How much CO2 can a Tree Store?
The U.S. Environmental Protection Agency (EPA) estimates that planting one acre of trees on marginal land would sequester 0.6 to 1.6 metric tons of carbon annually in the first five years of growth. Assuming that planting one acre of trees in the Southeast will sequester about 1.0 ton of carbon each year (slightly less than the median of the EPA estimated range), and that 1.0 ton of carbon is contained in 3.67 tons of CO2, then one acre of trees planted on marginal land will sequester (save, reduce, or prevent from escape to the atmosphere) about 3.67 tons of carbon dioxide each year during the first five years.
The actual amount of carbon sequestered by a forest depends on a large number of factors, including the region of the country, the type and mixture of trees in the forest, the age of the trees, the site class (relating to the height of the dominant trees at 50 years of age), and the reference land use as a baseline (e.g., clear cut forest, cropland, or pasture).
The Department of Energy (DOE), in its guidelines for reporting greenhouse gases, provides another example that is perhaps more specific to the Southeast. This example analyzes the effect of planting Southern Pine in the Southeast on cropland previously used to grow soybeans. The analysis estimates that planting pine trees instead of maintaining the land in crops will store carbon in the following amounts:
The above numbers measure the net effect of the project on stocks of stored carbon.
As trees grow older and bigger, they sequester more and more carbon each year. From the example, during the first five years of growth, the project trees sequester about one ton of carbon per year per acre. During the second five years of growth, they sequestered about 1.2 tons of carbon per acre per year and during the second ten years of growth (years 11 - 20), about 2.6 tons of carbon per acre per year.
#To estimate the average annual incremental flow of carbon attributable to the project, the stock measures are compared across time.
The annual flow of carbon for the first five years of the project was estimated as:
(10,000 - 0) / (5 years) = 2,000 lbs of C per acre per year.
The annual flow of carbon for the second five years of the project was estimated as:
(22,000 - 10,000) / (5 years) = 2,400 lbs of C per acre per year.
The annual flow of carbon for the last ten years of the project was estimated as:
(74,000 - 22,000) / (10 years) = 5,200 lbs of C per acre per year.
Trees, as they mature, sequester greater and greater amounts of carbon each year. A ten year old tree will sequester more carbon than a five year old, but not as much carbon as a twenty year old tree. Therefore, managing and maintaining established forests are a great way to obtain carbon sequestration additionality.