Always run water when using your garbage disposal, since the moisture helps break up the food, even when disposing of fat and grease. Soft or brittle debris like egg shells, cooked carrots, peas, mashed potatoes and small pieces of meat will be ground up by the disposal and flushed down the pipes, but hard materials like bones and coffee grounds will wear out the disposal and dull the blades. Fibrous materials like corn husks can jam up a disposal.