Our enriched horse dung substrate is manufactured by piling specific mushroom-loving materials together and allowing them to naturally decompose. During the decomposition process, the horse dung mixture generates its own heat up to 160 degrees Fahrenheit and killing any insects, larva and molds growing in the medium. As it heats up, the combined straw breaks into short pieces and the manure crumbles. The mixture then loses its smell and takes on the odor characteristic of the woodland brush.