Environmental Science Lab

( ENVIRONMENTAL SCIENCE LAB 110L New Mexico State University Plant and Environmental Science Department )

Lab 7: Carbon Sequestration and the Biosphere

The biosphere and global warming

Goals The main goal of this lab is to understand how carbon sequestration by the biosphere can help reduce greenhouse gasses in the atmosphere and help to lessen the affects of global warming.

Key Words Carbon cycle, photosynthesis,carbon sequestration and global warming

Introduction

Earlier in this lab we discussed the carbon cycle. We saw that the carbon on Earth is constantly being recycled. When we burn fossil fuels we are shifting carbon from its long term storage in the lithosphere to the atmosphere. The increased carbon in the atmosphere is believed to increase global warming effects.

One way to lessen the carbon in the atmosphere is to capture or sequester it back into the biosphere and lithosphere. In this week’s lab we will focus on sequestering carbon in the biosphere. Plants and living organisms are built of carbon and thus can sequester carbon from the atmosphere. Plants sequester carbon by taking up CO2 from the atmosphere to use as a substrate in photosynthesis. The longer the plant lives, the longer it can sequester the carbon. Also, the larger the plant is the more carbon it can sequester. Trees are large, long-lived plants that can be used to help sequester carbon. The question is: How much carbon can a tree sequester? Better yet: How much carbon can an orchard of trees sequester?

In the Las Cruces area the pecan industry provides a major source of trees. In this lab we will be visiting a local pecan orchard to learn how this industry not only promotes the local economy, but improves the environment through carbon sequestration. Your lab report will consist of a one page discussion of what you learned on this field trip, and a set of basic calculations to examine quantitatively how much carbon is sequestered by the pecan industry of southern New Mexico.

Lab Activity

Objectives

1. Understand what carbon sequestration is.

2. Explore the role of forestry in carbon sequestration.

3. Gain knowledge about the pecan industry in southern New Mexico.

4. Learn how industry can benefit the quality of the environment.

Procedure

This lab is a field trip. You will need to take notes to be used for you lab write up, so come prepared.

Calculations and Data Presentation

To do this section you will need the following data, so be sure your guide provides this information. Remember to show your work for each calculation.

D = Diameter of an average tree trunk in inches

D=22.34

H = Height of an average tree in feet

H= 30 ft

Yr = Average tree age in years

Yr= 30 years

T/Ac = Average number of trees per acre

T/Ac= 50 trees

Acres = number of acres of pecan trees planted in southern New Mexico

Acres= 50 Thousand

· Calculate the approximate amount of CO2 sequestered by one pecan tree in a year.

1. Determine the total green weight (TGW) of the tree. Use this equation for above ground weight of the tree:

W = 0.15D2H

Where W is above ground weight of tree in pounds, D is tree diameter in inches and H is tree height in feet.

The root system weighs about 20% as much as the above‐ground weight of the tree. Therefore, to determine the total green weight of the tree, multiply the above‐ ground

Weight of the tree by 120%.

TGW = W * 1.20

2. Determine the dry weight of the tree.

The average tree is 72.5% dry matter and 27.5% moisture. Therefore, to determine the dry weight of the tree, multiply the total green weight of the tree by 72.5%.

DW = TGW * 0.725

3. Determine the weight of carbon in the tree.

The average carbon content of a tree is generally 50% of the tree’s total volume. Therefore, to determine the weight of carbon in the tree, multiply the dry weight of the tree by 50%.

WOC = DW * 0.50

4. Determine the weight of carbon dioxide sequestered in the tree

CO2 is composed of one molecule of Carbon and 2 molecules of Oxygen. The atomic weight of Carbon is 12.0. The atomic weight of Oxygen is 16.0. The weight of CO2 is C + 2*O = 44.0. The ratio of CO2 to C is 44.0/12.0 = 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

WOCO2 = WOC * 3.67

5. Determine the weight of CO2 sequestered in the tree per year

Divide the weight of carbon dioxide sequestered in the tree by the age of the tree.

CO2/Yr = WOCO2 / Yr

6. Now that you know how much CO2 is sequestered in each tree annually, calculate about how much CO2 will be sequestered by an acre of pecan trees in a year by multiplying the weight of CO2 sequestered by the number of trees in an acre. You should be able to write your own formula for this calculation.

7. Calculate how much CO2 will be sequestered by the southern New Mexico pecan industry in a year. You should be able to write your own formula for this calculation.

Data Presentation

Turn in a formal report that data and results from Carbon Sequestration in the Lithosphere and Carbon Sequestration in the Biosphere.

Make reasonable and well support ideas about

a. Why carbon sequestration is important?

b. Compare both forms of carbon sequestration, which one is better and why?

c. Advantages and disadvantages of both carbon sequestration form?

d. Present complete calculations

e. Use your results to support your ideas

f. Cite your reference using proper citation form.

g. Your TA might provide extra direction of how to present the formal report.

h. Important: This formal report worth 2 lab activities.

Pre-lab Questions and Resources

What greenhouse gasses contain carbon? Are these greenhouse gasses contributing equally to global warming?

Wikipedia – Greenhouse Gasses http://en.wikipedia.org/wiki/Greenhouse_gas#Greenhouse_effects_in_Earth.27s_atmosphere

Approximately how much carbon sequestration occurs in the United States?

The United States Environmental Protection Agency: Carbon sequestration in agriculture and forestry

http://www.epa.gov/sequestration/faq.html