Eggshells as a Resource: Transforming Food Waste into Circular Economy Solutions
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HeTa Food Research Centre for Excellence
Eggs stand out as a crucial protein source for humans, boasting a wealth of essential nutrients while remaining cheap and readily available. Their versatile usage spans supermarkets, bakeries, restaurants, and households alike. Between 2010 and 2020, there was a notable 24.4% rise in global egg production, with the output reaching approximately 76.8 million tons in 2018. The trend is anticipated to continue as the demand for animal protein rises. China is a major contributor, accounting for around 35% of the world’s egg production.
Furthermore, the United States (6.5 million tons) and India (5.2 million tons) play significant roles in egg production, collectively contributing to almost 53% of the total global output (FAO, 2020). Eggshells account for 11% of the total weight of eggs (Oliveira, Benelli and Amante, 2013). In the context of such a huge egg production, the disposal of large amounts of eggshell waste has also become a very difficult problem. Facts have proved that a large amount of eggshell waste is discarded in landfills, which not only provides a good living space for bacteria but also produces odor and seriously endangers public health (Khemthong et al., 2012).
What useful substances are contained in eggshells?
The inorganic substances in eggshells account for about 96%, including calcium carbonate (94%), calcium phosphate (1%), magnesium carbonate (1%) (Stadelman, 2000). The remaining 4% is organic matter found in the eggshell membrane. The eggshell membrane’s collagen, hyaluronic acid, and chondroitin sulfate have very high application potential.
Chondroitin sulfate and Hyaluronic acid
Chondroitin sulfate is mainly found in cartilage such as the nasal bones, larynx, and trachea of humans, cattle, sheep, and pigs. It is also found in the fins, skulls, spines, and other tissues of fish.
Hyaluronic acid is mainly found in animal eyes, cockcombs and umbilical cords, and a small amount is found in animal cartilage. Chondroitin sulfate and hyaluronic acid are important biochemical raw materials in medicine, health products, and cosmetics.
As medical drugs, they have the effects of lowering blood lipids, anti-thrombosis, anti-tumor, treating arthritis, arteriosclerosis, cardiovascular and cerebrovascular diseases, hearing impairment, nephritis, hepatitis, and neuralgia. They can also be used as eye drops as food additives. Chondroitin sulfate can be used to emulsify, moisturize, and remove odors in food; adding chondroitin sulfate and hyaluronic acid to cosmetics can regulate skin cell metabolism, promote nutrient absorption, maintain skin moisture, and improve hair quality.
Collagen
Collagen is animals’ most abundant functional protein, accounting for 25% to 33% of the total protein. It is mainly distributed in tendons, muscle sheaths, ligaments, skin, cartilage, teeth, and bones of animals. Connective tissue is an extremely important structural protein that protects the body and supporting organs. Collagen has been widely used in many fields, such as food, medicine, cosmetics, health products, and biosynthesis. In the biomedical industry, collagen can be made into drug carriers, burn dressings, hemostatic sponges, heart membranes, etc.; in the functional food and health products industry, it can be used as food packaging materials, improving meat quality, beverage clarifiers, etc. The effective active ingredient of the mask. It can also be used as a medium for biological fermentation. The human body easily absorbs collagen peptides and has many physiological functions, such as protecting the gastric mucosa, preventing gastric ulcers, promoting calcium absorption, preventing and treating osteoporosis, promoting skin collagen metabolism, inhibiting the rise of blood pressure, and reducing serum cholesterol levels. It is an important food and an important additive in the pharmaceutical field. The market demand for it is constantly increasing, and its application prospects are broad.
What are the application potentials of eggshell waste? – How and where can eggshell waste be used?
Plant fertilizer
Eggshells are rich in calcium, are a large and inexpensive source of calcium, and are easily extracted. Calcium can raise or balance the pH of highly acidic soils (Commey and Mensah, 2019). This can provide a favorable growing environment for plants and increase yields.
Calcium supplements
Calcium from eggshells is easy to extract; making calcium tablets from them is a great way to do this inexpensively and efficiently. In addition to making calcium tablets, calcium can be added to human or animal food (such as cookies).
Biomedical material
The calcium in eggshells can be used as a filling material for teeth, hyaluronic acid has the potential to make corneas, chondroitin sulfate can be used to make fake cartilage, and collagen can be used as a filler in the medical beauty industry.
Packaging material
Eggshells can be incorporated into bio-based films, which has multiple benefits: increased strength, thermal stability, antimicrobial properties, gas barrier properties, and reduced hydrophilicity of the film surface (Xu et al., 2023).
Carbon dioxide sorbent
Emissions of greenhouse gases, including carbon dioxide, contribute to the global warming problem, so how to dispose of these gases is a major problem for people. Studies have shown that calcined eggshells can adsorb carbon dioxide, reducing the economic pressure on people to dispose of greenhouse gases and reducing waste (Waheed et al., 2020).
With global egg production and consumption on the rise, the problem of eggshell waste disposal will continue to grow. However, eggshells need not simply be discarded as useless waste. They contain valuable components like calcium carbonate, calcium phosphate, collagen, chondroitin sulfate, and hyaluronic acid that have diverse applications in agriculture, food, medicine, and manufacturing. Eggshells can be upcycled into plant fertilizers, calcium supplements, biomedical materials, packaging materials, and carbon dioxide sorbents. Implementing circular economy solutions that transform eggshell waste into useful products will reduce waste and generate environmental and economic benefits. Innovative technologies and business models allow the nutrients, minerals, and proteins in discarded eggshells to be recovered and reused in a sustainable closed-loop system. What is currently viewed as an undesirable waste product can be transformed into a valuable resource.
Reference
- Commey, A. and Mensah, M. (2019). An experimental study on the use of eggshell powde r as a pH modifier: Production of lime from eggshells. International Journal of Innovative Science and Research Technology, pp.766–768.
- FAO (2020). Database of Food and Agriculture Organization of the United Nations. [online] www.fao.org. Available at: https://www.fao.org/faostat/
en/#home . - Khemthong, P., Luadthong, C., Nualpaeng, W., Changsuwan, P., Tongprem, P., Viriya-empikul, N. and Faungnawakij, K. (2012). Industrial eggshell wastes as the heterogeneous catalysts for microwave-assisted biodiesel production. Catalysis Today, 190(1), pp.112–116. doi:https://doi.org/10.1016/j.
cattod.2011.12.024 . - Oliveira, D.A., Benelli, P. and Amante, E.R. (2013). A literature review on adding value to solid residues: egg shells. Journal of Cleaner Production, [online] 46, pp.42–47. doi:https://doi.org/10.1016/j.
jclepro.2012.09.045 . - Stadelman, W.J. (2000). Encyclopedia of food science and technology. pp.593–599.
- Xu, H., Li, J., McClements, D.J., Cheng, H., Long, J., Peng, X., Xu, Z., Meng, M., Zou, Y., Chen, G., Jin, Z. and Chen, L. (2023). Eggshell waste act as multifunctional fillers overcoming the restrictions of starch-based films. International Journal of Biological Macromolecules, [online] p.127165. doi:https://doi.org/10.1016/j.
ijbiomac.2023.127165 .
Further Reading
