Overview. Guiding questions

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1 Using biochar as a soil amendment Grade level: 5-8 Produced by 1 Stephen C. Chmely, Nicole Labbé, Chet Greer, and Partha Das The University of Tennessee Center for Renewable Carbon Overview In a process known as fast pyrolysis, organic material is rapidly heated to C (approximately F) in the absence of oxygen. This causes simultaneous physical and chemical changes to occur in the organic material. As a result, three families of products are produced: a liquid product, called bio-oil, which is currently the subject of intense research and development as a substitute for petroleum; a solid product, called biochar, which is chemically and physically similar to charcoal; and permanent gases such as carbon monoxide, carbon dioxide, methane, hydrogen, and others. Technically, any organic material can be used in a fast pyrolysis process. However, a particularly attractive feedstock is known as lignocellulosic biomass. This refers to non-edible, dry plant matter, which consists of a mixture of carbohydrate polymers (cellulose and hemicellulose) and aromatic polymers (lignin). Together, these polymers provide the plant structural support (rigidity) and protection from fungi, bacteria, insects, and other herbivores. Lignocellulosic biomass represents an abundant, renewable feedstock for the production of fuels, chemicals, and materials, since bio-oil could be used as a substitute for petroleum. The solid biochar produced from fast pyrolysis consists mostly of carbon and nonvolatile, inorganic nutrients, collectively known as ash. This material is beneficial for plant growth and development, not only because it contains the aforementioned nutrients, but also because of its ability to retain water and reduce soil acidity. In addition, biochar can be used as a means of carbon sequestration, which could mitigate anthropogenic climate change. Finally, biochar may have beneficial effects on soil microorganisms, which also have beneficial effects on growing plants. Accordingly, biochar can be utilized as a beneficial soil amendment to aid in the production of lignocellulosic biomass feedstock, and this makes biochar an integral part of the carbon cycle. In this module, students will use biochar as a soil amendment in an effort to determine what affect (if any) it has on the growth of various types of seeds. Students will plant seeds in the presence and absence of biochar and monitor the growth of the plants for a period of time (typically 1-2 weeks). Comparisons in crop yield will demonstrate the effects of biochar as a soil amendment. Guiding questions What is biochar? How is it produced? How does fast pyrolysis differ from combustion or burning? What are the main benefits of using lignocellulosic biomass as a fast pyrolysis feedstock? What are some beneficial aspects of biochar as a soil amendment? 1 Bonnie Ownley, Jessica McCord, and Manny Deleon are acknowledged for additional assistance in the preparation of this learning module.

2 Common Core State Standards The following represent some of the Common Core Standards covered in this module: CCSS.ELA-LITERACY.CCRA.R.8 Delineate and evaluate the argument and specific claims in a text, including the validity of the reasoning as well as the relevance and sufficiency of the evidence. CCSS.ELA-LITERACY.CCRA.SL.2 Integrate and evaluate information presented in diverse media and formats, including visually, quantitatively, and orally. CCSS.ELA-LITERACY.CCRA.SL.5 Make strategic use of digital media and visual displays of data to express information and enhance understanding of presentations. CCSS.MATH.PRACTICE.MP4 Model with mathematics. CCSS.MATH.PRACTICE.MP5 Use appropriate tools strategically. CCSS.MATH.PRACTICE.MP6 Attend to precision. Next Generation Science Standards The following represent some of the Next Generation Science Standards covered in this module: LS2.B Cycles of Matter and Energy Transfer in Ecosystems LS1.C Organization for Matter and Energy Flow in Organisms PS1.B Chemical Reactions

3 Time required 30 minutes initial discussion (Day 1) minutes initial planting (Day 1) minutes each day over 1-2 weeks for plant measurement (Days 2-14) 60 minutes for discussion (Day 15) Materials 1 bag of low-to-moderate quality top soil 1 bag chemical-free, lump charcoal Single variety of seeds, enough for 2-3 per cup Bathroom paper cups, enough for 3 per student Tablespoon or teaspoon for water measure A ruler for plant measure Hammer Plastic bag Tablespoon-sized serving spoon or small spade to distribute soil and biochar Permanent marker A sunny windowsill or other area for optimal plant growth Note Sheet Graph paper or access to a computer with Microsoft Excel or other spreadsheet software Notes: When purchasing topsoil, try to find low-cost, low quality material. Try to locate soil listed as fill dirt or similar. High quality potting mix already contains many nutrients, and addition of biochar might not give an appreciable difference in growth if high quality mix is used. Charcoal should be lump style and should have 100% natural or no chemical additives somewhere on the package. Formed briquettes typically contain some sort of flammable chemical additive that is detrimental to plant growth and should be avoided. Choose seeds that are fast growing so results are quick. Any seed will work here, but we have found that beans, peas, or grasses work particularly well as they grow relatively quickly and results are noticeable in a week or two. Seeds should be planted two or three per cup: once they sprout, you can choose to remove the smaller sprout(s) or leave all of them for measurements. Make sure you can distinguish between them for your measurements! Students can work individually or in teams. Each student (or team) should have 3 cups. Depending on their grade level, students should keep a note sheet of their measurements and any other observations they make. Alternatively, the teacher may elect to keep these on a single sheet or collect these and redistribute them daily (students will need to have the sheet every day for 1 or 2 weeks- please plan accordingly).

4 Activity Using the plastic bag and hammer, crush the lump charcoal into very small pieces. You can do this before your class and bring the biochar powder in a separate bag. This will ensure that the char and the soil mix thoroughly and the resulting material does not contain large lumps of charcoal. Decide how you want to divide students for the activity. Each student (or team) should receive 3 cups. Divide the students (or teams) into two groups: Group 1 will be the Control Group and Group 2 will be the Treatment Group. You might consider starting this activity on a Friday. This will allow the seeds the weekend to sprout and begin growing. Otherwise, you might not see any activity for the first few days after planting. Instructions Distribute only soil in the cups of the Control Group (approximately 5 heaping serving spoons per cup). Distribute soil (4 spoonfuls) and biochar (1 spoonful) in the cups of the Treatment Group. Place the biochar on top of the soil (no need to mix these together!) These amounts are only a guide, but should be identical to one another based on your spoon size. The soil or soil and biochar mixture should be about 1 cm (0.5 inches) from the top of each cup. Plant the seeds according to the package directions. Plant 2 or 3 seeds per cup. Add water (2 or 3 tablespoons will probably suffice, but add more depending on soil moisture). It is important to use the same amount in each cup. Note the amount of water you add on your Data Sheet. Guiding observations and questions Why are their two groups of students (control and treatment groups)? Why is ensuring the amount of biochar in each Treatment Cup is identical crucial to the success of the experiment? What are some physical characteristics of the soil? What about the biochar? How are they similar and how do they differ? Record these on your Data Sheet Why are there 2 or 3 seeds per cup as opposed to just one? Why is ensuring the amount of water used in each cup is identical crucial to success of the experiment?

5 Figure 1. Plant seeds according to the package directions, with 2 or 3 seeds per cup. Once the seeds have germinated, note any observations on your Data Sheet. Over the next week or two, take measurements of the seedlings daily. Mark a dot on the inside of the cup with a permanent marker near each seedling. Ensure these dots are the same distance from the top of the cup. These will be the bottom of your measurement. Measure from this dot to the top of each seedling (this is challenging- do your best!) Note the height of each seedling on your Data Sheet every day. You might also find it helpful to number these dots to keep track of the seedlings. What are some observations you have made regarding the seedlings? Did the seedlings germinate at the same time? Have some still not germinated? Which ones? Why do you think this is so? Why do you measure from the dot on the cup to the top of the seedling? Why not just measure from the surface of the soil to the top of the seedling? What are some advantages of having one seedling per cup? What about having multiple seedlings per cup? Alternatively, you can remove all but the tallest seedling from the cups and measure only one seedling per cup. Monitor the moisture in the soil and add water as needed. Note the days you water and the

6 amount of water added on your Data Sheet. After one or two weeks (this will depend on your seedlings height), the data collection phase of your experiment will be complete. You should have 5-10 days worth of height data as your plants have grown. Analyze your data: for each day, you will have data for 1-3 seedlings in each of 3 cups. Find the mean of these numbers and record it for each day. As an advanced exercise, find the standard deviation in addition to the mean. Make a chart of your data: in the first column, list whole numbers to represent the days 1-5 or In the next column, write the average height that you computed previously for each day. Make a graph of your data: label the ordinate (yaxis) average height and the abscissa (x-axis) day. Plot the points from the chart above on the graph. If you calculated the standard deviation, add it to your graph as error bars on each point. Have students compare their results and look for similarities and differences in their data. Draw a conclusion based on the presence of biochar: did the plants that were grown in the presence of biochar grow faster or slower? Can you make other observations about the plants? For example, the above experiment measures plant height: what other differences do you note in the plants (such as color or stem thickness)? From their note sheets, ask students to comment on the frequency of waterings. Did they have to water the plants grown with biochar more or less frequently? What other factors could have affected the growth of the plants? For instance, did all of the plants receive adequate sunlight? Was the classroom too warm or too cool for the plants to grow?

7 Vocabulary Acid specifically, a molecule that can donate a proton. Acidic soils are detrimental to plant growth and development. Anthropogenic climate change the significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. Anthropogenic refers to climate change that has been caused by the activity of humans (for example, burning fossil fuels). This is sometimes referred to as global warming. Aromatic in chemistry, describes a planar, cyclic compound containing delocalized electron density. In general, aromatic describes compounds with a particular odor. Aromatic compounds (chemistry definition) all display distinct odors, but not all odiferous compounds are technically aromatic. Ash the non-combustible, inorganic, solid remains of a fire. Typically, ash contains metal salts of potassium, sodium, and calcium (among others) that are beneficial to plant growth and development. Biochar the solid product of fast pyrolysis that contains carbon and ash. Biochar can be added to soil to aid in the growth and yield of crops. Bio-oil the liquid product of fast pyrolysis that contains a mixture of chemical components. Bio-oil is currently under investigation as a substitute for petroleum in the production of fuels (such as gasoline), chemicals (such as solvents and medicine), and products (such as polymers and plastics). Carbohydrate a large biological polymer that is comprised of carbon, hydrogen, and oxygen. Carbohydrates serve myriad roles in all living organisms: they can serve as an energy store (starch), provide structure (cellulose), participate in chemical signaling (hormones), provide foundational genetic information (DNA and RNA), and many others. Carbon the chemical element with symbol C and atomic number 6, present in all known life forms. Carbon is the chemical basis of all known life. Carbon cycle describes the exchange of carbon between living things and the air, soil, and water on Earth. The carbon cycle is a crucial component to terrestrial life. Carbon sequestration the process of capture and long-term storage of carbon from the carbon cycle. Carbon sequestration has been studied as a means to reduce the effects of anthropogenic climate change. Cellulose a carbohydrate found in plants that serves as their primary structural component. Cellulose is the most abundant organic polymer on Earth, and is the primary component in paper. Chemical change any change that results in the formation of a new substance. A chemical change is generally regarded as irreversible. Combustion describes the chemical change that occurs when an organic material reacts with oxygen to form new products, including carbon dioxide, water, and energy. Combustion is an irreversible process.

8 Edible describes a substance that is fit to be eaten. Fast pyrolysis describes the chemical and physical changes that occur when organic material is heated in the absence of oxygen (contrast to combustion) to form new products. The three major products of fast pyrolysis are bio-oil, biochar, and permanent gases. Feedstock a bulk raw material used as the input for an industrial process. Petroleum and lignocellulosic biomass are examples of industrial feedstocks for the production of gasoline. Hemicellulose any of a group of carbohydrates found in plants that, along with cellulose serve as a structural component. Hemicellulose lacks the structural rigidity of cellulose. Inorganic describes compounds that do not contain carbon (contrast with organic). Lignin a complex polymer of aromatic compounds, which, together with cellulose and hemicellulose, makes up the secondary cell wall of plant cells. Lignin is the second most abundant organic polymer on Earth. Lignocellulose refers to non-edible plant material that contains lignin, cellulose, and hemicellulose. Microorganism refers to a microscopic organism. Microorganisms can be single or multi cellular. Examples of microorganisms include bacteria, fungi, and algae, among others. Permanent gas a substance that remains gaseous under normal conditions. Nitrogen and hydrogen are examples of permanent gases. Organic describes compounds that contain carbon (contrast with inorganic). Petroleum a liquid mixture of hydrocarbons that can be refined to produce chemicals, products, and fuels. Petroleum is sometimes called a fossil fuel or crude oil. Physical change a change that affects the form of a chemical substance, but not its chemical composition. Ice melting to form liquid water is an example of a physical change. Polymer a substance that consists of a single unit (called a monomer) bonded to other identical units in a repeating fashion. Cellulose is an organic polymer of glucose monomers. Soil amendment a compound added to soil to improve its capacity to support plant life. Volatile describes a substance that easily changes to a gas at normal temperature.

9 Data Sheet Name: Day Measurements Observations Planting day None Initial watering, 10 ml each cup

10 Teacher Aid: Discussion Points What is biochar? How is it produced? Biochar is the solid product of fast pyrolysis. It is similar in appearance and composition to charcoal. Biochar contains mostly carbon, as well as smaller amounts of inorganic ash, which can be used by growing plants as a source of nutrients. Biochar is particularly useful as a soil amendment, and it contains a portion of the carbon transformed from plant material to make bio-oil, which can be used as a substitute for petroleum. Utilization of both the solid (biochar) and liquid (bio-oil) products of fast pyrolysis means less material is wasted in this process. How does fast pyrolysis differ from combustion or burning? Fast pyrolysis is carried out in the absence of oxygen (typically in a specialized chemical reactor that can exclude air). In fact, no flames are produced during fast pyrolysis, and the products are bio-oil, biochar, and permanent gases. In contrast, combustion is a chemical reaction that requires fuel, heat, and oxygen. In this process, characteristic flames are produced, and the products are carbon dioxide and water. What are the main benefits of using lignocellulosic biomass as a fast pyrolysis feedstock? First, lignocellulosic biomass is renewable; in other words, trees or grasses that are harvested to be used as feedstock material can be replanted and reharvested at a later date. In contrast, there exists a finite amount of petroleum on any reasonable timescale. In this regard, petroleum is not a renewable source of carbon. In addition, lignocellulosic biomass is (generally) inedible by humans, so there is not a concern about using food as a source of fuel. Finally, typical lignocellulosic feedstocks (such as switchgrass) can be grown on marginal land, which is farmland that is unsuitable for growing other cash crops. What are some beneficial aspects of biochar as a soil amendment? First, biochar contains inorganic ash, which consists of nutrients that a plant needs to grow. Adding biochar to nutrient-poor soil adds these beneficial nutrients. Also, biochar is effective at retaining water (because of the porous nature of the carbon contained in the biochar); in this regard, biochar improves the water retention properties of soils with large amounts of clay. Moreover, since biochar is derived from lignocellulosic biomass, using it to grow additional lignocellulosic biomass makes it a part of the carbon cycle. Finally, because biochar contains a large amount of carbon, burying it in the ground prevents that carbon from entering the atmosphere and contributing to anthropogenic climate change.