Eggshells: Kitchen Waste to Sustainable Resource

Every morning, millions of eggs are cracked in kitchens for breakfast, but have you ever wondered where the waste eggshells are discarded? What if everyday kitchen waste held the key to solving some of the world’s toughest environmental challenges? The researchers at the Pyrometallurgy & Materials Engineering (formerly Advanced Materials Technology) Department, CSIR-IMMT (Institute of Minerals and Materials Technology) Bhubaneswar, have developed a technology for which a patent has been filed, that transforms discarded eggshells and membranes into a revolutionary superhydrophobic coating, offering exceptional water repellency, corrosion resistance, and oil spill cleanup efficiency.

 THE HIDDEN TREASURE IN EGGSHELLS

Eggshells are often discarded as waste, but they hold a hidden treasure of re­markable benefits. Composed primarily of calcium carbonate, eggshells serve as an excellent natural source of calcium, essential for bone health and various biological functions. Beyond nutrition, eggshells have fascinating applications in science and technology. They can be transformed into eco-friendly materials for water purification, biodegradable packaging, and even advanced coatings for corrosion resistance. The eggshell membrane, a thin layer inside the shell, is rich in collagen and bioactive com­pounds, making it valuable in skincare, wound healing, and regenerative medi­cine. Additionally, eggshell-derived cal­cium carbonate is used in agriculture to enrich soil and in sustainable engineer­ing solutions. What seems like kitchen waste is, in reality, a sustainable resource with immense potential across multiple fields, from healthcare to environmental protection.

WHAT ARE SUPERHYDROPHOBIC COATINGS AND THEIR REAL-WORLD APPLICATIONS?

Superhydrophobic refers to surfaces that repel water, or simply, ‘water-hating surfaces’. If you’ve ever ob­served water droplets over a lotus leaf, or butterfly wings, where drop­lets bead up and roll off effortlessly over the surface, you’ve witnessed superhy­drophobicity in ac­tion. These coatings create a rough surface with tiny nanostruc­tures and a low surface energy, making it difficult for water droplets to spread out. Instead, the droplets stay spherical and slide away, carrying dirt and contami­nants with them. Inspired by the phe­nomena in nature, superhydrophobic coatings recently emerged as a ground­breaking solution for a wide range of ap­plications, such as self-cleaning surfaces by resisting stains, oil-water separation and corrosion prevention.

RESEARCH ON SUPERHYDROPHOBIC COATINGS AT CSIR-IMMT

At CSIR-Institute of Minerals and Ma­terials Technology (CSIR-IMMT), ex­tensive research is being conducted on superhydrophobic coatings to develop sustainable and multifunctional mate­rials for environmental and sensing ap­plications. The key focus areas include oil-water separation, corrosion resis­tance, self-cleaning surfaces, and wear­able sensing technologies. One major research thrust is the fabrication of eco-friendly, superhy­drophobic, and superoleophilic materials from waste resourc­es for efficient oil-water sepa­ration. A recent study reported the development of rice husk-derived silica (SiO2)/ reduced graphene oxide (rGO)-coated polyurethane (PU) foam, which exhibits superior oil-adsorption capacity and stability under extreme environmental conditions. This material achieved a water contact angle of 164°, demonstrating strong water repellency while allowing selective oil absorption. Its application extended to real-world scenarios, where it has been successfully integrated into a prototype device for crude oil recovery from water, showcasing its potential for large-scale oil spill remediation. Another exciting area of research involved superhydro­phobic three-dimensional (3D) zinc oxide foams (ZOFs) with hierarchical nanostructures for oil-water separation. Besides environmental applications, these ZOFs also demonstrated remark­able mechanical durability and piezore­sistive sensing capabilities, making them suitable for real-time human motion sensing and wearable sensor technology.

REAL-WORLD APPLICATIONS:

1. Self-Cleaning Surfaces: Buildings, windows, and solar panels coated with superhydrophobic materials stay cleaner for longer by preventing dirt buildup and reducing maintenance efforts.
2. Waterproof Electronics: Smartphones, laptops, and circuit boards can be pro­tected from water damage, enhancing durability and longevity.
3. Anti-Corrosion Coatings: Metals used in bridges, ships, and pipelines can be shielded from rust and corrosion, signifi­cantly extending their lifespan.
4. Oil-Water Separation: These coatings help in cleaning up oil spills and treat­ing wastewater by allowing oil to be selectively removed from contaminated water.
5. Anti-Icing and De-Icing Surfaces: Air­plane wings, car windshields, and power lines can resist ice formation, improving safety in cold environments.
6. Medical Applications: Superhydropho­bic coatings on surgical tools, implants, and hospital surfaces reduce bacterial contamination, promoting hygiene and infection control.

CHALLENGES WITH TRADITIONAL SUPERHYDROPHOBIC COATINGS

Superhydrophobic coatings, which repel water effectively, have been widely used for applications such as self-cleaning surfaces, anti-corrosion coatings, and oil-water separation. Traditionally, these coatings rely on fluorinated compounds, which offer excellent water resistance but come with significant environmental and health risks. These fluorinated substanc­es, often referred to as perfluorinated chemicals (PFCs), are non-biodegradable and can accumulate in living organisms, leading to long-term ecological damage. Additionally, their large-scale use raises concerns about their impact on human health, prompting researchers to find greener alternatives.

Images Courtesy: Surya Kanta Ghadei

THE ENVIRONMENTAL ISSUE OF EGGSHELL WASTE

At the same time, the disposal of egg­shell waste is an increasing environ­mental challenge. Billions of eggs are consumed globally each year, generat­ing millions of tons of eggshell waste. Improper disposal methods, such as landfilling, lead to inefficient waste management and environmental pol­lution. Eggshells take years to degrade, contributing to landfill congestion and waste-related issues. However, egg­shells are naturally rich in calcium car­bonate (CaCO3), a valuable material with potential applications in coat­ings, biomaterials, and environmental remediation.

EGGSHELL-DERIVED SUPERHYDROPHOBIC COATINGS FOR SUSTAINABILITY

In response to these environmental con­cerns, the author of this piece, who is a Senior Research Fellow at CSIR-IMMT and Joint PhD Student at AcSIR, Ghazi­abad, and RMIT, Australia, along with a team of scientists at CSIR-IMMT, has pioneered the development of fluorine-free, eggshell waste-derived superhy­drophobic coatings. This research team, composed of Dr Sourav Ganguly, Dr KJ Sankaran, and led by Chief Scientist Dr R Sakthivel, has successfully con­verted waste eggshells into functional coatings that offer superior water re­pellency, durability, and environmental sustainability.

SCIENCE BEHIND EGGSHELL-BASED COATINGS

The innovative technology lies in the complete utilisation of the chicken egg­shell waste. Eggshell waste, in general, is composed of two parts, one is the outer eggshell primarily composed of calcium carbonate and the other is the inner egg-shell membrane. The technology con­verts the outer eggshell to nano-struc­tured mimicking of the cactus structured hydrophobic functionalised calcium car­bonate powder, and the inner membrane into the activated carbon by utilising the pyrolysis method. Then both the mate­rials were deposited on the substrates following chemical reduction to form superhydrophobic coatings. This coat­ing is ideal for applications in industries where resistance to water and corrosion is critical, such as marine environments, pipelines, and automotive components.

One of the most promising uses of this technology is in oil spill recovery, where the superhydrophobic nature of the coating allows it to efficiently collect and remove oil from water surfaces, mak­ing it a valuable tool for environmental cleanup efforts. The technology devel­oped by the CSIR-IMMT researchers has been filed for patent in India (Application No: 202411064501), ensuring its protec­tion and potential for commercialisation. Additionally, the research has been peer-reviewed and published in the interna­tionally recognised journal Progress in Organic Coatings (Elsevier, Impact Fac­tor 6.5), validating the work and demon­strating its scientific credibility.

The technology developed by the CSIR-IMMT team is a prime example of how innovation can arise from waste materials. By turning the eggshell wastes into a high-performance, eco-friendly coating, the team not only innovated a more sustainable path in material science, but also demonstrated its versatile applications for environmental solutions.

IMPACT AND FUTURE PROSPECTS

The development of eggshell-derived superhydrophobic coatings is a game-changer in the field of sustainable mate­rials. By upcycling waste into high-value functional coatings, this research not only addresses the global problem of waste management but also promotes environ­ment-friendly alternatives to harmful fluorinated coatings. Future research aims to further enhance the durability and me­chanical strength of these coatings while expanding their application to smart coatings and biocompatible materials.

With advancements in eco-friendly, fluorine-free superhydrophobic coat­ings, industries are moving towards safer, more sustainable solutions. These coatings are set to redefine efficiency, durability, and environmental protection across multiple sectors, from consumer goods to industrial applications.

COMMERCIAL PROSPECTS OF EGGSHELL-DERIVED SUPERHYDROPHOBIC COATINGS

The development of fluorine-free su­perhydrophobic coatings derived from waste eggshells presents a highly prom­ising commercial opportunity across multiple industries. This eco-friendly, cost-effective, and sustainable alterna­tive to conventional superhydrophobic materials holds the potential for large-scale industrial adoption.

1. Green Coating Industry: A Fluorine-free Alternative

With increasing global regulations on fluorinated chemicals due to their envi­ronmental and health hazards, industries are actively seeking fluorine-free coat­ings. This eggshell-derived superhydro­phobic coating provides a sustainable substitute, opening commercial oppor­tunities in:

• Automotive coatings (water-repellent surfaces, rust prevention)
• Construction materials (self-cleaning walls, anti-corrosion protection)
• Textile and fabric industry (waterproof clothing, stain-resistant fabrics)
• Electronics industry (moisture-proof coatings for circuits and devices)

2. Waste-to-Wealth Business Model

This innovation leverages low-cost, widely available eggshell waste as a raw material, creating a waste-to-wealth business model. Large-scale industries dealing with food waste management and biomaterials recycling can commer­cialise this technology by:

• Partnering with egg-processing indus­tries to collect waste as raw material
• Setting up production facilities to process eggshell waste into functional coatings
• Collaborating with paint and coating manufacturers for integration into com­mercial products

3. Oil Spill Cleanup and Water Treatment Industry

With increasing concerns over marine pollution and industrial wastewater management, the oil-water separation capabilities of these coatings provide:

• Scalable solutions for oil spill cleanups in oceans, minimising environmental damage
• Industrial wastewater treatment appli­cations, helping industries comply with environmental regulations
• Affordable, reusable, and eco-friendly alternatives to synthetic oil-absorbent materials

4. Consumer Product Market

Superhydrophobic coatings are in high demand for household and consumer applications, including:

• Waterproof sprays for shoes, bags, and clothing
• Self-cleaning coatings for furniture, glass, and ceramics
• Corrosion-resistant coatings for home appliances and kitchenware

A STEP TOWARDS GREENER FUTURE

The development of eggshell waste-de­rived superhydrophobic coatings marks a significant step towards sustainability, innovation, and environmental responsi­bility. By transforming waste into high-value materials, this technology not only provides an eco-friendly alternative to conventional coatings but also helps in reducing landfill waste and pollution. With vast commercial applications across industries—ranging from automotive and construction to textiles and oil spill cleanup—this fluorine-free, cost-effective solution is poised to make a real-world impact. As industries shift towards greener alternatives, this breakthrough demonstrates how scientific advance­ments can drive sustainable solutions without compromising performance.

By embracing such waste-to-wealth innovations, we move closer to a cleaner, more sustainable future, where materials once discarded as waste find new life in protecting our environment and improv­ing daily life.

* The writer is Senior Research Fel­low, CSIR-IMMT, Bhubaneswar