The humble eggshell is far more than simple kitchen waste. This common byproduct is composed almost entirely of calcium carbonate, making up about 94 to 97% of its total weight. This chemical compound gives the shell a unique structure that is both rigid and slightly porous. Due to this high concentration of a naturally occurring mineral, eggshells can be repurposed into a variety of valuable materials, ranging from a dietary supplement to a household cleaning agent.
How to Prepare Eggshells for Safe Use
Before eggshells can be used, especially for internal consumption, they must be cleaned and sterilized to eliminate potential pathogens. Begin by thoroughly rinsing all shell pieces under running water to remove any residual egg white or yolk, as organic matter can harbor bacteria like Salmonella.
Sterilization is performed by boiling the shells in water for 5 to 10 minutes, or by baking them at 250°F (121°C) for 10 to 15 minutes. This heat effectively dries and sanitizes the shells, destroying any remaining bacteria.
Once sterilized, the shells must be completely dried and processed. For most external applications, the shells can be crushed into coarse pieces. However, for use as a dietary supplement or for fine abrasive cleaning, they must be ground into an extremely fine powder using a coffee grinder or a high-powered blender.
Using Eggshells as a Dietary Calcium Source
The primary nutritional value of eggshells lies in their high content of calcium carbonate. One average eggshell contains about 750 to 800 milligrams of elemental calcium, often enough to meet the daily requirements for many adults. Studies show that calcium derived from eggshell powder is readily absorbed by the body, with bioavailability comparable to purified calcium carbonate supplements.
When consumed, the calcium carbonate reacts with stomach acid, converting it into calcium chloride, which the body absorbs through the intestines. The eggshell also naturally contains trace minerals like strontium, magnesium, and phosphorus. This combination of minerals supports bone health and contributes to the shell’s efficacy for promoting bone mineral density.
To use eggshells as a supplement, the powder must be as fine as flour, as larger fragments can cause irritation to the digestive tract. The resulting powder can be easily mixed into soft foods such as yogurt, oatmeal, or smoothies. Consulting with a healthcare provider before beginning supplementation is strongly advised to determine the correct dosage and ensure it does not interfere with existing medications.
Practical Uses Around the House and Garden
Beyond nutritional applications, the physical and chemical properties of eggshells make them useful for a variety of tasks in the home and garden.
Soil Amendment and Plant Health
In the garden, eggshells serve as a slow-release source of calcium, an important secondary nutrient for plant growth. Incorporating crushed shells into the soil benefits plants prone to calcium deficiency, such as tomatoes, peppers, and broccoli. This helps prevent issues like blossom end rot, as the calcium strengthens the plants’ cell walls.
Pest Control and Seed Starters
The sharp, jagged edges of coarsely crushed eggshells act as a physical barrier against certain garden pests. Spreading a thick ring of these crushed pieces around the base of vulnerable plants deters soft-bodied creatures like slugs and snails. Additionally, half eggshells can be used as small, biodegradable starter pots for seedlings, which can be planted directly into the ground without disturbing the delicate young roots.
Household Cleaning and Flavor Improvement
Inside the house, the physical structure of the shell powder provides a non-toxic alternative for cleaning. Finely ground eggshell powder acts as a mild abrasive, useful for scrubbing away stubborn residue from pots, pans, and sinks without scratching sturdy surfaces like stainless steel or porcelain. This abrasive powder can be mixed with baking soda and dish soap to create an eco-friendly scouring paste.
Eggshells can also be used to improve the flavor of coffee. Adding a small amount of crushed eggshell to the coffee grounds before brewing reduces the finished product’s bitterness. This occurs because the shell’s alkaline calcium carbonate neutralizes some of the natural acids in the coffee beans, leading to a smoother cup. Note that putting whole or large pieces of eggshell down a drain is not recommended, as they can lead to stubborn plumbing clogs.