⬇️ Prefer to listen instead? ⬇️
- SMS keeps up to 60% organic stuff even after picking mushrooms.
- Compost from SMS can make soil have more air spaces and grow more plants by 25%.
- Using SMS again helps cut down on trash in dumps and helps farming that reuses things.
- SMS works well as animal bedding that controls wetness and smells.
- Research shows SMS might be good for cleaning up pollution and making energy.
If you've grown mushrooms at home, you've likely thought about what to do with the stuff left over after picking them. This stuff, called spent mushroom substrate (SMS), might seem like trash at first. But really, it's full of good organic stuff that can be used again. From gardening to making compost and even caring for animals, there are lots of ways to reuse mushroom substrate that fit with living in a sustainable way and smart growing.
What is Spent Mushroom Substrate?
Spent mushroom substrate is what's left after mushrooms have been picked. It's made of a mix of organic things based on the kind of mushroom grown—common things are wheat straw, sawdust, soybean hulls, rice bran, coffee grounds, coco coir, gypsum, or even manure. These things are food for the mushroom mycelium as it grows.
The substrate changes in a few ways as mushrooms grow. Fungi break down complex stuff in the substrate to get food, leaving behind organic stuff that's partly broken down. This change makes the substrate "spent," but only for growing more mushrooms—it can still be used for other things.
Is Spent Mushroom Substrate Really ‘Spent’?
Even though it's called spent mushroom substrate, it's not useless. It might not be good for growing mushrooms on a big scale again because it doesn't have as many nutrients, but it still has good organic stuff, wetness, helpful tiny living things, and nutrients that release slowly.
In a study in Bioresource Technology, Zhang, Li, and Fadel (2014) found that SMS can still have up to 60% organic stuff even after growing mushrooms. The tiny living things in SMS also include kinds that help with nutrients in the soil and stop diseases in soil. And, its material from plants continues to give structure that's helpful for soil and composting.
This makes SMS a good thing to use again in farming, gardening, yards, caring for animals, and even research. So think of it as compost material that's partly made or like a sponge full of good stuff for later.
Can You Reuse Mushroom Substrate to Grow Again?
Using SMS again to grow more mushrooms is possible but usually doesn't work as well. Because mushrooms take out sugars, proteins, and nutrients a lot at first, the substrate loses much of its food value. Trying again will usually give you smaller, weaker mushrooms and more chance of getting bad molds or bacteria.
But, growers who know more might try to make SMS better again by
- Adding new nutrients – Putting in wheat bran, rice bran, or gypsum.
- Mixing with new substrate material – Often half and half, to lower chances of bad stuff growing.
- Pasteurizing again – This step helps get rid of any bugs and bad things left.
Really, while you can partly reuse it for more mushrooms, it's usually better to find other uses for SMS besides growing mushrooms.
Use as Mushroom Substrate Compost in the Garden
One of the best ways to reuse mushroom substrate is by making compost. Because of its broken-down organic stuff and tiny life, SMS is great as a ‘green’ (full of nitrogen) part for compost piles.
Why Compost SMS?
- Full of small and big nutrients like nitrogen, phosphorus, potassium, and calcium.
- Makes compost better with its stringy, airy parts.
- Makes tiny life break things down faster, making compost ready sooner.
According to Gülser and Sönmez (2010), adding SMS compost to soil made soil have more air spaces, hold more nutrients, and grow more plants overall by up to 25%. This makes soil better for growing with better air and water—good for veggies, pretty plants, and fruit trees.
How to Mix SMS into Soil for Gardening Use
If you don't want to make compost first, you can put SMS right into your soil, but it's best to do it a little bit at a time to not mess up the soil's pH or salt levels, which can be high in some SMS.
Here are common ways to put it in
- Top dressing: Put a light layer of SMS around plants or garden beds to stop weeds and keep water in.
- Soil amendment: Mix SMS into the soil 2–6 inches deep to make soil have more air and better structure.
- Tree rings/mulch donuts: Use as a ring around fruit trees for slow feeding over time.
- Container gardens: Mix with potting soil about 1 part SMS to 4 parts potting soil for more nutrients and different tiny life.
Make sure the SMS is aged or partly composted to lower salt and ammonia before putting it right in soil. You can do this by letting it sit in a pile or bin for a few weeks, turning it sometimes.
Use SMS as Mulch or Ground Cover
Using SMS as mulch is an easy way to use your substrate again and make soil better at the same time. It's good for covering ground and breaks down slowly to help the soil.
Good things are
- Weed stopping – Blocks light from weed seeds.
- Water staying in – Less water goes away, which is good when it's hot.
- Soil keeping steady – Keeps soil temperature from changing a lot in winter and summer.
- Stopping soil from washing away – Good for hills or paths.
Use a 1–2-inch layer of SMS on the soil, but don't pile it right against plant stems or tree trunks. Over time, the substrate will break down and make the soil underneath better.
Community Use: Donate or Share with Gardeners or Farmers
If you don't garden or have a homestead, don’t throw SMS in the trash. Many local growers and groups want mushroom substrate compost because it makes soil fertile and better structured.
Who might want it
- Community gardens
- Urban farms
- School science or farming programs
- Garden groups
- Local compost places or groups that want zero waste
Use online places like Facebook gardening groups, Craigslist, or neighborhood sites like Nextdoor to find people who want it. Say what kind of SMS it is (like oyster, shiitake) and what it's made from if you know, to help gardeners know if it's good for them.
Animal Husbandry and SMS as Bedding
Another new way to use SMS is as animal bedding. It soaks up stuff well and is the right material, so it's good for lowering smells, wetness, and how much farm waste there is.
Great for
- Chicken coops (chickens, quails)
- Goat or sheep pens
- Rabbit cages
- Pig or cow stalls (on top of straw)
SMS bedding soaks up pee and poop well. After it's dirty, it can be composted and used on land as mixed organic stuff. But, make sure the SMS doesn't have mold and isn't dirty with bad things or bugs. Turning the bedding often will help control tiny life and smell.
Composting SMS with Other Organic Waste
While SMS is great for composting by itself, mixing it with other organic waste—like kitchen scraps, coffee grounds, or dried leaves—makes breaking down faster and more tiny life. This helps keep the right mix of carbon (brown stuff) to nitrogen (green stuff).
How to layer it
- Bottom layer: Straw, shredded newspaper, or leaves (carbon).
- Green layer: Half an inch to one inch of SMS (wet and full of nitrogen).
- More layers: Take turns putting brown and green layers to get different tiny life.
- Keep it wet: The pile should feel like a squeezed-out sponge; not too wet.
- Turn it weekly: Help air flow and make it break down faster.
In 6 to 12 weeks, you’ll have compost full of nutrients ready to use in raised beds, gardens, or around trees. If you’re composting in a bin, watch for heat—this is good, it means your pile is working right.
Signs SMS is No Longer Useful
While SMS can be used again a lot, even the best substrate gets to a point where it's no good anymore. If you're not sure if your SMS is still good for composting or putting on land, check for these bad signs
- Bad or gross smell – Good SMS should smell like earth; strong ammonia or sour smells mean it's breaking down badly.
- Bad mold growing – White mycelium is normal, but black, green, pink, or fuzzy mold is bad.
- Bugs or pests – Maggots, fruit flies, or beetles can mean it's dirty.
- Too packed down – If the substrate turns to clay or really fine dust, it doesn't have much structure left.
If these things are happening, throwing it away is safer and cleaner—it's best to use eco-friendly ways to get rid of it.
How to Dispose of Spent Mushroom Substrate Safely
When SMS is fully broken down or can't be used, getting rid of it should be done in a good way to not hurt the environment. Luckily, there are a few eco-friendly choices
- City green bins – Many cities take organic waste for big composting places.
- Bury it – Bury it in garden spots or empty soil areas to make soil better later.
- Home composting – Mix bad SMS with more carbon-based stuff.
- Put it on land – In the country, SMS might be allowed to be put on empty fields or edges to stop soil washing away and add organic stuff (check local rules).
Don't burn SMS, because it can release bad stuff into the air. The idea is to treat it as good stuff, not just trash.
Bonus: Future Potential for SMS in Bioremediation & Biofuel
As we learn more about sustainable farming, researchers are finding new uses for SMS in industry—mainly in cleaning up pollution and making energy.
Bioremediation
The stuff in SMS from fungi, like laccases and peroxidases, can help clean up bad stuff in dirty soil. These things break down bad waste, like oils, dyes, and metals. Studies are looking at using SMS in filters, landfill walls, or soil cleaning mixes.
Bioenergy Conversion
Because SMS still has plant material, it can be processed to make biogas or biochar. This helps with reusing energy and helps fix farm waste problems.
Future new things might be
- SMS-powered systems making methane or ethanol.
- Making dried SMS into fuel pellets for industry.
- Using it in systems to clean up mining or factory sites.
Mushroom substrate, not really spent at all, might become important in sustainable growth, turning farm leftovers into good resources again.
At Zombie Mushrooms, we think growing mushrooms is just the start—being sustainable begins when the grow bag is empty. Want to grow more than just your crop? Check out our sustainable growing kits, see our best sellers, or start your own closed-loop system today.
Citations
- Zhang, R., Li, X., & Fadel, J. G. (2014). Oyster mushroom growing with rice and wheat straw. Bioresource Technology, 93(3), 277-284.
- Ahlawat, O. P., & Tewari, R. P. (2007). Using spent mushroom substrate. National Research Centre for Mushroom, India.
- Gülser, F., & Sönmez, M. (2010). How spent mushroom compost affects soil and plant growth. Journal of Environmental Biology, 31(6), 923-927.
