What are the comprehensive utilization methods for spent mushroom substrate residue?

I. It can be reused as a substrate for secondary cultivation, using spent oyster mushroom substrate to cultivate straw mushrooms as an example. Oyster mushrooms mainly utilize lignin and hemicellulose in fibrous materials and consume very little cellulose. Therefore, in spent oyster mushroom beds, the cellulose content is relatively high, which exactly meets the nutritional requirements of straw mushrooms. The method is as follows: after harvesting the mushrooms from the cultivation substrate used for oyster mushrooms, break up the mycelial blocks and dry them in the sun for storage. When composting the straw mushroom substrate, add 20 kg of new cottonseed hulls, 20-30 kg of dry cow dung, 0.5 kg of urea, 1.5-2 kg of gypsum powder, and 1 kg of superphosphate to 100 kg of spent substrate, and compost according to the conventional method. The composting time can be shortened by 2-3 days, one turning of the pile can be reduced, fruiting begins 2-3 days earlier, and the yield is roughly the same as that of manure-straw compost.

II. It can be used as raw material for biogas digesters. When cottonseed hulls, rice straw, and sawdust are used as substrate to cultivate edible fungi, the residue is decomposed by mycelium, making it more easily utilized by biogas fermentation microorganisms, which can accelerate their decomposition of it, produce gas earlier, and achieve a higher gas production rate.

III. It can be used as spent mushroom substrate feed. Edible fungi have strong decomposing ability. In the spent substrate from edible fungi cultivated with straw as substrate, crude fiber is degraded by 50% and lignin by 30%. Because the spent substrate contains a large amount of fungal cell protein, the crude protein content increases from the original 2% to 6%-7%, and the fat content also increases by about 1 time. Through the decomposing action of mycelium, the cuticle layer and silica cell tissue on the surface of the straw material as well as the crystalline structure of the fiber are all destroyed, making it loose and porous, reducing mechanical strength, making it easy to crush, with a fragrant smell and good palatability, thereby improving nutritional value. When used to feed pigs, cattle, and other livestock, it is better than rice bran and can achieve the feeding effect of corn. Spent mushroom substrate feed can be fed directly to pigs and cattle, or it can be put into a green fodder pulping machine to make a slurry and then mixed with other feed; it can also be mixed directly with other feed without processing.

IV. It can be used as organic fertilizer. The nutrients contained in spent mushroom substrate residue include components that mycelium cannot directly utilize, mycelial metabolites, and fungal protein after decomposition of the mycelium. According to analysis, each ton of residue contains about 10 kg of nitrogen, 1 kg of phosphorus, and 10 kg of potassium, and the carbon-to-nitrogen ratio is small. The nutrients are in a readily available state and are easily absorbed and utilized by crops. Applying 3000-4000 kg of spent mushroom substrate residue per mu can increase corn yield by more than 10%, and increase wheat and soybean yields by about 30%. Applying spent mushroom substrate residue to farmland can not only improve soil fertility, but also help improve soil physical and chemical properties, promote the formation of soil aggregate structure, and enhance soil water-holding capacity and permeability. Organic acids and other substances in the metabolites can also stimulate the growth of rhizosphere nitrogen-fixing microorganisms, and some metabolites have an inhibitory effect on the growth of harmful microorganisms. It is a very ideal "fungal fertilizer."