Eggshell

Outer shell of hen's eggs, a by-product of kitchens and the egg industry, made mostly of calcium carbonate.

Characteristics

Mainly calcium carbonate, with small amounts of magnesium and nitrogen.
Raises soil pH; reacts faster when finely ground.
Cited in traditional agroecological literature as a calcium source.
In home recipes often dried, crushed or dissolved in vinegar.

Role in the preparation: Supplies calcium and acts as a mild liming material in compost, bokashi or mineral preparations.

Caution: Rinse and dry shells before storage to avoid odours, and check local regulations before any use.

Sources: Iowa State University - Eggshells as a liming material

Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.