Volume XXXII, Issue 1 Page 33

© 2016 National Earth Science Teachers Association. All Rights Reserved.

Abstract

Greenhouse gases are currently impacting Earth’s climate and will continue to do so at 

elevated rates until we find ways to mitigate our actions. Biochar production via pyrolysis 

is a means to sequester carbon in the soil long term. Biochar is highly resistant to breakdown and thus becomes a sink for carbon storage. This strategy is accessible to students 

and can give a sense of empowerment to make change. In the course of this unit, students 

learn about the carbon cycle while producing biochar, test biochar’s value as a soil amendment, and provide outreach on the carbon cycle to other students and the public. 

Biochar 

Excess greenhouse gases are linked to the climate change currently being 

experienced worldwide. One means of mitigation of the human impacts on 

the concentration of these gases is to hold carbon in sinks in order to reduce 

the likelihood that this carbon will cycle into the atmosphere. Biochar, which 

can serve as such a sink, is produced by pyrolysis (high temperature, low 

oxygen thermochemical decomposition) of organic matter. The production 

of biochar is one way to sequester some amount of carbon before it enters the 

atmosphere (Wolf et al, 2010). An additional documented benefit of biochar 

is as a soil amendment to improve yields (Cornell University Department of 

Crop and Soil Sciences, 2015). The chemical (negative surface charge density) 

and structural (high surface area) properties of biochar, when amended to 

soil, result in increased water retention and nutrient affinity. 

Students as Stewards Sequestering Carbon

Learning about, producing and testing biochar enables students to learn 

about the carbon cycle while empowering them take action to mitigate 

climate change (Figure 1). During the fall of 2013, Cornerstone Learning Community middle 

school life science students produced 45 kg of biochar in a 55-gallon drum pyrolysis unit (see 

Packard, 2009 for design). Students collected biomass (primarily woody debris) from the campus 

to add to the top-lift updraft unit made from recycled metal barrels and piping. The design of the 

pyrolysis unit minimizes the entrance of oxygen to the bottom of the container. The biomass is lit 

on the top and a flame is produced by the off-gassing combustible compounds, not the combustion 

of biomass. Once pyrolysis is complete, the char is quenched by spraying with water to ensure that 

Biochar for Carbon Sequestration: 

Investigation and Outreach

Karen Metcalf

Cornerstone Learning Community, 

Tallahassee, Florida

Figure 1. Small student-built 

top-lift updraft pyrloizer made 

from recycled cans. A fire is lit

from the top as biomass (in this 

case pine pellets) is gasified 

and the volatile gases combust

When pyrolysis is completed, the 

remaining material is quenched, 

leaving behind biochar
Page 34 The Earth Scientist

© 2016 National Earth Science Teachers Association. All Rights Reserved.

the char doesn’t burn to ash. The biochar produced was ground and mixed at the rate of 45 kg per 

4-foot by 10-foot by 1-foot raised bed garden (aging biochar in the soil before planting to enable 

nutrient and water absorption and bacterial colonization is recommended). 

Students worked collaboratively, consulting a regional planting guide, and 

then seeded a winter garden that included carrots, radishes, lettuce, cabbage, 

onions and kale. The experimental design included identical plots, varying 

only in the type of soil and soil amendment used to test for differences in 

vegetable biomass produced (Figure 2). The plots used compost, compost 

plus biochar, sand, and sand plus biochar to test for the effects of soil 

amendment and type on vegetable production.

Throughout the growing season and as vegetables were harvested, students 

quantified the growth in each plot and interpreted the effect of soil type on 

growth (Figure 3). Most vegetables produced more biomass in the compost 

soil type (as compared to sand) irrespective of the addition of biochar (with 

the exception of some very large radishes grown in sand). Of those grown 

with compost as a soil, the plants in plots amended with biochar grew 

larger. Some of vegetables produced much more biomass in biochar (such 

as Chinese cabbage and lettuce) (Figure 4) while others were larger, but 

not significantly so. Following their analysis of growth data, students were 

expected to generate a scientific argument about the value of biochar as a soil 

amendment. 

Sharing the Wealth

All of the vegetables harvested from the experimental garden became part 

of the school’s once-monthly lunch preparation and service at a local homeless transition facility (Figure 5). Students prepared salads and cooked 

dishes with the garden harvest. Based on experimental data, the project 

captured over 24,360 grams of atmospheric carbon that was converted into 

edible vegetable matter that has provided meals for homeless citizens. This 

combines with 45 kilograms of carbon that was sequestered for the long 

term (studies conservatively estimate 100+ years) in the form of biochar 

remaining in the garden. 

Figure 2. Experimental layout of raised-bed gardens. Treatments from left to

right are 1) compost plus biochar, 2) compost only, 3) sand plus biochar, and 

4) sand only

Figure 3. Students measuring biomass produced by plants in different soil 

treatments

Figure 4. Student experimental data showing biomass 

produced by leaf lettuce plants in different treatments

Figure 5. 

Student-grown 

vegetables 

being served at 

a transitional 

facility for 

homeless 

families
Volume XXXII, Issue 1 Page 35

© 2016 National Earth Science Teachers Association. All Rights Reserved.

Reaching Out to Others to Teach About Carbon

As the students finished up their analysis of the impact of biochar on plant growth, they thought 

about how to share this information with others. A display was designed and built to coincide 

with Earth Day (Figure 6). The students were tasked with generating ideas that would convey the 

message “carbon cycle” to visitors in elementary and middle school grades. The display took shape 

as a Build a Carbon Catcher activity, a large postcard with carbon cycle themed activities and individual trifold-displays of two of our school’s stewardship related activities (the biochar 

project, model solar car design, construction and racing). Students set up the display at 

our local Saturday Farmer’s Market. Students were able to share and educate passers-by. 

Visitors made ‘carbon catchers’ by decorating a small flowerpot and planting either a 

bean or sunflower seed. Puzzle pages with student-designed activities were distributed 

to visitors. Students also set up the display for our school Earth Day Festival. Students 

from kindergarten through fifth grade came to make carbon catchers and sidewalk 

Earth Day art, hear about biochar, and run a very popular Recycle Relay. This event was 

all in the hands of the students to run. They took charge of different roles and made it a 

big success. 

Learning Gains 

The results of pre- and post-tests were used to assess improvement in background 

knowledge about climate change and attitudes about the cause and impacts of changing 

climate. The survey instrument used for these tests is one from the National Center 

for Atmospheric Research Spark education group. The climate change questionnaire is 

from the module “Applications of chemistry through climate science” (Marschke, 2012). 

Thirty-seven of the objective questions from the questionnaire were used and eight of 

the questions addressing attitudes about climate change. The average student score on the objective portion of the pre-test was 74%. Post-test averages were three percent higher. Prior to starting 

the project, 80% of student responses indicated opinions that show urgency about human-induced 

climate change and the need to take action. These responses also went up three percent after the 

project was completed. The change in student scores however does not adequately represent the 

learning that took place through the project. The fact that this survey instrument was designed for 

high school students may have had some effect on middle school student scores. 

Overall, the project was highly successful as it enabled climate change to be woven through the 

curriculum for the year. The connection to service-learning is an important one for the Cornerstone 

Learning Community school. Thinking about how to best present the carbon cycle and climate 

change to younger students in the display gave these middle schoolers a chance to think deeply 

about how to explain this topic. Their efforts produced an engaging and fun activity booth that 

they were able to share with others in our community.

Next Generation Science Standards Addressed

SCIENCE AND ENGINEERING PRACTICES DISCIPLINARY CORE IDEAS CROSSCUTTING CONCEPTS

• Analyzing and Interpreting Data

• Constructing Explanations and Designing Solutions

• Engaging in Argument from Evidence

LS1.C: Organization for Matter and Energy Flow in Organisms

LS2.A: Interdependent Relationships in Ecosystems

LS2.B: Cycle of Matter and Energy Transfer in Ecosystems

LS2.C: Ecosystem Dynamics, Functioning, and Resilience

PS3.D: Energy in Chemical Processes and Everyday Life

• Cause and Effect

• Energy and Matter

• Stability and Change

PERFORMANCE EXPECTATIONS

MS-LS2-1. Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem

MS-LS2-4. Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations

MS-ESS3-5. Ask questions to clarify evidence of the factors that have caused the rise in global temperatures over the past century

Figure 6. Student designed and 

led Earth Day display and Carbon 

Catcher activity
Page 36 The Earth Scientist

© 2016 National Earth Science Teachers Association. All Rights Reserved.

Acknowledgements

This project was completed with support from the National Oceanic and Atmospheric 

Administration Climate Stewards Education Project. Thanks to Tony Brown of Longview Farms for 

valuable discussions and assistance with biochar production.

Resources

Biochar International: Biochar in Schools

http://www.biochar-international.org/teachers/schools

References

Cornell University Department of Crop and Soil Sciences, (2015) Biochar soil management. Retrieved 28 

November, 2015 from http://www.css.cornell.edu/faculty/lehmann/research/biochar/biocharmain.html. 

Lehmann, J. (2007) Bio-energy in the black. Front Ecol Environ 2007:5(7): 381–387. Retrieved from 

http://www.css.cornell.edu/faculty/lehmann/publ/FrontiersEcolEnv%205,%20381-387,%202007%20

Lehmann.pdf. 

Mann, Charles C. (2008) Our good Earth. National Geographic. September 2008, 80-107. Retrieved from 

http://ngm.nationalgeographic.com/2008/09/soil/mann-text.

Marschke, L. (2012) Applications of chemistry through climate science. Retrieved November 28, 2-15 from 

http://scied.ucar.edu/applications-chemistry-through-climate-science.

Packard, G. 2009. Making biochar: with Peter Hirst of New England Biochar. [video file] Retrieved 28 

November, 2015 from https://www.youtube.com/watch?v=RXMUmby8PpU. 

Wolf, D., J. Amonette, F. Alayne Street-Perrott, J. Lehmann & S. Joseph. (2010) Sustainable biochar to mitigate 

global climate change. Nat. Commun. 1:56 doi: 10.1038/ncomms1053. Retrieved from 

http://www.nature.com/ncomms/journal/v1/n5/pdf/ncomms1053.pdf. 

About the Author

Karen Metcalf is a middle school science teacher and IB Coordinator at Cornerstone Learning 

Community in Tallahassee, Florida. She was formerly a marine ecologist with a B.S. (Eckerd College), 

and M.A. (College of William and Mary) in marine science. Ten years in the classroom at the high 

school and middle school levels have allowed her to bring her love of the process of science and the 

marine environment to students. Karen’s goal is to teach science concepts while encouraging students 

to value sustainability, practice environmental conservation, and use critical thinking. Membership in 

NOAA’s Climate Stewards Education Project has facilitated special projects that support these goals. 

She is also the leader of Cornerstone’s Maker Club. Karen can be reached at kmetcalf@comcast.net.