This document discusses the role of eggshells in composting. It explains that eggshells are considered a brown material high in calcium carbonate. Eggshells provide benefits to compost by supplying calcium for plant metabolism and creating air pockets for aerobic microbes. However, eggshells can take a long time to break down. The document recommends crushing eggshells into tiny bits and mixing with nitrogen-rich materials to help them decompose more quickly and enrich the soil.