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© 2021 National Earth Science Teachers Association. All Rights Reserved.

Volume XXXVII, Issue 1

Abstract

Carbon sequestration by plants is one of the most important short-term processes that 

removes the greenhouse gas carbon dioxide from the atmosphere. As humans continue 

to release carbon from long term geologic sinks, through the burning of fossil fuels for 

example, understanding how carbon can be removed from the atmosphere by plants 

through photosynthesis is an important concept for students to understand. One way to 

attempt to measure this process is by measuring dry and ash weights of a plant to estimate 

the amount of carbon sequestered by the plant during its lifetime. This laboratory activity 

can be paired with the creation of a community garden that allows students to measure 

how much carbon can be sequestered through the creation of an individual green space 

and can connect to individual action on climate change. The green space used during the 

creation of this laboratory activity was funded by the National Oceanic and Atmospheric 

Administration (NOAA) Planet Stewards Program in 2018 (https://oceanservice.noaa.gov/

education/planet-stewards/). 

Introduction 

The atmosphere is made out of many gases and some of those trace gases are referred to as greenhouse gases. These gases are important for the atmosphere because they absorb infrared and emit 

their own infrared, heating the lower atmosphere. The heat given off by greenhouse gases creates a 

livable climate on Earth, a whole 330C warmer than it would be without the presence of greenhouse 

gases (ESRL, 2005). One of the most important greenhouse gases is carbon dioxide. Carbon dioxide 

is also an important gas in terms of plant growth. Plants use carbon dioxide from the atmosphere 

during the process of photosynthesis to create biomass (NOAA, 2019). This process of obtaining 

carbon from the atmosphere and holding it in solid form is referred to as carbon sequestration. 

Carbon sequestration has become more important in recent years with the increase of carbon 

dioxide in the atmosphere creating an enhanced greenhouse effect and contributing to the warming 

of our atmosphere. In fact, historical levels of carbon dioxide remained below 300 ppm (parts per 

million) over the past 400,000 years; yet, since the 1950’s, carbon dioxide has increased to over 400 

ppm (NASA, 2016).

Measuring 

Carbon Sequestration

Shannon Othus-Gault
Page 34 The Earth Scientist

© 2021 National Earth Science Teachers Association. All Rights Reserved.

All humans can help to sequester carbon from the atmosphere by creating their own gardens and 

increasing biomass on Earth’s surface. This goal of this laboratory activity was to teach students 

about important atmospheric processes, including the greenhouse effect and how atmospheric 

carbon can be sequestered by plants. Another goal of this activity was to measure the amount of 

carbon that can effectively be sequestered in a small green space as an example of what they can do 

in their own home and/or yard. 

Methods

Prior to performing this lab activity, my students were provided information on the greenhouse 

effect and the carbon cycle and also participated in class activities related to biogeochemical cycles 

and greenhouse gases, such as those provided by the Science Education Resource Center (SERC) 

through the EarthLabs project (SERC, 2016). This base knowledge was provided to allow students 

to connect the related lab activity to much larger Earth systems and processes. After finishing 

pre-lab work, students began to measure carbon sequestration by obtaining a whole-plant sample, 

including the root system. A sample can be collected from a school garden (as was done for this 

project) or can be collected from any appropriate place noted by an instructor or 

even parent. Once the sample was obtained, the whole plant was cleaned to remove 

as much excess soil as possible so that the most accurate dry weight of the plant 

sample could be measured. Once cleaned, the plant was dried. I allowed samples 

to air dry over several weeks; however, you could attempt to dry the plants more 

quickly in a low temperature, drying oven. Once these samples were dried, they were 

used by students to measure the carbon sequestered by the plant. To do this, the 

dried plant was weighed and that weight recorded. Next, the dried plant matter was 

burned in a controlled manner so that ash can be collected and weighed. 

By subtracting the weight of the ash from the weight of the dry sample, students 

were able to roughly estimate the amount of carbon that was sequestered by that 

plant. This activity works by essentially combusting the carbon matter in the plant 

and creating carbon dioxide, which is transferred to the atmosphere, and leaving 

behind the rest of the noncombustible matter of the plant. By comparing the dry 

weight with the ash weight, we can make a rough estimation of the carbon that had 

been contained in the plant sample.

Although measuring the carbon sequestered by a single plant can be useful, 

students can use plant counts within a 

garden to calculate how much carbon a 

larger green space or garden can sequester. 

During this activity with my own class, we 

obtained the amount of carbon sequestered 

by our garden by creating a garden map and 

counting the number of the different plants 

present in the garden.

Once students created their map and 

finished their plant counts, they multiplied 

the number of each example plant counted 

by the measurement of the carbon that type 

of plant sequestered. These final carbon 

calculations were added together to create 

a rough estimate of how much carbon was 

Figure 1: Picture shows the author demonstrating to 

students how to combust plant samples

Photo Credit: Shannon Othus

Figure 2: Picture showing the community garden and the distribution of plants used to measure 

carbon sequestration

Photo Credit: Shannon Othus
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© 2021 National Earth Science Teachers Association. All Rights Reserved.

Volume XXXVII, Issue 1

sequestered by our garden during that year’s sampling. These easy measurements can potentially allow students to plan for future growing seasons to 

maximize carbon sequestration with evidence-based observations from past 

growing seasons. 

Materials and Suggestions

This is clearly a lab activity that needs to be well supervised by an instructor 

due to the fact that fire is involved. Also, after students performed this lab 

activity for the first time in my classroom, I learned several tricks and tips 

for what materials are more successful for this activity and how to use those 

materials to fully incinerate the dry plant material. One of the most important materials you will need is a receptacle to burn your dry plant material. I 

obtained large food cans from the kitchen on our campus and they were big 

enough to allow for full combustion. You will also want to make sure that 

there are ventilation holes in these receptacles so that air can mix with the 

plant material during combustion. Also, make sure that the holes aren’t big 

enough to lose ash material. Another possible tip to allow for combustion to 

occur more rapidly would be breaking the plant into smaller pieces prior to 

incineration so the volume of the plant is more compact. I have also found 

that stem lighters are best for keeping appendages away from the flames but 

are also useful in continuing the combustion of materials if they need to be set 

alight more than once. Lastly, I would suggest heat resistant gloves to protect 

student hands. 

Student Assessment

Due to the current pandemic, I have only 

been able to run this lab activity with 

two classes using mature plants from my 

campus’s community garden. However, 

students were able to work together to 

calculate some estimates of carbon sequestered by the plants in our garden. Some of 

the dried plants were not able to be fully 

burned leading to a low overall calculation 

for the carbon sequestered by plants in the 

garden, kale plants in particular. Results 

based on student calculations from the 

Spring of 2019 can be found in Table 1.

Once students had finished calculating their measurements, they were then asked to answer several 

questions to put their carbon measurements into greater context of the greenhouse effect and 

climate processes, i.e., how does growing plants change the atmospheric concentration of carbon 

dioxide and, therefore, affect the greenhouse effect? The questions that I posed are as follows:

n	 How does carbon dioxide behave in the atmosphere (hint: what type of gas is carbon 

dioxide)? How can an abundance of carbon dioxide in the atmosphere become a problem for 

Earth’s biosphere?

n	 Vegetation is considered a carbon sink. Based on the word “sink”, what do you think that 

suggests in terms of the carbon that was sequestered by the plants you measured? In other 

Figure 3: Map shows the placement and number of plants 

found in the Yamhill Valley Campus Community Garden

The plant counts found on the map were used by students 

when calculating the total carbon sequestered in the garden 

through multiplying the number of plants present with the 

carbon measured by students

Table 1: Data collected and calculated by students to calculate carbon 

sequestered within the Yamhill Valley Campus community garden from the 

2019 General Science Earth System Science class

Year and

Season

Age of 

Plant

Plant

Type

Dry 

Weight

(g)

Ash 

Weight 

(g)

Carbon 

Weight 

(g)

Number of

Plants

Total Carbon

Sequestered 

(g)

Spring 2019 Adult *Kale 23.6 22.3 1.3 6

Spring 2019 Adult Peppers 80.6 11.9 68.7 5 3

Spring 2019 Adult Zucchini 310.0 128.0 182.0 5 9

Spring 2019 Adult Tomatoes 271.1 39.0 232.1 5 11

Spring 2019 Adult Eggplant 97.6 17.3 80.3 3 2

Total carbon sequestered by adult garden: 2662.7

* Incomplete burn of specimen
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© 2021 National Earth Science Teachers Association. All Rights Reserved.

words, how is the carbon sequestered by plants related to the carbon dioxide found in the 

atmosphere?

n	 How can sequestered carbon change the composition of the atmosphere? How could this 

sequestration affect the greenhouse effect?

n	 Knowing that this garden was used for food production, how can the harvesting of food 

from the garden affect the carbon weight measured? How does harvesting food from the 

garden affect the number that you calculated for the total carbon sequestered by the garden?

n	 Can you think of any other sources of error that could have affected the calculations you 

made for carbon weights and the amount of carbon sequestered by the plants in the garden?

These questions allowed students to think deeply about how plants and atmospheric composition are directly linked and how the greenhouse effect can be affected by plant growth. It also asks 

students to think about errors in their calculations since this activity is truly, a very rough estimation of carbon sequestration. 

Conclusion

Allowing students to connect their own personal activity to atmospheric composition and the 

greenhouse effect is an important lesson to learn as we begin to tackle the effects of anthropogenic 

climate change. This is a lab activity that is hands-on and allows for teachers and students to use 

green spaces, whether at school or at home, and for scientific exploration and data collection, which 

are important aspects of inquiry-based science learning. 

A list of materials, methods and lab questions, can be found at: 

https://docs.google.com/document/d/1eXa3vbX7uncsJr0hh37Kxz4MOQHbFwPrB1IOLAV

qK0A/edit?usp=sharing

References

NOAA Earth System Research Laboratories. Basics of the Carbon Cycle and Greenhouse Effect. 2005. https://www.

esrl.noaa.gov/gmd/education/carbon_toolkit/basics.html

National Oceanic and Atmospheric Administration (NOAA). Carbon Cycle. 2019. www.noaa.gov/

resource-collections/carbon-cycle

National Aeronautics and Space Administration (NASA). The Relentless Rise of Carbon Dioxide. 2016. https://

climate.nasa.gov/climate_resources/24/graphic-the-relentless-rise-of-carbon-dioxide/

Science Education and Resources Center at Carleton College. EarthLabs. 2016. https://serc.carleton.edu/eslabs/

index.html

About the Author

Shannon Othus-Gault began teaching as an outdoor school and science camp instructor at the 

age of 16 and has worked in the states of Oregon, Washington, California, New York and Wisconsin

Shannon has been teaching geology and Earth sciences for ten years at several Community Colleges 

but has committed to a single location, Chemeketa Community College at the Yamhill Valley Campus 

in McMinnville, Oregon. Prior to teaching, Shannon worked as a natural resource scientist for the

Washington Department of Natural Resources in the Forestry department mapping landslides and 

making landslide hazard maps. She can be reached at othussm@gmail.c