Formula & Calculator
Carbon Sequestration by Trees (Simplified)
Estimates the amount of atmospheric CO2 absorbed and stored by tree growth, converting captured carbon mass to equivalent CO2 mass.
Interpretation
CO₂ Sequestered = Tree Biomass Growth × Carbon Fraction × 3.67. Estimates the amount of CO₂ absorbed by a tree. Used in carbon offset and forestry projects.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| CO2 Sequestered | CO2 equivalent sequestered | kg CO2/year |
| Tree Biomass Growth | Annual biomass growth | kg/year |
| Carbon Fraction | Fraction of biomass that is carbon (~0.5) | |
| 3.67 | Molecular weight ratio of CO2 to carbon |
What it means
Trees absorb CO₂ during photosynthesis, storing carbon in their biomass. The amount of CO₂ sequestered can be approximated by multiplying the tree biomass growth (dry weight) by the carbon fraction (typically ~0.5) and then by 3.67 (the conversion factor from carbon to CO₂, since the atomic weight of C is 12 and CO₂ is 44, so 44/12 ≈ 3.67). This simplified model is used in carbon accounting, forestry projects, and urban tree planting initiatives. Example: A tree grows 20 kg of dry biomass in a year. Carbon stored = 20 × 0.5 = 10 kg C. CO₂ equivalent = 10 × 3.67 = 36.7 kg CO₂. This helps quantify the climate benefit of planting trees and is used in carbon offset markets.
Worked example
Carbon Sequestration by Trees – Two Examples
Real‑World| Parameter | Value |
|---|---|
| Biomass | 20 kg/yr |
| Carbon fraction | 0.5 |
| Parameter | Value |
|---|---|
| Biomass | 30 kg/yr |
| Carbon fraction | 0.5 |
Common mistakes
- Tree biomass growth: The increase in tree dry mass over a period – in kg or tonnes.
- Carbon fraction: The fraction of dry biomass that is carbon – typically around 0.5 for woody biomass.
- Factor 3.67: Converts carbon mass to CO₂ mass (molecular weight ratio: 44/12).
- Time period: The growth period must be defined (e.g., annual sequestration in tonnes CO₂/year).
- Limitations: This is a simplified estimate; actual sequestration depends on species, age, soil, and management.
Applications
Carbon sequestration by trees is estimated by multiplying the annual tree biomass growth (in kg) by the carbon fraction (typically around 0.5) and then by 3.67 to convert to CO₂ equivalents (since CO₂ molecular weight is 44, carbon is 12). This simplified method is used in urban forestry and land‑use carbon accounting to quantify the climate benefits of tree planting and conservation. Environmental consultants and city planners use it to assess carbon offset potential, to meet greenhouse gas reduction goals, and to value ecosystem services. By applying this formula, professionals can communicate the climate benefits of green infrastructure and support afforestation/reforestation projects.
- Urban forestry carbon offset calculations for cities and campuses
- Assessment of carbon sequestration in reforestation and afforestation projects
- Land‑use carbon accounting for greenhouse gas inventories
- Valuation of ecosystem services in environmental impact assessments
- Education and public awareness on climate change mitigation
Frequently Asked Questions
The CO2 sequestered by tree growth is estimated as CO2 Sequestered = Tree Biomass Growth × Carbon Fraction × 3.67. The factor 3.67 is the ratio of molecular weights of CO2 (44) to C (12). Biomass growth is the increase in dry mass, carbon fraction is typically ~0.5 for wood.
Using generic biomass growth rates across all tree species and climates. Actual carbon sequestration varies substantially with species, age, growing conditions (water, nutrients), and management. Region‑specific data should be used.
About 50% of dry tree biomass is carbon (by mass). This value is commonly used, though it varies slightly (45‑55%) among species and plant parts.
Biomass growth can be estimated from:
- Allometric equations based on diameter and height.
- Forest inventory data (volume increment).
- Remote sensing (LiDAR).
One tonne of carbon (C) combines with oxygen to form 3.67 tonnes of CO2 (since atomic mass of C is 12, O is 16, so CO2 is 44; 44/12 = 3.67). This converts carbon sequestered to CO2 equivalent.
Carbon in biomass = 1 tonne × 0.5 = 0.5 tonnes C. CO2 sequestered = 0.5 × 3.67 = 1.835 tonnes CO2.
- Tree species (growth rate, wood density).
- Age (young forests grow faster).
- Climate (temperature, rainfall).
- Soil quality.
- Management (thinning, fire).
Use allometric equations to estimate total biomass per hectare, then apply the carbon fraction and 3.67 factor. Forest carbon stocks are often estimated from national forest inventories.
- Assumes constant carbon fraction and does not account for below‑ground biomass.
- Does not include decomposition or emissions from harvesting.
- Ignores soil carbon changes.
- Not suitable for precise carbon accounting without site‑specific data.
The carbon in harvested wood products can be stored for longer periods. Some methodologies include a storage pool for products. The formula can be extended with product lifetimes and end‑of‑life fate (landfill, combustion).