Here's a few short clips from our horse manure video, which demonstrates the preparation of manure for use as a bulk substrate for growing mushrooms. While horse manure was chosen for this demonstration, this technique will work well with the manure from just about any grass and grain-eating animal such as cow, donkey, deer, moose, rabbit, etc.
The idea is to collect field-aged, dry manure. Unless you’re building a compost pile, don’t collect ‘green’ manure. To use uncomposted manure, you want to collect manure directly from the field, not the barns where it's fresh, green, and usually soaked with urine. Collect only manure that has been leached by the rain, and dried by the sun for at least a month or two. There will be zero objectionable odors. If it stinks, it’s not yet ready to collect. The full release of this video on Let’s Grow Mushrooms shows how to break up the dry manure, mix in a bit of gypsum, hydrate to field capacity, and pasteurize.
Marc R Keith