Chapter 3
Assessing Environmental Impacts of Wood Used as a Raw Material in North America

Derek R. Augood

Battelle Memorial Institute

This chapter discusses features of the methodologies used to assess the environmental impacts of using wood as a raw material in North America. The reader is assumed to be familiar with the general concepts of the life-cycle analysis and the inventory, impact, and interpretation—improvement stages identified by the Society of Environmental Toxicology and Chemistry (SETAC) in describing life-cycle assessment (LCA). Strictly speaking, such assessments cover the cradle to grave scenario: extraction of resources; manufacture of intermediates, ancillaries and main product; transportation, packaging, and distribution; use, recycling, and disposal. (Portions of the full scenario can be taken, but only if the reasons for doing so, the scope of the study and the boundary conditions are carefully described and justified.) Finally, it is assumed that inventory procedures are well defined compared with those for impact.

To discuss impact methodologies it is necessary to understand something of the life-cycles and possible impacts, and even general philosophies of approach, that can be involved.

Extraction

Although wood is called a "raw material" it should be recognized that, in LCA language this term applies to resources taken from the earth. In this sense, therefore, wood is not a raw material, but an intermediate material obtained from trees extracted from the forest. The soil, minerals, air, and water of the forest provide the basic raw materials and the environment for growing trees, and it follows that the boundary for LCA studies involving wood must include the forest operations.



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Chapter 3 Assessing Environmental Impacts of Wood Used as a Raw Material in North America Derek R. Augood Battelle Memorial Institute This chapter discusses features of the methodologies used to assess the environmental impacts of using wood as a raw material in North America. The reader is assumed to be familiar with the general concepts of the life-cycle analysis and the inventory, impact, and interpretation—improvement stages identified by the Society of Environmental Toxicology and Chemistry (SETAC) in describing life-cycle assessment (LCA). Strictly speaking, such assessments cover the cradle to grave scenario: extraction of resources; manufacture of intermediates, ancillaries and main product; transportation, packaging, and distribution; use, recycling, and disposal. (Portions of the full scenario can be taken, but only if the reasons for doing so, the scope of the study and the boundary conditions are carefully described and justified.) Finally, it is assumed that inventory procedures are well defined compared with those for impact. To discuss impact methodologies it is necessary to understand something of the life-cycles and possible impacts, and even general philosophies of approach, that can be involved. Extraction Although wood is called a "raw material" it should be recognized that, in LCA language this term applies to resources taken from the earth. In this sense, therefore, wood is not a raw material, but an intermediate material obtained from trees extracted from the forest. The soil, minerals, air, and water of the forest provide the basic raw materials and the environment for growing trees, and it follows that the boundary for LCA studies involving wood must include the forest operations.

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The extraction of trees from forests immediately raises several impact questions: Are the forests temperate or tropical? What tree varieties are present? Which are to be harvested? What are their ages, growth rates? What geology, terrain, and soil types are involved? What fertilizers or herbicides are used? What is the condition of the rivers and streams? What flora, fauna, and fish species have been identified? What is their condition? What will be the effects on atmosphere and climate? What ownership, social, or political effects are expected? Is the forest well managed (now and in the future)? These questions are complex and often interdependent. The public is concerned about several of them, probably because of news stories about the endangerment of animal species, the loss of rain forests to burning, and the loss of jobs. Most life-cycle studies to date have ignored many of the issues posed in the questions above. To be fair, the studies mainly have been inventories, concerned primarily with mass and energy data, which have discussed impacts using the "less is better" paradigm for the data at hand. Neglect also can be ascribed to the scarcity of data, the formidable complexity of the forest ecosystem, and the fact that forests need to be studied on at least a regional basis. Before tackling impact effects associated with the extraction of trees from forests, it appears that serious work should be undertaken to inventory the above factors. For example, some reports state that in some rain forests there are literally thousands of yet unidentified species. Several organizations have engaged some of these tasks, and a few organizations, upon careful study and if proven, will provide certification for good forest management. To a LCA practitioner of life-cycle analysis, such studies must appear worthwhile because, if carried to absolute standards, the data would be acceptable and would relieve the practitioner—and his/her audience—of many concerns. It should be noted that, although there is some discussion about the subject, forest management is not currently part of International Organization for Standardization (ISO) 14000. Also, ISO 14000 does not set absolute performance standards. The Canadian Standards Association has initiated some work in this arena—including studies aimed at selecting inexpensive and effective methods for obtaining impact data. Firewood and energy Firewood, the simplest wood product, raises important issues. Trees grow through photosynthesis—converting CO2 from the atmosphere and water to wood

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(small quantifies of other compounds are also involved). When the tree is burned, heat (as converted energy from the sun) is obtained and combustion CO2, is released back to the atmosphere. Crudely: If the tree (and its ancestors) has been around a long time and it is not replaced, the burning of the tree increases the concentration of CO2 in the atmosphere. (Them is a parallel here to the burning of fossil fuel where hydrocarbons are taken out of the earth and combustion CO2 ends up in the atmosphere.) If, however, the tree grows again or a new tree is planted (and it is nurtured), the combustion CO2 is reabsorbed to make new wood. (Here, it is relevant to note that compared with burning fuel oil the burning of wood is cleaner; it produces fewer oxides of sulfur and less ash, for example.) Thus: Trees convert primary compounds to wood—a valuable raw or intermediate material. Combustion of wood (or derivatives) provides energy obtained from the sun. A carbon cycle is involved, which is important because it includes atmospheric CO2—a major contributor to global warming. Wood is a renewable resource. In a broad sense, the growing of trees and the use of wood can tend toward a "sustainable" operation. All of this influences impact. Lumber Figure 3-1 illustrates the flow of materials and products associated with lumber. The extraction of the tree from the forest, transportation, and other products or activities (such as use of bark, sawdust, and fuels or preservatives) are not identified in this drawing. Figure 3-1 Flow of materials and products associated with lumber.

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Factors that influence impact as shown in the diagram include: Recycle loops, in which wood is shown to be recycled into particle board and mulch. These operations, particularly particle board manufacturing, eliminate the use of new wood, and because they do not seem to require much in the way of energy or other resources, can be considered generally beneficial in reducing impact. Lumber, which after use can be incinerated for energy recovery. The carbon cycle, which is more complex than that for firewood. Here, in addition to burning, some wood, in the form of mulch or once it is placed in landfills, decomposes to generate CO2 (at least partly as methane, a worse global warming culprit than CO2). Transportation and processing, of course, add more fossil-fuel-derived CO2 to the scenario. Degradation of wood (and paper) in landfills is intriguing. The biologic-bacterial action responsible for degradation, which may be thought of as low-temperature reaction or combustion, apparently depends on the presence of moisture. A really dry landfill could be used as a carbon sink. It could provide a route for taking CO2 out of the atmosphere and storing its carbon equivalent in the ground. The obstacle is the need for dryness. Other Products A chart similar to Figure 3-1 could be drawn for various paper products. Other exciting possibilities for using wood (biomass) as a raw material are being studied. These include the use of renewable wood as a raw material to generate heat and electrical energy in power stations, to manufacture chemicals, or to produce alternative nonfossil fuels for automobiles, for example. These developments will affect not only the carbon cycle but, among other things, will also affect SOx emissions, land use, and social systems. General Approach to Impact Evaluation Impact evaluation can range greatly in detail—with five different levels of complexity being recognized. The simplest method applies a ''less is better'' approach to inventory data virtually collapsing the inventory, impact, and improvement steps into one. The method is crude and lacks discrimination. For example, it is unable to decide whether less SOx is better than less CO2—to say nothing of more complicated issues. Nevertheless, the method provides a low-cost baseline and is effective in simple cases and in highlighting possible problem areas. Studies then rise in complexity to highly detailed, often expensive, ones that seek to provide impact determinations for the specific sites involved. This is similar to an extended risk assessment task. For a life-cycle project this becomes

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impractical because it implies that multiple risk assessment studies should be made across the whole life-cycle scenario. Current impact methods are at about the third level of complexity. It could be argued that one of the hopes for life-cycle analysis was to obtain a single number to rank impact-related desirability. (As an aside, some Swedish practitioners have described many impacts in monetary units.) The LCA techniques now in use aggregate many factors over a whole life-cycle. Perhaps the desire for a single unit stems partly from the fact that it is easy to handle mass and energy quantities—the only items used in early studies (mainly inventory studies). Whatever, the general approach to impact evaluation has proceeded to narrow down the number of parameters toward the ultimate single target. The host of impact items to be evaluated is large and might be described as an impact phase space. This incorporates the operations involved (possibly a large number of processes at different locations and, as an example, we will consider four processes identified as A through D), the impactors involved (possibly many chemicals and gaseous emissions, such as CO2, SOx and various other wastes), and impact effects or categories (global warming, acid rain, and human carcinogens). In approaching this problem, most current impact studies proceed from impact categories and chains through classification, characterization, and valuation stages. Impact categories and Chains Impacts can have chain effects extending to secondary and higher order, though not necessarily greater, impacts of different kinds. Moreover, several compounds initiate the same primary impact (acid rain is triggered by SOx, NOx, or HCl). The impact chain that stems from acid rain as an impact category is shown in Table 3-1. Impact Matrix Given several impact categories, a matrix can be constructed for a project to show which impacts could be expected after accounting for impact chains. As a hypothetical partial example, consider processes A through D shown in Table 3-2. TABLE 3-1 Impact categories and chains Stressor Primary Secondary Tertiary Quaternary SOx Acid rain Building deterioration Water quality Vegetation effects Soil effects Resources Aquatic biota Agricultural production Vegetation effects Reduced diversity and fishing

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TABLE 3-2 Sample impact matrix   Process or operationa     Impact category A B C D Acid rain   x x x Global warming x x x x Resource depletion x x x x Plant toxicity x     x Decreased water quality   x x   Human carcinogens   x     Solid waste x x x   a "Each "x" in this table indicates a process that generates the impact. Several impactors could contribute to this impact. Classification Classification groups together all compounds contributing to a given type of impact. As mentioned, SOx, NOx, and HCl can contribute to acid rain. Each "x" in Table 3-2 for acid rain may therefore represent the amount of SOx, NOx, and HCl taken from the inventory for a given process. Likewise, several compounds, including CO2 and CH4, contribute to global warming. Characterization The hazard potential of each compound (or activity) in an impact group is now normalized by applying a multiplier (called an equivalence factor) that expresses the potential for harm relative to a chosen baseline. For global warming, as an example, CO2 provides the baseline. Referencing processes B through D, extracted from Table 3-2, for example, we obtain the results shown in Table 3-3. The application of equivalence factors allows each impact category in matrices like that shown in Table 3-2 for operations A through D to be described in TABLE 3-3 Hazard potential   Operation     Item B C D Gas CO2 CO2 CH4 Weight w y z Equivalence factor 1 1 11a Total stressor in CO2 units = [w + y + 11*z]   a The equivalence factor for CH4 takes both initial potential and persistence into account.

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terms of total relative units. This total could be called "total characterized stressor value." Several groups are working to measure or estimate equivalence factors for various materials and impacts. Basic acidification factors have been developed; methods are available for human carcinogenicity (by using IARC designations); and factors for ozone depletion are well known. In some cases the translation of relative hazard potential to absolute impact is difficult to define—but these questions are receiving attention. Location It can be observed from the above that the impacts most easily handled are those that involve gases with global effects. This stems from the free release of gas into the atmosphere. The situation is different when liquid or solid wastes are involved; these ate released locally and do not have vast and open dispersion opportunities. This is a feature of the methodology in which aggregation begets aggravation. Thus, there is something lacking in lumping all wastewater quantifies together, or all quantities of a suspect chemical emission, across a life-cycle because releases are made in different areas having different topographies and sensitivities. Also, no dose rates—usually required for the more local risk assessment work—are immediately known. Some things can be done to ameliorate this situation, however, and more will be forthcoming. For example, in handling acid rain it has been shown that, by studying maps showing areas that have sensitive soils and by identifying regions with large acid gas emissions, it is possible to develop weighting factors (similar to the equivalence factors discussed above) to express regional differences across the continental United States (see Figure 3-2). The use of such factors can be viewed as a modifying tool and a partial return to risk assessment locales. Figure 3-2 Equivalence factors for acid gas emissions impacts in the continental United States.

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At this point it should be said that it is inappropriate to expect life-cycle analysis to handle local problems with risk assessment detail. To attempt to do so would prove prohibitive. The objective would be to develop impact evaluation to identify possible problems within and between systems and then, turning inward, to highlight where the ("local") problems might be—problems that can then be studied more carefully, as necessary. It should be pointed out that life-cycle analysis practitioners have more than just aggregated numbers at their disposal. Some details for specific operations (such as processes A or D in the foregoing discussion, for example) are already available for study. Valuation Once final total characterized stressor values are calculated, it is necessary to determine their relative significance. This is a judgmental exercise that can be undertaken by experts to rank the importance of the impact effects. This is aided by an analytical hierarchical process after another normalizing step is taken. The structure that could apply is shown in Table 3-4, along with a few hypothetical weighting values to illustrate a breakdown that might be obtained. The generation of weightings is essentially a subjective exercise—carried out in a structured manner aimed at providing consensus values. Different groups of experts—environmentalists, scientists, engineers, government officials, local politicians, citizens—have different agendas and will likely generate different Table 3-4 Hypothetical valuation structure  

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valuation factors. Overall, however, when a given set of such weighting factors is applied to the normalized total characterized values for the various impact categories, a single numerical figure is obtained that represents the method's assessment of the life-cycle's impact, including the experts' valuation. Several computer programs are under development to incorporate various aspects of these methodologies. Summary Life-cycle impact assessment is still in relative infancy. It is a complicated, challenging, and changing arena. Forests can be inventoried, planned, and managed intelligently—with the goal of doing so to absolute performance standards. This is a demanding, long-term task. Depending on definition, a large degree of sustainability can be obtained in using wood as a raw material. Wood is a renewable resource. Carbon cycle considerations are important. Wood offers opportunities to produce energy, chemicals, and alternative fuels while reducing increases in atmospheric CO2 concentrations. Computational methods for assessing impact currently permit a fair degree of comparison to be made between the impacts of systems. The results highlight areas for further examination. Work is continuing to improve the general methodology for impact assessment. Some aspects of the methods used tend toward risk assessment venues. Computer programs are being developed to handle impact calculations. No one has all the answers and much remains to be done. Progress, however, is remarkable.