Material assumptions (Typical values)
The following assumptions represent commonly cited average values for mature green compost:
Average dry matter content: 50%
Carbon fraction of dry matter: 20%
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:
500 kg × 20% = 100 kg carbon
Step 3 – Convert carbon to CO₂ equivalent:
100 kg C × 3.67 = 367 kg CO₂
Rounded and presented as a typical indicative value.
Indicative carbon storage result
Indicative carbon storage for green compost: Approximately 377 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 green 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 compost is applied and managed.
Emissions and lifecycle considerations
Emissions associated with collection, processing, 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
Carbon storage values for green compost are influenced by feedstock quality, composting method, degree of maturity and application rate. Poorly processed or immature compost may store less stable carbon.
Reference sources
IPCC (2019) – Refinement to the 2006 Guidelines for National Greenhouse Gas Inventories
UK DEFRA – Greenhouse Gas Conversion Factors and soil carbon guidance
FAO – Soil Organic Carbon: the hidden potential
Peer-reviewed literature on compost 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.