Carbon Sequestration Lab by Urban Texas Trees
Carbon sequestration is the removal of atmospheric carbon dioxide and the conversion of the gas into either a liquid or
solid by natural or artificial means. The net result is reduced levels of carbon dioxide in the atmosphere.
Plants, through the process of photosynthesis, remove carbon dioxide from the atmosphere and assimilate it into their
tissues in the form of glucose, cellulose and other organic compounds. In this way, vegetation and trees in particular can
be valuable tools for the reduction of atmospheric carbon dioxide levels.
Often companies looking to reduce the amount or impact of the carbon dioxide they produce will purchase what are
called carbon offsets, which are credits that in effect neutralize some of the CO2 they produce. These offsets are usually
in the form of paying to preserve or protect large areas of forest from development, which then in turn absorb a
calculated amount of carbon dioxide produced from the company.
This lab has three main components – 1) learning a protocol that scientists from around the world use to measure tree
above ground biomass in a forest, 2) using this biomass data to calculate the amount of carbon that a tree will absorb
over a year, and 3) determining the value of trees in urban residential yards to a homeowner’s goal of reducing their
household’s carbon footprint.
Pre-lab Questions
1. Write the equation for photosynthesis. What do we mean when we say atmospheric carbon dioxide can be
“sequestered” by all vegetation, and in large volumes by trees?
2. If a tropical rainforest can sequester 96 tons of carbon per hectare a year, and La Selva Biological Station in
Costa Rica is 650 hectares, how many tons of carbon are sequestered each year?
3. Besides forests, list three other carbon reservoirs.
4. What are two man-made sources of atmospheric carbon?
5. What measurement(s) and other data need to be completed to evaluate the carbon sequestered in a yard over
the period of a year?
6. What conversions or formulas will you need to complete the lab?
Objective
To practice collecting tree diameter at breast height, and use the data to calculate the amount of carbon stored
in an urban residential yard in Texas.
Procedure
Part I: Carbon Sequestration by an Urban Tree
1. Proceed to your group’s assigned tree outside.
2. You will be measuring tree circumference at breast height in inches, then converting it to diameter for the
carbon calculations.
3. Record your data before returning to the classroom.
4. In the classroom, use the following calculation to determine the diameter of your tree.
Circumference = (pi)d, where d= diameter at breast height.
5. Go to http://www.treebenefits.com/calculator/ and enter the appropriate zip code. Enter your tree species,
the diameter in inches for each tree, and the land use type upon which your tree sits (if your yard is bereft of
trees, use a different site and select the appropriate land use). The spread sheet will show you multiple types of
data based on your tree size. Use the tabs at the top of the page to observe the following for your tree:
Overall benefits – dollar value for services provided by the tree
Storm water - gallons of storm water absorbed by the tree
CO2– pounds of CO2 sequestered per year and the overall amount atmospheric carbon is reduced by this
tree in one year.
Part 2: Reduce your Carbon Footprint
1. Examine the yard layout and floor plan. The yard below is an average size city lot at 0.25 acres (70’ x 155’) or
10,850 sq. ft.
House size
Electricity Consumption in kWh per
month
Pounds of CO2 Emitted per 1 kWh
Electricity Generated
1500 sq ft.
920 kWh
1.222 lbs. CO2
2. Calculate the amount of electricity (kWh)consumed per year by the household.
3. Calculate the amount of CO2 emissions in pounds over one year for the electricity consumed by this house.
4. If the house is built on the lot with the six mature trees (provided below), calculate the amount of
atmospheric carbon that is reduced and pounds of carbon sequestered by all of the trees in the yard (singlefamily residential). Write your calculations in the data table that describes the trees on the lot.
Tree
Tree Species
Number
Circumference Tree
Pounds CO2
(in)
Diameter (in) Sequestered by
Tree
1
Winged Elm
58
18.5
2
Winged Elm
43
3
Sugarberry
62
4
Sugarberry
65
5
Sugarberry
32
6
Red Oak
48
Total Atmospheric Carbon Reduced per year by Trees in Yard
560
Pounds CO2 in
Atmosphere
Reduced by
Tree
674
Stormwater
intercepted
(gallons)
3685
Tree
Tree Species
Number
Circumference Tree
(in)
Diameter (in)
Pounds CO2
Sequestered by Tree
Pounds CO2 in
Atmosphere
Reduced by
Tree
Stormwater
intercepted
(gallons)
1
2
3
4
5
6
7
8
Totals for Pounds Sequestered, Reduced Atmosphere &
Stormwater intercepted =
Part 3: Analysis
House size
Electricity Consumption in kWh per
month
Pounds of CO2 Emitted per 1 kWh
Electricity Generated
(sq. ft.)
1.222 lbs. CO2
1. Based on your house size, estimate your electricity consumption in your household (ask your parents for a bill or
statement; if unsuccessful, use an estimate online based on the square footage of your house).
2. Calculate the amount of CO2 emissions in pounds over one year for the electricity consumed by your house.
3. What is the net carbon impact of your household simply based on the amount of carbon generated by electricity
usage and sequestered by trees?
4. What other consumptive or environmental factors might impact the overall carbon equation for your household
in terms of overall net carbon impact? (Provide at least 3-5 with a mix of carbon-generating and carbon-saving
factors)
5. When you drive by a woodland, see a copse of trees, or even in your front yard, does the value of a tree change
when a monetary figure, or other quantitative measure, is applied to it?
Part 4: Reflection