What's a good biological efficiency? Mushroom BE by species, and why the numbers disagree
Biological efficiency (BE) is fresh mushroom weight divided by dry substrate weight. Published BE is often 100% or more for oysters, about 45–145% for shiitake, 40–70% for king oyster and chestnut, and under 50% for maitake, but studies measure it differently. Here's BE by species, why figures disagree, and how to measure your own.
Derick8 min read
Biological efficiency (BE) is the fresh weight of mushrooms you harvest divided by the dry weight of the substrate, times 100. A good BE depends on the species: around 100% for oysters, 45–145% for shiitake depending on the source, roughly 40–70% for king oyster and chestnut in trials, and often under 50% for maitake, while lion's mane and its Hericium relatives range from about 26% to 92% in studies. Published figures disagree because studies weigh, count and grow differently, so the best yardstick is your own earlier runs, measured the same way each time.
Our sources include UC Cooperative Extension, Penn State, USDA SARE farm trials, Cornell Small Farms and peer-reviewed studies, checked 29 October 2026.
What is biological efficiency?
Biological efficiency measures how well a mushroom turns dry substrate into fresh mushrooms: BE (%) = total fresh weight of all flushes ÷ dry substrate weight × 100 (Food Science & Nutrition, via PMC). Our grow log guide works through an example.
BE can pass 100% because fresh mushrooms are mostly water: a UC Cooperative Extension deck puts oysters at 91% water and shiitake at 85% (UC Cooperative Extension), while the substrate is weighed dry.
Three numbers get called "yield", so check which one you're reading:
- Biological yield is the grams of mushrooms per bag (PLoS One, via PMC).
- BE divides that by the bag's dry weight, so blocks of different sizes compare fairly.
- Pounds per block is what farms track. SARE's five farms averaged 0.88 lb per 5-lb block started, as our cost-per-pound guide explains.
What's a good biological efficiency for each species?
A good biological efficiency for oysters is around 100%, shiitake runs from 45–74% in one sawdust trial to UC's 50–145%, king oyster and chestnut land nearer 40–70% in studies, and maitake is often below 50%. The rows mix general extension figures with single studies on different substrates and harvest windows, so read them as ballparks, not targets.
| Species | Published BE | Substrate and conditions |
|---|---|---|
| Oyster (Pleurotus) | 100–200% | UC Extension, general figure (UC) |
| Oyster, lab | 58–114% | Four crop straws (Studies in Fungi) |
| Oyster, on a farm | 18–41% | 10-lb straw bags on a Massachusetts farm, by straw treatment: fermentation, wood ash, heat pasteurization (29%) and lime (SARE) |
| Shiitake | 50–145% | UC Extension, general figure (UC) |
| Shiitake | 45–74% | Sawdust with 20% wheat bran, two harvests (PLoS One) |
| King oyster | 63–70% | Sawdust and cottonseed hulls (70%) or Burma reed mixes, per bag (Indian J. Microbiology) |
| Chestnut (Pholiota adiposa) | 41–68% | One cottonseed-hull and sawdust recipe for all five strains, two flushes (Mycosphere) |
| Lion's mane | about 43% | Rubber-tree sawdust, commercial scale (Scientific Reports) |
| Lion's mane | 89–92% | Rice straw and corncob in place of all the wood chips (89%), against 92% on the wood-chip control, lab trial (Frontiers in Plant Science, via PMC) |
| Four Hericium species | 26–70% | Oak sawdust with 20% rice bran (Bioresource Technology) |
| Maitake | 5–35% | UC Extension, general figure (UC) |
| Maitake | 36–47% | Oak sawdust; Penn State's best strains, then best supplement mixes (strains, supplements) |
| Reishi | about 25% | Sawdust with 20% wheat bran, 2–3 flushes over about four months (ICAR) |
Reishi is mostly sold dried, so its fresh BE matters less.
Why do biological efficiency numbers disagree?
Biological efficiency numbers disagree because studies weigh the substrate differently, harvest for different lengths of time, and grow different strains under lab or farm conditions. These are the differences that move the number most:
- Fresh or dry mushrooms. In one straw trial, oysters on maize straw came to 114% BE as fresh weight but 9.2% once the mushrooms were dried too, a figure the authors call "biomass conversion rate" (Studies in Fungi). Button mushroom breeders at Wageningen use the name BE for a dry-to-dry figure (Wageningen UR).
- How "dry" the substrate is. One substrate study defines BE against "oven-dry" substrate weight (Bioresource Technology). Bagged ingredients aren't oven-dry: a UC moisture table lists oak sawdust at 14.7% water and rice bran at 6.6% (UC Cooperative Extension). Weighing them straight from the bag makes BE look lower.
- How many flushes. In a button mushroom strain trial, Wageningen researchers advise harvesting "until no more mushrooms are produced" for a fair comparison, because some strains fruit more or less continuously instead of in flushes (Wageningen UR). In SARE's farm study, Cornell's blocks stayed in the fruiting room for 8 weeks, which shows in their higher yield (SARE farm book).
- Lab or farm. On the Massachusetts farm, heat-pasteurized straw averaged 29% BE in a grow room that reached 75–95°F in summer, and "contamination was not worked into the biological efficiency numbers" (SARE).
- Strain. Cornell says choosing the right strain "can easily triple yields" (Cornell Small Farms). The chestnut strains in the table ran from 41% to 68% on one recipe.
- Supplement. In a Penn State oyster trial on pasteurized cottonseed hulls and straw, yields "declined significantly" once a commercial slow-release supplement passed 6% (Applied Microbiology and Biotechnology). That figure is for one commercial supplement on hulls and straw, not bran: the shiitake and Hericium trials in the table used 20% bran.
- Block size. A shiitake trial found heavier bagged blocks (3.2 kg against 2.7 kg) gave more mushrooms, but "BE was not significantly affected" (Bioresource Technology). A bigger block makes more mushrooms, not a higher BE.
How do you measure your own biological efficiency?
Measure your own biological efficiency by finding each block's dry substrate weight before you bag it, weighing every flush fresh, and dividing once the block is finished. Doing it the same way every time matters more than any one method:
- Weigh the dry ingredients before adding water, then subtract the water they already hold. UC's worked 5-lb block needs 1.65 lb of truly dry ingredients, which weigh 2.05 lb before hydrating because they still hold 0.4 lb of water (UC Cooperative Extension).
- Or dry a sample. Before you bag and sterilize, weigh about 100 g of the hydrated mix and spread it thin on a microwave-safe plate. Microwave it for 2 minutes, then in 30–60 second rounds, stirring between them, until the weight drops by no more than 1 g. If it starts to char, use the last weight before it did. Nebraska Extension describes this method for hay (Nebraska Extension). The sample's moisture is the weight it lost ÷ its starting weight, and the block's dry weight = its wet weight × (1 − moisture).
- Weigh each flush right after picking, before you mist, at the same stage each time. A Cornell Small Farms and Fungi Ally guide warns against spraying fruiting mushrooms directly because they "act as sponges sucking up any liquid they touch" (Cornell Small Farms and Fungi Ally). Write down whether you trimmed the stems.
- Keep going until the block is done, then add up every flush.
- Count lost blocks separately. A block lost before it fruits scores 0%, so leave it out of your BE average but count it in your pounds per block started.
We found no source that settles whether the spawn's weight counts in the dry weight. One oyster study's formula divides by the "dry substrate per bag before inoculation", which reads as leaving the spawn out (AMB Express). Pick one rule and keep it.
How do you estimate BE for a grow kit?
Estimate a kit's biological efficiency by assuming its block is 55–67% water, so its dry weight is roughly 33–45% of what it weighs. UC's sawdust recipes are mixed to 60–67% moisture, and a shiitake trial did best at about 55% (UC Cooperative Extension, Bioresource Technology). For example, a 5-lb kit holds about 1.65–2.25 lb of dry substrate, so 1 lb of mushrooms over all its flushes is about 44–61% BE.
Treat that as a ballpark that runs high. One shiitake study found its substrate lost 16–17% of its weight to respiration during the spawn run (Edible Fungi of China, via Europe PMC), so a colonized kit holds less dry matter than it was mixed with. Our beginner kit guide covers what a first flush usually gives.
How do you track BE in Hypha?
Hypha, our grow tracking app, doesn't calculate biological efficiency, and it has no dry substrate weight field. It does keep the harvest side for you: tap Harvest Flush on a block and enter the Fresh Weight, in grams, kilograms, ounces or pounds. Each flush is numbered, and the Grow Summary shows the block's Total harvest. The harvest dialog's Dry Weight is for dried mushrooms, not substrate.
Leave the block's Size as its wet weight. Once you've created the block, open it and write its dry substrate weight in its Notes. When the block is finished, divide its total harvest by that weight. To work out BE for many blocks at once, Export my data in Profile settings downloads a .zip of CSV files: your flushes are in flushes.csv and each block's notes in grow_blocks.csv. Each strain's Performance section shows the Median per block harvest, which isn't adjusted for block size, so compare blocks of one size there. Flush logging and the export are on the free plan. Download Hypha.
FAQ
Is 100% biological efficiency good?
For oysters, 100% is a solid result: UC Extension puts average commercial oyster yields at about 1 kg of fresh mushrooms per kg of dry substrate (UC Cooperative Extension). For maitake, 100% would be far above any maitake figure in the table.
Why is my BE lower than published figures?
Many published figures come from lab trials, on recipes and strains chosen for the test. On the Massachusetts farm above, heat-pasteurized straw averaged 29%. Compare your BE with your own earlier blocks first, then change one thing at a time.
Does a higher BE mean better mushrooms?
No. BE measures how much fresh weight a block gives for its dry weight, not taste, texture or shelf life. Fresh mushrooms are mostly water, so weigh at the same stage and before misting each time, and your numbers will compare fairly from block to block.