EGG SHELL: AN IMPORTANT POULTRY BY-PRODUCT
Eggshells are waste materials from hatcheries, homes and fast food industries and can be readily collected in plenty. Eggshell waste disposal contributes to environmental pollution. Challenges associated with disposal of eggshells include cost, availability of disposal sites, odour, flies and abrasiveness. However, they can be processed into saleable products like fertilizer, used in artwork, human and animal nutrition and building materials and to produce collagen from the membranes.
Eggshells can be utilized for various purposes that minimize their effect on environmental pollution. Eggshells present healthy, balanced calcium due to its trace amounts of other minerals and is probably the best natural source of calcium. One whole medium sized eggshell makes about one teaspoon of powder, which yields about 750-800 mgs of elemental calcium plus other micro elements. Eggshell powder has been reported to increase bone mineral density in people and animals with osteoporosis. In laying hens in the late production phase, eggshell powder has been found to increase egg production and improve the quality of shells. Discarded eggshells are often used as a plant fertilizer and are effective liming sources. This is because eggshells contain calcium that raises, or neutralizes, the pH level of overly acidic soil. Chicken eggshells can be used as an alternative soil stabilizer like lime since they have the same chemical composition. Such stabilized soil can be used as sub grade materials in road construction works. Eggshell membrane consists of collagen as a component. Collagen is a type of protein, fibrous in nature that connects and supports other bodily tissues, such as skin, bone, tendons, muscles and cartilage. Collagen has been isolated mainly from bovine and swine skins and bones Collagen used in medicine, biochemical, pharmaceutical, food and cosmetics industries. After the outbreaks of Bovine Spongioform Encephalopathy, foot and mouth disease, autoimmune and allergic reactions, restrictions on collagen uses from these sources were enforced. Eggshell membrane collagen is very low in autoimmune and allergic reactions as well as high in bio-safety and is of similar characteristics to other mammalian collagen. Eggshells/shell membranes have multiple uses in nutrition, medicine, construction and art works.
The egg consists of nine different items, which are egg shell (the outer covering of the egg), air cell (the pocket of air at the end of an egg), shell membrane, thin albumen, thick albumen, chalazae (anchor yolk), vitelline membrane, germinal disk and egg yolk. An eggshell is the outermost covering of an egg. The shell color of an egg is representative of the breed of hen that produces the egg. White hens produce white eggs and brown hens produce brown eggs. In an average laying hen the process of shell formation takes around 20 hours. Eggshell serves to protect the egg against damage and microbial contamination, prevention of desiccation, regulation of gas and water exchange for the growing embryo and provides calcium for embryogenesis. The shell makes up 9-12 percent of an egg’s total weight. It contains 27 essential microelements. Shell contains calcium carbonate (94%), magnesium carbonate (1%), calcium phosphate (1%) and organic matter (4%). It also contains trace amounts of sodium, potassium, zinc, manganese, iron, copper, sulphur, water, protein, crude fat, ash, alanine, arginine, aspartic acid, cystine, histidine, leucine, lysine, isoleucine, tyrosine, valine , phenylalanine, proline, serine and threonine. Eggshell acts as a waste material from different domestic sources such as poultry farms, egg producing factories, hatcheries, homes and restaurant and results in increases pollution problems. Most eggshell waste is discarded without further processing by sending to landfill at a very high cost which is a very big issue. It is necessary to find an alternative method which would transform the waste eggshells into a valuable item, giving financial benefits to the competitive egg processing industry, apart from giving manufacturers a new profit stream. Egg shell can be used in variety of ways. Egg shells are used to enhance the soil fertility as it quickly decomposes and adds valuable calcium and other minerals to the soil. Crushed eggshell is scattered around the plants and flowers, which protect it from plant eating slugs, snails and cutworms, without using eco-unfriendly pesticides. Biodegradable eggshell halves are filled with potting soil and one or two seeds are added to each shell to start seedlings for the garden. It is one of the simple way to start a seedling in shells. When the seedlings are big enough for transplanting outside, the shells are cracked at the bottom and seedlings are planted. Eggshells contain 95% calcium, and hens need calcium to lay eggs that have those strong shells. If shells have been sterilized to kill bacteria they can be fed to laying hens. Egg shells are used as coating pigments for inkjet printing paper and are also used for various decorative purposes by using paint. It can be used as food additive in coffee in the filter which reduce the bitterness in coffee. It can also be used as a nontoxic abrasive on pots and pans. It acts as a natural drain cleaner. A couple of crushed eggshells can be kept in kitchen sink strainer. At all times it traps additional solids and they gradually break up and help to naturally clean pipes on their way down the drain. Egg shells also act as laundry whitener. These if scattered in areas most prone to cats, also help in keeping cats away. Eggshell particles are used in toothpaste as an anti-tartar agent. Egg shell is having important medicinal uses such as healing cuts, treating ingrown toenails, skin irritations, and itchy skin, skin-tightening and facial. Eggshells are dissolved in a small jar of apple cider vinegar (takes about two days) and the mixture is used to treat minor skin irritations. It also acts as a facial in which dried egg shells are ground with the help of mortar and pestle, mixed with egg white and the mixture is applied on face and then rinsed Egg shell is used as pet food. Dry eggshells are taken in oven at 2500 C, for 30 minutes and then put in a plastic zipper bag, sealed and the shells are crushed with a rolling pin until they are a fine powder. This is added in to dog’s food as a great calcium supplement to help in its bones and teeth growth. In addition, calcium carbonate from eggshell has an advantage for not containing toxic elements like calcium carbonate from oyster shells, which contains lead as well as other potential toxic elements such as aluminum, cadmium and mercury. Because of this property egg shell is used as a source of calcium supplement in animal and human. This supplement leads to increased bone density, less arthritic pain and even stimulates cartilage growth in man and animals. Egg shells are also used in as a calcium supplement in orange juice. Eggshell consumption helps stop bone loss in postmenopausal women. Applications of eggshells in the form of calcium lactate has been used as a firming agent, a flavor enhancer, a flavoring agent, a leavening agent, a nutrient supplement, a stabilizer and thickener. Eggshells have thus nearly as many uses as the eggs themselves. Egg shells can thus be used in such a way which may help to overcome the global eggshell waste problem, high disposal costs and environmental concerns.