How to calculate CO2 sequestration

Written by Wika Wulandari, Forestry and Carbon Specialist EcoMatcher.

In the intricate and dynamic ecosystems of forests, a crucial ecological process is unfolding that has significant implications for our planet’s carbon balance. Tropical forests are adept at producing 34% of oxygen [1]. This capability is not merely a passive feature of these ecosystems but a fundamental aspect of the photosynthetic process, wherein trees and plants convert CO2 and sunlight into energy, essential for their growth and sustenance.

The role of CO2 uptake in forests extends far beyond mere carbon sequestration. It is intimately connected to the growth and developmental dynamics of trees, primarily through its influence on biomass accumulation. Biomass, in this context, refers to the sum of all organic material that constitutes a tree’s physical structure – a tangible indicator of its growth. Trees distribute this biomass in two primary compartments: Above-Ground Biomass (AGB) and Below-Ground Biomass (BGB) (Figure 1 [2]). Above-ground biomass encompasses the parts of the tree that are visible above the soil line, including the trunk, branches, leaves, and any fruits or flowers. Below-ground biomass consists of the roots, which, though less visible, are equally crucial for the tree’s stability and nutrient uptake.


Figure 1. Tree carbon pools

This distribution of biomass is central to understanding how trees store carbon. The CO2 absorbed from the atmosphere is assimilated into both AGB and BGB. As a tree matures, its capacity to sequester carbon increases, making older trees more efficient at absorbing CO2. This relationship highlights the significance of forest conservation and the role mature trees play in mitigating climate change. By understanding and supporting these natural processes, we can enhance the capacity of forests to act as carbon sinks, thereby contributing to global efforts to balance our planet’s carbon cycle and combat the escalating challenges of climate change.

To accurately determine the amount of CO2 absorbed by trees, two critical measurements are taken directly from the tree: its diameter, measured in cm, and its height, measured in meters. These measurements are essential for calculating both the Above-Ground Biomass (AGB) and Below-Ground Biomass (BGB). The calculation of these biomass values is based on a specific formula that incorporates these two parameters 9 [3].

AGB = 0.25 x D2 x H


  • AGB: Above-Ground Biomass (pounds).
  • D: tree diameter measured at 1.37 meters from the ground (inches). This measurement is globally used as a standard to get a better result. However, if your tree is below 1.37 meters, you can still use the formula.
  • H: tree height (feet).

The overall green weight of the biomass is estimated to be 120% of the AGB value, based on the assumption that the BGB, which comprises the tree’s root system, accounts for approximately 20% of the AGB [3]. Therefore, BGB can be calculated as follows:

BGB = 0.2 × AGB

From these formulas, we can calculate the total biomass from a tree:

Total Biomass (TB) = AGB + BGB = AGB + 0.2 x AGB = 1.2 × AGB

On average, a tree consists of 72.5% dry matter and 27.5% moisture content. To calculate the tree’s dry weight, we could multiply the total weight of the tree by 72.5%.

Total Dry Weight (TDW) = TB × 0.725

Carbon occupies 50% of the total dry weight. Therefore,

Total Carbon (TC) = TDW × 0.5

With the value of total carbon, we can calculate the value of CO2 equivalent sequestered on a tree. CO2 has one molecule of Carbon and two molecules of Oxygen. The atomic weight of Carbon is 12u, and the atomic weight of Oxygen is 16u. The weight of CO2 in trees is determined by the ratio of CO2 to C is 44/12 = 3.67. Therefore, to determine the weight of carbon dioxide sequestered in the tree, multiply the weight of carbon in the tree by 3.67.

CO2 weight = TC × 3.67

It is worth noting that the CO2 weight above represents the CO2 sequestered in the entire lifetime of the tree. To ascertain the annual or yearly rate of CO2 sequestration, divide the total weight of CO2 absorbed by the tree’s age.



[2] DiRocco, T. L., Ramage, B. S., Evans, S. G., & Potts, M. D. (2014). Accountable accounting: carbon-based management on marginal lands. Forests5(4), 847-861.

[3] Shadman, S., Khalid, P. A., Hanafiah, M. M., Koyande, A. K., Islam, M. A., Bhuiyan, S. A., … & Show, P. L. (2022). The carbon sequestration potential of urban public parks of densely populated cities to improve environmental sustainability. Sustainable energy technologies and assessments52, 102064.