Follow The Carbon

Use rice to model carbon sinks

Implement this lesson:

After completing ‘Rainbow of pH’ lesson, Ocean Acidification in a Cup, and/or Shell Shifts

Learning objective:

Students will model the carbon cycles and its main reservoirs by measuring carbons equivalent in rice.

Next Generation Science Standards (NGSS)

Science and Engineering Practices

1-LS1-1 Use materials to design a solution to a human problem by mimicking how plants and/or animals use their external parts to help them survive, grow, and meet their needs.

Disciplinary Core Ideas

ESS2: Compare multiple solutions designed to slow or prevent wind or water from changing the shape of the land.

ESS3 Construct a scientific explanation based on evidence for how the uneven distributions of Earth’s mineral, energy, and groundwater resources are the result of past and current geoscience processes.

PS1.1 Develop models to describe the atomic composition of simple molecules and their structures

Crosscutting Concepts

MS-PS1-2 Cause and Effect Cause and effect relationships may be used to predict phenomena in natural or designed systems.

Texas Essential Knowledge and Skills (TEKS)

K.6A use the senses to explore different forms of energy such as light, thermal, and sound

K.9B examine evidence that living organisms have basic needs such as food, water, and shelter for animals and air, water, nutrients, sunlight, and space for plants

K10B identify basic parts of plants and animals

1.6(A) identify and discuss how different forms of energy such as light, thermal, and sound are important to everyday life

1.10(A) investigate how the external characteristics of an animal are related to where it lives, how it moves, and what it eats

2.9(A) identify the basic needs of plants and animals

2.9(B) identify factors in the environment, including temperature and precipitation, that affect growth and behavior such as migration, hibernation, and dormancy of living things

2.9(C) compare the ways living organisms depend on each other and on their environments such as through food chains

3.9(A) observe and describe the physical characteristics of environments and how they support populations and communities of plants and animals within an ecosystem

5.9(A) observe the way organisms live and survive in their ecosystem by interacting with the living and nonliving components.

5.9(B) describe the flow of energy within a food web, including the roles of the sun, producers, consumers, and decomposers

5.9(C) predict the effects of changes in ecosystems caused by living organisms including humans, such as the overpopulation of grazers or the building of highways

5.9(D) identify fossils as evidence of past living organisms and the nature of the environment at the time using models

Overview:

A gigaton of carbon (GtC) and a petagram of carbon (PgC) are the fundamental units of measurement of carbon at planetary cycling scales. One gigaton is equal to one billion metric tons of carbon (or one petagram, which is 1015 grams). They are interchangeable, and we will use GtC and PgC interchangeable in this lesson. In this lesson each grain of rice will represent 1 gigaton of carbon (GtC).

These investigations will help you model how carbon flows from one reservoir to another.

Note: Before you begin, notice the relative abundance of carbon in each of the five reservoirs. Rock contains far more carbon than the other four reservoirs combined. Since rock is part of the slow carbon cycle, it is not part of the exchanges you will model.

Pathway 1:

Flow between the Atmosphere and Terrestrial Biosphere

The natural flux between the atmosphere and terrestrial biosphere is about 120 GtC per year in each direction. In the terrestrial biosphere, photosynthesis removes about 120 GtC from the atmosphere each year. Decomposition of biological material and respiration from plants and soil microbes returns 120 GtC to the atmosphere each year.

Pathway 2:

Flow between the Ocean and the Atmosphere

Carbon cycles between the ocean and the atmosphere at a rate of 90 GtC per year in each direction. Most of this exchange occurs by diffusion at the surface of the ocean. Notice that, until now, the carbon cycle has remained in balance, and no reservoir has a net gain or loss.

Pathway 3:

Flow from Fossil Fuels

Human use of fossil fuels (the burning of which releases carbon dioxide into the atmosphere) is changing the balance of carbon, adding an additional 9.4 (±0.5) GtC to the atmosphere each year. Land use changes, such as deforestation, remove part of the carbon sink (materials in the natural environment capable of absorbing excess carbon), thereby “contributing” that addition of 1.5 (±0.7) GtC excess carbon. Human impacts are therefore contributing almost 11 GtC per year to the atmosphere.

Not all of this carbon goes into the Atmosphere, as other reservoirs are absorbing some of this added carbon. Each year 4 GtC (represented by 4 grains of rice) from the Fossil Fuels reservoir are absorbed by the Terrestrial Biosphere, and 3 GtC (3 grains of rice) are absorbed by the Ocean reservoir. This results in a net gain in the Atmosphere reservoir of 5 GtC (5 grains of rice) per year with a budget imbalance of 0.5 GtC per year indicating overestimated emissions and/or underestimated sinks (see the equation below).

Materials:

Five pounds or rice (or other small grain)
Cups or other containers for counting and weighing rice
Scale to determine mass ex. Triple beam balance
Permanent marker
4 gallon sized plastic ziploc bags
5 quart or sandwich bags
Carbon reservoir images

Advanced Prep:

Label four ziplock bags: atmosphere, ocean, terrestrial biosphere, and fossil fuels.
(optional) find a large container for Rock

Procedure:

Determine the mass of 500 grains of rice. Helpful hint: Each participant should count 100 grains of rice. Combine 5 of these to make 500 grains total.
Each grain of rice will represent 1 gigaton of carbon (GtC). Typically, 500 grains of rice has a mass of 15 grams.
Have students calculate the rice equivalent of the five carbon reserve amounts. An example chart is shown below.
Using a scale or triple beam balance, students measure out that amount of rice. Students place the measured rice into the four ziploc bags. You may want to divide participants into four groups-one for each carbon reservoir to make this more efficient.
You can use a box to determine the amount of carbon in rock that would be the equivalent of rock.

Carbon Reserve

Rock
Atmosphere
Ocean
Terrestrial Biosphere
Fossil Fuels

Amount of Carbon Storage

(GtC)

65,000,000
900
41,000
2,000
4,000

Mass of Equivalent Rice

Ex. 1,950,000
Ex. 27 grams
Ex. 1,230 grams
Ex. 60 grams
Ex. 120 grams

Modeling Pathway 1:
Flow between the Atmosphere and Terrestrial Biosphere

1. The natural flux between the atmosphere and terrestrial biosphere is about 120 GtC per year in each direction. In the terrestrial biosphere, photosynthesis removes about 120 GtC from the atmosphere each year. Decomposition of biological material and respiration from plants and soil microbes returns 120 GtC to the atmosphere each year.
2. To model this interaction, remove 120 grains of rice from the Atmosphere bag and place it in a quart-sized bag. Then do the same with the Terrestrial Biosphere bag. Exchange these two equal-sized bags while discussing how the carbon flows from one reservoir to another. Model this yearly exchange several times while reviewing the ways in which carbon cycles from one reservoir to the other.

Modeling Pathway 2:
Flow between the Ocean and the Atmosphere

1. Carbon cycles between the ocean and the atmosphere at a rate of 90 GtC per year in each direction. Most of this exchange occurs by diffusion at the surface of the ocean.
2. To model this interaction, remove 90 grains of rice from the Atmosphere bag and place it in a new quart-sized bag. Then do the same with the Ocean bag. Exchange these two equal-sized bags while discussing how the carbon flows from one reservoir to another. Model this yearly exchange several times, while reviewing the ways in which carbon cycles from one reservoir to the other.
3. Notice that, until now, the carbon cycle has remained in balance, and no reservoir has a net gain or loss.

Modeling Pathway 3:
Flow from Fossil Fuels

1. Human use of fossil fuels (the burning of which releases carbon dioxide into the atmosphere) is changing the balance of carbon, adding an additional 9.4 (±0.5) GtC to the atmosphere each year. Land use changes, such as deforestation, remove part of the carbon sink (materials in the natural environment capable of absorbing excess carbon), thereby “contributing” that addition of 1.5 (±0.7) GtC excess carbon. Human impacts are therefore contributing almost 11 GtC per year to the atmosphere.
2. To model this interaction, count 11 grains of rice from the Fossil Fuels bag.
3. Not all of this carbon goes into the Atmosphere, as other reservoirs are absorbing some of this added carbon. Each year 4 GtC (represented by 4 grains of rice) from the Fossil Fuels reservoir are absorbed by the Terrestrial Biosphere, and 3 GtC (3 grains of rice) are absorbed by the Ocean reservoir. This results in a net gain in the Atmosphere reservoir of 5 GtC (5 grains of rice) per year with a budget imbalance of 0.5 GtC per year indicating overestimated emissions and/or underestimated sinks (see the equation below).

Questions to Ask:

Pre-experiment

Where does the Earth store or hold on to its carbon?
There are five major carbon reservoirs. Can you name all five? (answer: rocks, atmosphere, oceans, terrestrial, biosphere, and fossil fuels)

Post-experiment

The experiments we modeled were fast changes to carbon. Why didn’t we model the slow changes?
Why do you think rock holds so much carbon?
How are humans unleashing carbon rock has held?

Extensions:

Watch a video on the carbon cycle:
https://www.youtube.com/watch?v=KNLUzqW8IuA

Evaluation:

Students create a carbon cycle chart