One of the most popular uses for boiled eggshells is in the garden. Crushed shells can be mixed into compost or sprinkled into soil to gradually add natural minerals over time. Some people also place coarsely broken shells around plants as a simple physical barrier that may help slow down certain crawling pests. Eggshells can even work as mini seed-starting containers—just fill half shells with soil, plant herb or flower seeds, and once the seedlings are ready, you can place the shell directly into the ground where it naturally breaks down. Back inside the kitchen, finely crushed eggshells mixed with soapy water can be used as a gentle scrub for cookware or sinks, offering an eco-friendly alternative to harsh scouring products.