Evaluating woody biomass options for North Carolina's electricity future

In this high-school lesson, students learn about the pros and cons of co-firing woody biomass fuels with coal to produce electricity.

A lesson plan for grades 9–12 English Language Arts, Science, and Social Studies

By Dana Haine

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As coal-burning power plants seek ways to reduce their carbon dioxide emissions in response to the North Carolina Renewable Energy Portfolio Standard (REPS), some are evaluating the use of woody biomass for the generation of steam, heat, and/or electricity by co-firing with coal. In this activity, students will learn about and assess the potential for various types of woody biomass to replace coal with emphasis on North Carolina’s biomass resources and their region specifically.

Students assume the role of various stakeholders and participate in a discussion with classmates who represent officials from a local power plant that is seeking to substitute twenty percent of its coal with woody biomass. The class will evaluate each available woody biomass option and come to a group consensus about which option, if any, is best from an economic, environmental, and public health perspective.

Woody biomass options to be evaluated in this lesson include: wood waste/forest residues (chips made from bark, sawdust, and other byproducts of milling timber and making paper; logging waste); torrefied wood; and pellets from higher value wood, including roundwood and short-rotation woody crops.

Essential questions

• What are the benefits and drawbacks that arise from a power plant choosing to substitute a portion of its coal with woody biomass?
• What local sources of woody biomass (within a fifty-mile radius) exist within your community?
• What are the economic, environmental, and public health factors that must be taken into account when comparing woody biomass to coal?

Teacher planning

Time required

• Part I. Time for independent research (in class or as homework) and small-group discussion (60 - 90 minutes)
• Part II: Time for in-class presentations and discussion (60 - 90 minutes)

Materials

Internet access or other current biomass resources (books, articles, brochures, etc. See resources section.)

Student handouts

Pre-activities

Introduce students to the basics of electricity generation by conventional fossil energy: coal, natural gas, oil is used to power turbines to generate electricity. Raise awareness of how these energy sources are acquired by humans as well as the consequences of these processes on the atmosphere, lithosphere, hydrosphere, and biosphere. Ask students to consider an alternative energy source for electricity generation — woody biomass — and the implications of harvesting it and using it for fuel in an effort to reduce our dependence on fossil fuels for electricity.

Activities

1. Ask to students to define the term “biomass” in their own words and collect their responses on the board in order to come to a consensus about what this term means. According to the U.S. Department of Energy biomass is “organic material made from plants and animals (microorganisms).” Remind students that all biomass contains stored energy from the sun since plants, and ultimately the animals that eat those plants, rely upon photosynthesis. Tell students that this lesson is going to focus on the use of woody biomass for electricity generation, also known as biopower. If needed, you may want to remind students that they don’t want to confuse biopower with biofuels, which is the conversion of biomass into liquid fuels (e.g., ethanol and biodiesel) for transportation. Feel free to go ahead and introduce them to the different types of woody biomass options used to generate electricity listed in step five.
2. Optional: For further discussion: Notice that the definition for biomass above would also technically include fossil fuels since they are ultimately derived from plants and animals that lived millions of years ago. Prompt your students to consider why fossil fuels are not considered to be examples of biomass; what features of fossil fuels distinguish them from biomass resources and ask why this distinction matters. In the renewable energy world, the term biomass refers to renewable energy sources like wood, crops, manure, etc., resources that come from living, or recently living organisms. When burned, these biomass resources do contribute CO₂ to the atmosphere but, unlike the CO₂ arising from combustion of fossil fuels that are involved in the long-term cycling of carbon, the CO₂ released is part of the short-term cycling of carbon. (See The Natural Carbon Balance from the Marian Koshland Science Museum website).
3. Next, introduce students to some of the ways electricity is generated from woody biomass: 1) by direct-firing where the woody biomass is burned to produce high-pressure steam that turns a turbine connected to an electric generator; or 2) by co-firing where a portion of coal is replaced by woody biomass in an existing power plant. Co-firing requires some modification to the coal-burning power plant, but these modifications would generally be less expensive than building a new direct-fired power plant.
4. Draw a T chart on the board; draw a “+” sign in the left hand column of the chart and a “-” sign in the right hand column. Invite the students to consider how woody biomass might be touted as a solution to reducing carbon emissions from conventional power plants and brainstorm the potentially positive and negative impacts of doing so. Do not worry about right or wrong answers, just record ideas based on what students know.
5. Inform students that as coal-burning power plants seek ways to reduce their carbon dioxide emissions, some are evaluating the use of woody biomass for the generation of steam, heat, and/or electricity by co-firing with coal. Tell students they are going to assume the role of different stakeholders and take part in a “public hearing” to be facilitated by a local coal-burning power plant seeking to substitute twenty percent of its coal with woody biomass. For woody biomass to be economically viable as a substitute for coal, sources should exist within a fifty-mile radius of the power plant; prompt your students to think about local resources for woody biomass which could include one or more of the following:
   

   Woody biomass option	Source	Examples
   Forest residue chips	Remnants from logging operations	tree tops, branches, bark
   Mill residues	Waste products from mill operations	bark, saw dust
   Urban wood waste chips	Home and business; construction sites	tree trimmings, shipping pallets, and clean, untreated leftover construction wood

6. Next, divide students into the following small groups, keeping in mind the personalities and interests of the students. The success of the public hearing will, in part, hinge on the personalities of the students in group one; it is recommended that the teacher select students who will be comfortable asking questions, challenging other groups’ presentations, etc. If needed, the teacher can always join group one to ensure a productive public hearing.
   • Group 1: Local coal burning power plant officials
   • Group 2: Clean air environmental non-profit organization
   • Group 3: Woody biomass development company
   • Group 4: Torrefied wood manufacturer
   • Group 5: “Anything But Coal Power!” citizen group
   • Group 6: Local forest owners
   • Group 7: Professional foresters
7. Provide each group with their group’s description and instructions for preparing for the public hearing (see the “Biomass group activity instructions”); either in class or as a homework assignment, direct students to conduct research and prepare their presentation for the public hearing. The “Woody Biomass vs Coal Comparison” chart will be useful for guiding their research and informing them about the kind of information they should include in their presentation; depending on the energy source they are investigating it may be difficult to find some cost information. If time will be allotted for in-class research, relevant resources such as facts sheets and news articles could be compiled in a folder that can then be given to each group to guide their research. Ask students to base their information on local data and resources as much as possible. Students may create a short PowerPoint presentation or design a campaign poster, fact sheet or brochure that supports their argument.
8. On the day of the public hearing, ask the students in group one to sit at the front of the room since they will represent the officials receiving the public comments. Ask if they have any opening remarks and at the conclusion of their opening remarks ask groups two through seven to take turns and briefly present their argument to the power plant officials, allowing time for questions at the end. Direct students to complete the “Woody Biomass vs Coal Comparison” chart as they listen to the various presentations.
9. At the conclusion of public hearing, allow five to seven minutes for group one to meet and discuss the presentations and come to a decision about whether or not they will move forward with substituting twenty percent of coal with woody biomass based on the information presented by their classmates. Alternatively, group one could make their deliberation public and let the class in on their discussion.
10. Next, ask the class if they agree with the decision of group one. Why or why not?
11. Finally, see if the class can come to consensus about which woody biomass option(s), if any, the local utility company should pursue in order to substitute twenty percent of its coal. The “Woody Biomass vs Coal Comparison” chart will be useful as the class comes to a consensus. Ask the students to explain their reasoning based on environmental, economic and social perspectives, revisiting the T-chart from the beginning of the lesson if desired. You may choose to ask students to reflect on this question individually in writing by asking them to respond to the question: “Is woody biomass a viable alternative to coal? If you think so, to what extent?”
12. Finally, you may want to ask the class, “How did public perception contribute to the decision the class made today?” According a January 2011 publication (see Resources section) released by the USDA Forest Service’s Southern Research Station, “a number of studies cite public perception as playing an important role in the success or failure of proposed biomass energy projects.”

Discussion extensions based on current events

If time permits, either of the following scenarios would make for an interesting discussion or you ask students to reflect on one or both questions in writing using the knowledge gained from this lesson.

• Throughout the Southeast, European companies are exploring or building mills to turn small diameter and other relatively low-value timber into wood pellets for export. In fact, groups three and four above are typically more interested in off-shore markets for power plants in Europe than in meeting domestic demands. Wood pellets or torrefied wood pellets allow efficient shipment on bulk ships overseas, therefore these industries are actually competing for resources as domestic coal-fired power plants comply with government policies requiring utilities to begin generating some renewable power. North Carolina is a target for these companies given its extensive forests and also paper and lumber mills; specifically, the decline in the paper and lumber industries is creating a new market for pulpwood and round wood. What do you think about shipping wood pellets across the ocean to be burned in inefficient coal-fired power plants?
• In October 2010, the NC Utilities Commission concluded that whole trees can count as a renewable energy resource. The argument from those who opposed such a ruling was that counting whole trees as a renewable fuel would risk the state’s forests to over-harvesting. Others have expressed concern that energy policy will create unfair competition for traditional forest industry by allowing whole trees to be included in the definition. In the interest of moving forward in NC with wood energy, Senate Bill 279 of the 2011 Session of the NC General Assembly seeks to clarify the definition of “Renewable Energy Resource” as it pertains to the North Carolina Renewable Energy Portfolio Standard (REPS) to include that “wood is a renewable energy resource and that wood need not be a waste product to qualify as a renewable energy resource.” This bill passed the Senate in May 2011 but must pass the House before it can become law. What do you think about cutting down whole trees with the intent of using them to generate electricity? In the case of North Carolina, what if cutting down these trees was one step towards restoring the state’s historic longleaf pine forests or other treasured ecosystems?

Culminating activities

Guest speakers/tours

• Invite someone from a local coal-fired power plant to speak to the class about options either in place or being considered to reduce carbon dioxide emissions.
• Invite someone who works in the biopower industry to speak to the class about the future of woody biomass for electricity generation.
• Invite a professional forester or consulting forester to visit your class and discuss trends in woody biomass in your county. A county specific list of consulting foresters can be found at the North Carolina Forest Service website.
• If possible, tour a local biopower facility:
  • Coastal Carolina Clean Power / EPCOR, Kenansville, NC
  • Corn Products 4501 Overdale Rd., Winston Salem, NC 27107 (336)785-0100
  • Craven County Wood Energy Plant
  • EPCOR — Roxboro facillity, 331 Allie Clay Rd. Roxboro, NC 27573 (336) 597-4798
  • EPCOR — Southport facility, 1281 power house Drive S.E., Southport, NC 28461 (910) 457-5056

Research extensions

• Invite students to investigate other kinds of biomass that can be used in biopower operations; these feedstocks can include poultry litter, manure that can be converted into methane gas by anaerobic digestion, and other, non-woody agricultural waste products. Also, agricultural crops such as switchgrass or miscanthus can be grown specifically as an energy crop.
• Ask students to identify any local examples of a biopower operation and write up a description of the plant.
• Have students conduct research to see if there has been any local opposition to the use of woody biomass in a local power plant. Have them bring in news articles to discuss, etc.

Modifications and alternative assessments

Students with special needs

Place students in mixed-ability groups for activity completion.

Academically gifted

• Students can work individually on their assigned biomass source.
• Ask students to summarize their assigned woody biomass source by writing a one page report or making a brochure or fact sheet.

Resources

U.S. Department of Energy, “ABCs of Biopwer”

Southern Alliance for Clean Energy, “Biopower Overview”

Union of Concerned Scientists, “How Biomass Energy Works”

Society of American Foresters, “Dictionary of Forestry”

“Net Benefits of Biomass Power Under Scrutiny” (New York Times)

The North Carolina Renewable Energy Portfolio Standard (Senate Bill 3)

NC State University Extension Forestry Service, “NC Woody Biomass”

NC State University Extension Forestry Service, “Understanding Forestry Terms: A Glossary for Private Landowners” (PDF)

U.S. Department of Energy’s Biomass Program

U.S. Energy Information Administration — Energy Kids

U.S. Forest Service, “Woody Biomass Utilization”

Wood to Energy: Using Southern Interface Fuels for Bioenergy (USDA Forest Service January 2011 Publication) (PDF)

Acknowledgements

Sincere thanks to the following individuals who thoughtfully reviewed and/or piloted this lesson:

• Daniel Arneman, Ph.D., Energy Services, University of North Carolina at Chapel Hill
• Phil Barner, Energy Services, University of North Carolina at Chapel Hill
• Paul Bonicci, North Carolina Civic Education Consortium, University of North Carolina at Chapel Hill
• John Bonitz, Southern Alliance for Clean Energy
• Sarah Duffer, Asheville High School
• Dacia Harris, Asheville High School
• Dennis Hazel, Ph.D., Department of Forestry and Environmental Resources, North Carolina State University
• Mark Megalos, Ph. D., Department of Forestry and Environmental Resources, North Carolina State University
• Sarah Robertson, Northwood High School
• Jacqueline Quick, Williams High School