What Can I Do With a Used Mushroom Grow Kit?

Mushroom grow kits are a fun and interesting way to have your own fresh mushrooms for cooking and medicinal purposes. But, when they’ve lived out their life cycle, you will have to dispose of the spent substrate in some way. You can compost, reuse or throw it away. If you don’t, it will attract other fungal spores, gnats and parasites.

How Do I Reuse a Mushroom Grow Kit?

Once your mushroom kit no longer produces mushrooms, don’t throw out your block right away. You can try for a second or third flush; some people report they can get as many as five from a single kit. All you have to do is soak the block again, return it to a fruiting environment and wait two weeks for it to pin again.

Oyster Mushrooms

Note that the following method is only good for Oyster Mushrooms, most others will develop contamination. Lion’s Mane and Shiitake mushrooms are very susceptible to contamination. So, if you see any green mold, try to cut it off or use a more definitive disposal method.

Removing the Mycelium

Prepare the substrate, also called a block or cake, according to your kit’s instructions. Remove the block from its container or other casing. It’s important to exercise care because some mycelium are more friable than others and they don’t hold together well.

Disinfect the Cake

It’s likely bacteria and mold spores accumulated on the block’s outer surface. So, you will have to sterilize it. Rub the block in a disinfectant to kill these contaminants but not the mycelia. You can use limewater or hydrogen peroxide. Massage the disinfectant over the surface to ensure nothing bad will survive.

Breakdown the Block

Then, breakdown the block and crumble it into small pieces. Mix it with things like broken egg shells, oat straw and coffee grounds to reinvigorate the nutrients. You should have more mushrooms in a couple weeks.

How Do I Put a Mushroom Grow Kit in a Compost Pile?

When the block is no longer capable of producing mushrooms, you can bury the block in your compost area. In the case of Oyster Mushrooms, simply bury the mycelia into soil. This may produce another flush too.

If you opt for the compost pile, there are a few things to note beforehand. First, understand that your block will attempt to colonize your compost pile, especially when the weather provides the perfect conditions.

Avoid Various Species in the Same Spot

Also, don’t put different species in the same area. They will compete with each other and this can create some problems. Because of the competition, they will more than likely not be edible.

However, once the mushrooms stop growing and become part of the organic matter, you can use this to plant seedlings, cuttings or transplant other growing things. The nutrients and minerals that spent mycelia blocks provide are invaluable to gardeners, farmers and others with a green thumb.

Can I Use a Spent Mushroom Mycelia Block for Gardening?

Gardeners in Helsinki, Finland have great harvests because they apply used mushroom substrate to their growing projects and operations. It’s actually a staple practice among gardeners and farmers. The mushroom block provides a blanket while giving plenty of nutrients.

If you want to do it this way, there are some things you should consider beforehand:

  • Put the spent and broken up mycelia block straight on the soil. Don’t place fabric or cardboard underneath because it reduces breathability between the soil and mycelia.
  • Ensure that what you put onto the soil is at least 5 centimeters thick. The more mushroom substrate, the better it will be.
  • The spent mycelia block should sit in a shady area. If you have to, add some bark, leaves, wood chips or gardening mesh over the top of the bed. This will keep the mushrooms moist and prevent them from drying out.
  • Don’t forget to water frequently and check the patch daily. This also means paying attention to the weather so that you’ll know when it’s moist enough or you need to water the soil.

Preparing the Block for the Trash

Regardless of the species, disinfect your mycelia block and break it up as if you would reuse it (see instructions above). Then scatter the pieces over your yard to supplement the soil.

You can use spent substrate as mulch for plants and flowerbeds too. Because most mushrooms don’t rob the immediate area of soil, they make good growing companions. They actually take away all the decaying matter which leaves all the good stuff for plants, like flowers and vegetables.

Plus, it offers another opportunity to get more mushrooms out of the deal.

How Do I Throw a Mycelia Block/Cake in the Trash?

If you’re looking to throw the cake in the trash, you should check your local waste laws and regulations before throwing it into the weekly garbage pickup.

Aside from Oyster Mushrooms, most spent mushroom mycelia cakes contain potentially illegal compounds. In this case you will have to destroy the cake before you dispose of it. You can do this by saturating the block with water, breaking it apart and tossing it in with some garbage to allow mold and rot to develop.

Toxic Waste

For this, do not put it in your regular weekly trash pickup. Take it away from the premises and dump it according to the hazardous waste guidelines in your area. If you don’t follow the local laws regarding this, you could receive an exorbitant fine or, in some municipalities, land you in jail.

Some people consider microwaving their spent mushroom cakes, then breaking them up and throwing them away. But the heat will just intensify the toxicity of the mycelia block. This can create even more problems and issues than it hopes to solve.

Can I Feed a Spent Mycelia Block to Livestock?

In the event you have livestock, you can feed them the spent block after disinfection and breaking it down.