Egg shells should not be seen as a waste product, but as offering a wealth of opportunities for egg processors. Egg shells already have a number of applications, but given their particular characteristics and the volumes produced, processors should be exploiting the opportunities they offer far more.
Global egg production generated about 8.3 million metric tons (MT) of egg shells in 2019, with most ending up in landfill, while shells generated by the processing business are thought to amount to 2.4 million MT when recovered after breaking.
When eggs are processed at current equipment’s maximum speed (600 cases per hour), during a 10 hour shift, an egg processing plant will generate about 13 MT per day – or the equivalent of two large adult African elephants!
The disposal is the “elephant in the room” issue, as many egg processors struggle to find ways to dispose of shells, with landfill ever-less likely to take them. Yet, there are numerous ways that value could be created from this by-product.
Egg shells have a rather unique composition, with 95% inorganic material, mainly calcium carbonate, within an organic matrix of proteins (3.4%) and a distinct ultrastructure giving the shell some very special characteristics.
When recovered after breaking, the shell is a combination of membranes that protected the egg white or served as the starting point for the mineralization process of the outer, calcified part of the shell.
Health and beauty to industry
A wide range of potential applications for pure egg shells (ES), egg shell membranes (ESM) and ES+ESM combined, have been investigated and show great potential.
After thermal treatment to eliminate potential sources of microbial contamination, crude eggshells and ES are already used as calcium supplements for both animals and humans.
Following treatment, ESM proteins are commonly used to modify the functional qualities of foods, such as gelling or foaming. They are also used as a source of small peptides and amino acids in dietary products.
Using egg shells’ excellent adsorbent characteristics, a product has recently been launched in China to remove pesticide residues, pathogenic bacteria and industrial waxes on the surface of fruits and vegetables.
Rich in collagens, ESMs are used in a number of cosmetic applications with claims including wrinkle prevention.
Where industrial applications are concerned, a thin film of unprocessed egg shells has been shown to protect construction materials due to UV-light, providing an environmentally friendly alternative to inorganic additives such as titanium oxide, currently used for photoprotection.
Crude eggshells treated at high temperatures have also been used as a catalyst for biodiesel production.
ES constitutes a suitable precursor for the synthesis of a high-capacity absorbent for the removal of various pollutants in wastewater, facilitating the removal of heavy metal ions or serving as a bio-adsorbent for various uses in the textile industry.
Better and wider use of egg shells would not only bring more value to the egg processing business, but would enhance its already strong environmental reputation.
Eggs could soon be in your plate as well as on it