Section III: Applying Knowledge Creating a Woody Biomass Supply Curve

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1 Section III: Applying Knowledge Creating a Woody Biomass Supply Curve Summary In this activity, students go to various Web sites, compile data, and make calculations to construct woody biomass supply curves for their region. The total delivered price of woody biomass is a key factor when determining the feasibility of bioenergy facilities. Background Woody biomass can be used to generate renewable energy for communities in the southern United States that are experiencing increasing population and have nearby forests. Using wood for energy can provide various environmental and economic benefits. The feasibility of bioenergy projects depends in part on the cost and availability of the woody biomass resources. Specifically, the economic availability, or total delivered price for a given quantity of woody biomass, is particularly relevant to the feasibility of bioenergy facilities. One way to express the economic availability of a resource is with a supply curve. A supply curve is a basic economic tool used to express the price of a resource at a given quantity of demand. For example, Figure 1 illustrates a hypothetical woody biomass supply curve. In this example, a small amount of biomass (Quantity 1) is available at low cost (Price 1) in the form of urban waste wood. More biomass (Quantity 2) can be acquired in the form of logging activity 14 n subjects Mathematics, Social Studies (Economics) n Key Questions 1. How much woody biomass supply is available in my county? 2. What factors impact the cost of woody biomass resources? 3. How much electricity generating capacity is available from various woody biomass resources? n Objectives By the end of the activity, students will be able to do the following: 1. Collect and analyze data to create a woody biomass supply curve (MA. 912.S.3.1; MA.912.S.3.2). 2. Explain factors that influence the price of woody biomass resources (SS.912.E.1.1; SS.912.E.1.4; MA.912.F.5.1). 3. Convert units of measure (MA.912.A.1.5). 4. Create and interpret woody biomass supply curve graphs (SS.912.E.2.2; MA.912.A.2.1; MA.912.A.2.2; MA.912.A.3.8). n Materials Computers with Internet access for each student Copies of Student Worksheet, Data Tables, and Wood to Energy Conversion Handout (one copy of each per student) Calculators Graph paper (two sheets per student) n Time Estimate Part I: 30 minutes Part II: 1 hour Part III: 1 hour Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve 143

2 In this activity, students go to various Web sites, compile data, and make calculations to construct woody biomass supply curves for their region. Price 3 Price (Delivered $MMBtu) Price 2 Price 1 residues Commercial timber Urban waste wood Quantity 1 Quantity 2 Quantity 3 Supply (Btu/yr) Figure 1. Hypothetical supply curve illustrating woody biomass resource categories. residues, though at a higher price (Price 2), and even more biomass (Quantity 3) can be purchased in the same way commercial timber is bought from tree farmers, though it would be the most expensive (Price 3).Thus, a supply curve shows the price of biomass at various levels of demand. If enough biomass (the X-axis) can be delivered sustainably at a low enough price (the Y-axis) then enough wood may be available to supply a bioenergy project. A more complete supply curve might include other available resources and/or account for transportation cost in ranking the economic availability of these different resource types and travel times. In this activity, students go to various Web sites, compile data, and make calculations to construct woody biomass supply curves for their region. The activity is divided into three parts: Part I: Locating the Biomass Facility Part II: Calculating Woody Biomass Supply and Cost Part III: Creating the Supply Curve Graph The Student Worksheet is divided into the following steps: I: Locate a Proposed Biomass Facility II: Calculate Urban Waste Wood Supply III: Calculate Supply IV: Calculate Costs of Woody Biomass Supply V: Create a Supply Curve Graph Depending on time constraints, student skill level, and homework assigned, the time required to complete each part will vary, but you will need at least 30 minutes for Part I and one hour each for Parts II and III. 144 Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve

3 Teacher Instructions teacher Preparation 1. Review the Background Information and Teacher Instructions. Additional, more detailed background information is available in the Supplemental Reading section: Florida Community Economic Profile, Assessing the Economic Availability of Woody Biomass, and Do-It-Yourself Supply Curves. 2. Review the Student Worksheet and the Teacher Key to familiarize yourself with the activity. If time permits, complete the worksheet. Due to the complexity of this activity, you may prefer to complete it as a demonstration with the class rather than as an individual assignment. 3. Download the Google Earth program onto all computers (go to com/ to download the program for free). 4. Ensure that each Web site link on the Student Worksheet works properly and is not blocked on school computers. Procedure Part I: Locating the Biomass Facility 1. To introduce the activity, explain the concept of supply curves and the relationship between price and quantity described in the Background Information. 2. Distribute copies of the Student Worksheet, Data Tables, and Woody Biomass Conversion Handout. During this part of the activity, students will complete Step I: Locate a Proposed Biomass Facility on the Student Worksheet. 3. When students are at computer stations, instruct students to open the activity PDF via the program Web site so they can utilize the active hyperlinks. 4. Next, instruct students to open Google Earth and locate your county. If possible, project the image from your computer onto a large screen so the class can follow along as you navigate the program. Allow a few minutes for students to become familiar with the county borders, terrain, and roads. 5. Discuss with students some of the factors that should be considered when locating a woody biomass power plant. This may include road infrastructure and surrounding land uses (for example, schools, residential, industrial, forest). 6. Ask students to imagine where in the region a woody biomass power plant could be located. Write the location ideas on the board. 7. Next, find the specific locations using Google Earth and try to assess the locations suitability based on the factors discussed. 8. As a class, select the best option for the proposed biomass facility. All students should record the latitude and longitude of the location on their Student Worksheets. Assessment Suggestions Objective 1: Ensure students have completed all sections of the Student Worksheet and Data Tables. Objective 2: Review student answers to Student Worksheet, Summary Question 1. Objective 3: Check student conversions and calculations in Student Worksheet and Data Tables. Objective 4: Review completed supply curve graphs and answers to Student Worksheet, Summary Question 3. Part II: Calculating Woody Biomass Supply and Cost 1. Students will complete Steps II: Calculate Urban Waste Wood Supply, III: Calculate Supply, and IV: Calculate Costs of Woody Biomass Supply on the Student Worksheet. 2. Walk around the computer stations to provide assistance to students as needed. Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve 145

4 teacher Teacher Instructions Extensions To incorporate additional technology into this activity, ask students to record data and create graphs in a spreadsheet program such as Excel. Ask students to present their supply curves to the class. Ask them to brainstorm ideas for why the supply curves are different. Discuss differences in the supply curve results (for example, location of facility, amount of forested area within 50 miles of facility, population of communities surrounding the facility, supply of logging residues and urban waste wood available, and haul time to proposed facility location). Have students write a brief, one-page report to the local utility company or elected government officials that summarizes the supply curve data and results. Students can also take on the role of an economic expert and make recommendations based on the data. Part III: Creating the Supply Curve Graph 1. Students will complete Step V: Create a Supply Curve Graph on the Student Worksheet. 2. When students have completed the Student Worksheets, go through the following discussion questions to summarize the activity: a. What are some important considerations in selecting a location for a proposed bioenergy facility? b. c. Example answers: Are there forests nearby? What is the distance to these forests? Are good transportation routes available? How far is this facility from urban areas? How might the facility impact other land uses? Based on the data you collected, do you think woody biomass could offer economic incentives to your region? Why or why not? Answers will vary. If the cost of biomass is much higher than that of the average cost of coal, this might place an economic burden on energy consumers. If it is competitive with the average cost of coal, woody biomass may be a viable alternative energy source and a new energy facility can bring jobs and income to the community. Coal costs an equivalent of approximately $3/MMBtu in Florida. Review your electricity generating capacity graph and estimate how many MW of capacity might be produced at a price competative with conventional coal energy. Answers will vary. Write student answers on the board and start a discussion about what might account for the differences in the cost estimates. Ask students to explain why the cost of an energy resource is a critical aspect of the overall viability of the resource for a particular community. After you collect Student Worksheets, you may want to review answers to the Summary Questions to conclude the discussion. The information in this activity has been adapted from Wood to Energy Outreach Program materials: Langholtz, M., D. R. Carter, & R. Schroeder. (2007). Wood to energy: Assessing the economic availability of woody biomass. Gainesville, FL: University of Florida IFAS Cooperative Extension Service. Langholtz, M., D. R. Carter, & R. Schroeder. (2007). Wood to energy: Do-it-yourself supply curves. Gainesville, FL: University of Florida IFAS Cooperative Extension Service. Langholtz, M., D. R. Carter, A. W. Hodges, A. Oxarart, & R. Schroeder. (2007). Wood to energy community economic profile, Florida: Alachua, Clay, Leon, Nassau, and Santa Rosa counties. Gainesville, FL: University of Florida IFAS Cooperative Extension Service. Resources Additional Wood to Energy Community Economic Profiles are available for download as PDF files at the InterfaceSouth Web site: interfacesouth.org/woodybiomass/community_profiles.html 146 Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve

5 Creating a Woody Biomass Supply Curve Student Worksheet (1 of 6) STUDENT NAME date period Follow the instructions on this worksheet. You will record information both on this worksheet and the Data Tables. I. Locate a Proposed Biomass Facility 1. First, you will select a location for the proposed woody biomass facility. Open the Google Earth program. Find your county by typing your county and state name in the fly to field. 2. Become familiar with the borders, terrain, and roads in your county. 3. As a class, use Google Earth to find and agree on a location for a woody biomass facility. 4. Use the placemark feature to mark the location. Record the county and state and latitude and longitude of the proposed facility location. County & State: Latitude: Longitude: II. Calculate Urban Waste Wood Supply (Data Table 1) Trees grow in urban areas, providing shade and beauty. These trees produce waste wood when they are pruned, damaged in a storm, or cut down. Woody biomass for energy can come from various forms of urban waste wood, including tree and yard trimmings, storm damage debris, the commercial tree care industry, utility line trimming and thinning, and green space maintenance. In this step, you will calculate the supply of urban waste wood produced in four towns, cities, or communities within 50 miles of your proposed facility. 1. Open Google Earth, navigate to the selected county, and find the placemark that shows the biomass facility s location. Use the ruler feature to explore the landscape within a 50 mile radius of the facility. You can also use a map to complete this step. 2. Using Google Earth or a map, identify four towns, cities, or communities that are within 50 miles of your proposed facility. Hint: If you are using Google Earth to do this step, you will need to zoom in to see these locations and use the ruler tool to estimate distances. Record these communities in the space provided below and in Data Table Go to the U.S. Census Bureau Web site, to find the population of each of these communities. On the right side of the page, type each community and state in the Population Finder field. Record this information in the space provided below and in Data Table 1. Small towns may not be listed; use local information sources. 4. An average of green tons of urban waste wood are produced per person per year in the United States 1. This estimate includes both the weight of the wood and the moisture content of the wood. To determine how much urban waste wood is being produced in each community you selected, multiply the population of the community by green tons. Make calculations below and record these figures in the space provided and in the Urban Waste Wood (green tons) column of Data Table 1. x.203 tons = green tons urban waste wood Community A Population x.203 tons = green tons urban waste wood Community B Population x.203 tons = green tons urban waste wood Community C Population x.203 tons = green tons urban waste wood Community D Population This worksheet will guide you through the process of creating a woody biomass supply curve for your community by calculating the woody biomass available from two sources: urban waste wood and logging residues. This activity has five steps: I. Locate a Proposed Biomass Facility II. Calculate Urban Waste Wood Supply III. Calculate Supply IV. Calculate Costs of Woody Biomass Supply V. Create a Supply Curve Graph 1 Wiltsee, G Urban wood waste resource assessment. NREL. Golden, CO. htpp:// fy99osti/25918.pdf. Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve 147

6 STUDENT Creating a Woody Biomass Supply Curve Student Worksheet (2 of 6) Important Terms: Moisture content is the weight of water contained in wood; expressed as a percentage of weight. Green ton of wood is wood that contains more than 10% water (or moisture content), usually refers to wood containing 40 to 50% water. Dry ton of wood is wood that contains 10% or less water (or moisture content). 5. To efficiently convert wood to energy, most of the water contained in wood must be dried prior to combustion. Therefore, to calculate the energy content of the wood, you must convert green tons of wood to dry tons. For example, urban waste wood has a moisture content of 40%, which means the remaining 60% is the weight of the wood. To convert green tons to dry tons, multiply the total green tons by 0.6. Record these figures in the Urban Waste Wood (dry tons) column of Data Table In addition, you must assume that a facility will not be able to collect 100% of available urban waste wood, so multiply this figure by 0.6 again, assuming you will only be able to collect 60% of the wood. Record these figures in the Collected Urban Waste Wood (dry tons) column of Data Table 1. You have now completed Data Table 1. Hint: Review the Wood to Energy Conversion Handout to get a better understanding of how much energy can be generated from various amounts of woody biomass. III. Calculate Supply (Data Table 2) Trees are used to make lumber, furniture, paper, and other products people use every day. Many forest landowners in the U.S. manage forests to produce wood for these products. When trees are harvested, logging residues (poor quality trees and tree components, such as crowns, limbs, stumps, and branches) are produced. In this step, calculate the amount of logging residue available in selected counties within 50 miles of your proposed site. 1. Go to Google Earth or use a map to identify three neighboring counties with forest canopy and the home county of your proposed facility. Record these counties, plus your own county, in Column 1 of Data Table Go to the U.S.D.A. Forest Service Timber Products Output Mapmaker Web site: 3. Select National RPA reports (above the second table) and click Continue at the bottom of the page. 4. This page has a lot on it, but don t let it intimidate you. Scroll down to your state, click Specific Counties, and use the CTRL key to select the four counties you are collecting data for. Click Continue at the bottom of the page. 5. The next page contains a chart that lists many tables (first column) and links (second column). Click on County Tables (second from the top in the second column) to get all of the tables for your counties. 6. Table C10 shows the Volume of timber removals by State/County, species group, removals class, and source. Note the logging residue totals (All Sources column) for softwood and hardwood from each county. Record the Softwood and Hardwood (cubic feet/year) data for each county in Columns 2 and 3 of Data Table 2. Note: The figures on the Web site are in thousand cubic feet/year, so you will need to add three zeros to each number when you record them in Data Table The figures you recorded in Columns 2 and 3 are now in cubic feet/year, which is a volume. Because wood used in biomass facilities is measured in weight, you need to convert the volume of residue into weight. 148 Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve

7 Creating a Woody Biomass Supply Curve Student Worksheet (3 of 6) STUDENT 8. To calculate green tons of softwood logging residues produced per year, multiply the reported cubic feet/year of softwoods by 30 lbs/cubic foot and divide by 2,000 lbs/ton. For example: cubic feet/year softwood logging residues x 30 lbs/cubic foot = 2,000 lbs/ton = green tons softwood/year Record the Softwood (green tons/year) for each county in Column 4 of Data Table 2. To calculate green tons of hardwood logging residues produced per year, multiply the reported cubic feet/year of hardwoods by 32 lbs/cubic foot and divide by 2,000 lbs/ton. For example: cubic feet/year hardwood logging residues x 32 lbs/cubic foot = 2,000 lbs/ton = green tons hardwood/year Important Terms: Hardwoods are trees with broad leaves such as oak, maple, and sweetgum. Softwoods are conifers such as pine and cypress. Hardwood is denser than softwood, so an equal volume of hardwood weighs more than softwood. Record the Hardwood (green tons/year) for each county in Column 5 of Data Table Add Columns 4 and 5 together and record Total (green tons/year) in Column Woody biomass collectors may not retrieve the entire amount of logging residue produced in a particular county. Assume that they collect only 60% of the residue available: multiply the total green tons of logging residue per year (Column 6) by 0.6 to get the Total Collected (green tons/year). Record these figures in Column 7 of Data Table Dry tons are 60% of the weight of green tons, so multiply by 0.6 again to get the Total Collected (dry tons/year). Record these figures in Column 8 of Data Table 2. You have now completed Data Table 2. IV. Calculate Costs of Woody Biomass Supply (Data Table 3) Next, calculate the total delivered cost of woody biomass resources for each of the communities and The price to purchase counties you selected. To do this, you need to assign + prices to the available resources calculated above. The price to harvest, process, load, and unload 1. Table 1 shows typical costs of urban waste + wood and logging residues in Florida as of December These numbers represent the The price to transport = cost to purchase, harvest, process, load and The total delivered cost of unload; and the cost per dry ton to deliver woody biomass resources to the facility location woody biomass by truck for one hour and return one hour with an empty truck (i.e., twoway, one-hour haul time). We can use these costs to estimate our cost analysis: The sum of purchasing, harvesting, and processing is Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve 149

8 STUDENT Creating a Woody Biomass Supply Curve Student Worksheet (4 of 6) a The cost of purchasing wood on site. Negative costs for urban wood waste reflect disposal costs, known as tipping fees. b Includes the costs of bundling, collecting, and chipping. c The cost of loading and unloading the wood, which requires additional equipment. d The cost per ton to transport wood for one hour and return with an empty truck (for a total of two hours of driving time). A truck can carry 23 tons and typically gets 6 mpg. e Equals the sum of the four cost categories $6.98 for urban waste wood and $37.80 for logging residue. These costs are already recorded for you in Data Table 3. table 1. Hypothetical supply curve illustrating woody biomass resource categories. Urban Waste Wood ($ dry ton -1 ) s ($ dry ton -1 ) Purchase Cost a Harvest and Process b Load and Unload c Sum Cost of Purchasing, Harvesting, Processing, Loading/Unloading Two-way Haul (per hour) d Example Total Delivered Cost of a One-hour Haul of Each Dry Ton e The cost of transportation increases with both the distance of the haul and the total time spent on the road. Use an online map program to estimate drive time from the source of the woody biomass resources to the proposed facility location. Go to the Google Maps Web site: Click on Get Directions. Input the community that is the source of the urban waste wood as the Start address and the location of the proposed facility as the End address (input the nearest intersection and community). Repeat this process three more times to get the estimated drive time (in minutes) from each source community to your proposed location. Record this information in the space provided below. Convert each estimated drive time from minutes to hours and record the times (in hours) in Data Table 3. Community A: Estimated drive time: = Community B: Estimated drive time: = Community C: Estimated drive time: = Community D: Estimated drive time: = Next, repeat the previous steps, putting each county name that is the source of the logging residue as the Start address and the location of the proposed facility as the End address. Record this information in the space provided below. Convert each estimated drive time from minutes to hours and record the times (in hours) in Data Table 3. County A: Estimated drive time: = County B: Estimated drive time: = County C: Estimated drive time: = County D: Estimated drive time: = 150 Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve

9 Creating a Woody Biomass Supply Curve Student Worksheet (5 of 6) STUDENT 5. Multiply each hour drive time by the amount provided in the Two-way Transport ($/ hour/dry ton) column of Data Table 3, and record these values in the Two-way Transport Cost ($/dry ton) column for each community and county. 6. Sum the amounts in the Cost of Purchase, Harvest, Process, Load, & Unload column ($6.98 for urban waste wood and $37.80 for logging residue) and the Two-way Transport Cost column to get the Total Delivered Cost ($/dry ton). Record these figures in Data Table Divide the amount in the Total Delivered Cost ($/dry ton) column by 16, and record these figures in the Total Delivered Cost ($/MMBtu) column. Hint: There are about 16 million Btu (MMBtu) per dry ton of wood. 8. Finally, rank the resources in order of lowest (1) to highest (8) cost based on the amounts in the Total Delivered Cost ($/MMBtu) column. Write those ranks in Data Table 3. You have now completed Data Table 3. Important Terms: Megawatt (MW) is a common measure of power plant electricity generation capacity, which is equal to 1,000,000 watts. British Thermal Unit (Btu) is a standard unit of energy equal to the heat required to increase the temperature of 1 lb of water 1 F. V. Create a Supply Curve Graph (Data Table 4) 1. Copy the community and county names in rank order (from Data Table 3) into the second column of Data Table 4 (in the order of cheapest to most expensive). Also record the type of resource (urban waste wood or logging residue) for each location. 2. Copy the Collected Urban Waste Wood (dry tons) and Total Collected (dry tons/year) for each location from Data Tables 1 and To create a supply curve graph, calculate the cost and weight by cumulative totals. Copy the amount of Dry Tons Collected per Year for the first ranked location into the first box in the Cumulative Tons column in Data Table 4. Now, add that amount to the amount of Dry Tons Collected per Year for the second ranked location and enter the total in the second box of the Cumulative Tons column. Continue this process to complete the Cumulative Tons column. 4. Calculate Megawatt (MW) Capacity by dividing Cumulative Tons by 6,600. Record these values in Data Table 4. Hint: 1 MW of electricity is produced when about 6,600 dry tons of wood is burned. 5. Multiply MW Capacity by 600 to find out how many homes per year your facility could power with woody biomass. Record Homes Powered values in Data Table 4. Hint: 1 MW/year powers approximately 600 homes. 6. On graph paper, create a graph with MW Capacity (from Data Table 4) on the X-axis and Total Delivered Cost ($/MMBtu) (from Data Table 3) on the Y-axis. Label the units on each axis. Create a second X-axis label underneath MW Capacity titled Homes Powered (from Data Table 4). 7. Plot the data points using two different colors, one for urban waste wood and one for logging residue and label these in the key of your graph. 8. Draw a line to connect the data points. Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve 151

10 STUDENT Creating a Woody Biomass Supply Curve Student Worksheet (6 of 6) Summary Questions 1 What variables might impact the cost of woody biomass resources in your region? 2 How does the cost of woody biomass resources in your supply curve compare to the cost of coal (Hint: coal costs an average of $3/MMBtu)? How does the cost vary based on the source of woody biomass? 3 How does the cost of urban waste wood and logging residue compare among the communities and counties? What do you think are some potential explanations for the differences in these costs? 152 Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve

11 Creating a Woody Biomass Supply Curve Data Tables (1 of 2) STUDENT n Data Table 1. Urban Waste Wood Community Population Urban Waste Wood (green tons) Urban Waste Wood (dry tons) Collected Urban Waste Wood n Data Table 2. s County Softwood (cubic ft/ year) Hardwood (cubic ft/ year) Softwood (green tons/ year) Hardwood (green tons/ year) Total (green tons/ year) Total Collected (green tons/ year) Total Collected (dry tons/ year) Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve 153

12 STUDENT Creating a Woody Biomass Supply Curve Data Tables (2 of 2) n Data Table 3. Cost Calculations Community/County Resource Cost of Purchase, Harvest, Process, Load, & Unload ($/dry ton) Two-way Transport ($/hour/ dry ton) Drive Time Two-way Transport Cost ($/ dry ton) Total Delivered Cost ($/ dry ton) Total Delivered Cost ($/ MMBtu) (Y-axis) Rank Order of Total Delivered Cost ($/ MMBtu) (1 = cheapest, 8 = most expensive) A. Urban Waste Wood B. Urban Waste Wood C. Urban Waste Wood D. Urban Waste Wood A. B. C. D n Data Table 4. Data for Cost and Supply Graph Rank Order Community/ County Resource Urban Waste Wood or Dry Tons Collected per Year (from Tables 1 & 2) Cumulative Tons MW Capacity (cumulative tons/6600) X-axis Homes Powered (MW Capacity x 600) Second X-axis Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve

13 Wood to Energy Conversion Handout STUDENT The following definitions and conversions are provided to help you determine how much energy a given amount of wood can produce. Moisture Content Moisture content is the weight of water contained in wood, expressed as a percentage of weight. There is no moisture (0%) in oven-dried biomass. Air-dried biomass contains about 20% moisture. Green or fresh biomass contains about 50% moisture. The moisture content of wood varies greatly among different species of trees and the size of the wood particle. Moisture content also depends on climatic conditions, the time of year that harvesting occurs, and methods of and amount of time in storage. Moisture content plays a large role in determining the quality of biomass resources and the amount of energy that can be derived from these resources. A dry ton of wood is wood that contains 10% or less moisture content. A green ton of wood is wood that contains more than 10% moisture content. Usually, a green ton refers to wood containing 40-50% moisture content. Useful Conversions Typical southern pine plantation = green tons ( dry tons) logging residues per year per acre depending on forest management practices 1 green ton of wood = dry tons of wood 1 dry ton of wood = million Btu 1 MW per year = 5,300-7,000 dry tons of wood per year 85, ,000 million Btu per year powers approximately 600 homes per year Should We Use Wood for Energy? Section III Activity 14: Creating a Woody Biomass Supply Curve 155

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