Why must glass and metal be separated from organic waste before composting?

In the context of solid-waste management, glass and metal must be separated from organic waste because they are inorganic materials that are not biodegradable.

Composting is a biological process that relies on microbes to metabolize and decompose organic matter into humus. Because inorganic items like glass and metal do not break down through these biological actions, they must be isolated from the organic portion of refuse to ensure the production of a uniform, high-quality compost product.123

Mechanical sorting operations use physical characteristics—such as size, density, and magnetic properties—to remove these inorganic contaminants. Separating these materials is essential for the efficiency of the composting process and the final utility of the compost as a soil conditioner or mulch.142