Using a Spent Grow Block for Compost

Mushroom Compost

You've cared for your mushroom grow block, maybe you've even attempted to grow a second flush of mushrooms! Now what? What do you do with this ten pound block of sawdust and grain sitting on your kitchen counter? Use it as compost!


  • Using your spent grow block as compost minimizes waste. Instead of throwing out your block, use all that healthy fungi to fuel your garden!
  • The primary ingredient in your grow block is red oak sawdust. Most most home compost piles need more brown matter to balance the high nitrogen level of the food scraps. 
  • Compost rich in fungal matter hosts more beneficial nematodes which help make nutrients bio-available for garden plants.  

Here's How:

  1. If it isn't already, remove the plastic bag surrounding your spent grow block.
  2. Crumble the grow block into your compost bin. 
  3. OR place the whole block in your garden, under a plant. The grow block will act as slow-release fertilizer while the worms slowly decompose it.