Understanding biological efficiency in mushroom cultivation

Steps

1. 1

   Weigh the dry substrate

   Record the dry weight of the substrate before you add water. This is the denominator of the calculation.

2. 2

   Weigh every flush

   Record fresh weight for each flush and add them together for the batch total.

3. 3

   Divide and multiply

   Divide total fresh weight by dry substrate weight, then multiply by 100 to get the percentage.

The formula

Biological efficiency = (total fresh mushroom weight ÷ dry substrate weight) × 100.

The word "dry" matters. If you measure substrate weight after hydrating, the number will look artificially low, because a large share of what you weighed was water. Standard practice is to weigh the dry ingredients — coir, vermiculite, hardwood pellets, bran — before mixing.

Typical ranges by species

Oyster mushrooms are the benchmark for high biological efficiency, commonly landing between 50% and 120% across a full flush cycle. King oyster and pioppino tend to sit lower, in the 35% to 80% range. Lion’s mane and shiitake are slower and typically return 20% to 60% on supplemented hardwood.

These ranges are guides, not targets. Substrate composition, spawn rate, hydration, temperature and fresh-air exchange all move the number significantly, and a well-run grow of a low-BE species can outperform a neglected grow of a high-BE one.

Reading BE% across a batch

Biological efficiency is cumulative, not per flush. The first flush is usually the largest, with each subsequent flush returning progressively less. This is why tracking BE% alongside flush number is more informative than a single figure — a batch that returns 60% in flush one and 40% across flushes two and three is behaving normally.

The clearest use of the metric is comparison. When two batches share a species and a substrate recipe but differ in BE%, the difference is usually traceable to one variable: hydration, spawn rate, or the temperature the batch was kept at.

Terms used in this guide

Spawn

Spawn is mushroom mycelium growing on a carrier material, most often sterilised grain, used to inoculate a larger substrate.

Substrate

Substrate is the material mushroom mycelium digests and grows through, such as straw, coco coir, hardwood sawdust or supplemented pellets.

Flush

A flush is one distinct wave of mushroom fruiting from a single batch, harvested together before the substrate rests and produces the next wave.

Biological efficiency (BE%)

Biological efficiency is the fresh weight of harvested mushrooms divided by the dry weight of the substrate, expressed as a percentage.

Hydration

Hydration is the amount of water in a substrate, usually expressed as a percentage of the dry ingredient weight.

Spawn rate

Spawn rate is the proportion of spawn to substrate in a batch, typically expressed as a percentage of the total wet substrate weight.