Material assumptions (typical values)
The following assumptions represent commonly cited average values for mature mushroom compost:
Average dry matter content: 50%
Carbon fraction of dry matter: 25–27% (range)
Carbon to CO₂ conversion factor: 3.67
Carbon storage calculation (per tonne of compost)
Step 1 – Dry matter per tonne:
1,000 kg × 50% = 500 kg dry matter
Step 2 – Carbon content of dry matter (range):
Low case: 500 kg × 25% = 125 kg carbon
High case: 500 kg × 27% = 135 kg carbon
Step 3 – Convert carbon to CO₂ equivalent:
Low case: 125 kg C × 3.67 = 459 kg CO₂
High case: 135 kg C × 3.67 = 495 kg CO₂
Rounded and presented as a typical indicative range.
Indicative carbon storage result
Indicative carbon storage for mushroom compost: Approximately 450–500 kg CO₂ per tonne
How this figure should be interpreted
This figure represents the amount of atmospheric carbon dioxide captured during plant growth and retained within the organic matter of mushroom compost while it remains in use.
It does not represent permanent sequestration, a carbon offset, or net lifecycle emissions. The duration of storage depends on how and where the material is applied and managed.
Emissions and lifecycle considerations
Emissions associated with production inputs, conditioning, transport, spreading and end-of-life treatment are not included in this calculation and must be assessed separately when considering overall environmental impact.
Product-specific notes
Mushroom compost is a secondary material arising from mushroom growing. Its carbon content can vary depending on feedstocks (e.g., straw-based substrates, manure inputs), growing cycles, and any post-use conditioning. Stability and storage duration depend on application rate, soil conditions and management.
Reference sources
IPCC (2019) – Refinement to the 2006 Guidelines for National Greenhouse Gas Inventories (carbon accounting principles; C→CO₂ factor)
UK DEFRA – Greenhouse Gas Conversion Factors and soil/land use guidance (context for carbon reporting)
FAO – Soil Organic Carbon publications (soil carbon context and stability)
Peer-reviewed literature on spent mushroom substrate composition, organic carbon content and soil organic matter stabilisation
This document is intended to support informed discussion and responsible material selection.
Good design begins with responsible decisions.
Future landscapes will be judged by today’s actions.