Bulk Substrates These are what we use to grow lots of mushrooms cheaply.

Most of the mushrooms we grow are Saprophytes, meaning they eat dead organic matter. Cellulose and lignin are favored foods, found readily in sawdust, woodchips, straw, newspaper, cardboard, coir, baggasse, lawn clippings, seed hulls, and many other potential waste products.

Supplements can be used to diversify the nutritional base, which can lead to faster and bigger yields. Many growers add Gypsum, at rates from 1% to 10% of the dry weight of the bulk substrate. Other common supplements include bran, grape pumice, grains, spent brewery grains, used vegetable oils, brewers yeast, bakery waste and spent tea and coffee grains…as well as left over food from your kitchen. Many of these supplements can attract competitors.

I like to soak coir in a bin.


Then mix the soaked coir with your supplements in a bucket

 I usually use presoaked(48 hours) wheat and gypsum, but have tried many others, and had good results.
I also added woodchips in the above photo-Eucalyptus somethingorother.
.
Here are some king oysters on coir 80% with left over cooked  brown rice 20%.