Millipede castings are quite similar to worm castings, being a superfood for plants. They are primarily detritivores, breaking down organic matter into delicious plant food. The castings can be used to mix into a potting or planting mix, as a tea, and many more to increase levels of nitrogen and healthy fungi and bacteria in soil.
These castings come from a variety of species, but primarily Narceus americanus at the moment. Other species may include Narceus gordanus, Trigoniulus corallinus, Anadenobolus monilicornis, and more.
Castings may include small amounts of leftover substrate from the millipede enclosures, as well as springtails. Heat treating the castings may kill any extra organisms in it, but also may reduce the effectiveness of the castings as a fertilizer.