materials with unexpected properties and extraordinary functions. Biotemplating is an emerging strategy for replicating nature structures to obtain materials with unique morphologies and improved properties. Recently, efforts have been made to use bio-inspired species as a template for producing morphology-controllable catalysts. Fundamental information, along with recent advances in biotemplate metal-based catalysts are presented in this review through discussions of various structures and biotemplates employed for catalyst preparation. This review also outlines the recent progress on preparation routes of biotemplate catalysts and discusses how the properties and structures of these templates play a crucial role in the final performance of metal-based catalysts. Additionally, the application of bio-based metal and metal oxide catalysts is highlighted for various key energy and environmental technologies, including photocatalysis, fuel cells, and lithium batteries. Biotemplate metal-based catalysts display high efficiency in several energy and environmental systems. Note that this review provides guidance for further research in this direction.

Agro-waste to sustainable energy: A green strategy of converting agricultural waste to nano-enabled energy applications

The rising demands of the growing population have raised two significant global challenges viz. energy crisis and solid-waste management, ultimately leading to environmental deterioration. Agricultural waste (agro-waste) contributes to a large amount of globally produced solid waste, contaminating the environment, and raising human-health issues on improper management. It is essential for a circular economy to meet sustainable development goals and to design strategies to convert agro-waste into energy using nanotechnology-based processing strategies, by addressing the two significant challenges. This review illustrates the nano-strategic aspects of state-of-the-art agro-waste applications for energy harvesting and storage. It details the fundamentals related to converting agro-waste into energy resources in the form of green nanomaterials, biofuels, biogas, thermal energy, solar energy, triboelectricity, green hydrogen, and energy storage modules in supercapacitors and batteries. Besides, it highlights the challenges associated with agro-waste-to-green energy modules with their possible alternate solutions and advanced prospects. This comprehensive review will serve as a fundamental structure to guide future research on smart agro-waste management and nanotechnological innovations dedicated to its utilization for green energy applications without harming the environment. The nanomaterials assisted generation and storage of energy from agro-waste is touted to be the near-future of smart solid-waste management strategy for green and circular economy.

Selective enrichment of glycopeptides using ground eggshell materials

The current research of protein glycosylation is focused on develop various functionalized hydrophilic materials that can effectively enrich glycopeptides. However, most of these materials require complex synthesis steps, plenty of chemical reagents, and high cost. In this study, we employed the natural eggshell for glycopeptides enrichment for the first time. Using horseradish peroxidase (HRP) tryptic digest as a standard sample, eggshell exhibited excellent sensitivity (0.05 fmol μL^-1), good selectivity [HRP tryptic digest:bovine serum albumin (BSA) tryptic digest = 1:1000], excellent size-exclusion effect (HRP tryptic digest:BSA protein = 1:10,000), good loading capacity (75 mg g^-1), and recovery (97.6 ± 0.3%). In addition, 153 and 114 glycopeptides were captured by eggshell from the serum tryptic digests of normal humans and diabetic patients, respectively. Benefiting from the singular porous structure and abundant biomass, eggshell performed excellently in the capture and separation of glycopeptides. These results demonstrated the potential of environmentally friendly eggshell in glycosylation proteomics analysis.

Catalytic pyrolysis of high-density polyethylene over nickel-waste chicken eggshell/HZSM-5

The main objective of the current work is to investigate the effect of nickel-waste chicken eggshell modified Hydrogen exchanged Zeolite Socony Mobil-5 (Ni-WCE/HZSM-5) on pyrolysis of high-density polyethylene (HDPE). Ni-WCE/HZSM-5 was synthesized via the impregnation incipient wetness (IWI) method with Ni and WCE mass loading of 4 and 12 wt% respectively. HZSM-5, CaO, WCE, WCE/HZSM-5, and Ni/HZSM-5 were prepared for comparison purposes with Ni-WCE/HZSM-5. All the synthesized catalysts were characterized for phase analysis, metal loading, surface morphology, and textural properties. The impregnation of nickel and WCE had significantly affected the original framework of HZSM-5, where the crystallinity percentage and average crystal size of HZSM-5 dropped to 44.97% and increased to 47.90 nm respectively. The surface morphology of HZSM-5 has drastically changed from a cubic-like shape into a spider web-like surface after the impregnation of WCE. The BET surface area of HZSM-5 has been lowered due to the impregnation of nickel and WCE, but the total pore volume has increased greatly from 0.2291 cm³/g to 0.2621 cm³/g. The catalyst performance was investigated in the pyrolysis of HDPE via a fixed bed reactor and the pyrolysis oil was further analysed to evaluate the distribution of C₆ to C₉> hydrocarbons. Among the tested catalytic samples, the highest pyrolysis oil yield was achieved by WCE (80%) followed by CaO (78%), WCE/HZSM-5 (63%), HZSM-5 (61%), Ni/HZSM-5 (44%) and Ni-WCE/HZSM-5 (50%). For hydrocarbon distribution in pyrolysis oil, the Ni/HZSM-5 produced the highest of total C₆ and C₇ hydrocarbons at 12% and 27% respectively followed by WCE/HZSM-5 (4% and 20%), non-catalytic (5% and 13%), Ni-WCE/HZSM-5 (0% and 15%), WCE (0% and 10%), HZSM-5 (0% and 6%) and CaO (0% and 0%).

Study on the preparation and properties of CaCO3 ultrafine powder derived from waste eggshell

In this study, eggshell-derived CaCO3 ultrafine powder was prepared from waste eggshell with the method of omnidirectional planetary ball mill. The particle size distribution was measured by laser particle size analyzer. Then, the parameters of grinding kinetic equation of eggshell powder were obtained by software fitting, and the grinding model and characteristic equation of particle-size distribution of the eggshell-derived CaCO3 powder were discussed. The results showed that the best grinding conditions were as follows: using 3 mm zirconia grinding ball, 400 rpm, 50% filling rate, 50% slurry concentration, and ball-milling time of 30 min. The grinding kinetic equation can well simulate the eggshell crushing process. The equation showed that with the prolongation of milling time, the large particle size of the eggshell powder gradually decreased, and the milling efficiency was 0 after 60 min. The Rosin-Rammler-Bennet distribution model could be used to describe the distribution characteristics of the cumulative particle size of the eggshell powder, and the fitting degree of particle size distribution at each milling time could reach R2 > 0.99. No chemical change occurred in the eggshell powder before and after grinding. However, the calcite crystal structure of eggshell-derived CaCO3 ultrafine powder becomes incomplete.

One-pot preparation of H2-mixed CH4 fuel and CaO-based CO2 sorbent by the hydrogenation of waste clamshell/eggshell at room temperature

The preparation of clean fuel or CO₂ adsorbents using industrial and domestic garbage is an alternative way of meeting global energy needs and alleviating environmental problems. Herein, H₂-mixed CH₄ fuel and CaO-based CO₂ sorbent were first prepared in one pot by the mechanochemical reaction of pretreated clamshell or eggshell wastes (carbon and calcium source) with calcium hydride (hydrogen source) at room temperature. In the above reactions, CH₄ was the sole hydrocarbon product, and its yield reached 78.23%. The H₂/CH₄ ratio of the produced H₂-mixed CH₄ fuel was tunable according to the need by changing the reaction conditions. It is inspiring that the simultaneously formed solid CaO/carbon products were efficient CaO-based sorbents, which possessed a higher CO₂ adsorption capacity (49.81-58.74 wt.%) at 650 °C and could maintain good adsorption stability in 30 carbonation/calcination cycles (average activity loss per cycle of only 1.6%). The three achievements of the idea are that it can simultaneously eliminate clamshell or eggshell wastes, obtain valuable clean fuel, and acquire efficient CaO-based sorbents.

Poultry eggshell-derived antimicrobial materials: Current status and future perspectives

Poultry eggs, the basic foodstuffs of human society, have been extensively consumed for domestic and industrial uses. A large amount of eggshell waste is generated and discarded every year, resulting in a waste of natural resources and a threat to the environment. In this context, the reutilization of eggshell waste has gained increasing attentions. Meanwhile, the overuse of antibiotics has led to the emergence of many drug-resistant bacteria, which greatly endangers public health. Therefore, manufacturing new materials with strong antimicrobial activities has become the focus of many researchers. Recent studies have revealed that eggshells can be applied as solid substances, the raw materials for calcium oxide, and the calcium source for synthesizing hydroxyapatite or other materials with antimicrobial activities. Herein, the preparation methods, antibacterial mechanisms and the applications of these eggshell waste-derived antibacterial materials are summarized in this review. Finally, the current challenges and future directions in this field are discussed.

Heterogeneous Catalyzed Biodiesel Production Using Cosolvent: A Mini Review

Biodiesel is gaining recognition as a good replacement for typical diesel owing to its renewability, sustainability, and eco-friendly nature. Transesterification is the leading route for biodiesel generation, which occurs during homogeneous/heterogeneous/enzymatic catalysis. Besides this, the usage of heterogeneous catalysts is considered more advantageous over homogeneous catalysts due to the easy catalyst recovery. Consequently, numerous heterogeneous catalysts have been synthesized from multiple sources with the intention of making the manufacturing process more efficient and cost-effective. Alongside this, numerous researchers have attempted to improve the biodiesel yield using heterogeneous catalysts by introducing cosolvents, such that phase limitation between oil and alcohol can be minimized. This short review is aimed at examining the investigations performed to date on heterogeneously catalyzed biodiesel generation in the presence of different cosolvents. It encompasses the techniques for heterogeneous catalyst synthesis, reported in the literature available for heterogeneous catalyzed biodiesel generation using cosolvents and their effects. It also suggests that the application of cosolvent in heterogeneously catalyzed three-phase systems substantially reduces the mass transfer limitation between alcohol and oil phases, which leads to enhancements in biodiesel yield along with reductions in values of optimized parameters, with catalyst weight ranges from 1 to 15 wt. %, and alcohol/oil ratio ranges from 5.5 to 20. The reaction time for getting the maximum conversion ranges from 10 to 600 min in the presence of different cosolvents. Alongside this, most of the time, the biodiesel yield remained above 90% in the presence of cosolvents.

Biowaste- and nature-derived (nano)materials: Biosynthesis, stability and environmental applications

Due to the environmental pollution issues and the supply of drinking/clean water, removal of both inorganic and organic (particularly dyes, nitroarenes, and heavy metals) to non-dangerous products and useful compounds are very important transformations. The deployment of sustainable and eco-friendly nanomaterials with exceptional structural and unique features such as high efficiency and stability/recyclability, high surface/volume ratio, low-cost production routes has become a priority; nonetheless, numerous significant challenges/restrictions still remained unresolved. The immobilization of green synthesized metal nanoparticles (NPs) on the natural materials and biowaste generated templates have been analyzed widely as a greener approach due to their environmentally friendly preparation methods, earth-abundance, cost-effectiveness with low energy consumption, biocompatibility, as well as adjustability in various cases of biomolecules as bioreducing agents. Natural and biowaste materials are widely considered as important sources to fabricate greener and biosynthesized types of metal, metal oxide, and metal sulfide nanomaterials using plant extracts. Integrating green synthesized nanoparticles with various biotemplates offers new practical composites for mitigating environmental challenges. In this review, degradation of dyes, reduction of toxic nitrophenols, absorption of heavy metals, and other hazardous/toxic environmental pollutants from contaminated water bodies using biowaste- and nature-derived nanomaterials are highlighted.

Effectiveness of Eggshells as Natural Heterogeneous Catalysts for Transesterification of Rapeseed Oil with Methanol

Heterogeneous catalysis has an advantage of easy separation of the catalyst after biodiesel is produced. CaO is known to be an efficient heterogeneous catalyst for biodiesel production. Taking into account that CaO is a key component of eggshells, the effectiveness of eggshells as a heterogeneous catalyst for rapeseed oil transesterification with methanol was investigated and optimal conditions of biodiesel production were determined applying RSM methodology. The influence of three independent variables on ester content was analyzed and a quadratic model was created. It was determined that this model is statistically significant. The optimum transesterification conditions when eggshells are used as a heterogeneous catalyst, and the process temperature of 64 °C, were determined as: the methanol-to-oil molar ratio 10.93:1; the catalyst amount 6.80 wt%; the reaction duration 9.48 h. The ester yield of 97.79 wt% was obtained under these conditions.

Recent Advances in Applications of Bioactive Egg Compounds in Nonfood Sectors

Egg, a highly nutritious food, contains high-quality proteins, vitamins, and minerals. This food has been reported for its potential pharmacological properties, including antibacterial, anti-cancer, anti-inflammatory, angiotensin-converting enzyme (ACE) inhibition, immunomodulatory effects, and use in tissue engineering applications. The significance of eggs and their components in disease prevention and treatment is worth more attention. Eggs not only have been known as a "functional food" to combat diseases and facilitate the promotion of optimal health, but also have numerous industrial applications. The current review focuses on different perceptions and non-food applications of eggs, including cosmetics. The versatility of eggs from an industrial perspective makes them a potential candidate for further exploration of several novel components.

Eggshell Microparticle Reinforced Scaffolds for Regeneration of Critical Sized Cranial Defects

Scaffold-based approaches for bone regeneration have been studied using a wide range of biomaterials as reinforcing agents to improve the mechanical strength and bioactivity of the 3D constructs. Eggshells are sustainable and inexpensive materials with unique biological and chemical properties to support bone differentiation. The incorporation of eggshell particles within hydrogels yields highly osteoinductive and osteoconductive scaffolds. This study reveals the effects of microparticles of whole eggshells, eggshells without a membrane, and a pristine eggshell membrane on osteogenic differentiation in protein-derived hydrogels. The in vitro studies showed that gels reinforced with eggshells with and without a membrane demonstrated comparable cellular proliferation, osteogenic gene expression, and osteogenic differentiation. Subsequently, in vivo studies were performed to implant eggshell microparticle-reinforced composite hydrogel scaffolds into critical-sized cranial defects in Sprague Dawley (SD) rats for up to 12 weeks to study bone regeneration. The in vivo results showed that the eggshell microparticle-based scaffolds supported an average bone volume of 60 mm³ and a bone density of 2000 HU 12 weeks post implantation. Furthermore, histological analyses of the explanted scaffolds showed that the eggshell microparticle-reinforced scaffolds permitted tissue infiltration and induced bone tissue formation over 12 weeks. The histology staining also indicated that these scaffolds induced significantly higher bone regeneration at 6 and 12 weeks as compared to the blank (no scaffold) and pristine gel scaffolds. The eggshell microparticle-reinforced scaffolds also supported significantly higher bone formation, remodeling, and vascularization over 6 and 12 weeks as confirmed by immunohistochemistry analysis. Collectively, our results indicated that eggshell microparticle-reinforced scaffolds facilitated significant bone regeneration in critical-sized cranial defects.

Fabrication, Characterization, and Evaluation of Eggshells as a Carrier for Sustainable Slow-Release Multi-Nutrient Fertilizers

Development of environment-friendly fertilizers to adhere to the sustainability in agronomic practices and to overcome the limitations posed by the conventional fertilizers has been an important challenge. In this study, a cost-effective biowaste eggshell (ES) material was utilized as a sustainable support for eco-friendly slow-release multi-nutrient fertilizers (SMFs) by simple impregnation of micro- and macronutrients. The synthesized multi-nutrient composite was characterized by various characterization techniques. The leaching tests were conducted using simulated soil solutions and tap water, which showed slow and steady release patterns of the impregnated nutrients. Also, the water holding and water retention capacity of soil were improved upon addition of ES-SMF. Further, the results of pot experiments showed enhanced plant growth of cucumber (Cucumis sativus) and tomato (Solanum lycopersicum) seedlings that proved the efficiency of ES-SMF to serve as an environment-friendly fertilizer in agriculture to attain sustainability.

Avian Egg: A Multifaceted Biomaterial for Tissue Engineering

Most components in avian eggs, offering a natural and environmentally friendly source of raw materials, hold great potential in tissue engineering. An avian egg consists of several beneficial elements: the protective eggshell, the eggshell membrane, the egg white (albumen), and the egg yolk (vitellus). The eggshell is mostly composed of calcium carbonate and has intrinsic biological properties that stimulate bone repair. It is a suitable precursor for the synthesis of hydroxyapatite and calcium phosphate, which are particularly relevant for bone tissue engineering. The eggshell membrane is a thin protein-based layer with a fibrous structure and is constituted of several valuable biopolymers, such as collagen and hyaluronic acid, that are also found in the human extracellular matrix. As a result, the eggshell membrane has found several applications in skin tissue repair and regeneration. The egg white is a protein-rich material that is under investigation for the design of functional protein-based hydrogel scaffolds. The egg yolk, mostly composed of lipids but also diverse essential nutrients (e.g., proteins, minerals, vitamins), has potential applications in wound healing and bone tissue engineering. This review summarizes the advantages and status of each egg component in tissue engineering and regenerative medicine, but also covers their current limitations and future perspectives.

Removal of Cd2+ and Pb2+ from Wastewater through Sequent Addition of KR-Slag, Ca(OH)2 Derived from Eggshells and CO2 Gas

The effect of heavy metals in aqueous solutions has been addressed by several methods. Precipitation using lime, slaked or quick, is one of the commonly used techniques. In this work, KR-slag was used in addition to Ca(OH)₂ that served as a seeding material. Furthermore, CO₂ has been injected into the suspensions for pH stabilization, which further increases the removal efficiency. Accordingly, results have shown a great performance regarding both removal efficiency and reduced sludge production. More than 99% of Cd²⁺ and Pb²⁺ was removed with 1 g/L of KR-slag, 0.5 g/L of Ca(OH)₂, and CO₂ injection at a rate of 1 L/min. The effect of carbonation has been evaluated by examining the removal efficiency before and after carbonation. Following the injection of CO₂, removal efficiency has increased from 58.7 to 99.8 and 71.2 to 99.3% for Cd²⁺ and Pb²⁺, respectively. Moreover, sludge volume from this treatment method was obtained as 103 mL/L, which is much less than the sludge volume obtained from the carbonation of only Ca(OH)₂, that is, 361 mL/L. Leaching of residues was also conducted to evaluate the environmental performance of the removal process. After carbonation, there was a lower concentration of metals when leached out in a wide range of pH solutions. Contrarily, it was observed that a relatively higher concentration of metals was released in acidic solutions due to the substitution of metal ions (Cd²⁺ and Pb²⁺) with H⁺ ions. Residues were then characterized by X-ray diffraction and differential thermal analysis/thermogravimetric analysis for phase identification. Both characterizations detected the presence of CaCO₃, which was an indication of the transformation of Ca(OH)₂ to CaCO₃.

Simple recycling of biowaste eggshells to various calcium phosphates for specific industries

Egg consumption is very high throughout the world and with it comes enormous amount of waste eggshells. To reduce and utilize these wastes, eggshell wastes were simply transformed to low- or high-purity calcium carbonate grades by washing, crushing, and drying to use as raw materials for producing highly valuable calcium phosphate products. Low-purity calcium carbonate grade was used to prepare triple superphosphate for using in fertilizer industry, whereas high-purity calcium carbonate grade was used to produce dicalcium phosphate dihydrate, monocalcium phosphate monohydrate, and tricalcium phosphate for using in mineral feed and food additive industries. All calcium phosphate samples obtained by simple, rapid, cheap, and environmentally safe method using eggshells and phosphoric acid were identified and their structural phases and impurities were determined by XRF, XRD and FTIR techniques. Thermal behaviors of raw materials and the prepared calcium phosphates excepted tricalcium phosphate were investigated by TG/DTG techniques. The methodologies described here will be useful to manage eggshells by converting them to highly valuable products, which can solve eggshell wastes problem from industries and communities. This finding supports the viewpoint of zero waste operation to produce value-added products for obtaining sustainable development, which may be selected as an alternative way for material recycling and waste management in the future.

Biotechnological Applications of Eggshell: Recent Advances

The eggshell (ES) provides protection against pathogenic and physical insults while supplying essential metabolic and nutritional needs for the growing avian embryo. It is constituted mainly of calcium carbonate arranged as calcite crystals. The global chicken egg production in 2018 was over 76.7 million metric tons. In industrialized countries, about 30% of eggs are processed at breaker plants that produce liquid egg products and large quantities of solid ES waste. ES waste is utilized for a variety of low-value applications, or alternatively is disposed in landfill with associated economic and environmental burdens. The number of patents pertaining to ES applications has increased dramatically in recent years; of 673 patents granted in the last century, 536 (80%) were published in the last two decades. This review provides a snapshot of the most recent patents published between 2015 and 2020, with emphasis on different biotechnological applications of ES waste, and summarizes applications for biomedical, chemical, engineering, and environmental technologies. Biomedical technologies include the production of calcium lactate, calcium phosphate, and health-promoting products, while chemical technologies include plant growth promoters, food processing and production, and biodiesel oil catalysis along with active calcium, carbon, soluble proteins, organic calcium, and ultrafine calcium carbonate sources. Engineering technologies address material engineering and nanoparticle production, while environmental technologies pertain to production of biomass, solubilization of sludge as well as production of magnetic ES adsorbents and adsorption of heavy metals, organics, total nitrogen and fluoride, soil pollutants, and radioactive compounds. Although the number of ES-based patents has exponentially increased in the last decade, exploration of innovative top-down approaches and ES development as a physical platform are new endeavors that are expected to further increase the upscaling of ES waste exploitation.

Transfer of enrofloxacin, ciprofloxacin, and lincomycin into eggshells and residue depletion in egg components after multiple oral administration to laying hens

Regardless of whether antimicrobial drugs are administered to laying hens legally or illegally, residues of these drugs may be present in the eggs. Even if the eggs are not intended for human consumption, byproducts/biowaste, such as eggshells, may contain residues of the drugs used, which may pose a risk to human health and the environment. In the presented research, 2 different groups of laying hens received enrofloxacin (10 mg/kg body weight) and lincomycin (20 mg/kg body weight) once daily for 5 d. Eggs were collected daily and the concentration of enrofloxacin, its metabolite ciprofloxacin, and lincomycin residue in the eggshells, whole eggs, egg yolks, and egg whites were determined by ultra-high-performance liquid chromatography-tandem mass spectrometry. This study demonstrates the transfer of enrofloxacin, ciprofloxacin, and lincomycin into the eggshells and provides evidence for the distribution into the eggshells after administration of these drugs to laying hens. The enrofloxacin residues were detected in the eggshell for 10 d after cessation of treatment, ciprofloxacin and lincomycin were rapidly eliminated and 2 d after finish drugs administration they were no longer detected in the eggshell.

A Survey of Recent Patents in Engineering Technology for the Screening, Separation and Processing of Eggshell

The chicken egg is a well-known complete food of human daily consumption which serves as a cost-effective, high-quality nutrient resource. About 30% of table eggs are directed to breaker plants in developed countries, leading to the generation of substantial eggshell (ES) waste, which is increasingly explored for potential value-added applications. The number of patents describing ES-based applications has increased dramatically in recent years. This review provides insight into the most recent patents published between 2015 and 2020, with focus on different engineering technologies for the screening, separation, and processing of ES. Screening technologies include detection of ES surface spots and glossiness, ES cracks, and mechanical properties, along with identification of chicken breed and enumeration of surface bacterial count. Collection and separation technologies describe separation strategies of ES from egg white (EW), egg yolk (EY), liquid egg, eggshell membrane (ESM), hatchlings, and cooked egg. Separation of ES from liquid eggs utilizes gravity, rotational forces, or air pressure. Processing of ES involves washing and sterilization along with cutting, crushing, and pulverization technologies that enable the collection of ES suitable for value-added applications. In addition, ES carving (mechanical and laser) opens up the realm of artwork and decoration. Furthermore, intact ES can be utilized for food serving. The exponential increase in innovative screening, separation, collection, and processing technologies reflects industrial interest to upscale low-value ES waste material, and is a first crucial step in the emergence of advanced technologies that exploit the biomedical, chemical, engineering, and environmental applications for ES.

Improved biodiesel production from waste cooking oil with mixed methanol-ethanol using enhanced eggshell-derived CaO nano-catalyst

In this report, the utilization of mixed methanol–ethanol system for the production of biodiesel from waste cooking oil (WCO) using enhanced eggshell-derived calcium oxide (CaO) nano-catalyst was investigated. CaO nano-catalyst was produced by calcination of eggshell powder at 900 °C and followed by hydration-dehydration treatment to improve its catalytic activity. The particle size, morphology, and elemental composition of a catalyst were characterized by using XRD, SEM, and EDX techniques, respectively. After hydration-dehydration the shape of a catalyst was changed from a rod-like to honeycomb-like porous microstructure. Likewise, average particle size was reduced from 21.30 to 13.53 nm, as a result, its surface area increases. The main factors affecting the biodiesel yield were investigated, accordingly, an optimal biodiesel yield of 94% was obtained at 1:12 oil to methanol molar ratio, 2.5 wt% catalyst loading, 60 °C, and 120-min reaction time. A biodiesel yield of 88% was obtained using 6:6 equimolar ratio of methanol to ethanol, the yield even increased to 91% by increasing the catalyst loading to 3.5 wt%. Moreover, by slightly increasing the share of methanol in the mixture, at 8:4 ratio, the maximum biodiesel yield could reach 92%. Therefore, we suggest the utilization of methanol–ethanol mixture as a reactant and eggshell-derived CaO as a catalyst for enhanced conversion of WCO into biodiesel. It is a very promising approach for the development of low-cost and environmentally friendly technology. Properties of the biodiesel were also found in good agreement with the American (ASTM D6571) fuel standards.

Multi-Class Procedure for Analysis of 50 Antibacterial Compounds in Eggshells Using Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

In this work, for the first time, Ultra-High-Performance Liquid Chromatography–Tandem Mass Spectrometry (UHPLC–MS/MS) method was developed for qualitative and quantitative analysis of veterinary antibiotics (cephalosporins, diaminopyrimidines, fluoro(quinolones), lincosamides, macrolides, penicillins, pleuromutilins, sulfonamides, tetracyclines, and sulfones) in hen eggshells. The sample preparation method is based on a liquid–liquid extraction with a mixture of metaphosphoric acid, ascorbic acid, EDTA disodium salt dihydrate, and acetonitrile. The chromatographic separation was performed on Luna^® Omega Polar C18 10 column in gradient elution mode and quantitated in an 8 min run. Validation such as linearity, selectivity, precision, recovery, matrix effect, limit of quantification (LOQ), and limit of detection (LOD) was found to be within the acceptance criteria of the validation guidelines of the Commission Decision 2002/657/EC and EUR 28099 EN. Average recoveries ranged from 81–120%. The calculated LOQ values ranged from 1 to 10 µg/kg, the LOD values ranged from 0.3 to 4.0 µg/kg, depending on analyte. The developed method has been successfully applied to the determination of antibacterial compounds in hen eggshell samples obtained from different sources. The results revealed that enrofloxacin, lincomycin, doxycycline, and oxytetracycline were detected in hen eggshell samples.

Valorization of Raw and Calcined Chicken Eggshell for Sulfur Dioxide and Hydrogen Sulfide Removal at Low Temperature

Chicken eggshell (ES) is a waste from the food industry with a high calcium content produced in substantial quantity with very limited recycling. In this study, eco-friendly sorbents from raw ES and calcined ES were tested for sulfur dioxide (SO2) and hydrogen sulfide (H2S) removal. The raw ES was tested for SO2 and H2S adsorption at different particle size, with and without the ES membrane layer. Raw ES was then subjected to calcination at different temperatures (800 °C to 1100 °C) to produce calcium oxide. The effect of relative humidity and reaction temperature of the gases was also tested for raw and calcined ES. Characterization of the raw, calcinated and spent sorbents confirmed that calcined eggshell CES (900 °C) showed the best adsorption capacity for both SO2 (3.53 mg/g) and H2S (2.62 mg/g) gas. Moreover, in the presence of 40% of relative humidity in the inlet gas, the adsorption capacity of SO2 and H2S gases improved greatly to about 11.68 mg/g and 7.96 mg/g respectively. Characterization of the raw and spent sorbents confirmed that chemisorption plays an important role in the adsorption process for both pollutants. The results indicated that CES can be used as an alternative sorbent for SO2 and H2S removal.

State-of-the-Art of Eggshell Waste in Materials Science: Recent Advances in Catalysis, Pharmaceutical Applications, and Mechanochemistry

Eggshell waste is among the most abundant waste materials coming from food processing technologies. Despite the unique properties that both its components (eggshell, ES, and eggshell membrane, ESM) possess, it is very often discarded without further use. This review article aims to summarize the recent reports utilizing eggshell waste for very diverse purposes, stressing the need to use a mechanochemical approach to broaden its applications. The most studied field with regards to the potential use of eggshell waste is catalysis. Upon proper treatment, it can be used for turning waste oils into biodiesel and moreover, the catalytic effect of eggshell-based material in organic synthesis is also very beneficial. In inorganic chemistry, the eggshell membrane is very often used as a templating agent for nanoparticles production. Such composites are suitable for application in photocatalysis. These bionanocomposites are also capable of heavy metal ions reduction and can be also used for the ozonation process. The eggshell and its membrane are applicable in electrochemistry as well. Due to the high protein content and the presence of functional groups on the surface, ESM can be easily converted to a high-performance electrode material. Finally, both ES and ESM are suitable for medical applications, as the former can be used as an inexpensive Ca2+ source for the development of medications, particles for drug delivery, organic matrix/mineral nanocomposites as potential tissue scaffolds, food supplements and the latter for the treatment of joint diseases, in reparative medicine and vascular graft producing. For the majority of the above-mentioned applications, the pretreatment of the eggshell waste is necessary. Among other options, the mechanochemical pretreatment has found an inevitable place. Since the publication of the last review paper devoted to the mechanochemical treatment of eggshell waste, a few new works have appeared, which are reviewed here to underline the sustainable character of the proposed methodology. The mechanochemical treatment of eggshell is capable of producing the nanoscale material which can be further used for bioceramics synthesis, dehalogenation processes, wastewater treatment, preparation of hydrophobic filters, lithium-ion batteries, dental materials, and in the building industry as cement.

Modification and characterization of chicken eggshell for possible catalytic applications

Researchers have shown considerable interest in finding a sustainable, low cost, and readily available substitute for the commercial calcium oxide (CaO) catalyst. In this work, raw chicken eggshell was modified by boiling and calcination at 900 °C for 3 h. The x-ray diffraction characterization revealed that while the proportion of CaCO₃ in the raw and boiled samples was found to be 79.3 % and 99.2 % respectively, the CaCO₃ had been converted to 63.8 % CaO and CO₂ in the calcined sample. This was due to the thermal decomposition during calcination. The outcome of the infrared spectroscopy showed that the raw and boiled chicken eggshell presented a similar absorption profile with peaks at 1 394 cm^-1, 873 cm^-1, and 712 cm^-1, which were as a result of the presence of asymmetric stretch, out-of-plane bend, and in-plane bend vibration modes. The major peaks presented by the calcined sample at 3642 cm^-1 can be attributed to the OAH stretching vibration and bending hydroxyl groups present in Ca(OH)₂. The Brunauer-Emmett-Teller surface areas for the raw, boiled and calcined chicken eggshell were found to be 2.33 m²/g, 3.26 m²/g, and 4.6 m²/g respectively, indicating increased catalytic activity of the calcined sample. Overall, boiling was found to have a negligible effect on the chicken eggshell, while high-temperature calcination greatly affected the pore size, surface area, composition, and thermal decomposition profile of the chicken eggshell sample.

Facile synthesis of Silver@Eggshell nanocomposite: A heterogeneous catalyst for the removal of heavy metal ions, toxic dyes and microbial contaminants from water

In this work, silver nanoparticles have been synthesized with an average particle size of 35 nm, within 90s, using microwave and Sapindus mukorossi extract as a stabilizing agent. The AgNps were surface immobilized on eggshells (ES) to obtain Ag@ES, which was characterized by UV-Vis, UV-DRS, FT-IR, ICP-OES, TGA-DSC, SEM-EDX, XRD and XPS. Its applicability as an environmental catalyst was evaluated by Cr (VI) adsorption, photocatalytic degradation of methyl orange, eriochrome black-T, methylene blue, rhodamine-B as model dyes and microbial inhibition against Staphylococcus aureus, Escherichia coli and Candida albicans. The results revealed that Ag@ES exhibited maximum adsorption capacity of 93 mg/g for Cr (VI) ion and degradation efficiency of ~90-98% for removing anionic and cationic dyes. Further, it showed a minimum inhibitory concentration of 15.6, 7.8 and 31.2 μg/mL for S. aureus, E. coli and C. albicans respectively. Moreover, the Ag@ES being a heterogeneous catalyst can be regenerated and reused without significant loss in its efficiency.

Recycled eggshells as precursors for iron-impregnated calcium oxide catalysts for partial oxidation of methane

There is a significant interest in converting eggshells into value-added products. Therefore, the goal of this research is to synthesize and study iron-impregnated eggshells as a catalyst for partial oxidation of methane. The objectives of this research were to test the effects of iron loading, flow rate, oxygen concentration, and temperature on methane oxidation. The catalysts were synthesized using ferric chloride hexahydrate at various loadings and tested in a heated stainless-steel reactor under different experimental conditions. The reaction products included C2–C7 hydrocarbons, carbon monoxide, and carbon dioxide depending on the reaction conditions. Results indicated that iron loading beyond 5 wt% caused a decrease in methane conversion. A decrease in oxygen concentration enhanced methane conversion with a substantial drop in the production of CO2. Besides, an increase in temperature resulted in a decrease in methane conversion with a simultaneous increase in the production of CO2 via overoxidation. The reusability experiments indicated that the catalyst was active for four reaction cycles. Our results indicate that eggshells can be used as catalyst support for methane partial oxidation and can simultaneously solve the waste disposal problems faced by the poultry industry.

Selectivity of SO2 and H2S removal by ethanol-treated calcined eggshell at low temperature

Eggshell is a food waste produced worldwide in substantial amount with very limited recycling activity. In this study, the potential of ethanol-treated calcined eggshell was tested as sorbent for SO₂ and H₂S. Three variables were selected in the preparation of sorbents via response surface methodology (RSM), i.e., concentration of ethanol in water (50%, 70%, 90%), reaction temperature (20 °C, 40 °C, 60 °C), and contact time (30, 60, 90 min). Central composite design (CCD) was used to develop a quadratic model to correlate the operating variables with the adsorption capacity. Analysis of variance (ANOVA) was performed to identify the significant factors of the experimental design. It was found that the reaction temperature during the sorbent preparation was the most significant factor. The optimum preparation conditions using RSM were found at 20 °C of reaction temperature with 76.37% of ethanol concentration for 67 min of reaction time. The maximum adsorption capacity for the optimized sorbent was found to be 27.75 mg/g and 9.55 mg/g for SO₂ and H₂S, respectively. The prepared sorbent was more selective towards SO₂ compared with H₂S. Moreover, the presence of 40% of relative humidity in the inlet gas further enhanced the adsorption capacity of both gases. The ethanol-treated calcined eggshell was further substantiated by FESEM, BET, FTIR, XRD, and XRF. Results showed potential usage of eggshell as a sorbent for SO₂ and H₂S gases.

Mini-review of waste shell-derived materials' applications

This mini-review reports curbing waste shells (i.e. seashells, eggshells, snail shells, etc.), environmental health issues and liabilities by using them as material for heterogenous catalysts, blended cement manufacture, concrete aggregate, ceramics and plastics additives, biofilter medium and biomedical applications. The traditional materials used in the manufacture of these products could be relatively cheap; however, there are considerable environmental issues (i.e., ecological damage, disruption of eco-system and air contamination) as well as intense energy consumption associated with the exploitation of depleting natural resources. Waste shells are a renewable and cheap alternative, and will simultaneously decrease manufacturing cost while reducing their burden on the environment. This paper emphasizes environmental sustainability by summarizing articles published on various applications of waste shell-derived biomaterials. The properties of waste shell-derived biomaterials are presented and discussed. The materials' properties suggest they are similar to limestone and their biological-natural origin and the high calcium carbonate content with a trace amount of other mineral elements makes them highly favorable for cement production, heterogenous catalysts and hydroxyapatite manufacture for biomedical and wastewater treatment applications. The purpose of this work is to offer new perspectives and direction for future research on waste shell-derived biomaterials while existing areas of applications demanding scale up are highlighted.

Sorption of Cd2+ and Pb2+ on Aragonite Synthesized from Eggshell

In the present work, waste eggshells were used as a precursor for the synthesis of aragonite crystals through the wet carbonation method. Cadmium (Cd2+) and lead (Pb2+) were removed by the synthesized aragonite from synthetic wastewater. The influence of initial solution pH, contact time, Cd2+ and Pb2+ concentration, and sorbent dosage were evaluated. The major sorption was observed in the first 100 mins and 360 mins for Pb2+and Cd2+ respectively reaching sorption equilibrium at 720 mins (12 hr). The sorption capacity toward Pb2+ was much higher than toward Cd2+. Both heavy metals displayed high sorption capacities at initial pH 6. The pseudo-second-order kinetic model fits well with the experimental data with a higher correlation coefficient R2. Two isotherm models were also evaluated for the best fit with the experimental data obtained. Langmuir isotherm best fits the sorption of the metals on aragonite synthesized from eggshells. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) results of sorbent after sorption showed that the mechanism of sorption was dominated by surface precipitation. Therefore, aragonite crystals synthesized from waste eggshells can be a potential substitute source for the removal of Cd2+ and Pb2+ from contaminated water.

Biogenic Pt/CaCO3 Nanocomposite as a Robust Catalyst toward Benzene Oxidation

Fabricating the highly dispersive and stable Pt nanoparticles (NPs) on an economical and environmentally friendly support is of great concern in the field of catalysis. Herein, a waste eggshell was used as the support to prepare supported Pt catalysts through a plant-mediated biosynthesis method, in which the Pt precursor was reduced to Pt NPs by employing Cacumen platycladi (CP) leaf extract. The temperature and atmosphere for thermal treatment of such eggshell-supported Pt catalysts were assessed to understand their effects on catalytic performance toward the oxidation of benzene. The optimal Pt/eggshell-Ar (calcined at 400 °C in Ar) demonstrated that the temperature required for 90% benzene conversion (T_90%) was as low as 178 °C (80 000 mL g^-1 h^-1) and could operate steadily for at least 300 h of onstream reaction. The structure of the catalyst after reaction is much the same as that of the unreacted one. Transmission electron microscopy (TEM), thermogravimetry (TG), and X-ray photoelectron spectroscopy (XPS) results showed that Pt NPs were evenly distributed on the eggshell supports, and the calcination conditions had important influences on the residual CP leaf extract, the average Pt NPs size, and the ratio of Pt⁰/Pt²⁺ over the catalysts. Density functional theory (DFT) calculations indicated that the interactions between Pt NPs and porous CaCO₃ could promote benzene activation adsorbed onto the Pt NPs. In addition, biogenic Pt catalysts were proved to overtake the chemically reduced counterparts in the field of catalytic performance; furthermore, both biogenic and chemically reduced Pt NPs supported on the eggshell demonstrated preferable catalytic activity than that of commercial 5Pt/C (com-Pt/C) catalysts. Collectively, immobilizing biogenic noble metal active components on the eggshell-based support could be a promising approach for the preparation of supported noble metal catalysts with excellent catalytic performance toward catalytic oxidation of volatile organic compounds (VOCs).

White Eggshells: A Potential Biowaste Material for Synergetic Adsorption and Naked-Eye Colorimetric Detection of Heavy Metal Ions from Aqueous Solution

In the present work, we have utilized a simple, no-cost, unmodified eggshell powder as a naked-eye colorimetric detector, which on simple dispersion in aqueous solution of metal ions exhibited characteristic color change from white to pale green, pale blue, yellow, pale yellow, dark yellow, pale pink, blue, and brown for metal ions V⁴⁺, Cr³⁺, Cr⁶⁺, Fe²⁺, Fe³⁺, Co²⁺, Cu²⁺, and Ag⁺, respectively. The effects of various parameters like concentration of metal ions, pH, temperature, and adsorbent dosage were investigated by batch sorption experiments. Also, Freundlich and Langmuir models were used to describe the adsorption isotherm. The eggshell powder before and after adsorption was characterized qualitatively by the naked-eye and quantitatively by diffuse reflectance spectroscopy-UV, Fourier transform infrared, atomic absorption spectroscopy, powder X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller, zeta potential, and X-ray photoelectron spectroscopy techniques. In addition, the competitive adsorption of metal ions in mixtures and the recycle experiments were carried out to prove the sustainability of the material. Further, the red, green, and blue alterations were extracted from the colorimetric array and subjected to hierarchical clustering analysis using the Ward method by calculating the Euclidean distance, which displayed facile discrimination of 10 heavy metal ions at 1 mM level. Thus, the unmodified eggshell powder has been proven to be an impressive value-added sustainable material for synergistic metal adsorption and colorimetric naked-eye detection of a series of metal ions with detection limits of 10^-4 M for Fe³⁺, Fe²⁺, and Cu²⁺; 10^-3 M for Cr³⁺, Cr⁶⁺, Ag⁺, and Co²⁺; and 5 × 10^-3 M for V⁴⁺.