Reusing Mushroom Substrate: A Personal Experiment

Reusing Mushroom Substrate

I’ve always been curious about whether we, as mushroom growers, are truly getting the most out of our substrate. After growing two flushes of pink oyster mushrooms, I decided to experiment with reusing the spent substrate. Here’s how it went.

Preparing the Spent Substrate

I started with a couple of spent pink oyster mushroom blocks. These had been sitting outside for a while, so they were pretty dry and a bit rough. My plan was simple: break the blocks down, rehydrate them, and then re-sterilize. Once sterilized, I inoculated the substrate with a different mushroom species—Phoenix oyster. The idea was to see if a new mushroom variety could pull more energy from the old substrate.

How to Reuse Mushroom Substrate: A Step-by-Step Guide

Reusing mushroom substrate can be effective, but it requires careful attention to detail. Here’s a streamlined process I followed to reuse spent pink oyster mushroom blocks to grow Phoenix oysters.

1. Break Down Spent Blocks

Start by breaking down your spent mushroom blocks. These blocks may have dried out, so crush them into small, manageable pieces. This helps the substrate absorb water and makes it easier for the new mushroom species to colonize.

2. Rehydrate the Substrate

Rehydration is key. If your blocks have lost weight, add water back in, but be cautious—don’t overhydrate. For example, if a block lost 1.8 kg, add about 1 kg of water. Too much water can hinder growth.

3. Sterilize the Substrate

After rehydration, sterilize the substrate. This kills any contaminants like bacteria or mold. Seal the substrate in sterilization bags and run them through a full sterilization cycle, typically 24 hours.

4. Inoculate with New Spawn

Once sterilized and cooled, inoculate the substrate with your chosen mushroom spawn—here, I used Phoenix oysters. Mix the spawn evenly throughout the substrate to ensure thorough colonization.

5. Incubate

Place the inoculated substrate in a warm, dark place for 2-3 weeks. Monitor for even mycelium growth and watch for any signs of contamination.

6. Prepare for Fruiting

Once fully colonized, move the substrate to your fruiting chamber. Make small cuts in the bags to allow mushrooms to emerge. Ensure the chamber has proper humidity, temperature, and light.

7. Troubleshoot Issues

If your equipment fails, as mine did when the humidifier broke, have a backup plan. Inadequate humidity can reduce mushroom quality and yield. Ensure your tools are reliable.

8. Harvest and Reflect

Despite setbacks, the reused substrate produced a decent yield of Phoenix oysters. While the yield wasn’t as high as fresh substrate, this process shows potential. Reusing substrate can be a viable option if managed carefully.

Results and Observations

The Phoenix oyster mycelium colonized the substrate beautifully, with a good spread throughout the block. The mushrooms that emerged were decent, though perhaps not as abundant or as high-quality as those grown on fresh substrate. Unfortunately, midway through the experiment, my humidifier broke down, which affected the humidity levels in the fruiting chamber. This likely impacted the results, leading to smaller caps and an uneven flush.

Even with the humidity issues, the reused substrate produced a respectable flush. This made me question whether we’re fully utilizing the nutritional potential of our substrates. Could there be more energy left in those blocks than we think?

Final Thoughts

Reusing mushroom substrate is possible, and it can yield a decent crop. However, the trade-offs include potential loss in quality and quantity. The real question for mushroom growers is whether the benefits of reusing substrate outweigh the costs. This experiment opened up new possibilities, and I’m eager to explore them further.