Mushrooms – The Great Recyclers. They play a key role in global carbon and nitrogen recycling. The carbon cycle is the circulation of carbon between living organisms and their surroundings. The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. In composting and growing our mushrooms contribute to both of these cycles. Mushroom composters are very resourceful and have learned to use a variety of ingredients in their compost. Our mushrooms are not very picky and as long as we compost the ingredients well, the mushroom crops do well. Depending on where they make the compost, sugar cane bagasse, almond hulls, cocoa shells, rice straw, wheat straw, poultry litter, horse manure, corn cobs, corn stalks, cotton seed meal, cotton seed hulls, mushroom stumps, spent brewers grain, hay and leaves are just some of the ingredients that composters use. Almost all of these ingredients are by-products. A by-product is a secondary product made in the manufacture or synthesis of something else. We compost these by-products that normally would go into fields, potentially polluting our streams and drinking water. We then use this compost to grow our healthy mushrooms.