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1 Technical Guidelines for Voluntary Reporting of Greenhouse Gas Program Chapter 1, Emission Inventories Part I: Appendix Page Section 1: Methods for Calculating Forest Ecosystem and Harvested Carbon, with Standard Estimates for Forest Types of the United States 2 APPENDIX A - Forest Ecosystem Yield Tables for Reforestation 58 APPENDIX B - Forest Ecosystem Yield Tables for Afforestation 110 APPENDIX C - Scenarios of Harvest and Carbon Accumulation in Harvested Wood Products 162 APPENDIX D - Summary of Data and Methods Contributing to Calculation of the Disposition of Carbon in Harvested Wood Products 204 Section 2: Guidelines for Using Models 228 Section 3: Measurement Protocols for Forest Carbon Sequestration 233 2 Chapter 1, GHG Inventories: Part I Appendix Section 1: Methods for Calculating Forest Ecosystem and Harvested Carbon, with Standard Estimates for Forest Types of the United States The material presented in Appendix Section 1 (this section) is adapted from a USDA Forest Service General Technical Report (Smith et al. 2006). 1.1 Introduction International agreements recognize forestry activities as one way to sequester carbon, and thus mitigate the increase of carbon dioxide in the atmosphere; this may slow possible climate change effects. The United States initiated a voluntary reporting program in the early 1990’s (U.S. Dep. Energy 2005). A system for developing estimates of the quantity of carbon sequestered in forest stands and harvested wood products1 throughout the United States is a vital part of the voluntary program. This system must be relatively easy to use, transparent, economical, and accurate. In this publication, we present methods and regional average tables that meet these criteria. Carbon is sequestered in growing trees, principally as wood in the tree bole. However, accrual in forest ecosystems also depends on the accumulation of carbon in dead wood, litter, and soil organic matter. When wood is harvested and removed from the forest, not all of the carbon flows immediately to the atmosphere. In fact, the portion of harvested carbon sequestered in long-lasting wood products may not be released to the atmosphere for years or even decades. If carbon remaining in harvested wood products is not part of the accounting system, calculation of the change in carbon stock for the forest area that is harvested will incorrectly indicate that all the harvested carbon is released to the atmosphere immediately. Failing to account for carbon in wood products significantly overestimates emissions to the atmosphere in the year in which the harvest occurs. We adopted the approach of Birdsey (1996), who developed tables of forest carbon stocks and carbon in harvested wood to provide basic information on average carbon change per area. The tables are commonly referred to as “look-up tables” because users can identify the appropriate table for their forest, and look up the average regional carbon values for that type of forest. We have updated the tables by using new inventory surveys, forest carbon and timber projection models, and a more precise definition of carbon pools. We also include additional forest types and background information for customizing the tables for a user’s specific needs. The look-up tables are categorized by region, forest type, previous land use, and, in some cases, productivity class and management intensity. Users must identify the categories for their forest, estimate the area of forestland, and, if needed, characterize the amount of wood harvested from 1 Traditionally, the phrase “forest products” includes paper, but the phrase “wood products” does not. The literature for forest carbon has not recognized this distinction. To be consistent with the literature, documentation relating to the 1605b program defines “wood products” as, products derived from the harvested wood from a forest, including fuel-wood and logs and the products derived from them such as cut timber, plywood, wood pulp, paper, etc. Included are both products in use and in disposal systems such as landfills (but which have not yet decayed, releasing carbon to the atmosphere as CO2 and/or CH4). 3 the area in a way that is compatible with the format of the look-up tables. The average carbon estimates per area in the look-up tables must be multiplied by the area or, as appropriate, harvested volumes, to obtain estimates in total carbon stock or change in carbon stock. The estimates in the look-up tables are called “average estimates,” indicating that they should be used when it is impractical to use more resource-intensive methods to characterize forest carbon, that is, particularly when more specific information is not available. Because these tables represent averages over large areas, the actual carbon stocks and flows for specific forests, or projects, may differ. The look-up tables should not be used when conditions for a project or site differ greatly from the classifications specified for the tables. Some users may require an alternative to an “all-or-nothing” use of the tables because they may have some information and need to use the tables to supplement, or fill in gaps, in carbon stocks. Alternatively, users may require slight alterations to the tabular data provided. Therefore, we also include the underlying assumptions and appropriate citations so that the tables can be adjusted to data availability and information requirements of individual activities. The accuracy of estimates from look-up tables will depend on how well the estimates in the tables represent the specific conditions of the land area or stratum for which estimates are required. In general, application of a regional estimate from a look-up table to a specific tract of land will get a rating of “C” to reflect the level of uncertainty inherent in this approach. However, a close match between the characteristics of the specific land area and the land characteristics defined by a look-up table could result in a higher rating. The following tabulation illustrates how look-up tables may be rated under the 1605(b) reporting system. This is intended as a guide to rating – individual circumstances must be carefully considered before conducting such an accuracy assessment. Rating Characterization Application of look-up tables A Most accurate (within 10 % of true value) Estimates in look-up tables validated with independent data for the specific site and management conditions. B Adequate accuracy (within 20 % of true value) Estimates in look-up tables modified or adjusted to match the specific site and management conditions. For example, estimates of carbon in live and standing dead trees are re- calculated using local biomass equations for a narrowly defined productivity class. C Marginal accuracy (within 30 % of true value) Typical application of regional look-up tables that generally match the site and management conditions. Sites are defined by region, forest type, and productivity class. Management includes regeneration after harvest, afforestation, and in some cases, “low” or “high” intensity. D Inadequate accuracy Use of look-up tables for sites or management conditions that are not represented by the tables. For example, using the Northeast, White-red-jack pine table for an intensively managed, thinned red pine plantation. 4 The focus of this document is to explain the methodology in a transparent way and present sets of look-up tables for quantifying forest carbon when site-specific information is limited. In the sections that follow, we introduce the tables and provide general guidance for their use. First, tables of forest ecosystem carbon are presented; these are followed by tables to calculate the disposition of carbon in harvested wood products. Additional information on methods and data sources follows these tables. This organization was adopted so that readers interested in using the tables can do so quickly. Both metric and English units are used for measures of area and volume.2 However, all values for carbon mass are expressed in metric units—tonnes (t)—unless specified otherwise. English units are included because most of the necessary input quantities are commonly expressed in units such as cubic feet/acre (for stand-level growing-stock volume) or thousand square feet of ⅜-inch plywood (a primary wood product), for example. Carbon stocks and stock changes are usually discussed and reported in metric units of carbon mass; this can lead to carbon in forests expressed as tonnes/hectare or in the United States as metric tons/acre. The forest ecosystem carbon tables are in Appendices A, B, and C; ancillary information on carbon in harvested wood is in Appendix D. 1.2 Forest Ecosystem Carbon Tables Tables of estimates of forest carbon stock are provided for common forest types within each of 10 U.S. regions (Fig. 1.1). Six distinct forest ecosystem carbon pools are listed: live trees, standing dead trees, understory vegetation, down dead wood, forest floor, and soil organic carbon. These pools are defined in Table 1.1. As an example, the table for reforested maple- beech-birch stands in the northeast is shown in Table 1.2. The complete set of tables are in Appendices A and B. The first two columns in each table are age and growing-stock volume; the remaining columns represent carbon stocks for the various carbon pools and are dependent on age or growing-stock volume. Pools are quantified as carbon densities, that is, tonnes per unit area (acres or hectares). The use of the tables can be summarized in three steps: 1) identify the most appropriate table for the particular carbon sequestration project; 2) extract the tabular information required for estimating carbon sequestration by the project; and 3) complete any necessary custom modifications or post-processing needed to suit data requirements. The information in the tables is based on a national-level, forest carbon accounting model (FORCARB2; Heath and others 2003, Smith and others 2004a), a timber projection model (ATLAS; Mills and Zhou 2003, Mills and Kincaid 1992, updated for Haynes 2003), and the USDA Forest Service, Forest Inventory and Analysis (FIA) Program’s database of forest surveys (FIADB; USDA For. Serv. 2005, Alerich and others 2005). Details are provided in the methods section. The two basic sets of tables in Appendices A and B differ only with respect to assumptions associated with previous land use. The first set displays carbon stocks on forest land remaining forest land, also called “reforestation” or “regrowth” of a stand following a clearcut harvest (Table 1.2, for example, and Appendix A). The second set displays accumulation of carbon stocks for a stand established on land that was not forest, called “afforestation” (Appendix B). 2 A tonne (t) is defined as 106 grams, or 2,204.62 pounds (lb). Other metric and English equivalents include 0.404686 hectare (ha) = 1 acre (ac), 2.54 centimeter (cm) = 1 inch (in), 0.0283168 cubic meter (m3) = 1 cubic foot (ft3), and 0.907185 tonne = 1 short ton = 2,000 pounds. 5 The separate set of afforestation tables accounts for lower carbon densities of down dead wood, forest floor, and soil carbon in the initial years after forest establishment on nonforest land. However, as stands mature, the level of carbon stocks in these pools approaches the regional averages represented in the reforestation tables. The tables in Appendices A and B provide estimates of carbon stock. The net change in carbon stock (sometimes called flux) associated with a growing forest can be determined by dividing the difference between two carbon stocks by the time interval between them. (See Examples 1.1 and 1.2 for information on using these tables.) PWW NE SC SE PWE PSW RMS RMN NPS NLS Figure 1.1—Definition of regions: Pacific Northwest, West (PWW); Pacific Northwest, East (PWE); Pacific Southwest (PSW); Rocky Mountain, North (RMN); Rocky Mountain, South (RMS); Northern Prairie States (NPS); Northern Lake States (NLS); Northeast (NE); South Central (SC); and Southeast (SE). Note that regions are merged for some tables, these combinations include: NLS and NPS as North Central; PWW, PWE, and PSW as Pacific Coast; RMN and RMS as Rocky Mountain; SC and SE as South; and RMN, RMS, PWE, and PSW as West (except where stated otherwise). 1.2.1 Modifications to Forest Ecosystem Tables The forest ecosystem tables provide regional averages as scenarios of forest growth and carbon accumulation, but they need not be used as the sole source of information on forest yield or carbon. For instance, a landowner may independently acquire estimates of growth or carbon accumulation that are specific to a particular carbon sequestration project. In this case, an appropriate use of the tables is to combine available data and to selectively use columns of carbon stocks to fill gaps in information. 6 Users must have a general understanding of the relationships between the columns of the table to most appropriately substitute site-specific information for a carbon pool. Some columns can be viewed as independent or dependent variables, depending on the carbon pool of interest. If new data are incorporated in a table, any dependent columns (carbon pools) probably will require minor adjustments (recalculations). Figure 1.2 illustrates the basic relationships underlying calculations of carbon stock. Stand age and growing-stock volume are from the ATLAS model and based on FIA data such that they reflect region, forest type, and typical forest management regimes. Pools of live and standing-dead tree carbon are estimated directly from growing-stock volume. Carbon stocks of understory or down dead wood are estimated directly from live tree carbon and are only indirectly affected by growing-stock volume. Growing-stock volume (stand volume in Figure 1.2) is the merchantable volume of wood in live trees as defined by FIA (Smith and others 2004c, Alerich and others 2005). Briefly, trees contributing volume to this stand-level summary value are commercial species that meet specified standards of size and quality or vigor. Users with other volume estimates for their stands must consider how to translate the volumes to be consistent with growing-stock volume. Thus, a landowner interested in applying these carbon estimates to another growth table should link tree carbon from the tables presented here to the new (separately obtained) estimates of growing-stock volume rather than to stand age (see Example 1.3). The methods section further explains how to use selected carbon pools from the table. 1.3 Tables for Harvested Wood Products Carbon Harvested wood products serve as reservoirs of carbon that are not immediately emitted to the atmosphere at the time of harvest. The amount of carbon sequestered in products depends on how much wood is harvested and removed from the forest, to what products the harvested wood is allocated, and the half-life of wood in these products (Row and Phelps 1996, Skog and others 2004). The central focus of the carbon in harvested wood products estimates is the carbon change from two pools: carbon in products in use and carbon in landfills. Carbon in harvested wood is initially processed or manufactured into primary wood products, such as lumber and paper. These are then incorporated into end-use products, such as houses and newspapers. Intact primary and end-use products are considered “in use” until they are discarded, and a portion of these discarded products go to landfills. Additionally, a portion of carbon initially sequestered as products is eventually returned to the atmosphere through mechanisms such as combustion and decay. This emitted carbon is classified according to whether it occurred through a process of combustion with some concomitant energy recapture. This distinction between the two paths for carbon emitted to the atmosphere is included to assess potential displacement of other fuel sources. The four categories for the disposition of carbon in harvested wood are defined in Table 1.1. Note that the carbon in the four categories sum to 100 percent of the carbon harvested and removed from the forest. 7 Stand Age Stand VolumeStand Volume Live TreeLive Tree Down Dead WoodStand Age Forest FloorStand Volume Dead TreeLive Tree UnderstoryStand Age Soil Organic CStand VolumeLive TreeDown Dead WoodForest FloorDead TreeUnderstorySoil Organic C Figure 1.2—Graphs indicating the basic relationships between the components of the forest ecosystem carbon tables. Figures are not drawn to scale; numerical representation for each graph is available from the tables. Dashed lines are qualitative representation of where afforestation tables (Appendix B) differ from the reforestation tables (Appendix A). Note that stand volume refers to growing-stock volume of live trees. The path that transforms trees-in-forests to wood-in-products can be described by the diagram in Figure 1.3. Quantities defined for the first three boxes in the diagram can serve as starting points, or data sources, for determining the disposition of carbon in wood products. Consistent with this, we provide factors for starting calculations of carbon in harvested wood products on the bases of forestland, the amount of industrial roundwood harvested, or the quantity of primary wood products produced by mills, depending on the data available (see definitions and details in the methods section). The forestland, or land-based, estimates are an extension of the forest ecosystem tables presented above. The other two starting points can be classified as product- based calculations, which are based on harvested logs or the output of mills. It is important to note that calculations from all three starting points (Fig. 1.3) focus on the same quantities of products in use or in landfills, and they all rely on the same model of allocation and longevity of end uses. They differ only in the level of detail available as the principal source of information on harvested wood – the path from input data to final disposition (Fig. 1.3). In the methods section, we provide the interrelated methods for calculating carbon in harvested wood for each of 8 these starting points. Additionally, Appendix D provides background data and details on these calculations for wood products. Roundwood classified as softwood or hardwood, and saw logs or pulpwood Trees in Forests quantified as growing stock or merchantable volume harvest and removal from forest processing at mills manufacture or construction Disposition: emitted or landfill Primary Wood Products such as lumber, panels, or paper Disposition: emitted or landfill Disposition: emitted or landfill End Use Products such as houses, furniture, or paper products recycling Figure 1.3—The transition of carbon in forest trees to end-use products represented by a sequence of distinct pools separated by processes that move carbon between pools. Calculations of carbon in harvested wood products may start with any of the first three pools: trees in forests, roundwood, or primary wood products. 1.3.1 Land-based Estimates The land-based estimates are provided as an additional set of forest ecosystem tables with harvest scenarios, which provide carbon estimates for harvested wood products over an interval after harvest (see Table 1.3 and Appendix C). At harvest, a large portion of carbon in tree biomass is allocated to the harvested wood pools, a second portion is assumed to decay rapidly after harvest (emitted at harvest), and the remainder stays on site in the forest as down dead wood or forest floor. The “emitted at harvest” carbon is assumed emitted at site soon after harvest; this is included to distinguish it from the two products emissions categories, which are emissions associated with processing, use, or disposal of harvested wood after removal from the site. Tree biomass allocated to harvested wood is removed from the site for processing, and it is allocated to the four disposition categories defined in Table1.1. Changes in the allocation of this pool of harvested carbon among the categories are tracked over an interval of stand growth following harvest (see columns 10, 11, 12, and 13 of Table 1.3). Note that the harvested products carbon pools are also quantified as carbon densities, that is, tonnes per unit area (acres or hectares), because they are derived from land-based carbon densities. These land-based estimates of carbon in harvested wood need not be limited to the examples in Table 1.3 or Appendix C. Similar calculations are possible for other harvest quantities, stand ages, or forest types. Factors for estimating and allocating harvested carbon from the forest ecosystem tables are included in Tables 1.4, 1.5, and 1.6. These are used to calculate the 9 disposition of carbon in harvested wood products (see Example 1.4). The stand-level volume of growing stock in live trees, such as 172.1 m3/ha in Table 1.3, is used to predict total carbon in harvested wood. Growing-stock volume from the ecosystem table is converted to categories of roundwood carbon mass according to factors in Tables 1.4 and 1.5. The disposition of this carbon in wood products is then allocated according to Table 1.6. Additional information on the use or adaptation of the harvest scenario tables can be found in the methods section that follows, Example 1.4, and Appendix D. 1.3.2 Product-based Estimates Harvest information is often available in the form of wood delivered to mills or the output of mills. As such, the product-based estimates of carbon in harvested wood products focus on quantities of wood as the starting point for calculating the disposition of carbon. Specifically, these starting points are industrial roundwood logs or primary wood products (such as lumber, panels, or paper) as indicated in Figure 1.3. Thus, quantities are of total carbon and not directly linked to forest area. The disposition of carbon in products based on an initial quantity, or carbon mass, of roundwood is allocated according to Table 1.6. The specific carbon content of primary wood products is calculated from factors in Table 1.7. The disposition of carbon over time for these primary products is according to factors in Tables 1.8 and 1.9, which provide the fractions of carbon from original primary products that remain in use or in landfills, respectively. Again, additional information on the use or adaptation of the tables for product-based calculations can be found in the section that follows, Examples 1.5 and 1.6, and Appendix D. 1.4 Methods and Data Sources for Tables The purpose of this section is to provide detailed information on data sources, models, and assumptions used in developing the tables or calculations described earlier. Also, we outline linkages between the carbon calculations. These further illustrate how the tables were developed and updated, how the methods were applied, and provide information needed to further modify or customize the tabular carbon summaries. In these tables, we provide estimates for as many as ten carbon pools. Forest structure provides a convenient modeling framework for assigning carbon to one of six distinct forest ecosystem pools: live trees, standing dead trees, understory vegetation, down dead wood, forest floor, and soil organic carbon (Table 1.1). These pools are consistent with guidelines of the Intergovernmental Panel on Climate Change (Penman and others 2003). The disposition of carbon in harvested wood is summarized in four categories that describe the end-fate of the harvested wood: products in use, landfills, emitted with energy capture, and emitted without energy capture (see definitions in Table 1.1). 1.4.1 Forest Ecosystem Carbon Forest ecosystem carbon is significantly affected by the following factors: region of the United States, forest type, previous land use, management, and productivity. The development and 10 format of the tables are based on Birdsey (1996): current stand-level carbon and growth-and- yield models were compiled as forest carbon yield tables. Forest types correspond to definitions in the FIADB and represent common productive forests within each region. The first two columns in each forest ecosystem table represent an age-volume relationship (also known as a yield curve) based on information from the timber projection model ATLAS (Mills and Kincaid 1992 with updates for Haynes 2003). ATLAS uses data on timber growth and yield and FIA data to develop a set of tables of growing-stock volume for projecting large-scale forest inventories representing U.S. forests for various policy scenarios. The yields (age-volume) represented in Appendices A, B, and C are broad averages; the basic set is from the appendix tables in Mills and Zhou (2003). Stand ages included in the tables are from the ATLAS yields, and these were limited to 90 years in the South and 125 years elsewhere. We assume all age- volume relationships are based on an average level of planting or stand establishment, that is, after clearcut harvest (reforestation) or as a part of stand establishment (afforestation). Additional tables are included for Southern pines and some Pacific Northwest forests to reflect stands with relatively higher productivity or more intensive management practices (see specific tables in Appendices A through C). These yields are based on ATLAS and timber projections prepared for Haynes (2003). Carbon estimates are derived from the individual carbon-pool estimators in FORCARB2 (Heath and others 2003, Smith and others 2004a, Smith and Heath 2005). FORCARB2 is essentially a national empirical simulation and carbon-accounting model that produces stand-level, inventory- based estimates of carbon stocks for forest ecosystems and regional estimates of carbon in harvested wood. Estimates of carbon in live and standing dead trees are based on the methods of Jenkins and others (2003) and Smith and others (2003). A new set of stand level volume-to- biomass equations was calibrated to the FIADB available on the Internet as of July 29, 2005 (USDA For. Serv. 2005). These are the bases for the carbon values for live and standing dead trees provided here. However the volume-based estimates of tree carbon from FORCARB2 required minor modification for the tables because many yield curves specify zero volume at both 0 and 5 years. This produced discontinuities over time in the estimates of tree carbon, usually in the second and third age classes. Carbon in tree biomass is accruing even if sapling trees remain below the threshold for classification of growing-stock volume3 but above the classification size where trees are considered part of the understory. Therefore, tree carbon at the first row of the table is set to zero, and carbon for year 5 (and occasionally the third age class) is based on a modification of the volume-based estimates. Briefly, a subset of the FIADB with younger stands was used to develop age-based regressions with biomass from tree data (Jenkins and others 2003); these regressions converged with the volume-based estimates, usually by age 10 to 15. We used a ratio of the two estimates to smooth estimates between the second and third age classes. Estimates in carbon density in understory vegetation are based on Birdsey (1996); estimates of carbon density in down dead wood were developed by FORCARB2 simulations. Estimates of these two pools are based on region, forest type, and live-tree biomass. (For additional 3 The minimum tree size for growing stock is 5 inches d.b.h.; significant tree carbon can accumulate in a stand before trees reach this threshold. 11 discussion or example values, see Smith and others (2004b) and Smith and Heath (2005)). The carbon density of forest floor is a function of region, forest type, and stand age (Smith and Heath 2002). Estimates of soil organic carbon are based on the national STATSGO spatial database (USDA Soil Conserv. Serv. 1991) and the general approach described by Amichev and Galbraith (2004). These represent average soil organic carbon by region and forest type in the Forest Service’s Renewable Resources Planning Act (RPA) 2002 Forest Resource Assessment database. For additional information, see USDA For. Serv. (2005) and Smith and others (2004c). Slight modifications to the direct application of FORCARB2 estimators were incorporated to develop the reforestation (Table 1.2 and Appendix A) and afforestation (Appendix B) tables. The reforestation tables are based on the assumption that at harvest, a portion of slash becomes down dead wood or forest floor at the start of the next rotation; these additional components then decay with time in the new stand (Smith and Heath 2002). The initial carbon densities for down dead wood and forest floor are listed in the first row of the Appendix A tables. Values for down dead wood are proportional to levels at the time of harvest and added logging residue (based on Johnson (2001)). Decay rates for down dead wood and forest floor are calculated from Turner and others (1995) and Smith and Heath (2002). The afforestation tables are based on the reforestation tables with the assumption that the residual carbon of down dead wood and forest- floor material remaining after harvest does not exist at the start of the afforested stands. Thus, these pools are set to zero at the first row of the table. Accumulation of soil organic carbon in previously nonforest land (the afforestation tables) is based on the accumulation function described in West and others (2004) with the assumption that soil carbon density is initially at 75 percent of the average forest value, which is within the range of values associated with soil organic carbon after deforestation (Lal 2005). Users with more specific data about soil organic carbon or effects of previous land use can easily modify the tables to reflect this information. The tables are designed to accommodate modification or replacement of selected data. Estimates for years or stand volumes not defined explicitly can be determined with linear interpolation (Example 1.2). The separate carbon pools, according to column, allow the user to extract or substitute values as needed to complement separately obtained site-specific information. However, users should be aware of the relationships between the parts as described in Figure 1.2 to substitute columns. Figure 1.2 can be used as a guide in customizing tables. As an example, a user with a model of stand growth for a particular project but still wishing to use the carbon estimates from a table should: 1) choose an appropriate carbon table by matching forest type, 2) make the appropriate substitutions of new data, and 3) then recalculate the carbon columns affected by the substitution. After the age and volume columns are replaced, recalculations based on interpolation are required for carbon pools of live and standing dead trees, understory vegetation, and down dead wood. Forest floor is determined by stand age, and values of soil carbon depend on assumptions that apply to reforestation or afforestation (Fig. 1.2). The substitutions and recalculations can be made by using a spreadsheet. Example 1.3 expands on this discussion and provides a numerical example. 12 As illustrated in Figure 1.2, most of the relationships between columns of the tables are nonlinear. As a consequence, small errors are possible when interpolating between two points, such as in the volume to tree carbon pairs. However, these errors likely will be minimal. The nonlinearity can produce more significant errors if the tables are applied to aggregate summaries of large forest areas, that is, substantially greater than 10,000 ha (Smith and others 2003). As a result, it is best to apply the tables to relatively smaller forest areas versus calculating large aggregate volume and area. 1.4.2 Harvested Wood Carbon The basic information required for calculating the disposition of carbon in harvested wood products based on each of the three starting points (Fig. 1.3) are in Tables 1.4 through 1.9. The purpose of this section is to provide sufficient background so that a user can apply these tables. However, some users may want to modify the estimates to incorporate alternate data or assumptions, so we also provide background data and detailed explanations in Appendix D of how these tables are generated. Methods for calculating the disposition of carbon in harvested wood and the starting points for making such calculations are organized according to the diagram in Figure 1.3. These starting points, which correspond to possible sources of data (independent variables) are: 1) the volume of wood in a forest available for harvest and subsequent processing (for example, growing-stock volumes in Tables 1.2 and 1.3); 2) roundwood harvest from a forest in the form of saw logs and pulpwood, which is a measure of wood available for processing at mills; and 3) primary wood products, that is products produced at mills, such as lumber, panels, or paper. We discuss methods and application of each of these, beginning with estimates based on primary wood products as inputs. The model that allocates carbon over time since harvest is the same for all three starting points, and this model is based on primary wood products (see Appendix D for details). Thus, the disposition is a function of primary wood product and time. Any of the additional calculations necessary for the “upstream” (on Figure 1.3) starting points are essentially required to translate input carbon stocks to primary wood product equivalents. Conversely, calculations at “downstream” starting points do not quantify all pools of harvested carbon. For example, a portion of the wood harvested from a forest ecosystem is processed into primary wood products, but carbon in other biomass remains on site as logging residue or is removed from site as fuelwood or what ultimately becomes waste in the production of primary products. Thus, identifying pools such as fuelwood is necessary for starting from the forest ecosystem to partition carbon and obtain the quantity going to primary products. Quantifying fuelwood is not possible, and unnecessary, for starting from data on a quantity of primary wood products. Before applying the forest ecosystem tables, users should identify: 1) the approach most appropriate for the data available, and 2) the type of summary values or results that are appropriate to the carbon accounting method and the forest carbon project. Each starting point requires slightly different input data and each accounts for somewhat different pools of carbon. Compatibility between available data and the appropriate starting point depends on identifying these differences. In addition to having different starting points to compute carbon stocks or 13 stock change, there may be differences in information needs, such as for carbon reporting. Carbon accounting requirements may specify tracking carbon harvested in one or more years and reporting carbon sequestered at one or more later years. For example, one may be interested in tracking products associated with a particular year or may be interested in the cumulative effects of successive harvests. Alternatively, an accounting method that focuses on the long-term effects of current rates of harvest and processing on future stocks of carbon in harvested wood products requires estimates of carbon in use or in landfills at 100 years after harvest (Miner, in press). Thus, all of our projection tables extend through 100 years. Consideration of imports or exports of harvested wood can complicate the calculations. The effect of considering the movement of harvested wood or wood products over boundaries depends on the approach used to account for carbon. Basic carbon accounting approaches, as presented by the Intergovernmental Panel on Climate Change (Penman and others 2003) are: stock-change, atmospheric-flow, and production. The accounting method presented here is a production approach: the disposition of carbon is estimated for all wood produced, including exports. Imports are excluded from accounting under the production approach. Currently, the IPCC does not provide guidelines on accounting methods for trade in harvested carbon. However, the additional information required to account for imports or exports is essentially the disposition, as described in this document, for the specific quantities of carbon imported or exported. A possible default assumption is that the disposition of carbon in exported wood is identical to that of carbon in products retained in the United States. Primary wood products. Primary wood products such as lumber, plywood, panels, and paper are the products of mills; they provide a product-based starting point for calculating the disposition of carbon in harvested wood products (Fig. 1.3). Specific primary products are identified in Table 1.7. Manufacturing or construction incorporates these primary products into end-use products such as houses, furniture, and paper. Each end-use product has an expected lifespan, and after use the primary products may be recovered for additional use, burned, or otherwise disposed of. After disposal, carbon in products is allocated to disposal pools, which ultimately leads to long-term storage in landfills or to emission to the atmosphere. Thus, the disposition of primary wood products are modeled through partitioning and residence times of a succession of intermediate pools to the final disposition categories as defined in Table 1.1. Table 1.7 includes factors for converting primary wood products into total mass of carbon. For example, 1000 ft2 of ⅜-inch softwood plywood averages 0.236 tonne of carbon. Tables 1.8 and 1.9 indicate the fraction of each primary product that remains in use or in landfills, respectively, for a given number of years after harvest and production, with the assumption that harvest and production are at time zero. The tables represent national averages. Table 1.8 lists the fraction of each primary product remaining in an end use product for up to 100 years after harvest and processing. For example, column 2 of Table 1.8 indicates that after 10 years, 77.7 percent of softwood lumber remains in an end-use product; end uses include residential or other construction, furniture, and wood containers. The change in carbon between the initial quantity of primary products and the amount specified in later years in Table 1.8 represents products taken out of use; these are then either sequestered in landfills or emitted to the atmosphere. Table 1.9 includes an estimate of carbon sequestered in landfills. In the example of softwood 14 lumber at 10 years, the fraction is 14.1 percent (column 2 of Table 1.9). Thus, the remaining carbon (8.2 percent), in softwood lumber has been emitted to the atmosphere by year 10. Recycling of paper products is an assumption built into Tables 1.8 and 1.9. (See Appendix D for details on paper recycling.) The value of including the effect of recycling on the disposition of carbon in harvested wood products can depend on the carbon accounting information needed. For example, recycling can affect quantities in use or in landfills if calculations are focused on a single cohort of carbon such as paper originally produced in a specific year. That is, accounting for effects of recycling can matter if tracking carbon from a single year or owner is important. We include recycling of paper because recycling is relatively common, its effects may be important, and statistics are available to include recycling in the calculations. Tables 1.8 and 1.9 can be used to calculate net change of carbon in harvested wood products, the cumulative effect of successive annual harvests, and carbon remaining at 100 years. The change in carbon stocks between successive years is net annual flux. The tables are based on the assumption that harvest and processing occur in the same year (year set to zero); they provide annual steps for 50 years. Values can be interpolated for annualized estimates between years 50 and 100. Cumulative effects of annual harvests are obtained by repeating calculations for each harvest and summing stock or stock change estimates for each year of interest. A numerical application for calculating the disposition of carbon in primary wood products is provided in Example 1.6, in which the cumulative effect of annual production at a mill is calculated. See Appendix D for additional information on model assumptions, values used to describe allocation and longevity, and calculations of the factors in Tables 1.7 through 1.9. Roundwood. Roundwood4 is logs, bolts or other round sections cut from trees for industrial manufacture or consumer use (Johnson 2001). Most roundwood is processed by mills, and it is this quantity of harvested wood that provides the roundwood starting point in Figure 1.3. Classification of harvested wood as roundwood is commonly a part of regional or State-wide statistics on timber harvesting or processing (Johnson 2001, Smith and others 2004c). A regional linkage between roundwood and the primary wood products model (discussed earlier) is the basis for establishing the disposition of carbon from roundwood. The allocation of roundwood to domestically produced primary wood products was constructed from Adams and others (2006). The resulting model of the allocation of carbon in roundwood according to region and roundwood category is represented as Table 1.6. Table 1.6 was developed in the style of similar tables in Birdsey (1996), which are based on Row and Phelps (1996). Inputs are carbon mass in roundwood according to region and roundwood category. Total roundwood is allocated to the four disposition categories (see definitions in Table 1.1), and changes in allocation are tracked as fractions over years 1 through 100 after 4 The definition and classification of roundwood as it is used here is important to quantifying and allocating carbon in harvested wood products. The calculations in this document use roundwood as essentially logs for industrial manufacture. Roundwood comes from both growing stock and other sources, and not all growing stock becomes roundwood. The definition of roundwood can also include fuelwood, but fuelwood and bark on roundwood are specifically excluded from “roundwood” as used in this document. Roundwood can be classified as sawtimber versus pulpwood (for example, Birdsey 1996, Row and Phelps 1996) but the more common usage is sawtimber versus poletimber (for example, Johnson 2001) or saw logs versus pulpwood. 15 manufacture or processing. Roundwood is classified by region (Fig. 1.1) and category: softwood saw logs, softwood pulpwood, hardwood saw logs, and hardwood pulpwood. Saw logs come from larger diameter trees and generally are utilized for solid wood products; pulpwood comes from smaller diameter trees and usually is used for pulpwood products. Some roundwood classifications are pooled across regions for Table 1.6; this is done where production of a particular type is relatively low. Roundwood, as classified for Table 1.6, excludes bark on logs and wood used as fuelwood. The allocation of emitted carbon to the fraction associated with energy capture is based on the allocation patterns in Birdsey (1996). A numerical application of Table 1.6 is provided in Example 1.5. See Appendix D for additional background information and sample calculations used to generate Table 1.6. Scenarios for Forest Ecosystem Harvest. The land-based starting point for calculating the disposition of carbon in harvested wood products is from the forest ecosystem carbon tables (for example, Table 1.3), as described in Figure 1.3 (trees in forests). Calculations starting with wood in forests are distinctly different from starting with products in two respects: 1) inputs are land-based measures of merchantable wood in a forest, such as growing-stock volume, and 2) estimates of carbon in harvested wood also include fuelwood as well as bark on all logs (roundwood and fuelwood). The bases for linking forest ecosystems to roundwood, and thus the disposition of carbon in products, are compilations of summary values from harvest statistics (Johnson 2001) and estimates of tree biomass (Jenkins and others 2004) applied to current FIADB survey data. Converting growing-stock volume to carbon mass in roundwood is based on factors in Tables 1.4 and 1.5. Table 1.4 is used to partition growing-stock volume according to species type (softwood or hardwood) and size of logs. This is followed by converting volume to carbon mass according to the carbon content of wood. These values for carbon in growing-stock volume are extended to estimates of carbon in roundwood according to factors in Table 1.5. The disposition of carbon is then based on Table 1.6. The harvest scenario tables were constructed from the ecosystem tables by appending a reforestation table (from Appendix B) to an afforestation table (from Appendix A) at a stand age designated as a clearcut harvest. Carbon in harvested wood products was added by applying factors in Tables 1.4 through 1.6. The Appendix C tables are examples of how forest carbon stocks can include carbon in harvested wood; these are not recommendations for rotation length or timing of harvest. Assumptions and background data for compiling Tables 1.4, 1.5, and 1.6 (as well as the other starting points for calculating carbon in harvested wood products) are included in Appendix D. Despite differences in input data and extent of harvested carbon included, all three starting points rely on the same model of allocation and longevity of end uses. They differ only in the level of detail available as the principal source of information on harvested wood (Fig. 1.3). 16 1.5 Uncertainty Estimates of carbon stocks and stock changes are based on regional averages and reflect the current best available data for developing regional estimates. Quantitative expressions of uncertainty are not available for most data summaries, coefficients, or model results presented in the tables. However, uncertainty analyses were developed for previous similar estimates of carbon, from which our tables were developed (Heath and Smith 2000, Skog and others 2004, Smith and Heath 2005). Similar quantitative uncertainty analyses are being developed for these estimates of carbon stocks and stock changes in forests and harvested wood products. Precision is partly dependent on the scale of the forest carbon sequestration project of interest. Overall, precision is expected to be lower as these methods are applied to smaller scale projects versus with regional summaries. That is, precision depends on the degree of specificity in information about a particular forest or project. It may be useful to distinguish between two basic components of uncertainty in the application of these tables. Uncertainty about the regional averages, which are based on data summaries or models, can influence estimates for specific projects, which generally are small subsets of a region. However, variability within region likely will have a much greater influence on uncertainty than regional values. This is shown in Figure 1.4, which is an example of the volume-to-biomass relationships used to estimate tree carbon from merchantable volume (columns 2 and 3 in Table 1.2). Each point represents an individual permanent FIA inventory plot where the 95-percent confidence interval about the mean of carbon in live trees is generally less than 5 percent of the mean. The regression line represents the regional average; the 95-percent confidence intervals about this mean are indicated in Table 1.10. These two relative intervals reflect regional variability in biomass relative to volume. For example, the 99th percentile of stand growing-stock volumes for this forest in the FIADB is 361 m3/ha and the mean carbon density for these plots is likely between 192 and 197 t/ha (Figure 1.4, ±1.4 percent of the expected 194 t/ha). The distinction between uncertainty about coefficients and regional or temporal variability may also apply to calculating the disposition of carbon in harvested wood products as well. Uncertainty about the actual allocation of roundwood to primary products may not be as important as year-to-year change or how activity at a single mill compares with the region as a whole. 17 0 100 200 0 100 200 300 400 Growing-Stock Volume (m3/ha) Live Tree Carbon (t/ha) Figure 1.4—A component of uncertainty associated with representing an average forest stand in the ecosystem tables. Individual points represent live tree carbon density for FIA permanent inventory plots for maple-beech-birch forests for the Northeast; the line represents carbon in tree biomass as predicted by growing-stock volume as used in Tables 1.2 and 1.3. 1.6 Conclusions Summing the two estimates, forest ecosystem carbon and carbon in harvested wood products, gives the total effect of forest carbon sequestration for an activity. To assure accuracy, conducting modest inventories will help show the adequacy of the tables in characterizing carbon sequestration. Carbon estimates depend on available data. Tables of average values cannot perfectly replicate each individual stand. Growth and yield information applicable to a particular stand can provide greater precision than regional averages. Similarly, carbon stocks in wood products that are calculated from quantities of primary wood products are likely to be more precise than products calculations starting simply from area of forest. However, the link between forest and sequestration in products may be less clear when starting from primary wood products. Forest composition, site conditions, and climate differ by regions, and climate, timber markets, and forest management priorities are subject to change from year to year. The methods described in this publication are most useful in identifying a general expected magnitude of carbon in forests, and to help plan carbon sequestration projects to achieve a certain goal. 18 1.7 Literature Cited Adams, D.A.; Haynes, R.W.; Daigneault, A.J. 2006. Estimated timber harvest by U.S. region and ownership, 1950-2002. Gen. Tech. Rep. PNW-659. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 64 p. Alerich, C.L.; Klevgard, L.; Liff, C.; Miles, P.D.; Knight, B. 2005. The forest inventory and analysis database: database description and users guide version 2.0. USDA Forest Service. June 1, 2005. http://ncrs2.fs.fed.us/4801/fiadb/fiadb_documentation/ FIADB_DOCUMENTATION.htm (2 December 2005). Amichev, B.Y.; Galbraith, J.M. 2004. A revised methodology for estimation of forest soil carbon from spatial soils and forest inventory data sets. Environmental Management. 33(Suppl. 1): S74-S86. Birdsey, R.A. 1996. Carbon storage for major forest types and regions in the coterminous United States. In: Sampson, N.; Hair, D., eds. Forests and global change. Volume 2: Forest management opportunities for mitigating carbon emissions. Washington, DC: American Forests: 1-25, Appendixes 2-4. de Silva Alves, J.W.; Boeckx, P.; Brown, K. [and others]. 2000. Chapter 5 – Waste. In: Penman, J.; Kruger, D.; Galbally, I. [and others], eds. Good practice guidance and uncertainty management in national greenhouse gas inventories. Hayama, Kanagawa, Japan: Institute for Global Environmental Strategies for the Intergovernmental Panel on Climate Change: 5.1-5.32. Haynes, R.W., coord. 2003. An analysis of the timber situation in the United States: 1952- 2050. Gen. Tech. Rep. PNW-560. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 254 p. Heath, L.S.; Smith, J.E. 2000. An assessment of uncertainty in forest carbon budget projections. Environmental Science and Policy. 3: 73-82. Heath, L.S.; Smith, J.E.; Birdsey, R.A. 2003. Carbon trends in U. S. forest lands: a context for the role of soils in forest carbon sequestration. In: Kimble, J.M.; Heath, L.S.; Birdsey, R.A.; Lal, R., eds. The potential of US forest soils to sequester carbon and mitigate the greenhouse effect. New York: CRC Press: 35-45. Jenkins, J.C.; Chojnacky, D.C.; Heath, L.S.; Birdsey, R.A. 2003. National-scale biomass estimators for United States tree species. Forest Science. 49: 12-35. Jenkins, J.C.; Chojnacky, D.C.; Heath, L.S.; Birdsey, R.A. 2004. A comprehensive database of biomass regressions for North American tree species. Gen. Tech. Rep. NE-319. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 45 p. [1 CD-ROM]. 19 Johnson, T.G., ed. 2001. United States timber industry—an assessment of timber product output and use, 1996. Gen. Tech. Rep. SRS–45. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 145 p. Lal, R. 2005. Forest soils and carbon sequestration. Forest Ecology and Management. 220: 242-258. McKeever, D.B. 2002. Domestic market activity in solidwood products in the United States, 1950 – 1998. Gen. Tech. Rep. PNW-524. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 76 p. Mills, J.; Kincaid, J. 1992. The aggregate timberland analysis system—ATLAS: a comprehensive timber projection model. Gen. Tech. Rep. PNW-281. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 160 p. Mills, J.; Zhou, X. 2003. Projecting national forest inventories for the 2000 RPA timber assessment. Gen. Tech. Rep. PNW-568. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 58 p. Miner, R. [In press.] The 100-year method for forecasting carbon sequestration in forest products in use. Mitigation and Adaptation Strategies for Global Change. Penman, J.; Gytarsky, M.; Hiraishi, T. [and others], eds. 2003. Good practice guidance for land use, land use change, and forestry. Hayama, Kanagawa, Japan: Institute for Global Environmental Strategies for the Intergovernmental Panel on Climate Change. 502 p. Row, C.; Phelps, R.B. 1996. Wood carbon flows and storage after timber harvest. In: Sampson, N.; Hair, D., eds. Forests and global change. Volume 2: Forest management opportunities for mitigating carbon emissions. Washington, DC: American Forests: 27- 58. Skog, K.E.; Nicholson, G.A. 1998. Carbon cycling through wood products: the role of wood and paper products in carbon sequestration. Forest Products Journal. 48(7/8): 75-83. Skog, K.E.; Pingoud, K.; Smith, J.E. 2004. A method countries can use to estimate changes in carbon stored in harvested wood products and the uncertainty of such estimates. Environmental Management. 33(Suppl. 1): S65-S73. Smith, J.E.; Heath, L.S. 2002. A model of forest floor carbon mass for United States forest types. Res. Pap. NE-722. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 37 p. Smith, J.E.; Heath, L.S. 2005. Land use change and forestry and related sections. In: Inventory of U.S. greenhouse gas emissions and sinks: 1990-2003. Washington, DC: U.S. Environmental Protection Agency: 231-239, Appendix 3.12. 20 Smith, J.E.; Heath, L.S.; Jenkins, J.C. 2003. Forest volume-to-biomass models and estimates of mass for live and standing dead trees of U.S. forests. Gen. Tech. Rep. NE-298. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 57 p. Smith, J.E.; Heath, L.S.; Woodbury, P.B. 2004a. Forest carbon sequestration and products storage. In: Bickel, Kathryn, ed. U.S. agriculture and forestry greenhouse gas inventory: 1990-2001. Tech. Bull. No. 1907. Washington, DC: U.S. Department of Agriculture, Office of Chief Economist: 80-93, Appendix C. Smith, J.E.; Heath, L.S.; Woodbury, P.B. 2004b. How to estimate forest carbon for large areas from inventory data. Journal of Forestry. 102: 25-31. Smith, James E.; Heath, Linda S.; Skog, Kenneth E.; Birdsey, Richard A. 2006. Methods for calculating forest ecosystem and harvested carbon, with standard estimates for forest types of the United States. Gen. Tech. Rep. NE-XXX. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. xx p. Smith, W.B.; Miles, P.D.; Vissage, J.S.; Pugh, S.A. 2004c. Forest resources of the United States, 2002. Gen. Tech. Rep. NC-241. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Research Station. 137 p. Turner, D.P.; Koerper, G.J.; Harmon, M.E.; Lee, J.J. 1995. A carbon budget for forests of the conterminous United States. Ecological Applications. 5: 421-436. U.S. Department of Agriculture, Forest Service. 2005. Forest inventory mapmaker, RPA tabler, and FIADB download files. http://ncrs2.fs.fed.us/4801/fiadb/index.htm. (2 December 2005). U.S. Department of Agriculture, Soil Conservation Service. 1991. State soil geographic (STATSGO) data base data use information. Misc. Publication Number 1492, USDA, Natural Resources Conservation Service, National Soil Survey Center, Fort Worth, TX. U.S. Department of Energy, Energy Information Administration. 2005. Voluntary reporting of greenhouse gases program. http://www.eia.doe.gov/oiaf/1605/frntvrgg.html. (2 December 2005). Wenger, K.F., ed. 1984. Forestry handbook, 2nd edition. New York: Society of American Foresters, John Wiley & Sons. 1335 p. West, T.O.; Marland, G.; King, A.; Post, W.M.; Jain, A.K.; Andrasko, K. 2004. Carbon management response curves: estimates of temporal soil carbon dynamics. Environmental Management. 33(4): 507-518. 21 1.8 Examples Example 1.1 – Obtain values for carbon stock and net stock change for stands of maple- beech-birch in the Northeast. Use Table 1.2 to determine values for live tree carbon stock at years 25 and 45 and calculate net stock change over the interval. Reading directly from the table, live tree carbon stocks are 53.2 and 87.8 t/ha for years 25 and 45, respectively. Net annual stock change in live tree carbon between year 25 and 45, which is from the difference in stocks divided by the length of the interval between stocks: Net annual stock change = (87.8 – 53.2) / 20 = 1.7 t/ha/yr The positive value for stock change indicates a net increase in carbon over the interval; this is consistent with the sign convention used for net stock change in this document. This tabular approach is applicable to all carbon pools in Appendices A, B, and C. Users must first classify the forest of interest and choose the most appropriate table. 22 Example 1.2 – Obtain an estimate of carbon stock when the value is not explicitly provided on a table, for stands of maple-beech-birch in the Northeast. Use Table 1.2 to calculate live tree carbon stock of a stand with volume of wood (growing-stock volume) of 150 m3/ha. This value is obtained by linearly interpolating between rows 7 and 8 of Table 1.2. The estimate of live tree carbon is between rows 7 and 8 because 150 m3/ha is also between those two rows, and live tree carbon is a function of volume (Fig. 1.2). Linear interpolation identifies a value for carbon stock between 101.1 and 113.1 t/ha that is linearly proportional to the position of 150 between 146.6 and 172.1 (from rows 7 and 8 of Table 1.2). Live tree carbon (if volume is 150 m3/ha) = (150.0 - 146.6) / (172.1 - 146.6) × (113.1 - 101.1) + 101.1 = 0.133 × 12.0 +101.1 = 102.7 t/ha The value 0.133 means the carbon stock is 13.3 percent of the distance between the two stocks listed on the table, 101.1 and 113.1 t/ha. 23 Example 1.3 – Modify a table to include independently obtained information about a forest carbon project In this example, assume you have a project with loblolly pine established after clearcut harvest on existing forest land in the South Central region. The volume yields (Wenger, 1984) are: Age Mean volume years m3/ha 0 0.0 10 30.6 15 122.6 20 187.9 25 238.9 30 277.9 The appropriate carbon table is Table A47, which is duplicated for this example. The goal is to construct a hybrid table from the new growth and yield estimates (columns 1-2) and the appropriate estimates for each of the carbon pools (columns 3-8). A47.— Regional estimates of timber volume and carbon stocks for loblolly and shortleaf pine stands on forest land after clearcut harvest in the South Central Mean carbon density Age Mean Volume Live tree Standing dead tree Under- story Down dead wood Forest floor Soil organic Total nonsoil years m3/hectare ------------------------------------- tonnes carbon/hectare----------------------------------- 0 0.0 0.0 0.0 4.2 9.2 12.2 41.9 25.6 5 0.0 10.8 0.7 4.7 7.7 6.5 41.9 30.3 10 19.1 23.1 1.3 3.9 6.8 6.4 41.9 41.5 15 36.7 32.4 1.6 3.5 6.2 7.5 41.9 51.2 20 60.4 42.2 1.8 3.3 5.9 8.7 41.9 61.9 25 85.5 52.0 2.0 3.1 5.8 9.8 41.9 72.8 30 108.7 59.6 2.1 3.0 5.8 10.7 41.9 81.2 35 131.2 66.6 2.3 2.9 5.9 11.5 41.9 89.1 40 152.3 73.1 2.3 2.9 6.0 12.2 41.9 96.4 45 172.3 79.0 2.4 2.8 6.1 12.7 41.9 103.1 50 191.4 84.7 2.5 2.8 6.4 13.2 41.9 109.5 55 208.4 89.6 2.6 2.7 6.5 13.7 41.9 115.1 60 223.9 94.0 2.6 2.7 6.7 14.1 41.9 120.1 65 238.4 98.1 2.7 2.6 7.0 14.4 41.9 124.8 70 252.9 102.2 2.7 2.6 7.2 14.7 41.9 129.4 75 264.6 105.5 2.7 2.6 7.3 15.0 41.9 133.1 80 277.1 108.9 2.8 2.6 7.6 15.2 41.9 137.0 24 To construct the modified table, copy the first two columns directly from the new yield table and then interpolate some of the carbon pool densities from Table A47. Estimates for live- and standing dead trees are dependent on growing-stock volume (as indicated in Fig. 1.2). These values can be determined by linear interpolation as described in Example 1.2. Similarly, understory and down dead wood stocks, which are dependent on the updated live tree carbon stocks (Fig. 1.2), can be determined by interpolation. For example, the value of down dead wood carbon stock in row two is based on linearly interpolating between rows three and four of Table A47, that is, down dead wood = (29.2 - 23.1) / (32.4 - 23.1) × (6.2 - 6.8) + 6.8 = 6.4 t/ha. Interpolation is not necessary for estimates of forest floor or soil organic carbon. Forest floor is a function of stand age, and soil organic carbon is 41.9 t/ha. The resulting modified defaults for South Central loblolly pine based on separately obtained growth and yield: Mean carbon density Age Mean volume Live tree Standing dead tree Under- story Down dead wood Forest floor Soil organic Total nonsoil years m3/ha ------------------------------------- tonnes carbon/hectare----------------------------------- 0 0.0 0.0 0.0 4.2 9.2 12.2 41.9 25.6 10 30.6 29.2 1.5 3.6 6.4 6.4 41.9 47.1 15 122.6 63.9 2.2 2.9 5.8 7.5 41.9 82.3 20 187.9 83.7 2.5 2.8 6.3 8.7 41.9 104.0 25 238.9 98.2 2.7 2.6 7.0 9.8 41.9 120.3 30 277.9 109.1 2.8 2.6 7.6 10.7 41.9 132.8 25 Example 1.4 – Calculate carbon in harvested wood products remaining in use at 15 years after harvest based on volume of growing stock at time of harvest Starting with an example from the Pacific Northwest, we will calculate the disposition of carbon in harvested wood products that are still in use at 15 years after harvest from the Douglas-fir forest described in Table C12. More specifically, we will show the steps involved to calculate that 53.3 t/ha of harvested carbon are in use at 15 years after harvest, starting from a harvested growing-stock volume of 718.8 m3/ha (Table C12). We use factors from Tables 1.4, 1.5, and 1.6. These calculations are land-based estimates of carbon in harvested wood products based on the “trees in forests” starting point identified in Figure 1.3. Additional details on expanding these calculations to other harvested wood categories within the table or to other forest types are in Appendix D. The sequence of steps required to determine carbon in use at year 15 are: 1) convert growing- stock volume to carbon mass according to four categories; 2) convert carbon in growing stock to carbon in roundwood; and 3) determine carbon remaining in products at the appropriate year. Step 1: We assume that an average harvest for a forest type group produces roundwood logs that can be classified as softwood or hardwood as well as saw logs and pulpwood. The conversion from volume of wood to carbon mass depends on the specific carbon content of wood. Factors in Table 1.4 are used to allocate the 718.8 m3/ha of growing-stock volume to four pools of carbon. For example, carbon in the softwood saw log part of growing-stock volume is the product of: growing-stock volume, the softwood fraction of growing-stock volume, the saw log fraction of softwood, softwood specific gravity, and the carbon fraction of wood fiber (0.5). The calculations from Table 1.4 are: Softwood saw log carbon in growing-stock volume = 718.8 × 0.959 × 0.914 × 0.440 × 0.5 = 138.61 t/ha Softwood pulpwood carbon in growing-stock volume = 718.8 × 0. 959 × (1 – 0.914) × 0.440 × 0.5 = 13.04 t/ha Hardwood saw log carbon in growing-stock volume = 718.8 × (1 – 0.959) × 0.415 × 0.426 × 0.5 = 2.61 t/ha Hardwood pulpwood carbon in growing-stock volume = 718.8 × (1 – 0.959) × (1 – 0.415) × 0.426 × 0.5 = 3.67 t/ha Thus, total carbon stock in 718.8 m3/ha of growing-stock volume is 183.60 t/ha. Step 2: We need to represent carbon in these four categories in terms of carbon in roundwood, which excludes bark and fuelwod. However, not all growing-stock volume becomes roundwood, and some roundwood is from non-growing stock sources. Factors in Table 1.5 are used to obtain carbon in roundwood. For example, carbon in roundwood is the product of: carbon in growing- stock volume, the fraction of growing-stock volume that is roundwood, and the ratio of roundwood to growing-stock volume that is roundwood. The calculations from Table 1.5 are: Softwood saw log carbon in roundwood = 138.61 × 0.929 × 0.965 = 124.26 t/ha Softwood pulpwood carbon in roundwood = 13.04 × 0.929 × 1.099 = 13.31 t/ha Hardwood saw log carbon in roundwood = 2.61 × 0.947 × 0.721 = 1.78 t/ha Hardwood pulpwood carbon in roundwood = 3.67 × 0.947 × 0.324 = 1.13 t/ha 26 Thus, total carbon stock in roundwood is 148.36 t/ha. Step 3: The disposition of carbon in harvested wood products is described by Table 1.6, which allocates carbon according to region, roundwood category, and years since harvest and processing. The allocation factors for product in use at year 15 for Pacific Northwest, West apply here. The two hardwood categories are pooled in this region. The calculation for carbon density of products in use is the sum of the products of roundwood carbon and the corresponding allocation factor, these are: Carbon in products in use at year 15 = (124.26 × 0.423) + (13.31 × 0.020) + ((1.78 + 1.03) × 0.174) = 53.33 t/ha. 27 Example 1.5 – Calculate the disposition of carbon in harvested wood products at 100 years after harvest and processing from roundwood data Using Table 1.6, assume that a harvest in the Northeast produced 2,000 t dry weight of roundwood. This represents 1,000 t of carbon because wood is assumed to be 50 percent carbon. The roundwood was harvested in the following proportions: 79 t carbon as softwood sawtimber, 51 t as softwood pulpwood, 465 t of hardwood sawtimber, and 405 t of hardwood pulpwood. Also assume that these quantities represent roundwood without bark and exclude fuelwood; thus Table 1.6 is the correct choice to calculate the disposition of carbon. The four roundwood categories are allocated to the classifications for the disposition of carbon in wood products by the appropriate factors for 100 years after production from the Northeast portion of Table 1.6. Total carbon in use = sum of four fractions = (79 × 0.095) + (51 × 0.006) + (465 × 0.035) + (405 × 0.103) = 65.80 t Total carbon in landfills = sum of four fractions = (79 × 0.223) + (51 × 0.084) + (465 × 0.281) + (405 × 0.158) = 216.56 t Total carbon emitted with energy recapture = sum of four fractions = (79 × 0.338) + (51 × 0.510) + (465 × 0.387) + (405 × 0.336) = 368.75 t Total carbon emitted without energy recapture = sum of four fractions = (79 × 0.344) + (51 × 0.400) + (465 × 0.296) + (405 × 0.403) = 348.43 t Total carbon in roundwood after 100 years is the sum of the four pools. Note that the total in this example is 999.5 t and not the 1,000 t we started with; this is due to rounding. 28 Example 1.6 – Calculate stocks of carbon in harvested wood products based on having primary wood products data such as products from a mill Given the information on softwood lumber and softwood plywood produced from 2000 to 2003 (in the following tabulation) we use Tables 1.7, 1.8, and 1.9 to calculate: 1) carbon in the primary products, 2) the accumulation of carbon stocks over a period of 4 years, and 3) total carbon stocks after 100 years. Note that Tables 1.8 and 1.9 provide the fraction of primary product remaining for a given number of years after processing; this example assumes that harvest and processing are at the beginning of each year (2000-2003) and estimates for the amount remaining apply to the end of each year. This is an application of calculating the disposition of carbon in harvested wood based on quantities of primary wood products, as described in Figure 1.3. Step 1: Determine initial carbon stocks for two primary products based on given quantities produced each year over the 4-year period by using factors from Table 1.7. For example, 93,000 MBF softwood lumber × 0.443 = 41,199 t carbon. The initial carbon stocks for two primary products, softwood lumber and softwood plywood: Quantity of primary product Carbon stock Year Softwood lumber Softwood plywood Softwood lumber Softwood plywood thousand board feet thousand square feet, 3/8-inch basis tonnes carbon tonnes carbon 2000 93,000 183,000 41,199 43,188 2001 85,000 175,000 37,655 41,300 2002 95,000 170,000 42,085 40,120 2003 100,000 173,000 44,300 40,828 Step 2: Calculate carbon stocks in end uses and landfills for each product for each year after production for the period 2000-2003 based on inputs of wood harvested and processed in each year. Use Tables 1.8 and 1.9 to determine stocks for each year since processing. Note that each of the 20 intermediate values in the following tabulation is based on the sum of carbon contributed from softwood lumber and softwood plywood. For example, the carbon stocks of primary products produced in 2001 are 37,655 t of softwood lumber and 41,300 t of softwood plywood. From this, a total of 3,820 t are in landfills at the end of 2003 (after 3 years). The quantity is calculated as: 3,820 t = (37,655 × 0.051) + (41,300 × 0.046). Disposition of carbon in primary wood products over four years: Carbon in end uses at end of: Carbon in landfills at end of: Year of production 2000 2001 2002 2003 2000 2001 2002 2003 2000 82,238 80,130 78,150 76,255 1,433 2,824 4,088 5,352 2001 76,947 74,977 73,127 1,339 2,640 3,820 2002 80,106 78,049 1,399 2,757 2003 82,952 1,451 Total 82,238 157,078 233,233 310,382 1,433 4,163 8,127 13,379 29 Thus, total carbon stocks for the end of 2002 are 241,360 t, with 233,233 t in end uses and 8,127 t in landfills. The balance of the cumulative total carbon in products from 2000 through 2002 has been emitted to the atmosphere, that is, 245,547 t initially in primary products minus the 241,360 t sequestered equals 4,187 t emitted from the primary products by 2002. Step 3: Calculate carbon remaining in end uses or in landfills at 100 years after each of the harvest years. The estimates are based on initial stocks of carbon in each primary product multiplied by the respective fraction remaining as obtained from Tables 1.8 and 1.9. For example, carbon in primary product from harvest and processing in 2000 and in use at 100 years is 20,222 t = (41,199 × 0.234) + (43,188 × 0.245). Carbon in: Year of production End uses Landfills --------------------tonnes carbon------------------ 2000 20,222 33,961 2001 18,930 31,770 2002 19,677 33,092 2003 20,369 34,273 Total 79,198 133,096 Thus, of the 245,547 t of carbon in primary products produced from 2000 through 2002, 24 percent remain sequestered in products in use, 40 percent in landfills, and 36 percent emitted to the atmosphere. 30 1.9 Tables Table 1.1.—Classification of carbon in forest ecosystems and in harvested wood Forest ecosystem carbon pools Live trees Live trees with diameter at breast height (d.b.h.) of at least 2.5 cm (1 inch), including carbon mass of coarse roots (greater than 0.2 to 0.5 cm, published distinctions between fine and coarse roots are not always clear), stems, branches, and foliage. Standing dead trees Standing dead trees with d.b.h. of at least 2.5 cm, including carbon mass of coarse roots, stems, and branches. Understory vegetation Live vegetation that includes the roots, stems, branches, and foliage of seedlings (trees less than 2.5 cm d.b.h.), shrubs, and bushes. Down dead wood Woody material that includes logging residue and other coarse dead wood on the ground and larger than 7.5 cm in diameter, and stumps and coarse roots of stumps. Forest floor Organic material on the floor of the forest that includes fine woody debris up to 7.5 cm in diameter, tree litter, humus, and fine roots in the organic forest floor layer above mineral soil. Soil organic carbon Belowground carbon without coarse roots, but including fine roots and all other organic carbon not included in other pools, to a depth of 1 meter. Categories for disposition of carbon in harvested wood Products in use End-use products that have not been discarded or otherwise destroyed, examples include residential and nonresidential construction, wooden containers, and paper products. Landfills Discarded wood and paper placed in landfills where most carbon is stored long-term and only a small portion of the material is assumed to degrade, at a slow rate. Emitted with energy capture Combustion of wood products with concomitant energy capture as carbon is emitted to the atmosphere. Emitted without energy capture Carbon in harvested wood emitted to the atmosphere through combustion or decay without concomitant energy recapture. 31 Table 1.2.—Example reforestation table with regional estimates of timber volume and carbon stocks on forest land after clearcut harvest for maple-beech-birch stands in the Northeast Mean carbon density Age Mean volume Live tree Standing dead tree Under- story Down dead wood Forest floor Soil organic Total nonsoil years m3/hectare -------------------------------------tonnes carbon/ hectare------------------------------------- 0 0.0 0.0 0.0 2.1 32.0 27.7 69.6 61.8 5 0.0 7.4 0.7 2.1 21.7 20.3 69.6 52.2 15 28.0 31.8 3.2 1.9 11.5 16.3 69.6 64.7 25 58.1 53.2 5.3 1.8 7.8 17.6 69.6 85.7 35 89.6 72.8 6.0 1.7 6.9 20.3 69.6 107.8 45 119.1 87.8 6.6 1.7 7.0 23.0 69.6 126.0 55 146.6 101.1 7.0 1.7 7.5 25.3 69.6 142.7 65 172.1 113.1 7.4 1.7 8.2 27.4 69.6 157.7 75 195.6 123.8 7.7 1.7 8.8 29.2 69.6 171.2 85 217.1 133.5 7.9 1.7 9.5 30.7 69.6 183.2 95 236.6 142.1 8.1 1.7 10.1 32.0 69.6 193.9 105 254.1 149.7 8.3 1.6 10.6 33.1 69.6 203.4 115 269.7 156.3 8.5 1.6 11.1 34.2 69.6 211.7 125 283.2 162.1 8.6 1.6 11.5 35.1 69.6 218.8 32 Table 1.3.—Example harvest scenario table with regional estimates of timber volume, carbon stocks, and carbon in harvested wood products on forest land after clearcut harvest for maple-beech-birch stands in the Northeast Mean volume Mean carbon density Age Inventory Harvested Live tree Standing dead tree Under- story Down dead wood Forest floor Soil organic Products in use In landfills Emitted with energy capture Emitted without energy capture Emitted at harvest years --------- m3/hectare --------- ---------------------------------------------------------------tonnes carbon/hectare-------------------------------------------------------- 0 0.0 0.0 0.0 2.1 0.0 0.0 52.2 5 0.0 7.4 0.7 2.1 0.5 4.2 52.3 15 28.0 31.8 3.2 1.9 2.3 10.8 53.7 25 58.1 53.2 5.3 1.8 3.8 15.8 56.0 35 89.6 72.8 6.0 1.7 5.2 19.7 58.9 45 119.1 87.8 6.6 1.7 6.2 22.7 61.8 55 146.6 101.1 7.0 1.7 7.2 25.3 64.4 65 0.0 172.1 0.0 0.0 2.1 32.0 27.7 66.3 34.5 0.0 39.7 14.1 7.5 5 0.0 7.4 0.7 2.1 21.7 20.3 67.1 22.9 4.7 43.1 17.5 15 28.0 31.8 3.2 1.9 11.5 16.3 68.2 13.2 8.1 46.2 20.7 25 58.1 53.2 5.3 1.8 7.8 17.6 68.9 10.3 8.8 47.1 22.0 35 89.6 72.8 6.0 1.7 6.9 20.3 69.2 8.7 9.1 47.5 22.9 45 119.1 87.8 6.6 1.7 7.0 23.0 69.4 7.6 9.4 47.8 23.5 55 146.6 101.1 7.0 1.7 7.5 25.3 69.5 6.7 9.6 47.9 24.0 65 0.0 172.1 0.0 0.0 2.1 32.0 27.7 69.5 40.4 9.8 87.8 38.5 7.7 NOTE: Emitted column is shown as positive values so that all nonsoil columns can be summed to check totals. 33 Table 1.4.—Factors to calculate carbon in growing stock volume: softwood fraction, sawtimber-size fraction, and specific gravity by region and forest type groupa Region Forest type Fraction of growing- stock volume that is softwoodb Fraction of softwood growing- stock volume that is sawtimber- sizec Fraction of hardwood growing- stock volume that is sawtimber- sizec Specific gravityd of softwoods Specific gravityd of hardwoods Aspen-birch 0.247 0.439 0.330 0.353 0.428 Elm-ash-cottonwood 0.047 0.471 0.586 0.358 0.470 Maple-beech-birch 0.132 0.604 0.526 0.369 0.518 Oak-hickory 0.039 0.706 0.667 0.388 0.534 Oak-pine 0.511 0.777 0.545 0.371 0.516 Spruce-fir 0.870 0.508 0.301 0.353 0.481 Northeast White-red-jack pine 0.794 0.720 0.429 0.361 0.510 Aspen-birch 0.157 0.514 0.336 0.351 0.397 Elm-ash-cottonwood 0.107 0.468 0.405 0.335 0.460 Maple-beech-birch 0.094 0.669 0.422 0.356 0.496 Oak-hickory 0.042 0.605 0.473 0.369 0.534 Spruce-fir 0.876 0.425 0.276 0.344 0.444 Northern Lake States White-red-jack pine 0.902 0.646 0.296 0.389 0.473 Elm-ash-cottonwood 0.004 0.443 0.563 0.424 0.453 Loblolly-shortleaf pine 0.843 0.686 0.352 0.468 0.544 Maple-beech-birch 0.010 0.470 0.538 0.437 0.508 Oak-hickory 0.020 0.497 0.501 0.448 0.565 Oak-pine 0.463 0.605 0.314 0.451 0.566 Northern Prairie States Ponderosa pine 0.982 0.715 0.169 0.381 0.473 Douglas-fir 0.989 0.896 0.494 0.429 0.391 Fir-spruce-m.hemlock 0.994 0.864 0.605 0.370 0.361 Lodgepole pine 0.992 0.642 0.537 0.380 0.345 Pacific Northwest, East Ponderosa pine 0.996 0.906 0.254 0.385 0.513 Alder-maple 0.365 0.895 0.635 0.402 0.385 Douglas-fir 0.959 0.914 0.415 0.440 0.426 Fir-spruce-m.hemlock 0.992 0.905 0.296 0.399 0.417 Pacific Northwest, West Hemlock-Sitka spruce 0.956 0.909 0.628 0.405 0.380 Mixed conifer 0.943 0.924 0.252 0.394 0.521 Douglas-fir 0.857 0.919 0.320 0.429 0.483 Fir-spruce-m.hemlock 1.000 0.946 0.000 0.372 0.510 Ponderosa Pine 0.997 0.895 0.169 0.380 0.510 Pacific Southwest Redwood 0.925 0.964 0.468 0.376 0.449 Douglas-fir 0.993 0.785 0.353 0.428 0.370 Fir-spruce-m.hemlock 0.999 0.753 0.000 0.355 0.457 Hemlock-Sitka spruce 0.972 0.735 0.596 0.375 0.441 Lodgepole pine 0.999 0.540 0.219 0.383 0.391 Rocky Mountain, North Ponderosa pine 0.999 0.816 0.000 0.391 0.374 Continued 34 Table 1.4.—continued Region Forest type Fraction of growing- stock volume that is softwoodb Fraction of softwood growing- stock volume that is sawtimber- sizec Fraction of hardwood growing- stock volume that is sawtimber- sizec Specific gravityd of softwoods Specific gravityd of hardwoods Aspen-birch 0.297 0.766 0.349 0.355 0.350 Douglas-fir 0.962 0.758 0.230 0.431 0.350 Fir-spruce-m.hemlock 0.958 0.770 0.367 0.342 0.350 Lodgepole pine 0.981 0.607 0.121 0.377 0.350 Rocky Mountain, South Ponderosa pine 0.993 0.773 0.071 0.383 0.386 Elm-ash-cottonwood 0.030 0.817 0.551 0.433 0.499 Loblolly-shortleaf pine 0.889 0.556 0.326 0.469 0.494 Longleaf-slash pine 0.963 0.557 0.209 0.536 0.503 Oak-gum-cypress 0.184 0.789 0.500 0.441 0.484 Oak-hickory 0.070 0.721 0.551 0.438 0.524 Southeast Oak-pine 0.508 0.746 0.425 0.462 0.516 Elm-ash-cottonwood 0.044 0.787 0.532 0.427 0.494 Loblolly-shortleaf pine 0.880 0.653 0.358 0.470 0.516 Longleaf-slash pine 0.929 0.723 0.269 0.531 0.504 Oak-gum-cypress 0.179 0.830 0.589 0.440 0.513 Oak-hickory 0.057 0.706 0.534 0.451 0.544 South Central Oak-pine 0.512 0.767 0.432 0.467 0.537 Pinyon-juniper 0.986 0.783 0.042 0.422 0.620 Tanoak-laurel 0.484 0.909 0.468 0.430 0.459 Western larch 0.989 0.781 0.401 0.433 0.430 Western oak 0.419 0.899 0.206 0.416 0.590 Weste Western white pine 1.000 0.838 0.000 0.376 -- -- = no hardwood trees in this type in this region. aEstimates based on survey data for the conterminous United States from USDA Forest Service, Forest Inventory and Analysis Program’s database of forest surveys (FIADB; USDA For. Serv. 2005) and include growing stock on timberland stands classified as medium- or large-diameter stands. Proportions are based on volume of growing-stock trees. bTo calculate fraction in hardwood, subtract fraction in softwood from 1. cSoftwood sawtimber are trees at least 22.9 cm (9 in) d.b.h., hardwood sawtimber is at least 27.9 cm (11 in) d.b.h. To calculate fraction in less-than-sawtimber-size trees, subtract fraction in sawtimber from 1. Trees less than sawtimber-size are at least 12.7 cm (5 in) d.b.h. dAverage wood specific gravity is the density of wood divided by the density of water based on wood dry mass associated with green tree volume. eWest represents an average over all western regions for these forest types. 35 Table 1.5.—Regional factors to estimate carbon in roundwood logs, bark on logs, and fuelwood Regiona Timber type Roundwood category Ratio of roundwood to growing- stock volume that is roundwoodb Ratio of carbon in bark to carbon in woodc Fraction of growing- stock volume that is roundwoodd Ratio of fuelwood to growing- stock volume that is roundwoodb Saw log 0.991 0.182 SW Pulpwood 3.079 0.185 0.948 0.136 Saw log 0.927 0.199 Northeast HW Pulpwood 2.177 0.218 0.879 0.547 Saw log 0.985 0.182 SW Pulpwood 1.285 0.185 0.931 0.066 Saw log 0.960 0.199 North Central HW Pulpwood 1.387 0.218 0.831 0.348 Saw log 0.965 0.181 SW Pulpwood 1.099 0.185 0.929 0.096 Saw log 0.721 0.197 Pacific Coast HW Pulpwood 0.324 0.219 0.947 0.957 Saw log 0.994 0.181 SW Pulpwood 2.413 0.185 0.907 0.217 Saw log 0.832 0.201 Rocky Mountain HW Pulpwood 1.336 0.219 0.755 3.165 Saw log 0.990 0.182 SW Pulpwood 1.246 0.185 0.891 0.019 Saw log 0.832 0.198 South HW Pulpwood 1.191 0.218 0.752 0.301 SW=Softwood, HW=Hardwood. aNorth Central includes the Northern Prairie States and the Northern Lake States; Pacific Coast includes the Pacific Northwest (West and East) and the Pacific Southwest; Rocky Mountain includes Rocky Mountain, North and South; and South includes the Southeast and South Central. bValues and classifications are based on data in Tables 2.2, 3.2, 4.2, 5.2, and 6.2 of Johnson (2001). cRatios are calculated from carbon mass based on biomass component equations in Jenkins and others (2003) applied to all live trees identified as growing stock on timberland stands classified as medium- or large-diameter stands in the survey data for the conterminous United States from USDA Forest Service, Forest Inventory and Analysis Program’s database of forest surveys (FIADB; USDA For. Serv. 2005, Alerich and others 2005). Carbon mass is calculated for boles from stump to 4-inch top, outside diameter. dValues and classifications are based on data in Tables 2.9, 3.9, 4.9, 5.9, and 6.9 of Johnson (2001). 36 Table 1.6.—Average disposition patterns of carbon as fractions in roundwood by region and roundwood category; factors assume no bark on roundwood and exclude fuelwood Northeast, Softwood Saw log Pulpwood Year after production In use Landfill Energy Emitted without energy In use Landfill Energy Emitted without energy 0 0.569 0.000 0.240 0.190 0.513 0.000 0.306 0.181 1 0.542 0.014 0.246 0.197 0.436 0.025 0.334 0.204 2 0.517 0.027 0.252 0.203 0.372 0.046 0.359 0.223 3 0.495 0.039 0.257 0.209 0.317 0.063 0.381 0.239 4 0.474 0.050 0.262 0.214 0.271 0.077 0.399 0.253 5 0.455 0.060 0.266 0.219 0.232 0.088 0.415 0.265 6 0.438 0.069 0.270 0.223 0.197 0.098 0.429 0.276 7 0.422 0.078 0.274 0.227 0.167 0.106 0.441 0.286 8 0.406 0.085 0.277 0.231 0.139 0.113 0.452 0.296 9 0.392 0.093 0.281 0.235 0.114 0.118 0.463 0.305 10 0.379 0.099 0.284 0.238 0.093 0.123 0.472 0.313 15 0.326 0.126 0.296 0.252 0.037 0.128 0.497 0.338 20 0.288 0.144 0.304 0.264 0.021 0.122 0.505 0.352 25 0.259 0.158 0.311 0.273 0.016 0.114 0.509 0.362 30 0.234 0.168 0.316 0.281 0.014 0.107 0.510 0.369 35 0.214 0.176 0.321 0.289 0.013 0.102 0.510 0.376 40 0.197 0.183 0.324 0.296 0.012 0.098 0.510 0.381 45 0.182 0.189 0.327 0.302 0.011 0.094 0.510 0.385 50 0.169 0.194 0.330 0.307 0.010 0.092 0.510 0.388 55 0.158 0.198 0.332 0.312 0.009 0.090 0.510 0.391 60 0.148 0.202 0.333 0.317 0.009 0.088 0.510 0.393 65 0.139 0.205 0.335 0.321 0.008 0.087 0.510 0.395 70 0.131 0.208 0.336 0.325 0.008 0.086 0.510 0.396 75 0.124 0.211 0.337 0.328 0.007 0.086 0.510 0.397 80 0.117 0.214 0.337 0.332 0.007 0.085 0.510 0.398 85 0.111 0.216 0.338 0.335 0.007 0.085 0.510 0.399 90 0.106 0.219 0.338 0.338 0.006 0.085 0.510 0.399 95 0.100 0.221 0.338 0.341 0.006 0.084 0.510 0.400 100 0.095 0.223 0.338 0.344 0.006 0.084 0.510 0.400 Continued 37 Table 1.6.—continued Northeast, Hardwood Saw log Pulpwood Year after production In use Landfill Energy Emitted without energy In use Landfill Energy Emitted without energy 0 0.614 0.000 0.237 0.149 0.650 0.000 0.185 0.166 1 0.572 0.025 0.246 0.157 0.590 0.021 0.202 0.186 2 0.534 0.048 0.255 0.163 0.539 0.039 0.218 0.203 3 0.500 0.067 0.263 0.170 0.496 0.054 0.232 0.218 4 0.469 0.085 0.271 0.175 0.459 0.067 0.244 0.231 5 0.440 0.102 0.278 0.180 0.426 0.078 0.254 0.242 6 0.415 0.116 0.284 0.185 0.398 0.087 0.263 0.253 7 0.391 0.129 0.290 0.190 0.372 0.095 0.271 0.262 8 0.369 0.141 0.295 0.194 0.349 0.102 0.279 0.271 9 0.349 0.152 0.300 0.198 0.327 0.108 0.286 0.279 10 0.331 0.162 0.305 0.202 0.308 0.114 0.292 0.286 15 0.260 0.198 0.324 0.218 0.252 0.127 0.310 0.311 20 0.212 0.221 0.338 0.229 0.226 0.130 0.319 0.325 25 0.178 0.235 0.348 0.239 0.211 0.131 0.323 0.335 30 0.152 0.245 0.356 0.247 0.198 0.132 0.327 0.343 35 0.131 0.253 0.362 0.254 0.187 0.133 0.329 0.351 40 0.115 0.258 0.368 0.260 0.178 0.134 0.331 0.357 45 0.102 0.262 0.372 0.265 0.169 0.136 0.333 0.363 50 0.090 0.265 0.375 0.269 0.160 0.138 0.334 0.368 55 0.081 0.268 0.378 0.273 0.153 0.140 0.335 0.373 60 0.073 0.270 0.380 0.277 0.146 0.142 0.335 0.377 65 0.066 0.272 0.382 0.280 0.139 0.144 0.336 0.381 70 0.059 0.274 0.384 0.283 0.133 0.146 0.336 0.385 75 0.054 0.275 0.385 0.286 0.127 0.148 0.336 0.388 80 0.049 0.277 0.386 0.288 0.122 0.150 0.336 0.392 85 0.045 0.278 0.386 0.290 0.117 0.152 0.336 0.395 90 0.041 0.279 0.387 0.293 0.112 0.154 0.336 0.398 95 0.038 0.280 0.387 0.294 0.108 0.156 0.336 0.400 100 0.035 0.281 0.387 0.296 0.103 0.158 0.336 0.403 Continued 38 Table 1.6.—continued North Central, Softwood Saw log Pulpwood Year after production In use Landfill Energy Emitted without energy In use Landfill Energy Emitted without energy 0 0.630 0.000 0.249 0.121 0.514 0.000 0.305 0.180 1 0.599 0.016 0.257 0.127 0.438 0.025 0.332 0.204 2 0.570 0.032 0.265 0.133 0.374 0.046 0.356 0.223 3 0.544 0.045 0.272 0.138 0.320 0.063 0.377 0.240 4 0.520 0.058 0.279 0.143 0.274 0.077 0.396 0.254 5 0.499 0.069 0.285 0.147 0.235 0.088 0.411 0.266 6 0.478 0.080 0.291 0.151 0.200 0.097 0.425 0.278 7 0.459 0.090 0.296 0.154 0.170 0.105 0.437 0.288 8 0.442 0.099 0.301 0.158 0.143 0.112 0.448 0.297 9 0.425 0.107 0.306 0.162 0.118 0.118 0.458 0.306 10 0.410 0.115 0.310 0.165 0.096 0.122 0.467 0.314 15 0.349 0.145 0.327 0.178 0.041 0.127 0.491 0.340 20 0.306 0.166 0.339 0.189 0.024 0.121 0.500 0.354 25 0.272 0.181 0.348 0.198 0.020 0.113 0.503 0.364 30 0.245 0.193 0.356 0.206 0.018 0.107 0.504 0.372 35 0.222 0.202 0.362 0.213 0.016 0.101 0.504 0.378 40 0.203 0.210 0.367 0.220 0.015 0.097 0.504 0.383 45 0.187 0.216 0.371 0.226 0.014 0.094 0.504 0.387 50 0.173 0.221 0.374 0.231 0.014 0.091 0.504 0.391 55 0.161 0.225 0.377 0.236 0.013 0.089 0.504 0.393 60 0.151 0.229 0.379 0.241 0.012 0.088 0.504 0.395 65 0.141 0.233 0.381 0.245 0.012 0.087 0.504 0.397 70 0.133 0.236 0.382 0.249 0.011 0.086 0.504 0.399 75 0.125 0.239 0.383 0.253 0.010 0.086 0.504 0.400 80 0.118 0.241 0.384 0.257 0.010 0.085 0.504 0.401 85 0.112 0.244 0.385 0.260 0.009 0.085 0.504 0.401 90 0.106 0.246 0.385 0.263 0.009 0.085 0.504 0.402 95 0.101 0.248 0.385 0.266 0.009 0.085 0.504 0.402 100 0.096 0.250 0.385 0.269 0.008 0.084 0.504 0.403 Continued 39 Table 1.6.—continued North Central, Hardwood Saw log Pulpwood Year after production In use Landfill Energy Emitted without energy In use Landfill Energy Emitted without energy 0 0.585 0.000 0.253 0.162 0.685 0.000 0.165 0.150 1 0.544 0.024 0.262 0.170 0.630 0.020 0.181 0.169 2 0.507 0.046 0.271 0.177 0.582 0.038 0.196 0.184 3 0.473 0.065 0.279 0.183 0.541 0.052 0.209 0.198 4 0.443 0.082 0.286 0.189 0.506 0.064 0.219 0.210 5 0.416 0.097 0.293 0.194 0.476 0.075 0.229 0.220 6 0.391 0.111 0.299 0.199 0.448 0.084 0.237 0.230 7 0.368 0.124 0.305 0.203 0.424 0.092 0.245 0.239 8 0.347 0.135 0.310 0.208 0.401 0.099 0.252 0.247 9 0.328 0.146 0.315 0.212 0.381 0.106 0.259 0.255 10 0.310 0.155 0.320 0.216 0.362 0.111 0.265 0.262 15 0.242 0.189 0.338 0.231 0.306 0.127 0.282 0.285 20 0.197 0.210 0.350 0.243 0.278 0.132 0.291 0.299 25 0.165 0.224 0.360 0.252 0.259 0.136 0.296 0.309 30 0.140 0.233 0.367 0.260 0.244 0.138 0.300 0.317 35 0.121 0.239 0.373 0.267 0.231 0.141 0.303 0.325 40 0.106 0.244 0.378 0.272 0.219 0.144 0.306 0.331 45 0.093 0.248 0.381 0.278 0.208 0.147 0.308 0.337 50 0.083 0.251 0.384 0.282 0.198 0.150 0.309 0.343 55 0.074 0.253 0.387 0.286 0.189 0.153 0.311 0.348 60 0.066 0.255 0.389 0.290 0.180 0.156 0.312 0.353 65 0.060 0.257 0.390 0.293 0.172 0.159 0.313 0.357 70 0.054 0.259 0.391 0.296 0.164 0.161 0.313 0.361 75 0.049 0.260 0.392 0.299 0.157 0.164 0.314 0.365 80 0.045 0.261 0.393 0.301 0.150 0.167 0.314 0.368 85 0.041 0.262 0.393 0.304 0.144 0.170 0.315 0.372 90 0.038 0.263 0.393 0.306 0.138 0.172 0.315 0.375 95 0.035 0.264 0.393 0.308 0.133 0.175 0.315 0.378 100 0.032 0.265 0.393 0.309 0.127 0.177 0.315 0.381 Continued 40 Table 1.6.—continued Pacific Northwest, East, Softwood All Year after production In use Landfill Energy Emitted without energy 0 0.637 0.000 0.197 0.166 1 0.601 0.016 0.207 0.176 2 0.569 0.031 0.215 0.185 3 0.541 0.043 0.223 0.192 4 0.516 0.055 0.230 0.199 5 0.494 0.065 0.236 0.205 6 0.473 0.074 0.242 0.211 7 0.454 0.083 0.247 0.216 8 0.437 0.090 0.251 0.221 9 0.420 0.098 0.256 0.226 10 0.405 0.104 0.260 0.231 15 0.351 0.127 0.274 0.248 20 0.315 0.143 0.283 0.260 25 0.287 0.154 0.289 0.270 30 0.264 0.163 0.294 0.279 35 0.245 0.170 0.298 0.287 40 0.228 0.177 0.301 0.294 45 0.213 0.182 0.304 0.301 50 0.199 0.188 0.306 0.307 55 0.187 0.192 0.308 0.313 60 0.176 0.196 0.309 0.318 65 0.166 0.200 0.310 0.323 70 0.157 0.204 0.311 0.328 75 0.149 0.207 0.311 0.333 80 0.141 0.210 0.312 0.337 85 0.134 0.213 0.312 0.341 90 0.128 0.216 0.312 0.345 95 0.121 0.219 0.312 0.348 100 0.116 0.221 0.312 0.351 Continued 41 Table 1.6.—continued Pacific Northwest, West, Softwoods Saw log Pulpwood Year after production In use Landfill Energy Emitted without energy In use Landfill Energy Emitted without energy 0 0.740 0.000 0.125 0.135 0.500 0.000 0.352 0.148 1 0.703 0.018 0.134 0.144 0.422 0.026 0.382 0.170 2 0.670 0.035 0.141 0.153 0.357 0.047 0.409 0.187 3 0.640 0.050 0.148 0.161 0.301 0.064 0.433 0.202 4 0.613 0.064 0.154 0.169 0.254 0.078 0.453 0.215 5 0.589 0.076 0.160 0.176 0.215 0.089 0.471 0.226 6 0.566 0.088 0.165 0.182 0.180 0.098 0.486 0.236 7 0.545 0.098 0.169 0.188 0.150 0.106 0.499 0.245 8 0.525 0.108 0.174 0.194 0.121 0.112 0.512 0.254 9 0.506 0.117 0.178 0.199 0.096 0.118 0.523 0.262 10 0.489 0.125 0.182 0.204 0.075 0.122 0.533 0.270 15 0.423 0.157 0.196 0.224 0.020 0.127 0.559 0.295 20 0.376 0.179 0.206 0.239 0.004 0.119 0.567 0.309 25 0.340 0.195 0.213 0.252 0.001 0.110 0.569 0.319 30 0.310 0.208 0.219 0.263 0.000 0.103 0.569 0.327 35 0.284 0.218 0.224 0.273 0.000 0.097 0.569 0.334 40 0.263 0.227 0.228 0.282 0.000 0.092 0.569 0.339 45 0.244 0.234 0.232 0.290 0.000 0.088 0.569 0.342 50 0.228 0.240 0.234 0.298 0.000 0.085 0.569 0.345 55 0.213 0.246 0.237 0.305 0.000 0.083 0.569 0.348 60 0.200 0.251 0.238 0.311 0.000 0.081 0.569 0.349 65 0.188 0.255 0.240 0.317 0.000 0.080 0.569 0.351 70 0.178 0.259 0.240 0.322 0.000 0.079 0.569 0.352 75 0.168 0.263 0.241 0.328 0.000 0.078 0.569 0.353 80 0.159 0.267 0.242 0.332 0.000 0.077 0.569 0.353 85 0.151 0.270 0.242 0.337 0.000 0.077 0.569 0.354 90 0.143 0.273 0.242 0.341 0.000 0.076 0.569 0.354 95 0.136 0.276 0.242 0.345 0.000 0.076 0.569 0.355 100 0.130 0.279 0.242 0.349 0.000 0.076 0.569 0.355 Continued 42 Table 1.6.—continued Pacific Northwest, West, Hardwood Pacific Southwest, Softwood All All Year after production In use Landfill Energy Emitted without energy In use Landfill Energy Emitted without energy 0 0.531 0.000 0.288 0.181 0.675 0.000 0.170 0.156 1 0.481 0.021 0.305 0.193 0.637 0.018 0.180 0.166 2 0.438 0.040 0.319 0.204 0.602 0.034 0.189 0.175 3 0.400 0.055 0.332 0.213 0.572 0.048 0.197 0.183 4 0.367 0.069 0.343 0.221 0.545 0.061 0.204 0.191 5 0.338 0.081 0.352 0.229 0.521 0.072 0.210 0.197 6 0.312 0.091 0.361 0.235 0.498 0.082 0.216 0.204 7 0.289 0.100 0.369 0.241 0.478 0.092 0.221 0.209 8 0.268 0.109 0.377 0.247 0.458 0.101 0.226 0.215 9 0.248 0.116 0.383 0.252 0.440 0.109 0.231 0.220 10 0.231 0.122 0.390 0.257 0.424 0.116 0.235 0.225 15 0.174 0.142 0.409 0.275 0.363 0.143 0.250 0.243 20 0.143 0.152 0.420 0.285 0.323 0.161 0.260 0.257 25 0.122 0.157 0.427 0.294 0.292 0.173 0.268 0.267 30 0.107 0.160 0.432 0.301 0.266 0.183 0.273 0.277 35 0.095 0.162 0.436 0.306 0.245 0.192 0.278 0.285 40 0.085 0.164 0.440 0.312 0.226 0.198 0.282 0.293 45 0.076 0.166 0.442 0.316 0.210 0.204 0.285 0.300 50 0.069 0.167 0.444 0.320 0.196 0.210 0.288 0.306 55 0.062 0.169 0.445 0.324 0.184 0.214 0.290 0.312 60 0.057 0.170 0.446 0.327 0.173 0.218 0.292 0.317 65 0.052 0.171 0.447 0.330 0.162 0.222 0.293 0.322 70 0.048 0.172 0.447 0.333 0.153 0.226 0.294 0.327 75 0.044 0.173 0.447 0.336 0.145 0.229 0.295 0.331 80 0.040 0.174 0.448 0.338 0.137 0.232 0.296 0.335 85 0.037 0.175 0.448 0.340 0.130 0.235 0.296 0.339 90 0.035 0.176 0.448 0.342 0.124 0.238 0.296 0.343 95 0.032 0.177 0.448 0.344 0.117 0.240 0.296 0.346 100 0.030 0.177 0.448 0.345 0.112 0.243 0.296 0.349 Continued
