If you’re wondering whether to use rice (paddy) straw or sawdust as a substrate for oyster mushrooms, you’re not alone. Let’s explore both options, including preparation, nutrition, and the time involved, so you can decide which works best for your farm.
Rice straw offers multiple processing options depending on your resources. You can pasteurize it with steam or hot water, treat it with lime, or even sterilize it. Lime pasteurization and hot-water methods are common for small- to medium-scale farms because they require less expensive equipment.
Sawdust, however, is a different story.
Sterilization is not optional — it’s essential.
Without sterilization, sawdust mixed with nutrient-rich supplements will quickly become a paradise for molds and bacteria.
This means you’ll need a sterilizer or pressure cooker to kill contaminants.
If you operate a large-scale production, you’ll need a big autoclave with a capacity of 175 to 350 cubic feet (5 to 10 cubic meters) and a trained operator to handle it since autoclaves use high-pressure steam for sterilization.
A practical alternative is a steam pasteurization chamber.
In this setup, small bags of substrate (similar in weight to those used in an autoclave) are loaded on carts, which are wheeled into the chamber.
Steam enters the chamber without creating excess pressure.
These chambers typically have two sets of doors: one side opens to load carts for sterilization, and the other side leads into a sterile inoculation room where grain spawn is added.
Unlike rice straw, sawdust is low in nitrogen, making it a weaker nutritional base for mushrooms. To get good yields, you’ll need to add supplements like wheat or rice bran, soybean meal, or even ground-up soybean pods or alfalfa hay. The challenge? These nitrogen-rich additives are exactly what molds love, which is why sterilization is critical.
Of course, you can use sawdust simply as a base for the substrate, acting primarily to retain the moisture needed for oyster mushroom mycelium to grow—without adding any nutritional supplements. And then, perhaps, it will be enough for you to simply pour hot water over these sawdust and keep them in water until their humidity becomes at least 69%.
However, this approach requires using a large amount of grain spawn—at least 20%-25% - to achieve good yields. In most cases, this is not economically efficient.
On the bright side, the extra nutrients can lead to higher yields when everything is properly sterilized. Nutritional supplements make a big difference, but they require careful handling to avoid contamination.
Sterilized sawdust substrates are typically packed into small bags weighing 2 to 3 kilograms (4 to 7 pounds).
This means more time spent filling, sealing, and handling each bag. A mechanical press can speed up the process, but it’s still a labor-intensive method compared to filling larger straw bags.
With rice straw, you can fill bigger bags more quickly and skip the precision packing required for sawdust. However, the soaking or pasteurization process also takes time and careful attention, so neither method is entirely hands-off.
A unique characteristic of paddy straw is that it absorbs water very quickly in many regions, often resulting in an over-saturated substrate.
This creates a challenge - how to remove the excess moisture.
One solution is to mix chopped straw with unchopped straw to make the substrate less dense.
The unchopped straw adds a springy structure, allowing excess water to drain through the gaps between the stalks to the bottom of the block. This structure also improves gas exchange, making it easier for the mycelium to colonize the substrate effectively.
When working with sterilized substrates like sawdust and bran, you’ll need a microbiologically clean environment to prevent contamination.
That means investing in cleanrooms, HEPA filters, or laminar flow hoods.
While straw pasteurization requires cleanliness too, it’s more forgiving, and you won’t need quite as much specialized equipment.
Both paddy straw and sawdust have their advantages. Rice straw is more versatile and easier to manage without expensive equipment. Sawdust, when properly supplemented and sterilized, can produce higher yields but requires significant investment in labor and cleanliness.
If your region offers cheap and plentiful sawdust — and you’re ready to tackle sterilization — it can be a fantastic option. But if time, simplicity, and lower upfront costs matter more, rice straw may be your best bet.
These are the pros and cons. 🤷
If you have any questions or want to share your experience, head over to my Facebook page and leave a comment—I’d be thrilled to hear from you!
